Wednesday, 17 December 2014

PGA144 follow-up

My initial measurements now show
NF 0.6dB (usual caveats apply)
Gain 2.5 to 20.5dB ( adjustable)
Input third order intercept >+8dBm!
Input return loss ~9.5dB
Notch at 98MHz, -43dB wrt 145MHz at full gain
Unconditionally stable

All subject to further tests, of course.

Also
+8 to +16v working.
110mA current consumption
Can be optionally powered over the coax

Mechanically mounted in a screened tinplate box.
Connectors-  SMA female.

The PCB can be used without the box, if you want to mount the preamp inside another rig. Provision is made for two separate types of SMA connector on input and output to facilitate this. You could even use miniature coax cable direct to the input trace.

Enough............

Sam

PGA144

The new 144MHz preamplifier. The picture shows the prototype kit, built up for tests. A couple more are under construction.



Sam





Monday, 8 December 2014

Debugging transverters

I spent several hours today, fault finding on a couple of Anglian transverters assembled by customers.
A few dry joints were found on the reflow-soldered PCBs. 
A thorough visual inspectio, after assembling the board into the box, would probably have found the problems.
I was always taught and in turn, when a telecoms instructor, that visual inspection is he first thing you do when looking for faults. Power supplies are second!
In the case of Anglian transverters a visual inspection is also essential after the board is seam soldered into the case. It is quite easy to disturb parts if care is not taken during this part of the assembly.
Yes, both units are now working correctly!

Sam


Monday, 17 November 2014

ISCAT-A

ISCAT-A beacon signals successfully decoded from G4JNT's personal beacon on 2300.350 this afternoon. Once Andy turned the beacon antennas roughly towards me decodes started quite regularly. As London Heathrow is pretty much on this path I assume it was principally aircraft into and out of the airport that were responsible.))))))
I am very impressed by ISCAT-A for aircraft reflection compared to JT65C at 2300MHz.
Generally, if you hear the reflection burst, you can expect to have a decode. When ISCAT-A reports below about -20dB decodes are less reliable, although more testing is required. In a large number of decoded frames the number of erroneous decodes was seen to be less than a dozen or so over a three hour period.

I am now turning my attention to enabling the PA switching to work with the preamplifier box so I can try a two-way QSO on the new band. You need to be very careful with sequencing when switching 250W at 2.3GHz on a single coaxial cable with connection to a very low noise preamp!

Sam




Sunday, 16 November 2014

2300MHz beacon

IIt was good to see signals from the G4JNT 2300.350MHz ( new band) personal beacon this afternoon. The computer managed to decode several two and three minute periods. Reception was principally by aircraft reflection ( know as AS or AR) and easily identified by the fast Doppler. JT65C is not an ideal mode for AR ( I personally prefer AR rather than AS) and Andy has said he will change the modulation scheme to ISCAT-A later this week. This scatter mode is better suited to aircraft reflection ( Maybe!).

I would not have been able to participate in the tests today except that I had a weekend visit from G4FRE. Amongst the various radio jobs we got done, Dave re-flashed my Apollo 32 LO synthesiser ( Google either Apllo 32 or N5AC) so that it now thinks it is an Apollo 256 and now has 1078 rather than 1078.5MHz as one of the output options (1078 *2 = 2156 + 144 = 2300).
Dave also updated my K3 and P3 software to the latest version. I didn't know it had changed. Now I can use 10MHz as an IF for 472kHz.......

With Andy's personal beacon on 2300.350MHz it was possible to use my 67 element Wimo yagi to listen via my homebrew 13cm transverter and K3 transceiver. Currently the yagi is connected via 5dB of loss direct to the shack where a 0.3dB G4DDK VLNA13 feeds the transverter. I am tempted to NOT put the preamp at masthead as the engineering required gets complicated as two feeders plus power feeding needs to be provided. I am not convinced the effort required is worthwhile at this stage. But.......
Whilst Dave was here he loaded up my 40m inverted V on several bands, in turn, and connected his Anan10 in order to WSPR and see where we could get to. I don't have a record of where the signal got to but I was impressed with 10m and may well connect my own transmitter to the same dipole and have a go. It is months since I did any WSPRing on then on 40m.
I may also be in line to get a WSPR Ultimate 3 transmitter. Should be different!

Back to sorting the 13cm preamp interface. I can run around 250W in the shack. With 5dB feeder loss the coax is not going to freeze........

Sam




Wednesday, 12 November 2014

2300Mhz

I managed to get the Wimo 67 element yagi on test today. A judicious bending of the driven element away from the first director improved the match to over 30dB. This was measured on a HP network analyser with the connecting cable normalised out of the measurement so it is the actual yagi match.
A VLNA13 preamp ( 0.27dB) at the feed point allowed me to see sun noise and readily show the difference between cold sky and ground.
I terminated a length of LMR400 to use as the ( sole) feeder from shack to the yagi, up at over 12m.
Tomorrow I plan to connect the preamp, set up the 200W plus  HPA and then wait for someone else to turn up on the 2300Mhz band. That could well be G4FRE, now next week.......

Sam

Tuesday, 11 November 2014

Exercising my 146Mhz NoV

After buying a 'gaming' USB headset with boom microphone last week I set up my K3, with USA 144-148Mhz internal transverter, for use with FreeDV digital voice.

Set up was simple but getting the transmit level right proved a bit more of a problem than I expected.
At around 14:30 today, in tests, I managed to hear G4BAO on 146.900MHz, using one of the recommended digital channels at the top end of the new band. 

I immediately saw the characteristic 16 carriers of the FDMDV transmission from John. The SNR was not that high, but John's voice was unmistakeable, if a little Stephen Hawking like!
When it came to my turn to transmit I hit the soft PTT and spoke into the boom microphone. After adjusting the distance to the microphone so that the 'Frm MIc' waterfall showed the level to be about 1/2 of maximum, I sent a report and then I turned it back to John. He immediately confirmed successful reception. As the signal is nothing like we are normally used to it was difficult to give a useful signal report. This is one of the things we will have to sort out with digital voice! My initial stab is 33D where the D stands for digital distortion. Later, when I wound the mast up a few metres, the report was more like 45D

After switching to 1600 wide from standard 1600 we compared results again.  It would appear there was little difference except that the carriers occupied a bit more bandwidth. There was no noticeable improvement in quality. The signal was best described as distorted but intelligible at low SNR, improving to acceptable at higher SNR, corresponding to the peaks of QSB.

So, what are my impression of the FreeDV contact at the relatively low EIRP of 10dBW?
The multipath signal over the 78km path had a lot of errors. SNR was low and when we switched to SSB ( at 144.285MHz) it was obvious that conditions over this normally reliable path were not good. My SSB report to John was 53 to 55. There was lots of QSB.

I understand that a newer version of FreeDV, aimed at VHF, is under development. This will have a different voice model and maybe some Forward Error Correction (FEC). There is little need to restrict the bandwidth to 1.2KHz at VHF and maybe an increase in rate and bandwidth will be worthwhile when signals are distorted by VHF multipath and doppler spread?

I hope to work a few more stations on 146.900MHz and compare results.


Tuesday, 4 November 2014

Changing shacks

Now that outside temperatures are falling it is time to migrate back to the indoors shack. Although I have lots of space in the outside shack, it is very difficult ( and expensive) to keep warm when outside temperatures fall below about 12 degrees C
My solution two years ago was to establish an indoor shack in the spare room and run a couple of Heliax coax cables from a patching frame in the outside ( garage) shack, under the lawn and then along the fence line to the side of the house. As well as the two main coax lines I have a six wire screened control cable between the garage and indoor shack. I also have a third coax for HF that shares some of the common route but goes to the bottom of the garden. All cables enter the house through Huber Suhners lightning arresters.
With these few connections full remote operation is a bit of a challenge. I decided ( for now) against using e.g. Remote Rig or similar due to cost.
Last winter I ran my K3 as the 144MHz IF over one of the coax cables, with the various microwave transverters in the outside shack connected to the IF as required. The problem with this arrangement is that the losses in the long, concatenated, coaxial cables between the mast mounted transverters for several of the bands and the indoors IF were just too high and tended to radiate enough to be heard locally on 2m!
The solution this winter is to locate an Anglian 28/144MHz transverter in the outside shack and feed 28MHz IF over the coax. Yes, there is still a danger of egress and ingress at these frequencies, but the coax is pretty good at 10m.
Since the K3 and the Anglian 28MHz IF are separate ( transmit and receive are independent) and I didn't want to use up both of the coax cables between the two shacks, I intend to use a couple of 3dB splitter/combiners rather than relays in order to separate the transmit and receive paths. Tests with two MiniCircuits splitters and a 6dB attenuator have shown that the idea works well. 
The second coax cable will be used for a second system, with another rig.
PTT is activated over one of the screened cables and when the transverter is switched to transmit the Anglian +12V on transmit signal is connected to another control cable wire ( through a current limiting resistor) to light an LED in the indoor shack as confirmation that the transverter has switched.
I also use a Bird sensor on the 2m transmit output in the outdoor shack and feed the sensor output back over a third control cable wire to the meter ( still in the Bird housing) in the indoor shack in order to check that there is actually transmit output.

Friday, 31 October 2014

144MHz masthead preamp

 
Most of today was spent building a144MHz masthead preamplifier. I have not used a masthead preamp on 144MHz previously, but for MS and especially EME, a preamp is essential and I really wanted to see how much difference it would make.

The active preamp stage uses a PGA 103+ PHEMT on a WA5VJB PCB. 

G4SWX and I have previously developed a 'better' 130MHz High Pass Filter that has a deep notch in Band2 to suppress FM strong signal effects and a 150MHz Low Pass Filter at the output to suppress high frequency signals reaching the following receiver.
A preamplifier in a box is of little use without a method of powering it at masthead and switching the antenna between transmit and receive.
I chose ( eventually) to use one of the larger Schubert ABS enclosures. These are now available from G3NYK in the UK.
I use a Relcomm SDL 12V coax relay with three N connectors. The relay is rated to 1500W at 150MHz
Power for the preamp and relay is fed over the receive coax and a homebrew bias tee. The bias tee can be seen on the right in this photo. The preamp is in the tinplate box In the centre.




Following my usual masthead practice, the relay is mounted with the three N connectors through the box lid.
N connectors are used to connect to the preamplifier input and output. A short low loss coax cable connects the relay normally open port to the preamplifier input.

The numbers?
Noise figure 0.70dB
Gain 23dB
These numbers are with the relay and two short lengths of coax in front of the 0.5dB preamp stage.

Sam





Sunday, 26 October 2014

144MHz transverter and the lunar probe 4M


I have been busy rewiring the 144MHz transverter module into a previously used Vero LBX case. The temporary version I was using hadn't got the frequency locking or PA wired in.
I've spent several days re-wiring it so that I had these additional facilities available when required.

The basis of the transverter is the Anglian with the PA board using an RA08H1317M PA module and my ZLPLL 116MHz LO that can be locked to my 10MHz shack standard.
Now that I've finished the wiring I want to connect it back into the 144MHz antenna and see how it performs compared to the K3 internal 144MHz transverter on the same antenna.

I have been monitoring the 4M lunar probe on 145.980MHz as it makes its way towards the moon and lunar fly-by. Currently the probe is about 31 hours from fly-by (which will happen below our horizon) and now almost as far away as the moon. 

As my 2m yagi cannot be elevated I am stuck with monitoring when the spacecraft is within the main lobe or first sidelobe of my antenna. Even so, for several hours before AOS and LOS the spacecraft can be copied successfully and the JT65B modulation decoded much of the time.
My last decode was about 14:00Z today. It should become copiable again sometime after about 17:30 today. 
By then I should have the new transverter plumbed in and able to try it out on a VERY weak signal!
Sam






Thursday, 23 October 2014

Wrong again!

Oh dear, I do seem to get myself into some awkward situations.
In all innocence I earlier tweeted a picture of a commercial video coder/modulator. I was told in good faith that it should be suitable for use within the new 146-147MHz ham band allocation, when frequency translated from its current 70MHz. I should have followed my inititial instincts that it wouldn't be suitable when using QPSK modulation, even at rates significantly below 1Msymbols/sec. 

It seems I innocently walked into an ongoing debate between some parts of BATC and the RSGB. 

It can be done, but it seems that what was being proposed would be unsuitable in view of the difficulties of achieving a suitable SPD at the band edges and consequent potential interference to safety of life services operating above 147MHz and our fellow satellite enthusiast just below 146MHz.

Whilst not wishing to discourage anyone from using DATV in the new band ( or indeed 10 or 6m) it looks like more effort needs to be put into solving the spectrum occupancy issues. This is what radio amateurs are good at.

It seems to me that the current wish to use a number of free ex-commercial coder/modulators may be clouding the real issues. 

It should be added that I am referring to fast scan digital TV. Slow scan variants look fine but may not offer anything new or innovative and hence not enhance our case to keep 146-147MHz in the future, or indeed give us a bit more spectrum in this region.

I hope these issues can be overcome and a real solution found.

Finally, these are my personal views and do not represent those of any organisation.

Sam


Sunday, 19 October 2014

144MHz transverter construction

Now that I have finished my 'run' of talks on the Anglian, I have stripped out my temporary homebrew 144MHz transverter unit, ready to add in the PA and the 116MHz GPS locked LO.
Both these units were used as demo pieces for my talks.
I have mounted a small (40mm) diameter fan to the rear panel so as to blow or draw some cooling air across the PA components as the PA will be mounted to one of the case side walls. There will be no external heat sink on the case. At 4W PEP out and class AB operation, the aluminium case wall should be sufficient to dissipate the heat of the PA with quite acceptable temperature rise inside the case.
I will post a picture of the finished transverter on here later this week ( optimistic?).

Sam


Saturday, 18 October 2014

More on the Anglian

I have almost cleared the backlog of orders for the Anglian 144MHz transverter, thanks to sterling efforts by G7OCD to get the boards assembled.
If anyone is interested in one of the transverter kits, featured in DUBUS 3/14 and covered in my RSGB Convention talk, I am now able to take more orders.
The cost of the transverter has deliberately been kept low, and assembled boards offered, in order to allow more amateurs to build their own high performance 144MHz transverter, rather than relying on commercial 144MHz black boxes with their (usually) indifferent performance!



Sam

Thursday, 2 October 2014

144MHz set up

I have now added a Gemini 2 to my 144MHz set up. It is currently being driven by my K3 and internal K144VX transverter.
I will be migrating the 144MHz over to my Anglian transverter after the RSGB Convention. I don't have a spare Anglian 8W PA whilst my demo one is slated for show at my Anglian talk!
The Gemini gives close to 300W saturated output for 5W input. 
It is small and convenient and sits well on the operating bench, next to the K3.




Sam

Sunday, 14 September 2014

Some results from using the Anglian with K3

One of the things I dislike about the internal K3 144MHz transverter is the number of birdies that appear in the DX part of the 2m band. This has always tended to put me off using the K3 on 144MHz.

I spent some time testing yesterday with the antenna replaced by a 50R load.
Rather that use an objective set of measurements such as an analyser at the IF output, I used the simpler technique of just listening. After all this is what most operators really notice!
Incidentally, not all the birdies seen on the P3 or other SDR attached to the IF output are audible at the receiver output and are possibly due to shortcomings of the SDR in the P3 or other SDR (SDR-IQ in my case).

Tuning from 144.00 to 144.500MHz, with the internal transverter, I recorded about 10 significant birdies. Some weak and some medium strength. There were no strong birdies.

With the Anglian selected as an external 144 to 28MHz transverter the number of birdies dropped to under half those with the internal transverter and many of those that remained dropped in level to barely noticeable. I have therefore decided that the Anglian is a better choice for Dxing. Well, I would, wouldn't I?

I suspect that the problem with the internal transverter is more down to lack of screening than anything else, although the extra IF output filtering incorporated in the Anglian also probably helps.

I plan to do some objective testing in due course.



Sunday, 7 September 2014

Red in beak and talon

Just been watched a Goshawk kill and devour a starling in the garden.
Fierce looking bird!


Saturday, 6 September 2014

144Mhz results

I took the opportunity to listen and operate during the 144MHz Trophy contest.
100mW is not a lot to use during such a contest and indeed I worked one ON using the 100mW and he told me he was using 1kW! There was a slight difference in the reports with 40dB power difference......
What was interesting was the difference in ability of some stations to hear me and others to not even notice that anyone was calling them. How much was down to receiver blocking at their end and how much to shear QRM will never be known. 
An interesting evening.
Sam


144MHz antenna




After my recent changes to the YU7EF 9 element 144MHz long yagi feed point I changed over the 6/4m yagi for the 144MHz one.
I wanted to check out the new preamp on the 2m antenna.
The first thing I noticed was how quiet the YU7EF yagi is. As long as I don't beam towards the house ( approx 10 to 20T) the back ground noise is extremely low, although punctuated by the usual pulse noise from a nearby electric fence and some computer/data equipment carriers.

The plot above shows the return loss ( match of the yagi directly at the feed point. This was achieved by the usual calibration procedure at the yagi, using short,open, term.
A across the range 144 to 145MHz the return loss is around 20dB. I'm not so happy about the way the match starts to deteriorate rapidly above 145MHz.
The original 6/4m feeder is Ecoflex 10. There is now a short length of RG213 beteen the EF10 and the yagi feed point. This will be replaced with something of lower loss once the masthead preamp is installed.


The feed line loss is 1.9dB. Measured as half the two way loss from the shack to the yagi with a cal short circuit replacing the yagi. This is a great way to check installed cable.

Sam



Friday, 5 September 2014

Preamp plot

The yellow plot is preamp input match ( Return loss) and the blue plot is the insertion gain.
Both plots are from 50MHz to 500Mhz
Marker 1=98MHz
Marker 2=144MHz
Marker 3=220MHz
Marker 4=432MHz
The red line is 0dB


A 144MHz preamplifier

As mentioned earlier on my twitter account (@dxing) I have spent much of the day 'fettling' with a PGA103+ preamplifier, getting one ready to use with my Anglian transverter.

                                           



The basic PGA Amp I have been selling has no RF filtering and is subject to overload from nearby strong out of band signals. This is not ideal.

The third order input intercept (IIP3) measured previously seems to have been overly optimistic when compared to recent results. The latest measurements have been done more carefully and at slightly lower levels than previously. Even so, the IIP3 still measures better than +1dBm and is currently beyond the range of my test gear.

By adding a different configuration LPF to the input it has been possible to better noise match the PGA103+input; place a big notch in the middle of the band 2 FM ( possibly still the worst interferer for 144MHz systems in the UK) and yet keep the noise figure low. The LP filter is a variant on a design suggested by G4SWX

A simple 150MHz LPF at the output rolls the gain off above this frequency with minimal impact on gain and reducing 432MHz and 220MHz( DAB) response.
My preamp measures 0.6dB noise figure, 25.4dB gain and >+1dBm IIP3
Stability is excellent. 
An attenuator may be required at the output, in some circumstances, as the gain is rather high for most applications.

I am not planning to produce kits at this stage.

I will produce a full construction article in due course for anyone wanting to build the preamp. First, I want to do some more testing in conjunction with the Anglian transverter.

Sam


Sunday, 31 August 2014

New Anglian transverter PCBs

First sight of the new PCBs for the next batch of 144 and 70MHz transverters!
Beautifully made boards with gold flashing rather than tinned.
Now to order even more parts to populate them..........
Pictures later.
Sam

Saturday, 30 August 2014

Return from EME2014

It has taken me several days to recover from the trip to EME 2014 in Brittany. Not because of the travel but because of illness. Somewhere I managed to ingest some shellfish. I never knowingly ate any, but...... It has taken until today to get my appetite back!

Illness aside, it was a good Conference, with lots of interesting information gained, enthusiasm for EME renewed and, more importantly, lots of old friendships renewed and new ones made.

Pleumeur Bodou is an interesting place. As well as being a world famous satellite site, where the first successful transAtlantic transmission was made from Andover Maine to Europe (when Goonhilly mixed up left and hand and right hand circular polarisation) in July 1962 on Telstar, it is on the Rose Granite Coast with lots of spectacular great granite boulders all along the coast.

I worked their 5.7GHz amateur band EME station, TM8PB, back in 2012, using my 2.3m EME dish, so was pleased to personally see the station at the other end of my contact.

In the photo you can also see a long 2m EME yagi bolted to the side of the dish!


In all there were 110 registered attendees plus a number of partners, making a total in excess of 150. The Pleumeur Bodou radio club hosted the event with the organisation being made by F2CT and his XYL together with a number of other French radio amateurs. They did a great job ( except for the weather!). 
It rained on and off for the two days of the Conference, with a long enough break to take the group photos. These will appear elsewhere in due course. I wasn't able to take any group photos this year.

An enjoyable few days. My thanks to the organisers for a job well done. Maybe a few points off for the caterers................!

The next International EME event is scheduled for Venice in 2016.

Sam







Friday, 22 August 2014

116MHz frequency locking

At last I got round to connecting my ZLPLL 116MHz source to the Anglian 144MHz transverter.
I am pleased to report it works really well. I could detect no difference in the quality of received signals supporting the observed good phase noise 'measured' on the spectrum analyser.

I was initially a bit concerned at the high level of the source harmonic output. However, when connected to the Anglian it injection locks the internal 116MHz crystal oscillator, leading to a really clean injection signal. 

Monitoring the 144MHz output, with the input 28MHz drive signal supplied by my R&S SMG low noise signal generator, the output spectrum was just as clean as with the internal ( unlocked) oscillator.

Driving the ZLPLL with a clean 10MHz GPS locked reference signal from the SMG, the Anglian signal sounded excellent. I am really pleased with these results, which I will be reporting in my talk at the EME Conference in three day's time!

The ZLPLL as used to provide the locked 116MHz LO for the Anglian.

Google ZLPLL for details of the source. Note that Wayne can no longer supply the OCXO version of the Source, although TCXO and external-only versions are available and OCXOs may be back in due course.

Sam


Thursday, 21 August 2014

EME 2014

Early Sunday morning Dave, G4HUP, and I will be off to France via Weymouth and St Malo 
for the EME2014 conference, being held in Pleumeur Bodou, Brittany, on Monday and Tuesday next week.
Pleumeur Bodou is the site of the former French TransAtlantic satellite station and is credited with making the first successful TransAtlantic TV transmission with the USA. Goonhilly had previously failed due to a misunderstanding as to what defined the sense of circular polarisation to be used! I well remember Richard Dimbleby, on the BBC, sat waiting for the first pictures from the USA and seeing a terribly noisy picture, that was decidedly unusable. FranceTelecom got it right the following day. They weren't first, but were first with a good picture.........there, that will get me into trouble with our French hosts!

I am very much looking forward to the Conference. This will be my fifth EME Conference, the first being in Wurzburg, Germany, followed by Florence, Dallas and then Cambridge. It will be interesting to see where the next one will be. We will be voting for the next venue at Pleumeur Bodou. Venice is one of the known proposals for 2016

My presentation slides are now finished (apart from the usual final polishing that always takes place....) and they now contain new data on the performance of the Anglian 144MHz transverter. It has been interesting preparing the talk for a generally technically well-versed audience from across the globe.
I hope to use the same slides in my talk on the Anglian at the RSGB Convention in October.

Unfortunately, I have been inactive on EME for more than two years. I am currently looking at a smaller dish for use at 10GHz. It should be easier to steer onto the moon and will give me an opportunity to develop my 10GHz capability. Much of the 10Ghz gear is ready to go, but I have only just found a source of suitable dishes.

I hope to have more to say about 10GHz EME in due course.

Sam






Tuesday, 12 August 2014

Filters for beacons

Today I built two 432MHz beacon low pass filters. One is destined for GB3UHF in Kent and the other for GB3NGI in Northern Ireland.
The filters were designed using ELSIE and the implementation is silver plated wire coils and paralleled ATC fixed capacitors and 6pF Voltronics ( I think) ceramic trimmer capacitors. The filters are assembled in small Eddystone diecast boxes with 17mm flange N female connectors as shown.

The measured performance of the filters matches the ELSIE predictions quite well. Insertion loss is below 0.2dB with a return loss of well over 20dB ( depending slightly on tuning for minimum insertion loss).

Sunday, 10 August 2014

Frequency locking 116MHz

I spent part of the day playing with frequency locking my Anglian 144MHz transverter.
The transverter has facilities to either inject or extract a 116MHz LO signal.
Although I had conducted this test previously on my DDK2001 source board, I still needed to check that it also worked with the Anglian LO.
I was pleasantly surprised to see just how far off frequency the on-board 116MHz could be and still lock, with extremely clean output.
Not only that but the level of external 116MHz required to achieve lock proved to be extremely small, easing the requirements on the external source.
This has raised the possibilities of sub harmonic locking! I will be exploring this over the next few days.
All this is being done as content for my EME 2014 Conference presentation.
Sam

Monday, 4 August 2014

My grandfather in WW1

I am posting this as a tribute to my paternal grandfather, Edward Jewell.
'Ted' joined up to the Royal Sussex Regiment on the 19th February 1915 at the age of 18.
He was sent to France on 10th December 1915

On the 14 February 1916 (St Valentines day) he was wounded by shell fire and evacuated to Boulogne and thence returned to to England on the St David hospital ship.

After several months in the Norfolk Hunstanton VAD hospital he was turned to France on 29th September 1916. To the Somme, again!

He still had shrapnel in his upper body. It could not be removed without further damage.

On November 28 1916 he was digging a trench in the Somme when it caved in on him. He and others were buried or trapped.

My grandfather was buried up to his waist in mud and water for three days. When found and dug out he was evacuated  to an unidentified field hospital in France. There he was diagnosed as having trench foot and subsequently had both feet amputated on the 12th December.

He was returned to England and then had a double Syme's amputation of his lower legs. Separate to the removal of his feet.

He spent months at Roehampton hospital recuperating and for the fitting of artificial limbs.

He married Grace in November 1920. My father was born in 1921.

Ted lived until he was 72 when he died of a massive heart attack at the Royal Berkshire hospital in Reading. 

He suffered deteriorating health from the time of his amputation, but managed to live a full life.
I am very proud of my grandfather.

Sam


Monday, 21 July 2014

Rain water

Since my mast had been luffed over for several days due to thunder storms ( Sunday was particularly bad on the east coast) and heavy rain I thought I ought to check out the 10GHz transverter. Normally I put a cover over the transverter and over the masthead preamps to keep rain water off when it is in this state. When the mast is upright the boxes are reasonably waterproof, but not necessarily when they are on their side.

When I opened the 10GHz transverter diecast box I found some rainwater had indeed entered the box. Part of this was due to the fact I had not fully tightened down the four lid screws and part due to the fact that I hadn't applied sealer to the lid/box seam.
With the water removed, the box dried out and the dessicant bags replaced I set about upping the transmit power. I had suspected that the DB6NT transverter tx gain pot had been turned way down to accommodate my usual 2W of 144Mhz drive. With the pot readjusted I was easily able to get 10W output as indicated on the remote meter in the shack. This using 100mW on 144MHz in the shack.

After scraping the old sealant off the box seams I replaced the lid, screwing the four holding screws down tight. Then I used a mastic gun to squeeze Down Corning 745 non-corrosive sealant along all the box seams.

A quick test and up went the mast again.

All appears well, but with 6m open to North America, it didn't have any on air tests as I preferred to call  a VO. Unfortunately It seems the opening was not reaching thisart of the East Anglian coast as all I hear was the one VO and I couldn't make myself heard to him!

So I went away to do some measurements on a commercial 2m preamp ready for a published review in Radcom........

Sam


Wednesday, 9 July 2014

96Mhz LO

I've been meaning to upgrade the 96MHz LO in my homebrew 23cm transverter. My own design OXCO has proven to be less than ideal. Having rescued a 106.5MHz G8ACE from an old 3cm transverter I thought I would convert it to 96Mhz in order to drive the multiplier chain in my 'Kirton' 23cm transverter ( see RSGB Microwave Handbook Vol 2).
I spent much of today calibrating the crystal turn-over temperature and then refitting the OCXO in place of the original OCXO.

With the 96MHz oscillator running on frequency I was able to hear the GB3MHZ 23cm beacon using just a three element WA5VJB PCB yagi in the shack. It sounded much cleaner that with the old OCXO,  but some of that may be down to the new beacon hardware, commissioned since I last used the transverter.

Driving the 'Kirton' transverter from the 50-100mW 144MHz output of the 'Anglian' transverter, driven in turn by the ICOM IC756Pro3, I was able to see 15W out of the PA module connected to the Kirton.


Just right to drive the 200W SSPA!!!!

The picture above shows the inside of the HB transverter with the OCXO lower right and the Mitsubishi PA module inside the huge heat sink on the back of the transverter. The 'Kirton' module is inside the tinplate box in the centre of the photo with a nice connectorised multiple band pass filters over it. This is used on receive only and effectively removes all potential out of band interferers!


At 15W out the spectrum analyser shows the output spectrum from 10MHz to 2.9GHz. The second harmonic is a credible 50dBc, but even so a 1.3GHz LPF will be needed at the output if this is connected to an antenna.

Here, the spectrum is centred on 1296.2MHz, with a span of 100kHz. The output looks pretty clean, so I think I am going to be able to use the transverter again. Looks like the TS2000X may be finding itself redundant. At least for a while!

Sam





Tuesday, 8 July 2014

10Ghz QSO

Had a 3cm QSO with G4BAO earlier this evening. There was some  evidence of some rain enhancement but if it was then it was forward scatter as the note was almost T9.

Whilst listening to John there were a few times where we both failed to entity when the other station went over. The old Piep tone, whilst deprecated by some other amateurs as being too CB like, does make it much easier to identify the end of an over when conditions are poor and there is lots of QSB. It can add a single pip or 'k' at the end of transmission.

I remembered I had a Roger Piep 77 unit, wired for my old ICOM IC275H, which hadn't been used for some years. I wondered if it would work with the ICOM 756 Pro3 that I am using to drive my Anglian 2m transverter and 3cm transverter? 

Yes, it does!

The Roger Piep 77 is now wired into the mic lead of the Pro3 to see if it really does help.

I note that the Roger Piep 77 is still available ( I think I bought mine at Weinheim, many years ago) from the manufacturer NF/HF Technik in Germany. Google on Roger Piep77 for details.

Sam




Tuesday, 1 July 2014

Back from Friedrichshafen

All over!
A very enjoyable weekend in Germany spoiled only by the rain on Sunday.
It looked to me like there were more visitors to Friedrichshafen this year, compared to last. Hall A4 was completely full of traders, unlike last year when it was anything but full. Also this year Hall A5 was in use for a Maker faire event. I spent just a short while in A5, but enough to notice that it was nearly all about 3D printers! I was particularly fascinated by the Steam Punk exhibit with 'steam' TV and such like.......
No big purchases this year, but a number of smaller items were worth purchasing including SMA cables, crystal heaters and a rather nice transverter case for one of the new transverters.

I was invited to join the Spectrum Workshop run by G3PSM? This was in preparation for the 2015 world radio conference and in particular the IARU Region 1 preparations. Presentations included one on 70Mhz by G3SDL as well as Murray, G6JYB, on Galilleo and 23cm. The amount of work that goes on behind the scenes into preparing for these conferences is amazing.

The LGBT ( look it up) boat on Saturday night was a bit of a disappointment due to the storm that came in over the lake. We ended up watching the lightning flashes over the lake whilst finishing off a rather nice bottle of German white wine. The boat didn't get back until about 5am.

The Sunday  journey back to Zurich by ferry and train was done in heavy rain that only really gave up once we reached the airport. But before that trip it was one last visit to the Messe to pick up any last minute bargains ( they were all gone!) and  then a visited to the Zeppelin Museum. This was my first visit to the museum and is a must if you go to Friedrichshafen. How come I hadn't visited before?
I was impressed by the large engines used in the Zeppelins, but I was even more impressed by the lightweight construction used in the airship design. Really impressive. No Zeppelins in the air during this visit!
 
I am already looking forward to next year.

Sam





Wednesday, 25 June 2014

French air traffic controllers

Just learnt that the strike will end in the morning, so hopefully our EJ flight to Zurich will be on time!
Looking forward to the weekend in Friedrichshafen, seeing the new gear on sale as well as the surplus bits, but most important, looking forward to seeing old friends from across Europe (and beyond).

pro 3 update

An interesting discovery. The power output control on the Pro3 also controls the transverter output level. I never expected that, but it has enabled me to get a little more output on 10GHz by increasing the 28MHz drive level.   Simples!!

Sam

Friedrichshafen

Getting ready for tomorrow. Flying (I hope) from Luton to Zurich and then train and ferry to Friedrichshafen. However, I am concerned about the delays on many European flights due to the actions of the French Air traffic controllers. It is amazing just how much European airspace is controlled by the French. Yesterday's Zurich flight arrived mid evening and would have caused us to miss the last ferry. Hopefully, it won't happen tomorrow as Easyjet wises-up to what flights, to where, will work and what won't.

There is a quite a large contingent going from East Anglian, using the Luton/Zurich/Romanshorn/Friedrichshafen route, so there is some scope to do car rental etc if flight delays cause us to miss the last train/ferry. I hope it doesn't come to that.

I am very much looking forward to seeing some of the new gear on show at FHM. And buying all those bits I don't really need, but do, because I can!

As usual, I will be donating a prize to the ARI EME Contest organisers. I am not really sure how this began, but it seems to have become a tradition.........this year I have decided to donate an Anglian 144MHz transverter kit. I hope it is appreciated.
I'll be at the QSL wall at 1pm local on Friday for the usual EME meet-up.

Sam

Tuesday, 24 June 2014

Plumbing the Anglian

I wanted to use my Anglian 144MHz  transverter with my ICOM Pro3, as the 28MHz IF. The problem was that the Anglian was designed with a K3 in mind so has separate transmit and receive IF ports.
Since the Pro 3 only produces around -20dBm IF output (typically ICOM) there was also the problem of  whether there would be enough IF drive, especially with another 3dB loss due to the MiniCircuits IF coupler.
The first tests were encouraging when the receive noise level came up significantly on the Pro3 when the transverter was connected and the transverter port activated.
I found I could get about 40mW 2m out of the Anglian with full -20dBm, 28MHz drive. Removing the two  parallel 120R dump resistors and placing a 10R across the 100R in the input attenuator I could bring the 144MHz output power back up to 100mW. As the Pro 3 transverter output is quoted in mV I assume the output impedance it wants to look into is not necessarily 50R?
100mW of 144MHz IF is just sufficient to get to about 7 W output from my 10GHz transverter, with the current setting. When I next take the 10GHz off the mast or luff it over, I will increase the transmit gain to compensate.

I'm now looking forward to the UK AC on 10GHz this evening. I'm also hoping Englnd will have won their last World Cup match as well!

Sam

Monday, 23 June 2014

A bit of 10GHz

What's going on?
First Peter, G3PHO resurrects his 3cm gear and works Neil, G4BRK. John, G4BAO works Neil, then Graham, G4FSG and I have a QSO on 3cm. Both of Graham and I have recently put our 10GHz systems back into use.
Unfortunately I didn't manage to work Peter, whilst Neil and John had to go QRT. However, I hope to be on for tomorrow evening's UKAC on UHF.

Maybe a bit of resurgent interest in 3cm?
I will try to get my ICOM Pro 3 and Anglian transverter on in place of the FT817 tomorrow. The spectrum display will be very useful, I think.

Sam


Saturday, 21 June 2014

New ones on 6m

No one could ever accuse me of being a 6m band fanatic. But when the Es season comes round I do get enthused about what I can work on this glorious mode.
Taking advantage of today's 6m contest and some quite intense Es conditions I was able to add a few new DXCCs to my growing total.
Today I added Gibraltar, Macedonia and Andorra. None of these could be regarded as exotic and indeed all are within that first reflection range, so should have been worked previously, but somehow I had missed them!
My total is now 57 DXCC entities and 203 locators.

My station on 6m today was  80W from my K3 and a 5 element 6/4m dual band YU7EF yagi ( courtesy of G4ERO). Alternatively I could have used the ICOM Pro3, which I rather like as a 6m rig. 

There won't be any new ones tomorrow as I am off to RAL at 06:30 in the morning and not back until mid evening..............

Sam



Friday, 20 June 2014

RAL

Getting bits ready to take to the Rutherford Appleton Labs (RAL) Microwave Round Table on Sunday. It clashes with our own local ESWR ( Ipswich) rally, but I had already made arrangements go to to RAL when the date of the ESWR was announced. So RAL it is.
I will be taking the usual VLNA preamps, PGA Amp kits, MAR6 kits as well as a selection of Kent's PCB antennas.
In addition to these usual items I am going to take a small batch of Nacton 4m transverter kits, Anglian 2m transverter kits and some PA/LPF short kits.
To round it off I will take some coaxial couplers, SS coax switches, and isolators. These are the remaining items from G4PBP's estate.
If anyone reading this is going on Sunday and wants me to reserve any of these items for them, please let me know. Several items are already reserved. He who hesitates loses..........

At this time next week I should be in Friedrichschafen with G4BAO, G4FSG, WA5VJB and G4CBA, French air traffic control strikers permitting! 
More about this next week.

73 de Sam



Sunday, 15 June 2014

More 10GHz tests

I substituted a three ring Chaparall feed and  DEMI 10GHz preamp (W5LUA) coax preamp into my DB6NTG3 transverter. Power was fed over the receive coax.
At the shack end the bias tee injected 13.5V.
One of my Anglian 144 transverters brought the signal (noise) down to 28-30MHz.
My SDR-IQ was then tuned to 29Mhz and dispersion set to 100kHz.
Using this set up I was able to measure 3.8dB sun to cold sky and 1.9dB ground to cold sky.

According to EMECalc these numbers are self consistent with the gain of the dish and type of feed, system noise figure of 1.2dB etc. at an SFI of 129 ( given for today) so I am quite pleased with my initial tests. 

The three ring Chaparall feed only gives, according to VK3UM,  45% feed efficiency. I know this can be improved upon so the next stage may well be to try and obtain a decent circular polarised horn feed for the dish, followed by an increase in dish size to 1.2 or 1.4m

Sam

Saturday, 14 June 2014

Sun noise on 10GHz


I have temporarily mounted my 'old' Channel Master 90cm onto the EME mount, since I hadn't got round to reinstalling the 2.4m dish.


Using a standard Ku band LNB into my spectrum analyser at 1256MHz IF I was able to do some testing.
I now know that the correct elevation in between 23 and 23.5 degrees. I measured the max noise from the sun and then checked the angle that the elevation frame pointed and the elevation angle of the sun at that time according to VK3UM EME Planner. My measurements average just under 23.5 degrees. I later found that the Channel Master 1.2m dish shows 23 degrees. I suspect I am not far out!
I also noted that for maximum noise the shadow of the LNB saddle should be aimed at the base of the bottom tripod stay.

This is clearly shown in the second photo.
Anyway, the average sun noise to cold sky measured 7dB at a solar flux of 153. This compares with an indicated number of about 6dB using VK3UM EMECalc at 10.368MHz. I would expect a few tenths of a dB more at 11GHz.
Of course the VK3UM results depend on what assumptions you make!
In this case 0.65dB noise figure with no loss ahead of the LNB and the feed is a linearly polarised Chapperal three ring.
YMMV!

Sam

Monday, 9 June 2014

10GHz update

Having replaced the IF RG58 the transverter is now working well.
I get a good signal from GB3PKT at St. Osythe.
I believe I am not on the main lobe from the beacon antenna, so the strength of the signal is moderate. It's probably ideal for propagation monitoring. The amount of rain scatter on the beacon, earlier this afternoon, suggests this will be a useful feature during heavy rain. There was a storm out Essex way. Not much rain hereabouts.
Now to investigate the effect of the two wind generators that that have been installed a few hundred metres east of this QTH!
Sam

Sunday, 8 June 2014

10Ghz part 2

I temporarily put the 10GHz transverter on the mast this afternoon. I was surprised at how little the 144MHz receiver noise level increased when it was powered up. On further investigation I found that the locked 106.5MHz LO from the shack was delivering only around -5dBm at the transverter LO port. From previous measurements the DB6NT G2 needs typically +6dBm. The loss of signal turned out to be in the 20m of RG58 coax from the shack to masthead. What is more the second cable carrying the 144Mhz IF had even more loss! Those rodents again?

I think both cables need to be replaced although the high loss of the LO cable has, for now, been overcome by adding a PGA Amp in the LO box in the shack. That delivers +20dBm to the RG58 coax and +9dBm to the transverter. This is not ideal practice, but will do for the moment.
It certainly explains why the 3cm system had become progressively more deaf until I took it out of service two years ago.
I think I will replace the IF RG58 with LMR400 as the IF signal has to be routed on to the indoor shack. Even more loss!
Progress at last and maybe QRV on 3cm from mid week!
Sam


Saturday, 7 June 2014

10GHz


Having reached my initial target of 200 locators on 6m I thought I would take a break for a few days and have another go at getting the 10GHz transverter system back on air.
What I didn't expect was that the DC feed that powers the 10GHz system at the top of the mast would take so much effort to bring it up to scratch. I have a Manson 13.5V PSU in the garage that is turned up to give +16V to mast head. The masthead 10GHz transverter has internal 11V and 12v  linear regulators, so I can allow for a small voltage drop at the maximum 8.3A that the transverter takes at 10W out.

But......
When my etching tak was accidentally tipped over several months ago the enchant went everywhere, including on the PSU.....
Fortunately the damage was not too bad and only the thick DC leads and connections suffered significant damage.
I have now replaced the original connections with 50A PowerPole connectors. I don't need 50A. 10A is sufficient, but the thick mast-feeding wires (8mm audio cable) won't fit into the standard (30A) Powerpole connector receptacle.
I have also incorporated an in-line fuse holder with 10A mini blade ( auto) fuse. This should have been done long ago, but I relied on the short circuit protection inside PSU. Not good practice!
Another idea I have is to use one of G4HUP's High side switches to be able to turn the 16V on and off remotely with a simple logic level output from my remote USB 8 channel relay.

Finally, with the Powerpole connector, I can now disconnect the masthead system from the shack PSU when the are storms around.  Something I could only do previously with some effort!

Sam



Thursday, 5 June 2014

Those CB radios

Seems that both radios work exactly as they should and that after being almost 50 years old!
Don't ask me how I know they work.
However, I am amazed that after all these years they still do what it says on the tin.
The receivers are super regens and they make one heck of a racket all the way up to 50MHz, judging by the noise increase on the P3 connected to the K3 when the CB receiver is switched on.
The power output is difficult to measure, but I suspect it is less than 100mW. The output transistor is a small ceramic device in a package not unlike the BFR91. 1965 technology.

Close examination of both transceivers shows they are in excellent condition after all this time. The leather cases are in good condition and even the telescopic aerials are undamaged. Remarkable!

Time to carefully stow them away with the rest of my growing collection of hand  held 'walky talkies'.

Sam


Wednesday, 4 June 2014

Retro radio

When does radio become retro?
I've never been particularly enamoured of vintage radio. AR88 and CR100s have never appealed to me.
I was introduced to two-way radio communications during the first wave of CB in the UK. I have to add that I never actually broke the law by transmitting speech on 27Mhz, but I did often hear American CB'ers voices emanating from the various 27MHz radio control receivers I built. Particularly in the early 1960s. I did have a radio control license.

                                      

Later my friends bought and used 27MHz walks talkies. I lusted after one of these but could never afford one. Those pull-out telescopic antennas ( less than 5foot to qualify for FCC part 15 unlicensed equipment) and the snugly fitting leather cases just looked the part.

Recently my local antiques shop in Felixstowe included a pair of beautiful Radifon SRT-602 27MHz walk talkies, in their original leather cases no less, for £20/pair. The boiler plate on the rear says made in August 1965. The cases are metal ( no cheap plastic here). They take a 9v PP3 battery. There is no sign of battery corrosion in either unit.

After several weeks of passing by the shop on my way into town I decided I really ought to buy them before someone else with a similar fetish bought them!
I eventually agreed £18 for the pair and carried them home.
I have no intention of using them. That would be illegal. However, I will check them out on my spectrum analyser and signal generator.
It says 6 transistor, 11channel on them, but I believe that really means they are on the old FCC channel 11 as there is no provision for a channel switch or even space on the PCB for more than one or two crystals.
I will publish a bit more about them after a few measurements.
Sam

Sunday, 1 June 2014

Nacton transverters again

I have decided to launch the Nacton 4m transverter again.
I still have boards left over from the first two runs and enough tuneable coils to make it worth doing whilst we sort out the Anglian 4m transverter. This frees up Anglian boards to meet the demand for 144MHz transverters!
One difference will be that the Nacton short kits will be a little 'shorter' than the first batch, but in turn will be a bit cheaper!
There will be more info on my web page shortly.
I still have lots of both 4m and 2m PA/LPF short kits as well.
I have now heard a number of Nacton transverters on air and they sounded fine. That partly persuaded me to do the re-launch!

Sam



Thursday, 29 May 2014

144MHz PA details

I have just posted a PDF article on my web page (www.g4ddk.com) showing details of the 144MHz 8W PA that complements the Anglian 144MHz transverter.
More transverter kits should be available in June. I am waiting for delivery of more 116Mhz crystals.

Sam

Wednesday, 28 May 2014

Suffolk Show

I spent much of today at the Suffolk show on Trinity Park, Ipswich.
I was asked by Dave, G4HUP, if I was interested in joining the Leiston Amateur Radio Club in the BBC Radio Suffolk WW1 At Home corral to help run a Morse session for visiting children and their parents.
I was an honorary BBC Volunteer for the day!

I had the opportunity to check out the TV uplink van and ask questions about transmit powers (16W from a TWT capable of 400W output), which satellite they were using and something about the video coding in use. All very interesting.

Two Morse signalling stations were set up, a few metres apart, using just a pair of wires to connect them. The kids were invited to either send or receive short predetermined Morse messages (slogans) that were taken from WW1 posters.
There was a steady stream of participants from the time I arrived around 11am until we shut up for the night at 6pm.

I was surprised at the enthusiasm of some of the kids for the code. And some of the them were naturals when it came to sending. A short demonstration of timing used sending dashes and dots and they were almost timing-perfect.

During the day Dave was interviewed by a BBC Radio Suffolk presenter and Dave even persuaded him to have a go at sending code live on the radio. I bet that surprised a few listeners!
Dave also appeared briefingly on Look East TV this evening, supervising a few kids sending receiving code.

All together a very interesting day. And the rain held off all day. It sure didn't look like it was going to be dry first thing this morning.....

Sam


Wednesday, 14 May 2014

4m Es

Managed to work my first 4m ES this evening after my first tropo contact outside the UK this year.
EA7KB and EA7BPO were nice signals from IM76 square. I missed the ZB2, which would have been a new DXCC for me from this QTH although I worked ZB2BL on 4 back in the early 1980s from my QTH in Staffordshire. In fact Jimmy was my fourth QSO on the band. After that it was all downhill..........
All the effort to get the Nacton transverter and 150W PA back on line today ( and part of yesterday) were worthwhile.
Sam

Sunday, 11 May 2014

144MHz

With the success of the Angllian 144MHz transverter kit I have started to wonder if I should get back on 144MHz and try to work some DX?

One thing that was always missing from my earlier 2m systems was a low noise mast head preamplifier. Thinking about the amount of cable loss ahead of the indoor shack transceiver/transverter it is obvious that I need some low noise mast head gain to obtain adequate sensitivity.

One possibility is to cut out the RF stage and filters from a now-unused Nacton transverter PCB to give a  low noise matched, low noise, preamp with a well matched on-board 144MHz output band pass filter.

From independent tests on the Nacton transverter the SPF5043 low noise front end is capable of better than +3dBm IIP3 with adequate out of band signal suppression, gain of around 20dB and good stability. I would expect a noise figure below 0.8dB. That is more than adequate for 144Mhz terrestrial use even in this formal area.
Conveniently, the RF stage and filters can easily be cut out from the Nacton PCB.

O
I will report results ( if it works!).

Sam



Friday, 9 May 2014

Cable tests

Recently I was pleased to be given some N crimp connectors for my LMR400 cable. However, my every attempt to obtain a suitable crimping tool had met with a lack of success. I know they are advertised on EBay, but even this proved a non-starter. I have now found one at the right price through my Chinese connector supplier and the price is excellent. But it won't be here until next week at earliest.
Bernie, G4HJW, came to my rescue by loaning me his crimping tool.
I replaced one of the existing N connectors on a length of LMR400 I had removed from the mast duct last month. With the troublesome connectors replaced with what at first sight seem to be low cost N crimp connectors, my measurements of loss and return loss using my HP5753C network analyser are within a fraction of a dB of Time's figures for LMR400 at various frequencies between 50MHz and 2.4GHz. I feel more confident of putting that cable back into use now.

Sam


Friday, 2 May 2014

144MHz transverters

Several transverters have been built up using the new populated PCB. Performance has been confirmed, so we have confidence that the design does what it says on the 'tin'!
I will complete the documentation later today and it will be available on my web page g4ddk.com

The supply of boards will be limited for the next few weeks as we ramp up production and await more parts.  
Please be patient if you are waiting for an Anglian 144MHz transverter.

Sam


Tuesday, 29 April 2014

Anglian update

The first of the Anglian boards have been delivered and incorporated into kits.
These were sold at the recent Martlesham Microwave Round Table together with one that was donated to the raffle.
More assembled boards are expected later this week. Before any more of these are sold in kits I intend to build up another 144MHz transverter and check everything is working as it should. In the meantime I am busy writing the 'manual' for the Anglian. This will contain a comprehensive description, kit building instructions and alignment details. It will also have some ideas for transverter interfaces. As you can imagine, it takes time to write all this, photograph each stage and then check the information against a sample build.  An initial estimate is that the final document will be around 20 pages. Fortunately, much of it has been written already!

Sam


Tuesday, 22 April 2014

Virtualnames.com

I am hoping my web access failure is just due to a temporary Virtualnames web server access problem.

Sam


Sunday, 20 April 2014

What's been happening?

I've been busy assembling our new greenhouse for the last few weeks, so it has kept me away from doing much amateur radio.

However the greenhouse is now finished and this week I will be devoting to getting ready for the Martlesham Microwave Round Table next weekend.

Today the Anglia transverter boards are being assembled with the pick and place machine and reflow soldering. I hope to be able to put together a few 'kits' for sale at Martlesham this coming week.
More 2m kits will become available in the next few weeks and the 4m version will appear in the next few months.

I have largely completed the 2m documentation, but it may need refining after the next review!

I have measured 4 Anglia or Anglia-like transverters and it seems safe to say that the receive converter is achieving better than 0dBm input third order intercept when measured in the most stringent way. Noise figure is about 1.5-1.6dB with 24-25dB gain.
Transmit converter output is over 100mW with excellent IMD.
The output spectrum is really clean.

The output power can be raised to over 6W with one of the Mitsubishi RF MOS amplifier modules. I have a new PCB for this module.





Wednesday, 9 April 2014

2.3GHz

As a result of the future of 2.3 and 3.4GHz OFCOM document that appeared yesterday I thought it might be useful to see whether I needed to be concerned about interference levels to the MOD equipment at Boscombe Down. The other MOD sites are significantly further away from this QTH as not to be a problem at almost any time.
I have been running the numbers for potential interference levels at Boscombe Down on 2.3GHz  from this location. Using the G0MJW software and the simplified path model ( no terrain data) it would appear that my 100W at the feed point and 20dBi antenna ( possibly 22dBi) gives around 6dB margin over what would be required. These numbers are for a 10% exceed.
The overall loss is 205dB, dominated by tropo scatter with diffraction and refraction both being significantly higher.
The G3YGF plots in Vol 1 of the RSGB Microwave Handbook confirm these losses.
It looks like I can operate without being too concerned that I am causing interference to the MOD down in BD!

Sam

Tuesday, 8 April 2014

Anglian results

I have completed my initial testing of the new Anglian 144MHz transverter. 
I only found one minor error on the PCB, and that is easily remedied.
The receive converter performed better than I expected, probably as a result of it being housed in a screened tin plate box. Later this week the first (#1) unit will go off for independent testing. At the same time the boards are being readied for production. With luck and a following wind, the first transverter kits will be ready for sale at Martlesham, although quantities may be limited at this stage.
For sure, the new Anglian transverter will be worth waiting for !

Sam


Sunday, 6 April 2014

Back on 4m

I found a little time today to reconnect the 4m system. I was too late for this morning's 4m contest and anyway, Sunday mornings are not normally good for me as I have chores to do, like the Sunday morning shop run and usually a coffee with a couple of the local radio amateurs. All very pleasant and far better than just talking to them on the radio!
With the 4m transverter connected to the K3 and over the long coax to the outside shack to pick up the Larcan power amp and heavily filtered preamp ( necessary due to the long coax run) I was able to hear the RAL beacon but not the Tring beacon. The YU7EF dual band antenna seems to have survived the winter.
Sam


Tuesday, 1 April 2014

Dispensing solder paste

At long last I got round to firing up the air(brush) compressor and paste controller in order to use the controlled cartridge solder paste dispenser. Once I'd set everything up I was able to manually dispense spots of solder paste onto the victim PCB. Much easier on the thumb than using a manual syringe.
The components were then manually placed onto the paste spots and after checking everything was in the right place, the PCB was placed in the toaster oven and 'solder' pressed on the reflow soldering controller. 12minutes later and the board was perfectly soldered.
It doesn't make sense to reflow solder simple little boards unless there are lots of them or they use some awkward part like a QFN or DFN package.
The intention is that I will make VLNA and transverter boards available, ready assembled.

Dave, G4HUP, will be demonstrating reflow soldering at the up-coming Martlesham Microwave Round Table (MMRT) www.microwavers.org and follow the events link. 
There may even be a chance to have a go at reflow soldering for yourself!

Sam




Friday, 28 March 2014

An early look at the Anglian

Sneak preview before I show it at the monthly Codger's meeting tomorrow!

I have just completed assembling the first Anglian 144MHz transverter. The Anglian is a direct development of the Nacton transverter, but features a significantly better performance. A 70MHz version will also be available, replacing the Nacton transverter. And for those who prefer a 'real' 6m band radio instead of an HF rig with a 6m section bolted on, the Anglian could be what you are looking for!













Monday, 24 March 2014

Nacton PA

I have published the 7W 4m band PA paper to go with the Nacton 4m transverter on my web page. Www.g4ddk.com 
PCBs are now available from me together with suitable wire for the LPF and the various passive components. I don't sell the PA modules. These are available from GH Engineering in the UK

Sam


Monday, 17 March 2014

That duct again!



For the last few days my remote rotator control has been playing up. The symptoms were that the pot in the G1000DXC has failed. I thought this unlikely as the rotator is a only a few years old. Resistance tests with a multimeter were inconclusive. 
Having thought about the problem overnight I became more convinced than ever that the rotator. cable was faulty. 
This morning I pulled the cable from the duct and there, a metre or so into the duct, the cable was showing clear rodent damage......


Once the cable dried out and the wires were separated, I tested the rotator and all worked as it should.
The problem was what to do. I could have bought a replacement cable from W&S for a little over £50, but the chances are that the cable would probably be of the same 'delicious' grey PVC that the rodents like. Clearly after four such attacks something more drastic was required. The answer was to splice in a new long centre section where the cable goes through the duct. I already had a length of black 6 wire recovered from the previous G400 rotator system. That cable had been in the duct for at least 8 years with no damage or apparent attacks from rodents.
With the rotator cable reinstalled everything seems to work well and if I decide to abandon the remote rotator controlit will be say to tap into the rotator downlead and parallel off a cable to the house. The rotator control box can then be moved between the indoor shack and the outdoor shack as required!





Now that the antennas can be pointed where they are wanted it was time to sort out why I couldn't get any output power reading on the remote Bird 43.
I eventually found the problem. More in another blog.

Sam





Wednesday, 12 March 2014

Just a test

I thought I had lost my Blogpress access. I guess not!

Saturday, 8 March 2014

4m PA module






This is the first 4m PA module for the Nacton, built on the new PCB.
The photo shows the PA on a temporary heat spreader plate. It is difficult to photograph the PA once it is mounted inside the Hammond housing.

The documentation for the PA is nearly complete.

Sam




- Posted using BlogPress from my iPad

Thursday, 6 March 2014

On closer inspection the gnawed cable probably happened a while ago and I missed it as it was right on the opening of the duct. The exposed copper inner has already started to go green, indicating it happened a while ago.

I've pulled that cable and cut out the gnawed section. It is surprisingly free of signs of water ingress more than a few cm either side of the damage.

I have decided to re-terminate a shorter section of this Ecoflex 10 cable and connect it to the spare FSJ4-50 still in the duct. The rodents seem less interested in that type of cable!

Tomorrow I hope to finish this last stage of the cable rationalisation and become QRV on 23cm again. I've also decided to use the 23cm coaxes for 13cm saw well. More in this in another blog.

The Anglian transverter PCBs have arrived, as have the PCBs for the small Mitsubishi modules for 4m and 2m. I now need to complete the documentation for these boards before making them available.

Sam



- Posted using BlogPress from my iPad

Location:Cable problems