Wednesday, 26 December 2018

Persistent cough

Whatever the bug is, it is persistent. It just won’t clear. It seems to be very common, as well. I hear a number of people reporting a similar problem.
Hopefully, not too much longer.....three weeks is long enough.......

I have managed to do a bit more observing of the Es’Hail-2 satellite and further optimised my receiver. I still can’t get a good comparison with the beacon reception by other amateurs as each seems to have a different set up and hence way of making measurements on the 10706MHz engineering (broadcast) beacon. The problem seems to relate to making a measurement in the beacon centre carrier level in a known resolution bandwidth. Simple  you’d think? A number of levels have been given for signal level, but without resolution bandwidth these are meaningless.

This morning I decided to have another look. The engineering beacon centre frequency has always sounded ‘rough’ and showed several ‘carriers’ within the narrow passband I was looking at. This is with the LNB I had modified for external 25MHz reference input. It just didn’t ‘feel’ right. That radio engineer’s feeling for a signal? Not knowing whether the engineering beacon actually had some form of data modulation, close to the carrier, it was difficult to tell what was going on. 
As a test I set my RF Explorer signal generator to 10706/4MHz and connected it to a WA5VJB LPY antenna. The resulting forth harmonic showed quite strongly on the SDRUno display and with the same ‘data modulation. It was now clear that the external locking on the LNB was not working as intended.  As an aside, the TCXO in the RF Explorer showed within a few hundred Hz of the beacon centre frequency. 
I have a spare,  unmodified, Octagon LNB (27MHz reference version), so I substituted it for the modified one and looked again at the beacon. Now the beacon  centre frequency was clean and sounded it on the headphones. 
I’ll waterproof the system again, later, and remeasure signal levels.

I have a spare high performance 10GHz LNA and horn feed system. I am going to look carefully at using that for the satellite in preference to the LNB. Although that is a cheap approach, I am beginning to wonder if the noise figure will turn out to be too high, down at 10489MHz?
I’ll need to use my spare DB6NT transverter and the feed/LNA and an IF at 265MHz
The Minitouner will tune into the required frequency range, so no need to worry about that.

Happy New Year

Saturday, 15 December 2018

IC9700 thoughts

Apologies for no posts for a few days, but I’m recovering from a rather nasty viral infection, caught last weekend, and which is only slowly responding to doctor’s orders! I’ve not been anywhere near the shack for almost a week and the time has allowed me to reflect on what I expect of the new ICOM 9700. 

Two and a half years ago I purchased an IC7300, more in hope than expectation of a good, useable, design. I was most pleasantly surprised at how good it is, especially as a K3 with all the bells and whistles owner and user. The IC7300 turned out to be, for me as very part time HF operator, a far more user friendly rig than the K3. Undoubtedly the K3 scores well on many points, and although I know personally that it has much VHF and microwaver input to increase it’s appeal to upper bands amateurs. Its range of transverter interfaces is unmatched, with easy (too easy?) access to a wide range of  level, frequency and offset adjustments and a superb IF interface facility.  But that P3 is nothing short of useless for anything serious and although I have installed the SVGA interface, I don’t see any significant overall improvement compared to using an SDR-IQ as the ‘go to’ spectrum and waterfall display and it has the advantage of ‘Continuum Noise’ measurement when used with Spectravue which the P3 doesn’t offer. If you haven’t used this measurement you can’t be a serious radio ham!!, we won’t mention the awful encoder interface on the P3 beyond could Elecraft chosen anything worse? Yes, there are ways round all this, but I want a self contained radio that doesn’t need a PC/laptop and a 27inch monitor on my bench just to see that weak signal in the noise.
The Internal 144MHz transverter is poor. I will leave it at that. A well-known UK amateur had a far more descriptive suggestion.

No, the IC7300 is not a panacea. The German transverter interface had a major problem that was slow to be acknowledged. I’m told it’s now been sorted. I’ve not revisited it. I reverted to the good old power attenuator solution.

Given all this, why am I looking at the IC9700?

First  let me say that I have some reservations about the design and these will only be resolved once I manage to get one on my bench. 
Living as I do on the east coast, I have a few unusual conditions to contend with. On 23cm I am very close (<5km) to the GB3MHZ Martlesham 23cm beacon. When I borrowed an IC910X, some years back, and first tried it on 23cm, it was completely unusable. The phase noise from the IC910 Lo (VFO) was so poor that reciprocal mixing from the beacon was apparent 700kHz away in the usual DX frequency area of the band.
When the North Sea path opens up Belgian (in particular) radar can be rather strong. Most rigs have a noise blanker than can cope with the noise. It is not like car engine ignition or an electric fence. The radar beam sweeps past and produces multiple pulses and these are very often accompanied by forward reflections from objects out to sea (and maybe reflections from inland objects) that add together to sound like a buzz. Some rigs (like the TS2000x) can cope rather well with this, other fail miserably. This will be a severe test for the IC9700.

Another problem is likely to be on 144MHz where I have a number of well placed, adequately ‘endowed’ EME stations in the surrounding counties. The K3, with an Anglian transverter, copes quite well. The TS2000X (which always needed a masthead preamp) did not. 

So, what am I waiting for?

I’ve read (re-read) the specs, asked questions of the manufacturer’s representatives at Dayton, Friedrichshafen and in the UK and not (no surprise there then) gotten the answers I wanted. So now I have decide that the price is just about affordable to buy one and see how well it copes at this QTH.
I believe I have the experience from being the designer of many transverters for all of these bands to make sound judgement on performance and to write up my experiences on my blog.

I’ve paid my deposit and now I wait..........


Thursday, 6 December 2018

Iceni v1.1 - another view

The new board in its housing
100mm x 62mm x 40mm


(Backup) Iceni V1.1

I finished my tests on the new PCB for my Iceni 70cm transverter. The mixer upgrade to version 1.0 boards required a cut and strap modification. Whilst easy to do it didn’t look too nice. My new V1.1 PCB incorporates the mixer upgrade and fixes a couple of small track breaks. I ordered a few boards for test,  but now I will have to order more boards for issue with future Iceni kits.
All tests on the transverter were successful.

Saturday, 1 December 2018

More Es-Hail-2 LNB tests

Having been diverted onto other things for the last few days, I thought I would take advantage of the wet day (here) to finish routing the IF cable round my shack, install SDRUno on my shack PC and connect the LNB IF lead to the RSP2 Pro.  First problem....the RSP2Pro internal bias tee is only 4.7V and I need closer to 13V. Solution was to use a temporary external bias tee.
Tuning to 1008MHz and the dish pointed at the 28E slot, the 10MHz wide dispersion (span) of the RSP shows a big signal from whichever digital channel it is on 10758MHz on vertical polarisation.
Tuning between stations shows a big drop in signal level. 
Now to do some definitive tests on cold sky to ground, sun (if I can manage to point at it) and satellite noise floor. Until the Es’Hail-2 amateur transponder is activated these tests can only be indicative. 
Problem 2.  There is some concern about the OTSLO LNB internal waveguide size being too small at 10.450GHz,  causing excess loss and consequence higher noise figure.  There are claims that the horizontal probe may be further enough away from the backstop (rear short circuit) that the loss may not be so high and it may therefore be necessary for me to turn my LNB 90 Degrees to use that probe. That has some implications for weatherproofing. More testing required.