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........


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!


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.


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.