23cms news
Oct. 5th
Conditions over the 1296MHz Trophy were pretty disappointing, with only 5 QSOs made, ODX being GW8IZR (IO73), and no continental QSOs, although DF0HS/p was heard - the only non-UK station. All beacons were down with me, but I am also convinced it is time to start on the masthead preamp.
Sep. 19th
Thanks to good conditions that elusive first QSO has been made, with F6CCH (IN96), worked with 5W to the 44 ele, followed by G8DKK (IO91), another new square and country!
At the Leicester Show I picked up an M67715 amplifier kit, which should drive the large linear to full output, and leave room to reduce the IF drive level, and this should give me 30W+ output, or about 15W at the feedpoint.
Aug. 24th
A real antenna has now been installed on the mast. After much perusing of specs and user reports, I settled on the Wimo 2344 44 el. Yagi, which is beautifully put together, and assembles very easily from the box (though I would have called it a 36 ele myself - I only ever count the reflector as a single element, no matter how many rods it contains!) Signals from GB3MHL are now 6-12dB better than they were an hour ago. As expected, construction was quick and simple and the dodgy c/o relay has also been upgraded to a CX530, so I can now happily switch more power than I can generate. Now looking forward to some conditions, and a chance to make that elusive first QSO!
The PA driver has been cut back to one (stable!) BLU98 stage. The second stage is identical yet still oscillates, and I suspect the device itself might be damaged, maybe emitter ballast fried, but I don't have the kit to test it completely yet. Gain of the working stage is 7-8dB, and with the feeder and changeover relay brought up to scratch, I believe I now have 4-5W at the antenna, subject to the calibration of my power metering.
Aug. 12th
The rotator is now installed, and conditions uninstalled... After a couple of unsuccessful on-air tests, I discovered that the two-stage BLU98 driver amp I had built for the large PA was unstable when boxed.
Although it worked fine on the bench, once packaged the earthing and some screening needed to be improved, as it appeared to be squegging at VHF. The basic design for the amplifier was found on the website of Crawley Amateur Radio Club, in an article by G3GRO, to whom credit for the basic design. Credit for cramming two into one box with inadequate earth and screen, and hence the instability, is purely mine. Until it goes back in line, I am QRV with about 500mW to the antenna (30mW into 2 x M57762, less 1dB in relay and 2dB in feeder). Fortunately the modules are paralleled through a Sage wireline 3dB coupler at either end, so the VHF parasitics never reached them!
Aug. 9th
The old coax relay has been rebuilt and tidied up, and now exhibits much less loss at 23cms! Maybe even a QSO could be possible? The 1296MHz antenna is back on the mast, and fixed beaming east, but the rotator will arrive on Monday. PI7QHN (JO22) was heard earlier today, but subsided as the heat of the day killed off the duct, and I'm hoping it will return tonight or tomorrow morning. Looking forward to that first QSO!
Aug. 6th
I found that the N-types on the H100 were not very reliable, and signals from GB3MHL are now much stronger! There seems little point making a masthead preamp from the junk box now - the only spare device I have is a BFR91, which has a noise figure worse than the current sum of feeder loss plus transverter noise figure, so it would only increase noise and decrease dynamic range.
The Double Quad antenna (right) looks very lonely on top of the mast. In the absence of a rotator, my "DX" spotting strategy is to guess which direction will be best for tropo in the morning, then fix the antenna before going to bed. Now that the 15m insulator disguised as a feeder has been sorted out, there's a chance DX may be possible tomorrow!
GB3MHL is currently hovering around S2-3 with the antenna turned towards northern Europe (060 degrees).
NEC modelling of the antenna proved (a) very difficult, and (b) that the claimed 10dBd gain for this antenna is realistic for the 4 degree lobe. The difficulty arose in having to model a solid reflector as a series of wires not more than 0.1 wavelengths apart which - I believe was responsible for two programme crashes. Don't be too alarmed, my laptop suffers from Windows XP.
Aug. 4th
Activity on 23cm is currently limited to getting the station ready, although I have heard my first signal on the band, GB3MHL, and it was as weak as expected considering there is no masthead RF stage yet, and the feeder is 15m of H100. The antenna, a double-quad element with a PCB for reflector, should have 10dBd gain, approx. It is currently fixed beaming towards GB3MHL until a rotator (or skeds on a known bearing?) can be arranged! And then the antenna will be upgraded at the same time.
The station is useable now, but the only c/o relay I have will handle only 10W at 1296MHz, so until it goes at the top, I can only run 10W approx. at the wrong end of the feeder. I'm sure local contacts will be possible, so am listening for other signals!
There's just a small chance I have enough spare components knocking around to put together a masthead preamp, otherwise I shall have to spend some money and get a kit!
Now that the weekend's tropo conditions have subsided, GB3MHL has dropped in strength, and is hovering around my noise floor. It's signal is just detectable using a spectrogram on the audio output. I'm sure that given some path loss figures etc, I'll soon know whether the RX is behaving as expected.
So, apart from the antenna, rotator, preamp and high power c/o relay, the 23cms station is nearly ready...
