Thursday, 29 April 2021

23cm progress with the IC-9700 and linear amplifiers

I have worked 9 DXCC on 23 cms in a little less than two years. Some of this has been on SSB (16 QSOs), some on FT8, JT9 or JT4 (30 data contacts) and even one contact to Sweden on CW. This totals 16 squares, leaving large numbers of workable squares not yet reached. Some others are harder to reach but might be workable someday.

All 1296MHz band contacts at GM4FVM up to 26 April 2021

Why does Eddie EHV appear to be floating on Dogger Bank in the North Sea? Typo by me - I think he should be in IO84XT. He is appearing under both locators. D'oh. Log book correction needed here.

The distribution on the map leaves some pretty obvious reachable countries not worked, such as GW, EI, LX, ON, SP, OK, LA, and of course GU and GJ. Activity is low on 23cms and several local squares have little or no activity at any time. During contests there is more activity and I can often work four or five stations during UKAC, not that I try to work too many stations during UKAC. I prefer to identify likely targets and work the best DX rather than the maximum number of stations.

During tropo lift conditions it is common to have stations on 70cms ask me if I have 23cms, which often allows some DX stations to be worked. I can also fish on PSK Reporter looking for active stations who I can then try to work - this is another big advantage of data modes.

Aircraft scatter has produced some good results. Two of those countries have only been worked on aircraft scatter, well so far anyway. Those QSOs usually have to be arranged in advance. During lockdown the number of planes seems to have about halved, but there are still quite a few "heavy" aircraft around, including freighters.

So I have gradually amassed a reasonable number of contacts. The total is 47 QSOs  with best dx to DF5VAE at 1001km. These results have exceeded my expectations by a large margin.

I still think that I can do better on 23cms.

My 23cms project started with the arrival of the IC-9700 with its 10W output. Neil G4DBN gave me an antenna, I had enough coax, I bought two plugs and a masthead preamp and off I went. I never expected much and I certainly thought my station would stay like that for good.

Later I added a 100W amplifier from Riccardo IK5CON.

All through this short story I have been plagued by doubts about measuring my output power. The Wavenode power meter I use showed that the IC-9700 only put out about 4 watts and the linear only 50W - both about half what I would have expected. At first I blamed the IC-9700, now I blame the meter. Without any way of calibrating the meter, I was left in the dark.

Lest you think that I am being negligent by operating without a proper power meter, I can measure my mains input power very accurately and I have definitely been operating legally. Unless of course my amplifier has an efficiency greater than 100% and is generating its own power internally.

Recently, Sid, G8SFA, offered me the loan of an amplifier capable of about 200W output. Certainly the Wavenode shows that my power has increased by 3dB over the 100w amplifier.

G8SFA 1296MHz linear amplifier

It is very kind of Sid to lend me this piece of kit. The snag I have now is that despite the extra power I cannot work him using his amplifiers at both ends. In this case it is the terrain which is causing the problems. Sid has improved his antenna. I can hear him but he cannot hear me. He is 100km away in Prudhoe and he cannot detect me, yet I have worked Charly, DF5VAE, on an island in the Baltic Sea at ten times the distance.

Trying to work Sid is the sort of challenge that makes amateur radio interesting for me. There are hills between us, in contrast with Charly. Surprisingly, the path from here to Ruegen is almost line of sight even accounting for the curvature of the Earth. We both have elevated sites close to the sea. There are no intervening hills in Denmark along the way which are high enough to get in the way. Everything else between us is either North Sea or Baltic Sea. Here I have the Cheviots between me and Sid.

I have run tests with Tom GM8MJV and Jon GM4JTJ. They both kindly spared the time to test Sid's linear and the tests confirm that it does indeed produce the expected difference in received signal. It also seems to sound good and looks like it produces a narrow signal. So, thanks to Sid, I have enough power now and the otherwise excellent IK5CON amplifier can serve as a backup.

What I really need is a better antenna for 1296MHz. In the photo below we see a new team member examining the 23cm antenna, or at least, the shadow of the 1296MHz antenna ... she is not impressed.

Paddy observing the shadow of the 23cms and 4m antennas, other masts are in the distance

A new shack companion, Paddy, has arrived safely but so far she is proving to be rather different from the much missed previous Officer Of the Watch, Katy. She does not like the shack for a start. Wait for winter I say. The shoe will be other other paw then.

I am keen to work Sid on 1296MHz. An antenna with more gain should help. Is this my next step on a band I never really expected to be so productive?




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