Having received an offer from Ted VK1BL to help me find and fix the problem in my 13cm transverter, I spent an evening with him on 13th June. Moving through the various functional blocks in the transverter we found
- The receiver was working quite ok, it was very close to the right frequency and was fairly sensitive, hearing -120 dbm from the HP sig gen pretty well
- The output from the PLO was good and at a level of +7 dbm as recommended for the mixer
- The output from the sequencer board, which includes attenuators and a level setting control for the IF signal, 144 MHz in this case, was working well and we calibrated that at -10 dbm for input to the mixer, with 0.5w drive on 144 mhz from the ft817
- The output from the mixer and filter was at the expected level, about -13 dbm
- The output from the tx IF amplifier/driver was +10 dbm, which was adequate for the power amplifier
- The power amplifier had the correct negative bias and positive voltage on the correct terminals
- But the power output to the antenna socket was zero.
- The power output from the amplifier (before the relay) was about +35 dbm (approx 2.5 watts)
- The relay board was examined and was found that the DC to the relay coil was intermittent. Resoldering the pins of the relay, a surface mount type, fixed that intermittent and made it a reliable connection. The output to the antenna socket was then +35dbm or 2.5w.
- Transverter considered fixed.
With that result I discussed the possibility of an activation on Saturday morning to prove it in the field. Andrew VK1AD offered to activate Mt Stromlo and I decided to visit South Black Range. Coincidentally it was the day when bonus points commenced for VK2 summits above 1200m, so I half expected to find some snow on the higher parts of this summit, as it had recently snowed down to about 900m.
No snow, quite cold at about 3 or 4C when I got there, but it warmed up to about 8C by midday.
After initial contacts on 144 then 1296 we switched over to 2403 MHz and found we were able to make easy contact, my signal received a 5×8 report from VK1AD and I received his signal at an indicated strength 5.
Note: the distance of this contact was about 47.5 km, not bad for 2.5 watt transmitters. The locators of the two summits are QF44MQ (Stromlo) and QF44SN. The visual horizon is 35km so this is beyond “line of sight”. But how far over line of sight is it?
According to my iphone app DistBear the distance between centres of the two grid subsquares is 47.5km. So 2.4 GHz worked fine, well over the visual horizon. To get a more accurate distance I used the website https://sotamaps.org, using the “range mapping” option, we get a more accurate measure of the distance, at 48.7 km. I am sure there will be longer contacts made on this band using the same equipment.
The antenna in use for 2.4 GHz at my end is shown in the photo below attached directly to the 2.4 ghz transverter, was the SG-LAB PCB antenna, a 2 element HB9CV type on loan from Andrew VK1AD. The 2403 MHZ equipment was placed on a rock and turned so that the antenna pointed roughly towards Mt Stromlo, albeit through many trees nearby.
After completing the contact on 2.4 GHz I moved to HF and ran a few contacts on 7023 khz using the Pixie half watt morse transceiver (on a 50 x 50 mm PCB), then moved to the KX3 radio and ran contacts on 40m and 80m SSB and CW. I left the summit just after 12 noon, after spending 2 hours there. The temperature had risen to 8C by then.
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