|The indoor stuff: Ultimate 3S QRPp transmitter, 20-watt 630m amp, power supply|
After initial erroneous indications with my antenna analyzer (more about that in a future post including an A/B comparison with a RigExpert AA-55 Zoom) I was able to trial and error my way to resonance on 475 kHz.
I had low expectations of performance and waited to throw the 'On' switch until two other Texas stations appeared on the WSPR map indicating their status as receiving stations. I had mentally resigned myself that just maybe one of those nearby stations might be able to decode my sub-watt transmissions.
Within minutes of the first 2-minute WSPR transmission, 9 stations appeared on the WSPR database indicating reception - one of those was ZF1EJ; others were on the east coast. By the next morning 55 unique stations had decoded my signal. These included all 10 US call districts and, my best DX, K9FD/KH6 on the island of Molokai.
To say that I was amazed is an understatement. Less than a watt ERP, a poor ground system and a frequency below the AM broadcast band...despite all that, I was decoded numerous times and with surprisingly decent S/N ratios in many cases.
Long story short: If you're tempted to try the 630-meter band but are put off by the fact that you live on a city lot, don't let that stop you.
Besides the feed system, the antenna is 90 feet of ladder line (conductors shorted together just inside the bucket's lid) going almost completely vertically up to an 80m dipole strung between two tall oak trees at the 90-foot level. The transmitter was a G0UPL Ultimate 3S with 250 mW out driving a WA3ETD converter/amp to 20 watts. Modeled antenna (in)efficiency was -13 dB gain, thus the 1 watt ERP.
|My bucket list contains a bucket ;-)|
|Effect of various numbers of windings on antenna's resonant frequency|
|475 kHz, 1 watt, 12 hours|