Dear Group,
Because Hartmut was able to copy the 6-2/3 WPM CW and Alan
appears optimistic, VO1NA will be on tonight at 10 WPM
0001 -1000 UTC 14 May.
I was out making FS measurements today and seek a critique on
my method which is as follows. A ferrite wound with ~100
turns (0.57 mH) (1.5 cm diam , 8 cm long) is resonated with a varicap
and inductively coupled (2 turns) to a 1m length of coax.
This is attached to a stick which is deployed out the car window
and rotated so as to give the maximum signal at about 3 km from
the TX. An attenuator is (-10 dB) inserted in the coax from the ferrite
antenna and the Burhans preamp (30 dB) which is connected to an FT-817
with IPO on, RF gain set to max, mode CW, 500 Hz filter in, and tuned to
137.77kHz. Without the attenuator, there are problems with the 817
AGC. The 600 ohm line output of the FT817 is fed to a 10 dB
attenuator and then to a 600:600 ohm xfmr and then to a soundcard
of a laptop running I2PHD ARGO (QRSSC 3, normal speed). The antenna is
rotated until consistent dB readings are displayed on ARGO.
A beacon sends a 5 second carrier and ID.
The car and antenna location are kept constant between measurements.
I suspect that ARGO may reference its readings against the background
noise and not be absolute. Running 1000 watts (4.5 amps) to 100m of
wire up 10 m showed a 3 dB advantage over the previous system: 100 watts
to a sloping 100m wire with the far end up 25 metres.
Thanks and 73
Joe VO1NA
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