Topband: Flag/Pennant Question
n4is at comcast.net
Wed Nov 30 05:28:15 PST 2011
They have perfect cardiod patterns just like the full sized models BUT
negative 45 db "gain" is fairly useless for DX"
Working with antennas with low gain is a huge challenger however 100%
possible. I worked 249 counties on 160m ad 39 zones in the last 5 years
living in a suburban area west of Fort Lauderdale.
My RX antennas gains are -43 db for the VWF and -48db for the HWF. My noise
floor varies from -96 dBm to -85 dBm, very noisy when you compare to rural
areas that can be low as -120 dBm of noise on 160m.
Interaction with any resonant TX or RX antenna must be reduced detuning it
during RX. If you are not willing to detune your TX antenna don't even try
to work with low gain RX antennas, it will be a waste of time.
Common mode noise management and very good shield is a must to reduce man
made noise. Also low NF preamps are necessary to keep a good signal noise
near the receiver noise floor.
George AA7JV is working with small loops with a new concept with some
consistent results. The issue with small loaded loops is the thermal noise
of the loop limiting the possibility to amplifier signals bellow the thermal
noise of the loop.
Dr Dallas idea with multiple turn's loops was to raise the gain and reduce
the thermal noise but the additional inductance spoiled the cardioid patter
on 160m, it seem to work on LF.
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