3271RE: [loopantennas] Re: Looking for 3 band receiving loop...
- Apr 1, 2007Paul,
I, for one would be very interested to see your loop design
[mailto:firstname.lastname@example.org]On Behalf Of gplynas
Sent: 01 April 2007 15:19
Subject: [loopantennas] Re: Looking for 3 band receiving loop...
Many years ago I designed a broadband loop for monitoring
radio-navigation beacons which had to cover the frequency range of 195
kHz to 480 kHz. Our previous loops were tuned single-frequency. I
designed this one by looking at the loop as the "inductor" in a Pi
network, with a transformation ratio from (radiation resistance + loss
resistance) to the input impedance of the amplifier, and with a
break-point above the highest frequency. I fed this into an FET
amplifier with high input impedance. A resistor of about 10k
furnished a return to ground at the amplifier input and stabilized the
gain. The whole circuit was then feed with +15 VDC through the coax
from the receiver.
This worked well, with a response that was reasonably flat over more
than 2 octaves. I think the same concept could be used from 160M to
40M. By design, I was able to reject the broadcast band signals which
could overload a broadband design.
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