Topband: W7IUV Preamp from Low Band DXing

[Larry Molitor]

Ford Peterson <ford at cmgate.com> wrote:
How would I modify the W7IUV design to accomplish make it variable gain?
I'm thinking the box needs 4 preamps so that when any antenna is selected
with one switch, the gain is precisely calibrated to bring the noise floor
on that antenna to S0.

I have a similar situation. Fortunately the solution is easy once you accept that even the lowest output RX antenna has far more gain than is need to establish system noise figure.

Just use attenuators in front of the preamp on the higher level RX antennas to bring them down to the same level as the lower output antennas. If you use RG-6 type cable and F connectors, you can get cheap 75 ohm attenuators and just screw them on. 

I built a "RX antenna control box". It has a selector switch for different antennas, filters that can be switched in and out of line, switchable attenuators, a single preamp, and switchable outputs.( to allow different receivers) A fairly simple solution which allows adjustments on the fly and many possibilities without having to go outside in the WX.

73,

Larry - W7IUV
DN07dg - central WA
http://w7iuv.com

 
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