Radio W4KAZ

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W7IUV PreAmp in RX System

After building the 80m/160m splitter, it seemed like the signal levels from the K9AY were down a bit, probably from losses in the filters.  So after looking around at pre-amps, and procrastinating on buying the Ar2 preamp, I again landed on the W7IUV site.

W7IUV has updated his preamp schematic, and it looked easy enough.  Building the project was simple after gathering some suitable parts.

Trying the pre-amp out seemed to show that it was more or less filling the desired role quite well. With the preamp engaged, levels from the K9AY were now on par with signal levels from the transmit antennas on both 160m and 80m.  The preamp is installed in the shack just ahead of the band splitter.   Noise levels on the RX system were down about two to three S units from the TX antenna in these moderate noise conditions.

During the 160m contest this weekend, the RX system got its chance to proove itself.  Noise levels here were moderate – not as quiet as good winter conditions, but not S9+ summertime noise either.  The RX antenna with the preamp turned on was always the best choice on weak signals in these conditions.  It also necessary to switch the K9AY around a lot – signals were not always best in the expected direction because of higher noise to the north.   The southeast direction was dead quiet, but from here in central NC there isn’t much to listen to on 160m to the SSE. The actual compass direction on the SE leg is about 10 degrees south of southeast.

So the short version is that the preamp is an improvement when splitting the RX antenna for two radios.  

Future projects/curiosities:

  • Try moving the preamp out to the base of the K9AY, probably in a new K9AY switch box
  • Test the RX with the splitter removed, preamp on/off.


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