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[linrad] Linrad for microwaves

Those of you who have read my webpages over the years know that I had previously used Linrad a bit as a sort of panoramic adapter for microwave work. [I think there is still an old picture from 2 or 3 years ago of the W3CCX beacon at 2.3 GHz on my website somewhere].

But when I moved things to the new QTH this fell by the wayside.

MY setup for this was not ideal, as my receive chain at that time sufferred from too little signal at the input to my then homebrew Linrad converter, which was just a TUF-1H mixer.

I had planned to get Linrad running for monitoring the microwaves for the VHF Contest just ended, but I ran out of time to do so.

This weekend I finally got around to doing it. I did it in a sort of jury-rigged way, but it works GREAT, and relaying that positive message is the purpose of this note.

I have all of the electronics for 2.3 GHz thru 24 GHz inclusive on the tower, and I downconvert to 28 MHz on the tower and just run a single 28 MHZ IF cable down the tower to the shack.

I wanted to use the Antennspecialisten Hardware that I have in place, so I made a simple 28 MHz to 144 MHz upverter using a TUF-1H.

I put a Cougar amplifier in the [28 MHz portion of the] microwave receive chain in the shack just before the TUF-1H, to give me a 10 dB signal boost.

I put a Minicircuits splitter in the receive line after the Cougar amplifier, and fed half the signal to the FT1000 and the other half to the Upverter and Linrad.

I of course calibrated the Linrad system again after installing the upverter, using a pulser etc as outlined on Leif's webpages, and feeding the pulser etc into the input of my Upverter.

My shack is on a nice hill, but in the middle of a forest, and with the towers down I can never hear [or see on Spectran, etc.] any of the W3CCX beacons which are about 50 miles distant, due to the attenuation of looking thru the forest.

However, with Linrad I was able to easily see the distant and otherwise invisible 3456 MHz beacon on the waterfall, and to then copy its CW with a 20 Hz filter. By using the Lin2FT program to bring the FT1000 on frequency, I could select the narrowest CW filters on the FT1000 and turn on its DSP and with the DSP 120 Hz or 60 Hz filters also copy the beacon using the FT1000. But I never would have been able to find it without Linrad. I came back and did the same thing the next day as it was so unbelievable. I had done this experiment probably 100 times without Linrad and NEVER detected anything!

I was really amazed by this demonstration and wanted to relay it to the group.

I can't wait for the next Microwave contest to use Linrad to see 90 KHz of microwave spectrum at a time.

PS I found that most of my system birdies are 'fixed' and don't move when I change band segments with Linrad. I could therefore cycle up or down 25 KHz in Linrad to see which signals to ignore.

I still haven't installed the STAR ground at the new QTH. I know I should do that but just haven't had time yet. Even so, my center discontinuity is not a significant problem.


ROger Rehr

Roger Rehr