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[linrad] Linrad on the air

Much of the traffic of this reflector is involved with technical issues concerning Linrad setup and use, and with the associated hardware. It occurs to me that reports of actual on-the-air use of Linrad may also be of interest. After all, for most of us, that is the ultimate purpose of the effort we put into any aspect of our stations, be it antenna, transmitter, receiver, or various other accessories and software.

I have had Linrad running for just three weeks, and my present setup is simple. I use only one polarization channel and process the audio output from my TS2000 transceiver. In its widest SSB filter setting, the TS2000 provides a bandwidth of about 5 kHz. Of course, Linrad handles the computational burden very easily: the CPU load on my 2.7 GHz Pentium 4 is usually between 1% and 10%, depending on the exact parameters selected.

Although my receiving system is minimal for Linrad and I have much to learn in using the program, I have now made several 144 MHz EME CW QSOs using it. My station is really a "tropo" station, not an EME station. I run about 700 W to 4 x 9el yagis aimed at the horizon, with no elevation control.

I can already say that Linrad provides the following advantages:

1. Excellent waterfall display for locating the desired signal and discriminating against birdies;

2. Very easy single-mouse-click tuning;

3. Smoothly and continuously adjustable filter bandwidths and shapes;

4. Automatic frequency control that keeps a CW signal centered in the bandpass, compensating for changing Doppler and oscillator drifts.

I have not yet gained much experience with the noise-blanking capabilities of Linrad, so I cannot comment usefully on this feature. I believe I will need larger bandwidth before its main benefits can be realized. Dual polarization is also very much on my "To Do" list. I have compiled and tested the JT65 decoder under Linux, but have not yet tried sending Linrad output into it.

In the meantime, I am writing to encourage others to get on the air with this extremely capable software radio "back end". And when you do, please share your Linrad operating experiences with the rest of us!

-- 73, Joe, K1JT