[linrad] Linrad on the air

[Joe Taylor <joe@xxxxxxxxxxxxx>]

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

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