[linrad] RE: question regarding LINRAD

[Leif Asbrink <leif.asbrink@xxxxxxxxxxxxxxxx>]

I have not thought about it. It would be another complication
to newcomers;-)

For optimum operation you should place the noise floor equally for
both channels. This should be done in hardware for dynamic range reasons
but fine adjustment within a couple of dB could be done in Linrad.
That would be another parameter: "Noise floor balance".

Then you need to know the gain of the two channels and differences
between preamp noise figures and noise pick-up has to be known and
added to antenna gain differences. In a good system these factors
can be neglected but with very different antennas differences in
the noise temperature could be as lerge as the gain difference.

With a X-yagi system using identical antennas for +45 and -45 degrees
it is all very simple because signals with close to perfect
H polarisation are easily available. They allow accurate calibration
of everything. In a + configuration accurate calibration is very 
difficult because there is no way to produce a 45 degree test signal. 
Ground reflections make it close to impossible unless you have
high towers for test antennas with 45 degree polarisation and good
gain.

I have not decided anything at the moment. Right now I am working
on mounting methods for my next antenna. Simulations with stacking
harness and towers are time-consuming.......



73

Leif / SM5BSZ




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