Re: Linrad Block Diagram

[Dave Sublette <arrl.net; k4to@xxxxxxxxxxxxxxxx>]

Leif Asbrink wrote:
> Hi Dave,

<SNIP>
> 
> But first, verify that the noise floor in Linrad drops
> by at least 15 dB when you switch off the DC power to
> the transistor in the very first amplifier nearest the
> antenna:-)
> 
> 73
> 
> Leif / SM5BSZ
> 
>
Well Leif, you have pin pointed my problem. I do not have enough gain in 
the IF output of my microwave transverters. My transverters are mounted 
at the 185 foot level on my 200 foot rotating tower, which is located 
250 feet behind my shack. There is about 7 dB of loss in the feedline. 
Even though I have a preamp ahead of the transverter, there is still not 
enough gain in the system.

I have identified the problem and have another transverter with higher 
IF gain ready to install. It also has a phase locked LO.  I have one 
more phase locked LO to build for my 2.3 ghz transverter. Then I can 
bring the box down from the tower and install the new system.

My comments about the sensitivity of the SDR system using Linrad were 
not a complaint. I am really very happy with it. In fact, I am just 
amazed at how good it is.

I am not an experienced microwave guy. I am learning slowly and enjoying 
the process. I have been building and using microwave stuff for 5 or 6 
years. I have a pretty good test bench with automatic NF meter, signal 
generators through 18 ghz, an HP8569B spectrum analyzer and an HP436B 
power meter. I have the usual assortment of power supplies and a 
Tektronics 475 scope.

I am 66 years old and am a retired EE. I never worked in RF for the most 
part of my career. I erected all three of my towers, 70, 150 and 200 
feet unassisted and still do all my own climbing and maintenance. I hope 
it keeps me young.

Keep up the good work.

73,

Dave, K4TO


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