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Re: Linrad Block Diagram
- Subject: Re: Linrad Block Diagram
- From: Dave Sublette <arrl.net; k4to@xxxxxxxxxxxxxxxx>
- Date: Thu, 20 Dec 2007 22:15:30 -0500
Leif Asbrink wrote:
> Hi Dave,
> 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
> 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.
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