[Test-Equipment] RF spectrum analysis

[Fuqua, Bill L]

   The suggestions I made are only for receiving signals.
A possibility would be to use a DDS generator and SDR receiver. However, it would be best if the
SDR was offset a bit since they don't work well detecting signals at Zero frequency, the frequency of the local oscillator.
So you would really need a dual or two DDS generators. 
   The ideal way to do it would be with a Vector Network Analyzer or a Scalar  Network Analyzer. I usually only need ampliude
information. Since I use spectrum analyzers anyway I also use a tracking generator more most things. I do have VNA capability but
rarely need it. 
   Here is an example of a VNA that can be breadboarded if you have two DDS generators. 
There are even simpler solutions if you are only interested in amplitude only (scalar) results. 
The trick is the driving software. 

73
Bill wa4lav


________________________________________
From: test-equipment-bounces at mailman.qth.net [test-equipment-bounces at mailman.qth.net] on behalf of David [davidwhess at gmail.com]
Sent: Sunday, January 19, 2014 1:49 PM
To: Discussion of Electronic Test Equipment
Subject: Re: [Test-Equipment] RF spectrum analysis

On Sun, 19 Jan 2014 09:28:20 -0800, you wrote:

>A couple of years ago I got seduced back into my old hobby of ham
>radio---just what I don't need, a hobby! I would love to have a way to run
>the same sort of frequency response curves at RF for checking the resonances
>and Q's of tuned circuits, antennas etc. I could do it manually with my grid
>dip meter, calibrated receiver, and VTVM, but now I'm spoiled! Does anyone
>have a method, program, or a piece of hardware (down converter?) that yields
>a graphic representation of a frequency spectrum? Any suggestions would be
>greatly appreciated.

I have done this manually with a signal generator and oscilloscope.  If you want
the phase information to make a complete bode plot then you need a vector
network analyzer of some sort.

At low frequencies this is the best option I am aware of:

http://www.syscompdesign.com/CGR-101_ep_41-1.html

For higher frequencies I would look for something like this:

http://sdr-kits.net/VNWA3_Description.html
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