OT: Amplifier's close in IMD product test

[Ken Bessler]

Does anyone know how to test an amplifier, or for that matter a transceiver,
for close
in IMD products? What kind of equipment is needed?

Ken KG0WX
K2 #4913, XG2

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[Don Wilhelm-3]

Ken,

In my understanding, the "close-in IMD" is only applied to receivers.  The
ARRL Handbook describes the setup in the Test Procedures chapter under
Receiver Performance Tests - although they only desribe the 20 kHz setup,
the 5 kHz setup should be the same, but the frequencies will be closer.  2
signal generators, a Hybrid combiner, attenuators, the receiver under test,
and an audio voltmeter are the tools used.

Amplifier and Transmitter IMD is different, and the output is measured while
being driven with a 2 tone generator - 900 Hz and 1900 Hz are typical tones.
The output is most easily monitored and analyzed with a Spectrum Analyzer.
The ARRL Lab uses the setup shown in Figure 25.84 of the ARRL 2005 Handbook.

73,
Don W3FPR

> -----Original Message-----
>
>
> Does anyone know how to test an amplifier, or for that matter a
> transceiver,
> for close
> in IMD products? What kind of equipment is needed?
>
> Ken KG0WX
> K2 #4913, XG2
>
>

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[N2EY]

In a message dated 2/14/06 6:54:20 PM Eastern Standard Time,
[hidden email] writes:


> Does anyone know how to test an amplifier, or for that matter a
> transceiver,
> for close
> in IMD products? What kind of equipment is needed?
>

That's what a "two-tone" test is for.

The RUT (Rig Under Test) is set up for SSB operation, and two pure sinewave
nonharmonically related audio tones in the audio passband are fed into it.
Output is examined with a spectrum analyzer.

A perfect rig would emit two carriers and nothing else. Imperfections
(odd-order IMD products) show up as carriers besides the two desired ones.

73 de Jim, N2EY
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[Brian Broggie-2]

And a great source for those two tones is an Elecraft 2T-Gen!

Brian - W6FVI

[hidden email] wrote:

>In a message dated 2/14/06 6:54:20 PM Eastern Standard Time,
>[hidden email] writes:
>
>
>  
>
>>Does anyone know how to test an amplifier, or for that matter a
>>transceiver,
>>for close
>>in IMD products? What kind of equipment is needed?
>>
>>    
>>
>
>That's what a "two-tone" test is for.
>
>The RUT (Rig Under Test) is set up for SSB operation, and two pure sinewave
>nonharmonically related audio tones in the audio passband are fed into it.
>Output is examined with a spectrum analyzer.
>
>A perfect rig would emit two carriers and nothing else. Imperfections
>(odd-order IMD products) show up as carriers besides the two desired ones.
>
>73 de Jim, N2EY
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>Elecraft mailing list
>Post to: [hidden email]
>You must be a subscriber to post to the list.
>Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft   
>
>Help: http://mailman.qth.net/subscribers.htm
>Elecraft web page: http://www.elecraft.com
>
>
>  
>

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