[Amps] Checking for IMD

[m.ford]

Is anyone using the SDR-14 for IMD measurements? I bought one last
year for just that purpose but ended up using it as a receiver instead.
I want to buy another one to use for bench work. Unfortunately I just got
taken by an SA dealer on ebay for 1500 so I wont look there again.

The SDR-14 certainly looks promising for a FFT based IMD analyzer.

Mike  k1ern


----- Original Message ----- 
From: "Martin AA6E" <aa6e at ewing.homedns.org>
To: <amps at contesting.com>
Sent: Friday, August 11, 2006 10:43 AM
Subject: Re: [Amps] Checking for IMD


> Bill,
> 
> I've wondered about this, too.  The lab method is to use a high-priced 
> spectrum analyzer, but couldn't you do something useful with a soundcard 
> based spectrum analyzer?  You would need to have a linear detector and a 
> two-tone audio source.  This would be similar to the IMD measurement you 
> get with a PSK31 monitor.  The trouble is you need pretty good dynamic 
> range to measure a healthy system.
> 
> You could check the boxes being sold by www.cleanrf.com as described in 
> the latest CQ.  They let you look at "linearity" on a scope.  My take is 
> that you will only catch gross non-linearity (overdrive), but you 
> wouldn't get quantitative IMD numbers with this approach.
> 
> 73 Martin AA6E
> 
> Bill Turner wrote:
>> Is there a simple procedure one can use for checking the IMD of an
>> amplifier? Frankly, it's something I have never tested myself, instead
>> just keeping the amp tuned correctly and underdriving when using SSB.
>> I've never gotten any complaints of splatter so I think it's under
>> control. Since I do mostly RTTY and some CW it has not been an issue
>> but I would like to be able to check it. 
>>
>> Any recommended reading on the issue?
>>
>> Bill, W6WRT
>> _______________________________________________