[Amps] Checking for IMD

[Michael Tope]

----- Original Message ----- 
From: "Joe Subich, W4TV" <w4tv at subich.com>
To: <garyschafer at comcast.net>; <amps at contesting.com>

>> Even if there is some receiver IM generated it only needs to 
>> be a few db below what we are looking for to be masked.
> 
> However, absent AGC to prevent overload, the dynamic range of 
> many IF strips (particularly where the primary filtering is 
> provided by DSP) is less than 30 or 40 dB.  If you are looking 
> at - 35 dB 3rd order and - 40 dB 5th order, that is pushing the 
> real dynamic range of the IF.   
> 
>> By the way most spectrum analyzers have filters with a rather 
>> broad shape factor compared to our receivers and seem to do 
>> just fine.
> 
> Most spectrum analyzers have much better IF strips (and fewer 
> conversions) that the typical amateur receiver.  They are 
> optimized for dynamic range and not selectivity ... they have 
> to be.  
> 
> 73, 

Sounds like the Flex Radio SDR-1000 would be ideally suited 
for this task. It has very a simple conversion scheme, high 
dynamic-range, and no analog AGC (either derived or applied). 
With a 44 KHz sampling rate sound card it should easily provide 
15 to 20 KHz of useable spectrum viewing with good dynamic 
range. 

73, Mike W4EF...........................................................