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Re: [Amps] Checking for IMD

To: "Joe Subich, W4TV" <w4tv@subich.com>, <garyschafer@comcast.net>,<amps@contesting.com>
Subject: Re: [Amps] Checking for IMD
From: "Michael Tope" <W4EF@dellroy.com>
Date: Mon, 14 Aug 2006 19:40:43 -0700
List-post: <mailto:amps@contesting.com>
----- Original Message ----- 
From: "Joe Subich, W4TV" <w4tv@subich.com>
To: <garyschafer@comcast.net>; <amps@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...........................................................

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