[Amps] Checking for IMD

[Gary Schafer]

> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
> Behalf Of Michael Tope
> Sent: Monday, August 14, 2006 10:41 PM
> To: Joe Subich, W4TV; garyschafer at comcast.net; amps at contesting.com
> Subject: Re: [Amps] Checking for IMD
> 
> 
> ----- 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...........................................................

Isn't that an FM radio? If so no good for a spectrum analyzer front end.

By the way the HP141 has no less than 4 conversions.

73
Gary  K4FMX