[1000mp] Improving IM3 DR with Mark V and Inrad Roofing Filter

[Zoli Pitman HA1AG]

You don't have to be a spaceship designer to know this, it is enough if you complete a few semesters at a technical university as these are very general (though valid) statements.  

The question is what is the resulting gain (or attenuation) of the INRAD roofing panel (or any other devices or circuits inserted into the RX chain) and how much intermod it creates itself. Everything else is a gain distribution and IM calculation exercise. 

and gentlemen... all these statements about  "I always had IM issues with this or that" without quoting exact and reproducable measurements are useless and often nonsense. 

73, zoli ha1ag



----- Original Message ----
From: Adam Farson <farson at shaw.ca>
To: All about Yaesu 1000mp <1000mp at mailman.qth.net>
Sent: Sunday, January 27, 2008 6:49:37 PM
Subject: RE: [1000mp] Improving IM3 DR with Mark V and Inrad Roofing Filter


Hi Mike,

Gilles' findings with increased IMD tie in with a statement by Roger
 Winn of
Racal (UK). Mr. Winn used to design HF receivers for the Royal Navy; as
 you
can imagine, this is an extremely demanding application.

"The up-converting architecture, with a roofing filter at a first IF
 above
the highest RF frequency, allows the designer to limit the bandwidth
presented to the first IF chain and second mixer. The bandwidth of this
filter is a trade-off. Its 3 dB BW must be sufficient to pass the
 widest
emission the receiver is required to handle, but not so narrow that IMD
 and
temperature-drift effects in the filter become a concern." 

Cheers for now, 73,
Adam VA7OJ/AB4OJ





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