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

[Adam Farson]

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


-----Original Message-----
From: 1000mp-bounces at mailman.qth.net [mailto:1000mp-bounces at mailman.qth.net]
On Behalf Of Mike Schatzberg
Sent: 27-Jan-08 09:42
To: All about Yaesu 1000mp
Subject: [1000mp] Improving IM3 DR with Mark V and Inrad Roofing Filter

Hello 1000MP Fans:

I came across an interesting posting on the Contest Group of Quebec website.
The posting is from November 26, 2007, from Gilles, VE2TZT.

Although written in French, it appears that Gilles had quite a problem
during CW contesting with the new Inrad Roofing Filter installed in his Mark
V.
You can see his posting here:

http://contestgroupduquebec.com/index.php?option=com_simpleboard&Itemid=41&f
unc=view&id=528&catid=2

So basically he says that he didn't see any improvement advantage after
installing the Inrad filter, and he even experienced a degradation of the
resistance to intermodulation products on 40 meters where he has a
particularly good antenna.

His article concludes that performing the simple modification to the Inrad
Roofing Filter board as suggested on the VA3CR website, fixed the problem,
and he has now no issues while contesting.

73 and Happy DXing,

Mike
W2AJI

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