From: Bill Tippett <btippett@alum.mit.edu>
Reply-To: tentec@contesting.com
To: tentec@contesting.com
Subject: [TenTec] Inrad #352 Filter for Orion
Date: Sun, 06 Jun 2004 21:39:10 -0400
Rob Sherwood NC0B of Sherwood Engineering recently
made some IMD measurements of the Inrad #352 650 Hz roofing
filter (inserted in Orion's 1000 Hz position) that several of us made
as a special order in January. Here is a summary of Rob's results:
> At 5, 10 and 20 kHz, there is no significant difference between the
> stock 1.0 kHz Ten-Tec filter and the Inrad filter.
> At 2 kHz spacing, the improvement is on the order of 6 to 7 dB.
> At 1 kHz spacing the improvement is closer to 10 dB.
> There is some strange hysteresis of a couple dB, as you change the
level
> around. The IMD does not act exactly as one would expect.
> I am guessing the digital AGC is doing strange things, causing the
> hysteresis.
>
> The insertion loss of filters #2 and #3 are identical to the Ten-Tec
1.0
> kHz filter.
The bottom line summary is that the #352 allows Orion to retain
its 20 kHz spacing IMD performance of ~96 dB all the way down to
1 kHz for the modest cost of about $40 if you are willing to warm up
your soldering iron. Rob's summary below includes only 1000 Hz filter
data but you can calculate performance numbers for the #352 using the
above data:
http://www.sherweng.com/Dayton_2004/Dynamic_Range_Data.pdf
More info on building these filters is at the site below:
http://users.vnet.net/btippett/inrad_.htm
Barry N1EU also has a site on building the filter using NPO disc
capacitors instead of the supplied surface mount caps, but qsl.net is
down at the moment and I cannot bring up the URL.
73, Bill W4ZV
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