[TenTec] RX-366? - Shielded Filters

[Rick - DJ0IP / NJ0IP]

Kim,

It is a fact that better shielding can improve filter blow-by, which means
the ultimate attenuation is improved by use of shielding.  This is very
significant in rigs which depend on a single crystal filter for their
selectivity.  However few rigs do that anymore.  Also, if there is blow-by
elsewhere due to inadequate input/output shielding, then shielding the
filter won't help.

Since the implementation of passband tuning, rigs have received a second IF
and crystal filter for the purpose of tuning their curves passed each other.
The addition of a second IF filter on a different frequency contributed
significantly to the ultimate attenuation of the radios (generally an
additional 30dB).  As a result, the impact of a filter not having shielding
is no longer as critical as it was.

Also, there is a difference in whether we are speaking of a true IF filter
in a traditional radio, or a roofing filter in modern DSP radios.  They play
slightly different roles.  Today's roofing filter need not have the tough
specs of the main crystal IF filter.  That's why we often see 4 or 5 pole
Xtal filters as roofing filters.  They suffice. Going to 8-pole filters
doesn't improve the ultimate selectivity.  

To answer your question specifically, we would have to measure it in a lab.

My gut feeling is, it doesn't really help for the roofing filter, but it
definitely cannot hurt.

73 - Rick, DJ0IP
(Nr. Frankfurt am Main)


-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Kim Elmore
Sent: Thursday, April 24, 2014 5:20 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] RX-366?

Yes, I saw that. While it's a comforting thing to see, and it seems like it
should make for a better filter, does it make any practical difference in
filter performance?

Kim N5OP

"People that make music together cannot be enemies, at least as long as the
music lasts." -- Paul Hindemith

> On Apr 24, 2014, at 10:01, Barry N1EU <barry.n1eu at gmail.com> wrote:
> 
> The Ten-Tec filters are completely enclosed/shielded while the Inrad 
> filters are not.
> 
> 73, Barry N1EU
> 
> 
> -----Original Message-----
> 
>> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Kim 
>> Elmore
>> Sent: Wednesday, April 23, 2014 9:51 PM
>> To: Discussion of Ten-Tec Equipment
>> Subject: [TenTec] RX-366?
>> 
>> I'm considering getting RX-366 with a full set of filters. Which are 
>> the better roofing filters: the InRad or the TT filters?
>> 
>> Also, I couldn't find any mention of the RX366 on the TT site. Did I 
>> miss a memo?
>> 
>> Kim N5OP
>> 
>> "People that make music together cannot be enemies, at least as long 
>> as the music lasts." -- Paul Hindemith 
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