[TenTec] RX-366? - Shielded Filters

[Kim Elmore]

This is for the additional roofing filters in my RX366. I agree that 
shielding doesn't hurt but, as you note, it probably doesn't help all 
that much for this application, either.

Kim N5OP

On 4/24/2014 3:44 PM, Rick - DJ0IP / NJ0IP wrote:
> 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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