Henry,
The Collins filters vary quite a bit. In the ft1000mp, the Collins 500
hz filter (455 if) and (the CW soldered in) Yaesu 500 (8m if) cascaded
are significantly less selective and less deeply skirted than the INRAD
400 hz filters for both IF's cascaded. If you want to hear the
difference, let me know and we can arrange a telephone call, and I can
let you *listen* to the difference.
In the 160 meter cw test I got between stations up & down 500 hz that
are 20 over s9, and the INRAD cascade renders them *inaudible* unless
they have key clicks. The difference after I switched was stunning. Hard
to believe, but I am afraid that some of these new Collins filters seem
quite inferior to the Collins of old.
I have the 500 hz Collins filter in the sub-receiver now.
73, Guy.
henrypol2@juno.com wrote:
>
> While all the 'lawyers' have been discussing contest rules, I have been
> thinking about contest equipment; so, here is something for the
> 'technical types'....
>
> At the risk of being flamed about the subject relevance to contesting, I
> am seeking knowledge about the resurgence of Collins mechanical IF
> filters in new HF rigs (for CONTESTing, of course). With the imminent
> changes in the ham licensing regulations, coupled with the increasing
> band activities due to Sun spot number growth, I am on a quest to
> possibly improve the adjacent signal handling capabilities of my trusty
> TS850 and backup TS830.
>
> Please consider the following:
>
> The Yaesu FT-1000MP includes a Collins filter in the 455 KHz IF. When I
> first inquired as to why they used a mechanical filter versus a crystal
> filter, I was informed (don't remember who) that it was more for the
> nostalgic aspect related to Yaesu's founder JA1MP, in which the Collins
> filter was the latest technology back then.
>
> The recent QST review of the Yaesu FT-847 noted the availability of an
> optional Collins IF mechanical filter.
>
> A review of the latest AES catalog (Summer 98) for Yaesu equipment and
> options noted Collins filters available for the FT1000/D, FT920, and
> FRG100B receiver.
>
> A look at the Signal One web page (www.bbcyber.com/signalone/) for their
> MILSPEC 1030CI transceiver (modified Icom IC781) noted the use of two
> Collins 2.1 kHz filters cascaded at the 455 kHz IF.
>
> AOR's (www.aorja.com) "High Performance DDS HF Receiver", model AR3030,
> uses the Collins mechanical filters. They state "in contrast to ceramic
> filters, Collins mechanical filters are more expensive and rarely used in
> any but the very top of the range and professional equipment". This
> statement was obviously written by someone in marketing and not
> engineering.
>
> Now the questions:
>
> Why are these filters better than the more popular standard
> stock/optional crystal filters? Are they better than the INRAD (formerly
> IRCI) filters? What kind of insertion loss is associated with the
> mechanical filters versus the 5-8 dB for INRAD crystal filters? Is there
> a good book/article that discusses this subject?
>
> Please respond directly to me.
>
> 73,
> Henry Pollock - K4TMC
> Raleigh, NC
>
> _____________________________________________________________________
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> --
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--
Guy L. Olinger K2AV
k2av@qsl.net
Apex, NC, USA
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