[RTTY] Crystal filter width preferences for RTTY contesting

[Jeff Blaine AC0C]

John,

Thank you.

Today we have been looking at the actual widths vs. the named widths on some 
of these filters.  There is a lot more disparity on the low bandwidth end 
than on the wider filters which is a bit of a surprise to me.

The K3 Inrad 250, for example, is 370 @ -6db.  So it may fit into all of 
these categories.

To help know which category to put your recommendation in, may I know what 
kind of filter/rig you are running now most of the time for RTTY contesting?

73/jeff/ac0c

--------------------------------------------------
From: "John Barber GW4SKA" <ska at bartg.org.uk>
Sent: Tuesday, August 25, 2009 4:27 PM
To: "Jeff Blaine AC0C" <keepwalking188 at yahoo.com>; <rtty at contesting.com>
Subject: Re: [RTTY] Crystal filter width preferences for RTTY contesting

> Simple maths for this used to be shift plus twice the baud rate; 170 + (45 
> x
> 2) = 260Hz
>
> I have used  250, 300 and 400Hz for contesting at various times. 250 is 
> fine
> almost all the time; never found the need for wider than 300. That would 
> be
> my choice for 2 options.
>
> 73,
> John GW4SKA
>
>
> ----- Original Message ----- 
> From: "Jeff Blaine AC0C" <keepwalking188 at yahoo.com>
> To: <rtty at contesting.com>
> Sent: Tuesday, August 25, 2009 6:23 PM
> Subject: [RTTY] Crystal filter width preferences for RTTY contesting
>
>
>>
>> Gentlemen,
>>
>> I and a few other guys are working on a project to get a very high 
>> quality
>> set of crystal filters built for the Yaesu FT2000.  The rig is an
>> otherwise very fine unit but the front end is a mess.  This project is an
>> attempt to address these short comings.
>>
>> And one of the questions that have come up is what the IDEAL width would
>> be for the RTTY contester.  So I would like to ask your kind option here.
>> Anyone can reply this - while this is about a specific rig, I would like
>> serious answers from serious operators so we can help to ensure the 
>> filter
>> guys pick the proper width.
>>
>> So the question (in 2 parts) is like this.
>>
>> ASSUMPTIONS:  Assume we are not going to rely on the DSP - and that the
>> width of the DSP is wider than the crystal so it's essentially not being
>> used for bandwidth limiting.  And assume that the final solution may have
>> 2 filter sockets.  Shape factor of the filters is around 1.5:1 and the
>> ringing, while present and measurable, is at such low levels as to be
>> inaudible.
>>
>> Q1. If you only were to get 1 filter, what width would it be?
>>
>> Q2. If you were to want to fill both filter slots, what widths would 
>> these
>> 2 filters be?
>>
>> Thanks for your comments!
>>
>> 73/jeff/ac0c
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>
>
>
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