[RTTY] Crystal filter width preferences for RTTY contesting

[Jeff Blaine AC0C]

John,

That's great to know.  Looking at the -6db point, I want to say that Inrad 
filter runs close to 300 hz or so.

Thanks for your comments


73/jeff/ac0c

--------------------------------------------------
From: "John Barber GW4SKA" <ska at bartg.org.uk>
Sent: Wednesday, August 26, 2009 11:47 AM
To: "Jeff Blaine AC0C" <keepwalking188 at yahoo.com>; <rtty at contesting.com>
Subject: Re: [RTTY] Crystal filter width preferences for RTTY contesting

> Jeff,
>
> The radios are FT1000D. One has 250Hz Yaesu filter, the other has 250Hz
> Inrad!
>
> It's a good point to consider a wider option for S+P, but both the above 
> are
> fine for run in a test. I do fine tune things to get right in the filter
> centre before every operation.
>
> 73, John GW4SKA
>
>
> ----- Original Message ----- 
> From: "Jeff Blaine AC0C" <keepwalking188 at yahoo.com>
> To: "John Barber GW4SKA" <ska at bartg.org.uk>; <rtty at contesting.com>
> Sent: Wednesday, August 26, 2009 4:00 AM
> Subject: Re: [RTTY] Crystal filter width preferences for RTTY contesting
>
>
>>
>> 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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>>
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>
>
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