[RTTY] Crystal filter width preferences for RTTY contesting

[John Barber GW4SKA]

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
>>> _______________________________________________
>>> RTTY mailing list
>>> RTTY at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/rtty
>>
>>
>>
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