Re: SRF-M37V and SRF-M37W-Performance differences?


Michael Slattery
 

Hi Gary

Yes, I am a member of MWC and I've avidly read your fanatical
loopstick and other articles. Indeed Gary, it was your article in MW
News January 2008 about the Sony SRF-59 that rekindled my interest in
MW DXing. You've got such a readable easy style of writing that
retains the interest, making the reader want more. Your sheer
enthusiasm really leaps from the page. Sincerely, have you ever
thought of becoming a professional author?

There are many who owe you for founding the Ultralight movement. Not
just DXers, but also the radio vendors. The hobby could not have a
better advocate! Your articles have been responsible for my obtaining
the SRF-59, SRF-T615, DT-210L & DT-400W radios and generally 'doing'
radio again. Unfortunately I've yet to hear any TA DX on any of them.

73
--
Michael Slattery G8PNX
Sheffield, UK

On Sat, 4 Apr 2009 14:37:39 EDT, you wrote:

Hi Michael,

Thanks again for your filter modification work, and your kind comments.

Actually both Guy Atkins and Steve Ratzlaff are far more experienced in
filter modification work than me, and I've simply managed to learn a few things
by having the privilege of working with them. My own contribution to the ULR
experimentation efforts here has been in loopstick improvements, in attempts to
make these tiny radios as sensitive as possible. If you are a member of MWC,
you may have seen a few of my fanatical loopstick articles that were
published in Medium Wave News.

About a year ago, I learned the harsh lesson that sensitivity improvements
alone were not going to make a major difference in chasing 9 kHz-split DX with
Ultralight radios. A small radio needs both a major sensitivity boost and a
major selectivity boost in combination, to make a radical improvement in
overall performance.

By a tremendous stroke of luck, one of the primary filter experts in the USA
(Guy Atkins) lived right in my small home town, here in Washington state.
Our cooperation last summer (along with contributions by John Bryant) produced
the first major breakthrough in ULR 9 kHz-split DXing performance, the fully
modified Eton E100. Steve and I were attempting to create something similar
with the DT-400W in the winter, but despite our unrealistic expectations, we
ran up against the harsh reality that all the commercially available 450 kHz
IF filters are mediocre for transoceanic DXing.

73 and Best Wishes,

Gary DeBock


In a message dated 4/3/2009 7:45:52 P.M. Pacific Daylight Time,
knallebo@yahoo.co.uk writes:




Hi Gary :)

Thank you for your kind thanks for my mod articles. I'm sorry that
some folk may have been misled into thinking the selectivity
enhancement would be much greater.

There was not that much effort expended in development. On obtaining
both the DT-210L and the DT-400W I was extremely disappointed by the
very poor selectivity. My gut reaction was that I had to do something
about it and whilst I was 'at it' I took a few photos reckoning that
it may be of use to someone somewhere!

I'm fully aware of the performance provided by the premium filters you
and others have been using for 9-kHz split DX chasing. I've used them
myself in my AOR AR7030 for many years but not yet in a ULR.

Some thoughts: I know you and Guy Atkins have spent quite some time
developing filter mods for various ULRs. I wonder whether it might be
worth investigating the Collins Low-Cost Series of mechanical filters
that have a superior passband ripple to ceramic filters possibly
enhancing the intelligibility of reception. Expensive, but when only
the best will do. Inrad have a 2kHz 8 pole variant:
<_http://www.inrad.http://www.ihttp://www.inrht&cat=5&<WBR>p_
(http://www.inrad.net/product.php?productid=19&cat=5&page=1) >
or a 2.3kHz 10 pole variant:
_http://www.inrad.http://www.ihttp://www.inrht&cat=5&<WBR>p_
(http://www.inrad.net/product.php?productid=18&cat=5&page=1)

In the DT-200VX and DT-400W, if space cannot be found for the filter
within the case maybe one of the AA cells could be disposed of to
create a space for the installation the filter. The remaining AA cell
bay could then be loaded with a 3.6V Lithium AA cell.

Thanks once again for your consideration.

73

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