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@... 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

For Gary, Vince and John in South Africa (and Horacio and Huelbe in South America),
This question was raised by one of our dedicated TP and TA DXers on the IRCA mailing list, and I'm sure that some of you could answer his question quite well. Do you notice that long-range DX conditions are much better in the months of August, September and October (like here in the Northern Hemisphere), or during the months of March and April? Any opinions would be greatly appreciated!
73, Gary DeBock
Having been an ardent TP and TA DXer for several seasons, I've noticed that in my part of the world, the Fall equinox far exceeds Spring equinox for TP and TA DX. My question is thus: Do our DU colleagues experience the same Fall/Spring differences (ie their Fall/Spring), or do they mimic our September superiority over March? Has there been any research in this area, and explanation for the differences? .....Walt Salmaniw, Victoria, BC.
------------------------------------------------------------------------
Worried about job security? Check out the 5 safest jobs in a recession <http://jobs.aol.com/gallery/growing-job-industries?ncid=emlcntuscare00000003>.

De: huelbe_garcia@...
Asunto: Re: [ultralightdx] Sangean DT400W dealer shop in Houston TX?
Para: ultralightdx@...
Fecha: sábado, 4 abril, 2009 4:26

Hi Horacio,

I don't know if this helps you... .

Last month I bought a DT210V as a gift for a friend of mine. I bought it from eBay seller nu_image_corp. It was received quickly, and I was able to track the parcel using USPS and Brazilian Postal services. Nu_image_corp has a very reasonable shipping fee. So, I can recommend nu_image_corp' s work.

I've just check his store and it has a DT400W:

http://cgi.ebay. com/Sangean- DT-400W-Personal -Pocket-AM- FM-Weather_ W0QQitemZ2503958 37010QQcmdZViewI temQQptZWeather_ Devices?hash= item250395837010&_trksid=p3286. m20.l1116

or search for eBay using code "250395837010" (without the quotes)

73,

Huelbe.


Horacio Nigro wrote, On 04/04/2009 15:21:

A friend wants to buy the DT400W, a friend of him going to Houston TX in the near future. Is there any shop there to buy it? Thanks for help. Horacio A. Nigro Montevideo Uruguay

I'm going to tackle an alignment on my new radio. My question? What's the preferred method to resecure the coil after the wax is scraped away. Tape, glue, wax ? Want to make sure I can easily do over if needed.

Now I know that there many members of this site with many more logs than
117 but I'm just a little bit proud of 117. I got up early this AM and had
a quick look at the paper and then sat down and picked up the DT400W and
tuned to 640 and heard the familiar CFMJ from the Toronto area
transmitting @50k watts, but underneath I just barely made out a woman's
voice with a British accent, I turned the the DT400 and nulled CFMJ just a
little, then I grabbed the crate loop and tuned the freq. It was the BBC
World Service being relayed from WOI in Ames Iowa at all of 1000 watts at
that time of the day, I confirmed their programming sched on their
website, BBC from 12:00AM till 6:00AM. Ames is 1452Km from my listening
post in Smith Falls, On.
This is the stuff that makes DXing such a rewarding hobby, at least for
me, my wife doesn't know what the heck I'm talking about.

Jack Leonard
Smiths Falls, On

I'm going to tackle an alignment on my new radio. My question? What's
the preferred method to resecure the coil after the wax is scraped
away. Tape, glue, wax ? Want to make sure I can easily do over if
needed.

Jeff

Hi Michael,

Thank you for your work in developing the LTM450HT filter modifications for
the Sangean models, and for uploading the information to DXer.Ca.

Steve and I were working toward the specific goal of transforming the 450
kHz Sangean models into very effective 9-kHz split DX chasers for transoceanic
reception, such as we had successfully accomplished with the 455 kHz Eton
E100 model last summer. We knew before commencing the work that 450 kHz
"consumer-grade" filters are not comparable with the premium Murata CFJ455K5 filters
we used in the E100, but we wanted to try anything available, since a vastly
improved Slider loopstick had already been successfully transplanted into the
DT-200VX (as described in a DXer.Ca article), greatly boosting the model's
sensitivity.

Unfortunately, the project was probably doomed from the start, due to
unrealistic expectations. If you have ever used one of the premium 455 kHz Murata K
filters for transoceanic DXing, you will probably understand how quickly a
DXer can become spoiled with the phenomenal performance. Anyway, we never
meant to be dismissive of your LTM450HT modification for domestic DXing, and hope
you will understand that our 9 kHz-split DXing performance requirements are
far more demanding than those of the average DXer. We regret any impression
to the contrary.

73 and Best Wishes, Gary DeBock


In a message dated 4/2/2009 6:50:21 P.M. Pacific Daylight Time,
knallebo@... writes:

Whether the 450 kHz filter modification would be useless or not probably
depends on the type of DX you pursue.

Before carrying out a mod you have to determine what you expect.

As the author of the DT-210L & DT-400W filter mod articles, I find the
comment that the mod is 'not worth all the effort' frankly incredible!

The mods were not offered as a panacea for turning these radios into
9/10kHz-split DXers machines. That would be impossible with the type
of filters (6kHz @6dB BW) used. Rather, the articles were offered in
the spirit of improving the usability of these radios in the domestic
context. The give-away line in my article was 'the intrinsic quality
of the audio remains.' By implication therefore, the mod filter is not
especially selective merely an improvement on the original.

The moral of the story is to make sure any ULR you intend to mod for
9/10kHz-split DXing has a 455kHz IF system and the ability to tune in
at least 1kHz steps or better. 450kHz IF radios are a waste of time
since narrow filters with a good shape factor are simply unavailable.

Whilst agreeing fully with the remark by Steve about skirt selectivity
and filter size, I have to ask:

Was the LTM450HT filter used? Nothing else will bring much improvement
except for a LTM450IT or even narrower filter, if you could find one.
The 'T' suffix in the filter model number is important since these
have superior skirt selectivity over those without the 'T' suffix.

Living here in the UK I frequently wonder what North American DXers
mean by a 'high RF environment'mean by a 'high RF environment'<WBR>. Among
of one 150kW & two 400kW MF transmitters & less than 1 mile of two 1kW
MF transmitters.

The DT-210L & DT-400W filter mods have transformed the reception
capabilities of these radios close to these powerful signals. Before
the mod, five (9kHz) channels either side of the frequency of one of
these strong locals were rendered useless for weak signal reception by
the original filter. After the mod I am able to hear weak signals on
the immediately adjacent channels (±9kHz) with only a small level of
adjacent channel interference.

Perhaps your RF environment(Perhaps your RF environment(<WBR>s) are not r
that is the reason you are not reaping the reward from the mod?

--
Michael Slattery
Sheffield, UK

Hi Michael,
Thanks for your comments. Yes, I used the LTM450HT filter in the DT-400W
mod, purchased from the eBay UK seller Mainline. I bought 5 of them and
tested several on the bench before installing one. All had the same poor
skirt selectivity. Initial skirt depth was about 40 db, not bad at all
considering the tiny size of the filter, but it quickly rose to 25 dB about
5 kHz either side of the passband. That's not good enough to give decent
adjacent channel selectivity in strong RF environments. The Murata K 455 kHz
filter that I've installed in Eton E100's and CCrane SWP's has 75-80 dB
skirt depth and it doesn't rise past the passband. It's physically
approximately 4 times longer than the LTM filters, and is an example of an
excellent ceramic filter, and its performance is reflected by its
approximate $50 price.
I'm happy the LTM450HT filter mod worked well for your particular RF
environment. It didn't produce the desired results for me. Apparently our
North American urban RF environments are more challenging than one might
think. :) I don't have that problem in the rural area where I live, with no
strong stations nearby; I send radios to Gary DeBock to test. He's able to
properly evaluate how radios perform in his urban RF environment.
73,
Steve
----- Original Message -----
From: "Michael Slattery" <knallebo@...>
To: <ultralightdx@...>
Sent: Thursday, April 02, 2009 6:47 PM
Subject: Re: [ultralightdx] Re: SRF-M37V and SRF-M37W-Performance
differences?

Whether the 450 kHz filter modification would be useless or not probably
depends on the type of DX you pursue.

Before carrying out a mod you have to determine what you expect.

As the author of the DT-210L & DT-400W filter mod articles, I find the
comment that the mod is 'not worth all the effort' frankly incredible!

The mods were not offered as a panacea for turning these radios into
9/10kHz-split DXers machines. That would be impossible with the type
of filters (6kHz @6dB BW) used. Rather, the articles were offered in
the spirit of improving the usability of these radios in the domestic
context. The give-away line in my article was 'the intrinsic quality
of the audio remains.' By implication therefore, the mod filter is not
especially selective merely an improvement on the original.

The moral of the story is to make sure any ULR you intend to mod for
9/10kHz-split DXing has a 455kHz IF system and the ability to tune in
at least 1kHz steps or better. 450kHz IF radios are a waste of time
since narrow filters with a good shape factor are simply unavailable.

Whilst agreeing fully with the remark by Steve about skirt selectivity
and filter size, I have to ask:

Was the LTM450HT filter used? Nothing else will bring much improvement
except for a LTM450IT or even narrower filter, if you could find one.
The 'T' suffix in the filter model number is important since these
have superior skirt selectivity over those without the 'T' suffix.

Living here in the UK I frequently wonder what North American DXers
mean by a 'high RF environment'. Amongst others I live within 15 miles
of one 150kW & two 400kW MF transmitters & less than 1 mile of two 1kW
MF transmitters.

The DT-210L & DT-400W filter mods have transformed the reception
capabilities of these radios close to these powerful signals. Before
the mod, five (9kHz) channels either side of the frequency of one of
these strong locals were rendered useless for weak signal reception by
the original filter. After the mod I am able to hear weak signals on
the immediately adjacent channels (±9kHz) with only a small level of
adjacent channel interference.

Perhaps your RF environment(s) are not really that challenging? Maybe
that is the reason you are not reaping the reward from the mod?