wrote in message
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On May 6, 1:47 am, "Dale Parfitt" wrote:
wrote in message

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On May 5, 8:29 pm, "Dale Parfitt" wrote:





"D.K." wrote in message

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Hi all,
I'm considering to upgrade my receiver ICOM R75 with CW narrow
filters.
My
main interest is NDB listening in the LW band.
There are 2 possiblities:
a) ICOM FL101 (CW narrow 9mHz IF, 250Hz) + ICOM FL53A (CW narrow
455kHz,
250Hz)
b) INRAD 121 (CW narrow 9010.6kHz, 250Hz) + INRAD 122 (CW narrow
455kHz,
250Hz)
Which combination is the better one in terms of quality and
efficiency.
Price does'nt matter.
Any advice is welcome!
Thanks in advance

D. Kremp
France

Unlike the crowded HF bands where a narrow IF filter is required to
prevent
strong close in stations from commanding the AGC, audio filters will
work
extremely well at LF. I use the now out of production Alpha Delta VRC
console for both LF and microwave EME- it beats the DSP front end
filters
in
my Icom PRO III 100% of the time at narrow BW.

Dale W4OP- Hide quoted text -

- Show quoted text -

Dale, with all due respect I question that. I had both a Datong FL3
and Autek QRF-1A = both superb audio filters, but not in the same
class at all as the Icom IC-756PROIII DSP filters.

If these were such great filters for modern radio's why are they all
out of production now?

Certainly if you have an older RX with poor filters those old audio
filters will do you very well, but not with the latest batch of DSP
radio's.

John Plimmer, Montagu, Western Cape Province, South Africa

Hi John,
The conditions I am talking about are very weak signal CW with no
atmospheric or manmade noise in the passband- the background is very
steady
cosmic background.. I'm not the only one that has come to this conclusion.
Another microwave EMEer is using the audio filters on his IC-7800.
A number of other EMEers have visited my station, and hands down agree,
the
VRC outperforms the radio's IF filters. This was also true of an IC-746 I
had dedicated only to EME. For general HF CW work- I much prefer the PRO
III's DSP filters. But for extremely weak lunar reflected CW, with its
libration fading (never present on HF signals) the VRC does it. Not sure
why
hat console disappeared. My guess would be 2 things:
1.Most rigs today come with much more filtering than they did 15 years ago
2. The VRC scaf filters are about the only good thing in that box. The
pushbutton switches are a mess and ther audio amp overdrives easily.

73,
Dale W4OP- Hide quoted text -

- Show quoted text -

Hi Dale,
Thanks for that reasonable explanation - I have not done that type of
CW DXing, only NDB's usually in very noisy conditions. You would like
a Datong FL3 if you could ever get your hands on one - beautifully
made and solid as a tank.

JP Montagu

Hi John,
I know of the filter, but have never seen one in captivity. I'll keep my eye
out- always looking for that edge over the guys with the bigger dishes.

Dale W4OP