There's been some discussion about filters etc recently which reminded me of
a question I wanted to ask the group...
What receivers/tranceivers work well on LF? and possibly..
What receivers or transceivers don't work very well?
All I need is something like this:
IC735; rather deaf, needs external preamp/filter.
TS850; excellent, especially with two CW filters.
The receiver itself in not the whole story.
In the early days of 73kHz experiments I used an old IC-707 with a
Datong converter. I found its performance was very poor with lots of
birdies and breakthrough. On a visit to Mike, G3XDV, I listened to
his 73kHz setup, which comprised the same Daytong converter but with
an IC 706 as the tunable IF. His receive setup sounded totally
different with nice crisp sound and the occasional 'gunshot' static.
The difference in performance was the result of Mike using a tuned
circuit preselector and a carefully adjusted variable attenuator.
Much of my early work on 73kHz and 136kHz was done using a Drake 4C
with 1500, 500 and 200Hz Sherwood filters and first IF roofing filter
- with a double-tuned circuit preselector and a variable attentuator
(potentiometer). and I was happy with this (except for poor frequency readout).
When 136kHz became available my main problem was Loran. This holds
the S-meter at S6 at 1.5kHz bandwidth and at narrower bandwidths the
filter rings due to the Loran. John, G4GVC, was having more success
on receive than most and after hearing John's TS-850 receiver setup,
I bought a second-hand TS-850. The filters and bandwidth control,
plus 3+OFF AGC setting make this the best receiver I have ever used
in over 40 years of Ham Radio. But it still needs a preselector and
variable attenuator to get the best out of it.
My feeling is that if Loran is not a problem at your QTH then any
modern transceiver that has good sensitivity at LF and has a CW
filter will work provided that the gain distribution throughout the
receive system (antenna, converter, receiver front-end, audio) is
under control. The component between the headphones also contributes
to receiver efficiency. I find that a 500kHz filter is the best in
the presence of Loran.
However, I recently asked if anyone knew of a Level Meter D2155 made
by Siemens that I recently aquired. I got no response so I assume
that no one knows about it. So I decided to try it as a very good
receiver, and it seems very good except that the bandwidths of 3.7kHz
and 20Hz are a bit strange. With the narrow filter on I do not hear
Loran and it converts all signals and noise to a single note but it
does not ring. A normal CW signal stands out but is rather 'soft'.
I used it for the first time this morning, 3/10/99, and the fist
signal received was (I think) DL calling CQ on 136.54. The D2155 was
not tuned quite onto him before he went over. The next signal was
G4GVC and we had a QSO. John's signal was -80dBm. G3BDQ called me but
I had to go QRT. His signal was -78dBm. You may all be getting a
different type of report from me in the future!
Next Tuesday morning I will be running tests on 72.1kHz on Slow CW
and listening/looking on that band and on the 136kHz band for
replies. If you want a sked let me know.
--
Regards, Peter, G3LDO
<g3ldo@zetnet.co.uk>
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