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Old January 14th 05, 04:46 AM
running dogg
 
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Default Nulling QRM

I've noticed in the last couple days that I can't get the BBC on 9525 at
0300, so I've had to listen to their 5975 freq out of Antigua. The
problem is that 49m is for me full of noise. The noise is so great that
it reduces the BBC to an unintelligible mumble, especially on my Degen.
So I fired up my Yaesu FRG-8800 and tried using SSB to null the noise,
but no luck, even though the LSB setting greatly reduces it I am still
left with a mumble level of audio. The signal is strong, it's just that
the QRM is stronger. I'm using about 50 feet of longwire (my old
antenna) coiled up inside because I can't have an outside antenna for
now. Any suggestions?



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Old January 14th 05, 06:01 AM
ShortwaveMan
 
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I have had some luck with some stations that have a heterodyne. I set the Dx 394 to 1 khz step and tune up or down by about 2 Khz away from the strongest part of the station's signal and the sometimes reduces the noise enough that the signl is almost clear.

If you have other forms of noise such as flourescent lights, mercury vapor or sodium arc lights and such, I'm not sure you can get much help reducing the noise without moving the antenna farther from the source. Noise coming from televisions, computers and other things that have digital circuitry produce noise that can only be quelled by turning off the equipment itself while you want to DX.

As other posts have already mentioned, matching the antenna at the connection of the feed line can be helpful as well as grounding the receiver; the ground wire should not be inordinately long.

I hope that helps. Keep in mind that atmospheric activities can degrade or obscure a signal. If the ionosphere is not reflecting signals favorably, the noise will win out no matter what you do.

Peace +

"running dogg" wrote in message ...
I've noticed in the last couple days that I can't get the BBC on 9525 at
0300, so I've had to listen to their 5975 freq out of Antigua. The
problem is that 49m is for me full of noise. The noise is so great that
it reduces the BBC to an unintelligible mumble, especially on my Degen.
So I fired up my Yaesu FRG-8800 and tried using SSB to null the noise,
but no luck, even though the LSB setting greatly reduces it I am still
left with a mumble level of audio. The signal is strong, it's just that
the QRM is stronger. I'm using about 50 feet of longwire (my old
antenna) coiled up inside because I can't have an outside antenna for
now. Any suggestions?



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Old January 14th 05, 09:28 AM
RHF
 
Posts: n/a
Default

RD,
..
Try an In-Door Antenna 'designed' for Shortwave Listeners
with RFI and EMF Noise Problems . . . The Loop Antenna !
..
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..
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..
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..
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..
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..
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..
* Using an In-Line Pre-Amp with TV 'type' Coax Cable
[Shielded] Loop Antennas
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..
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..
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to your TV Coax Cable [Shielded] SWL Loop Antenna
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..
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..
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..
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for 'portable' AM/FM Shortwave Radios
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..
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..
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..
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Twin Lead
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..
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..
..
iane ~ RHF
..
All are WELCOME at the Shortwave Listener (SWL) "Antenna Ashram"
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..
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- - If You Build It {SWL Antenna} You Will Hear Them - -
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Old January 14th 05, 10:36 AM
Ron Hardin
 
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You're probably out of luck.

An actual beam antenna would work, meaning one with large forward
gain and resulting low response in most other directions, which you
aim AT the station you want to listen to. More dollars than most
SW listeners want to spend, if one is even available for the frequency
you want.

A small antenna can produce NULLs which you put on the stations you
don't want, eg. a loop or a loop+whip phased array, but the nulls
are small and everything else still pours in as before, and at night
the direction of arrival is not likely to be stable enough to null
even a single station unless it's a local (and so has a stable
direction).

A long wire has forward gain, though I forget whether it's along
the antenna or broadside to it. It's certainly along in the case
of a beverage antenna, so maybe it's along. Aim that at the
station you want and see if it helps. Be sure to look up the
great circle direction, they're not what you'd think.

--
Ron Hardin


On the internet, nobody knows you're a jerk.
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Old January 16th 05, 08:39 AM
starman
 
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Ron Hardin wrote:

A long wire has forward gain, though I forget whether it's along
the antenna or broadside to it. It's certainly along in the case
of a beverage antenna, so maybe it's along. Aim that at the
station you want and see if it helps. Be sure to look up the
great circle direction, they're not what you'd think.


A 'real' longwire is directional towards the far end of the wire. A
random wire or inverted-L is generally non-directional if it's less than
a wavelength long. Most are somewhat directional on the higher HF
frequencies because the wire is at least one wavelength long.


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