Dave,
This sounds suspiciously like the dreaded "Touch Controlled Lamp Syndrome".
Check and see if you can find another copy of the signal about 200 KHz in
either direction. If so, do a survey of your immediate surroundings to
locate any touch controlled lamp dimmers or appliance on/off switches.
These diabolical noise sources cannot be silenced by merely turning the
device off with the touch controller. The device must be disconnected from
the mains completely to kill the noise. No receiver noise blanker that I
have any experience with will touch this kind of noise.
These devices are also pretty good receivers. The ones my neighbors had
were particularly sensitive to RF energy at 7 MHz. I could sit at my shack
window and watch the neighbors lamps cycle through the typical
off...dim...medium...bright...off sequence as I keyed as little as 50W CW
on 40 meters. I finally started keying up at about 3 A.M. and leaving the
lamps on medium every night. The neighbors thought the lamps were haunted
so they got rid of them in a few weeks. I got rid of three different lamps
in 2 different houses that way. I was just kidding about "haunted".
Actually, they thought they were defective and came over to ask if they
could be fixed. I showed them that the modules were fairly tightly sealed
and couldn't be easily worked on. I may have muttered something about fire
hazard. But I don't specifically recall... Anyhow, the electrical repair
place they went to estimated fairly high on the repair and the one he fixed
didn't stop the funny behaviour so they gave up and got real switches put
into the lamps.
Anyhow, the symptoms for this noise are:
1. Covers only about 20 KHz of the band.
2. The transition form outside the noise to inside the noise band is
_VERY_ abrupt considering the wideband nature of the noise in the noise
band. When tuned across the noise band, the receiver goes from no
noise at all to full amplitude noise within a tuning range roughly
equal to the width of whatever filter is in the receiver.
3. Identical noise bands are apparent about every 200 KHz or so up and
down the band.
4. If the device is receiving your transmissions, the noise can be changed
by keying the radio and listening to the noise. It doesn't really go
away but the way it sounds changes and the center frequency sometimes
changes a bit.
5. If it is a dimmer, the maximum noise amplitude coincides with "device
off" state. Minimum noise coincides with "maximum brightness" state.
Hope this is helpful!
73, Eric N7CL
--
Eric Gustafson N7CL | The mountains are high and
6730 S. Old Spanish Trail | the Emperor is far away.
Tucson, AZ 85747-9498 |
| You can't work 'em
INTERNET: n7cl@mmsi.com | if you can't hear 'em.
--------------------------
To: <topband@contesting.com>
>Date: Tue, 3 Dec 1996 12:40:13 -0500 (EST)
>From: Dave Pascoe <dave@mathworks.com>
>
>I'm finally back on the band after a long hiatus. It's nice to be
>back.....I love 160.
>
>Antennas: Inverted-L, about 70' vertical
> EU Beverage, about 880' long
>
>This morning while listening for JAs I came across some unusual QRN
>between 1902 and 1925 kHz. My first thought was that it was an electric
>fence. But the noise doesn't appear below 1900 kHz or above 1925 kHz!
>It comes and goes, and appears both on the inverted-L and the Beverage.
>It doesn't appear to be periodic or contain any kind of pulsing
>characteristics, but I only listened to it for a short time.
>
>Has anyone encountered anything like this? I'll do more investigating
>tonight and tomorrow morning and post any findings.
>
>73,
>
>Dave Pascoe dave@mathworks.com http://www.mathworks.com
>KM3T 508-647-7362 FAX: 508-647-7002
>
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