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Old 27th Sep 2012, 5:29 pm   #1
David Simpson
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Default 80m Interference

I've just recently decided to renew my efforts to get my old Sailor Radio AM rig(ex Marine Band) back on air. However, I'm experiencing a repeditive 1sec "buzz-buzz from my 66TS Rx. Both on the crystal channels of 3615,3640 & 3690KHz and on the dial selection of those frequencies.
This interference is still there with the house mains supply completely switched off. And, my HF equipment is completely supplied by an independant 24V DC battery supply anyway(as if back aboard an old fishing boat). Also,my much newer Sailor Rx1117(all singing/all dancing synthisized freq selection) experiences exactly the same interference.
My aerial is a half-wave - centre fed by a 4" ladder feeder, orientated E - W.
I'm usually listening out,at times, between 1500 & 2000hrs, but from about 1700hrs onwards - the CW & SSB guys get busy.
I've just made one or two CQ calls with my 76D Tx(10W/95%Mod/Class C), but haven't raised anyone yet.
Just wondering if there are any Forum Ham guys from the north of Scotland who have heard similar interference ?


Regards, David MM6 ACI
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Old 27th Sep 2012, 7:07 pm   #2
Ian - G4JQT
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Default Re: 80m Interference

Type "radio interference" into YouTube. There are lots of examples. Some are just from people wanting identification, but others are examples of known noises, like power-line data transmission, BT Home Hub, etc.

Good luck.

Ian
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Old 29th Sep 2012, 5:54 pm   #3
David Simpson
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Default Re: 80m Interference

Ian, thanks for the YouTube info. I've listened & listened to dozens of examples, but nothing matches my problem.
Most You Tube contributors had fancy modern Icom or Yaesu or Kenwood sets with built-in spectrum analysers & such. Me - I'm just using an old ex marine band HF AM Tx/Rx about 45 years old.
My interference is a constant buzz-buzz. Every second and lasting a second, approximately. Not a rough sparky sort of buzz, and nothing like mains hum. The nearest I can describe it - like someone constantly reveing a 4stroke motorbike some distance away down a tunnel. As I said initially, this is even with the house mains completely switched off(which means the BT home hub is switched off), no plasma screen TV's, no computers on - nothing. There are no HV pylons anywhere nearby. We're on the end of an underground 16mm sq straight concentric cable from the 11KV/240V pole mounted T/F about 200 yds away. There is a pole mounted BT line about 25m south of my aerial, but considerably lower.
There are a few wind turbines in our area. The nearest biggish one is about half a mile away, and a wee one about 1/4 mile away. But the interference is independant of wind conditions. Its still there on a calm day.
For its age, my Sailor 66TS AM Rx is a great radio, a selectable filter facility & excellent sensitivity & volume control. Which means I can eliminate about 50% of the interference, but its still a nusience when listening to some of the more distant transmissions on my fixed crystal channels.
Another thing, as folk's transmissions fade in & out due to ionospheric conditions, so does this bloomin interference, which might indicate its source as some distance away, even accounting for agc response.

Regards, David
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Old 29th Sep 2012, 6:12 pm   #4
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Default Re: 80m Interference

I reckon that that is PLT interference: seems to be everywhere these days.

Al.
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Old 29th Sep 2012, 9:11 pm   #5
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Default Re: 80m Interference

Take a look at UKQRM for PLT interference.
 
Old 29th Sep 2012, 11:04 pm   #6
Ian - G4JQT
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Default Re: 80m Interference

Quote:
Originally Posted by David Simpson View Post
...Another thing, as folk's transmissions fade in & out due to ionospheric conditions, so does this bloomin interference, which might indicate its source as some distance away...
You say it fades in and out which would suggest it was sky wave - some distance away as you said. But Sky-wave interference would be noted over much of the UK, and fade out in the daylight. Is there anyone else you know who can hear it?

If it were the dreaded PLT (data through the mains in various forms) you would probably have found an example on YouTube that more or less matched your noise.

If you have (or can borrow) a portable radio that covers the frequencies affected, have a walk around your area. Even if you do find a 'hot spot' it can be misleading as interference is often re-radiated from mains wiring in lamp posts, telephone poles, etc.

Regards,

Ian
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Old 30th Sep 2012, 11:07 am   #7
David Simpson
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Default Re: 80m Interference

I'll be meeting up with some local Ham guys in a couple of weeks time & shall ask around.
We are third last on our BT rural pole mounted line. Hydro-Electric's 11KV line which supplies our nearby transformer is itself a spur in rural farmland. Cant think of any reason why it should be carrying data transmissions.
Right enough, a drive around the local countryside with a portable HF AM Rx is something I'd considered. I might be able to borrow one from a yacht owning pal in Findochty.
If I was a pro-active member of the Ham community, I'd probably be up-to-speed on ether intrusive problems. But my ventures onto the airwaves only occur when I'm infrequently inclined to a vintage ex marine band HF set's repair or renovation. This latest venture stems from my (seemingly sucessful)attempt to convert a Johnson Transmatch to replace the PA tank circuit of a tempremental(80m-wise)Sailor 76D Tx. The Johnson's secondary coil configuration also facilitates the use of an Advance 77B VVM as a decent power meter. But thats another story.

Regards, David
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Old 30th Sep 2012, 3:24 pm   #8
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Default Re: 80m Interference

Hi David, I can't help with identifying your interference but a program called Mixw, from the Ukraine. Mixw.net I think, gives you a waterfall type spectrum analyser display that may help. Quite a program, it also decodes RTTY etc. Dead easy to use, just connect audio from your radio to the sound card, and its free!. I'm using it with an old laptop powered by a non switched mode PSU so as to reduce interference, my main PC/monitor gives far too much hash.

Hope this helps
Peter
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Old 1st Oct 2012, 10:27 am   #9
James Duncan
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Default Re: 80m Interference

Hi David


I think you are suffering from a bad termination on some power line or piece of electrical equipment in your area.could also be a pulse from a UPS nearby.
check with a portable radio to see what spectrum is covered by the noise,
just walk around to find the direction and location.A old radio with a directional antenna would be best.
You can also request Ofcom to investigate, that is their job.

all the best
Hamish
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Old 1st Oct 2012, 11:11 am   #10
Andrewausfa
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Default Re: 80m Interference

David,

Just a suggestion but reading your reply that the audio reports on Youtube don't seem to match what you're hearing, could you tune to 4625 USB? Is the sound you're hearing like this? I've picked up harmonics from this station on the 80m band before.

Andrew
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