Interference on MW band

[zenitht]

Hi there

I have a McMichael Model 374 whic works quite well on SW and LW, but on MW there is interference as you head towards the lower metres end and completely swamps the signal.
It is in the form of a sharp buzz that gets progresively louder the lower down the scale you go.

Only on MW though.

I would appreciate any ideas.

Thank you very much

Graham

[Ghostuser]

Interference from a plasma display or from fluorescent light fittings is sometimes like that.
Nigel

[zenitht]

Hi there

Thanks but neither of them in my kitchen I'm afraid.

Graham

[Sideband]

They don't have to be in the same room as the radio Graham or even in the same house!! !

Much has been said about interference from computers, low energy lamps, DVD's, video's and TV's etc in fact virtually anything modern that uses a switched mode supply will cause interference to a greater or lesser degree. Try searching on this forum for interference. I'm sure you'll find some interesting comments !

If the interference is from anything in your house, try switching things off in turn and see what happens. I have considerable interference on MW with a lot of my valve sets...usually the older ones that require an external aerial. However if I move them up into the loft and try them there, they all work very well indeed.


Rich.

[paulsherwin]

Hi Graham. Common sources of interference are:

Anything with a switch mode PSU
Fluorescent lighting
Computers and monitors
Digiboxes, even in standby
TVs
ADSL modem/routers

This is not an exhaustive list, and as Rich says the culprit may not even be in your house. I had serious interference on my mains phase for about 18 months which made LW unusable. It disappeared early this year and so far hasn't returned. I never found the cause, but it wasn't on my side of the electricity meter

Paul

[zenitht]

Richard

Thanks for your useful suggestions. I'll try moving it to somewhere else in the house or garage and see if it improves.

Best regards
Graham

[zenitht]

Paul

Again, thanks for taking the trouble to offer some useful help, it's very much appreciated.

Many thanks
Graham

[Station X]

There is a possibility that the interference is being generated within the radio. Try operating it somewhere else, say at work or in a friends or relatives house as far from your own home as possible. If the interference is still there, then it's internal to the set.

You could also try disconnecting any external aerial and shorting the aerial connector to earth. This should make external interference disappear.

[zenitht]

Hi there

I would just like to thank everyone who replied to my cry for help. Thanks to you I have identified that it is intermittent external interference swamping the low end of only the MW Band.

Mmmm........think I'll re-wire the house this weekend, shouldn't take long !

Regards
Graham

[Sideband]

Glad all the suggestions helped .

I once had a strange pulsing noise on MW (slight), LW (worse) and SW (partly). This was not just on vintage sets but also on a modern comms receiver with synthesized tuning although it has to be said that the comms receiver was much better at getting rid of it and with an ATU I could tune it out.

I only discovered the culprit when my wife was printing something out one afternoon. The pulsing changed rapidly during paper feed and carriage return. It was the old Canon printer and further tests showed it was chucking out horrendous muck all over the AM bands. I did improve things by making up a mains filter but the real cure was a new printer.

Rich.

[paulsherwin]

I once had a compact fluorescent that chucked out RFI, but only when it had been running for 5 minutes. It took a while to track down.

Paul

[Skywave]

Originally Posted by paulsherwin

I once had a compact fluorescent that chucked out RFI, but only when it had been running for 5 minutes. It took a while to track down.

Paul

Ditto - only mine were (and still are) 5ft., qty = 2. Broadband interference from LW to about 7 MHz + & immediately from switch-on.

After a lot of experimentation, I found that only by fitting 1uF 1000v dc wkg. caps. across the ac feed to each would they shut up!

I hope that this is helpful & relevant.

Al.

[Geoff G4ICD]

Originally Posted by zenitht

Hi there

I have a McMichael Model 374 whic works quite well on SW and LW, but on MW there is interference as you head towards the lower metres end and completely swamps the signal.
It is in the form of a sharp buzz that gets progresively louder the lower down the scale you go.

This is a common problem that is usually self inflicted, have a look in your house (could also be next door) for a switch mode psu that feeds the low voltage halogen lights.............had this dozens of times and it is usually the so called transformer that powers the lights, if it is, then change it for a proper transformer........