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Steven Wilcox's picture
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"pulsing" FM interference
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I have a Musical Fidelity kw250s combined CD/Tuner/mono block amps unit.


I have a roof top aeriel and although I much prefer the quality of sound on FM to DAB I am getting a pulsing interference on FM.  It's not noticeable on louder music but can be annoying in quieter classical passages.  The interference consists of a fairly quiet noise pulsing about once per second.  I also have a problem with what I believe to be DC on my mains supply that is causing the tarnsformers to buzz and I wonder if the two things might be connected?


 Any thoughts on what the problem is likely to be, and how to rectify it would be very welcome.

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Re: "pulsing" FM interference

Have you got any mobile phone chargers plugged in? If so, remove them. I had exactly this problem and removing them from the plug sockets solved the problem.

It could also be another type of charger - laptop etc?

Anonymous
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Re: "pulsing" FM interference

I had a similar problem when we were on the BARB panel. It was their box.

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Re: "pulsing" FM interference

So assuming you are on the BARB panel, there's your solution.

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Re: "pulsing" FM interference

Has your rooftop aerial connections been checked lately? Do you have good quality 75 ohm double-screened coaxial cable? Maybe you are not using an optimum aerial type for your local reception conditions.



Check out this excellent guide first... http://www.aerialsandtv.com/fmanddabradio.html

"We are currently awaiting the loading of our complement of small lemon-soaked paper napkins for your comfort, refreshment and hygiene during the journey."

Steven Wilcox's picture
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Re: "pulsing" FM interference

Thank you for the suggestions.


 I'm not on the BARB panel - I had to look up what this is as I'd never even heard of it.


 I've tried disconnecting all chargers but this hasn't worked I'm afraid.


 So, any further suggestions still welcome.

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Re: "pulsing" FM interference

Chebby -thanks for your comments also - I was writing my response to the previous comments as you were posting yours!


 I only quite recently had a full aeriel instal but wasn't very happy with the job done - the freeview reception was very poor in some rooms and I had to get another installer in to check it out.  They installed a couple of new sockets which seemed to help for a while but the freeview reception from one room is now poor again - even though the aeriel has a line of sight to the transmitter only a few miles away.


The FM aeriel for my MF Unit is actually plugged into the TV wall socket as it gets far better reception from this than the one marked FM.  I've yet to try a TV in this room so don't know if this will work in the FM socket.


I think I may need to get an installer out to do a thorough check - as it happens the organisation whose website you refer to is in my home City (Sheffield) so I may even try them - they certainly seem to know what they're talking about and are keen to supply quality products.

Anonymous
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Re: "pulsing" FM interference

Steve

I live near Sheffield and also run a Pure FM tuner from the TV aerial (since I had a freesat dish installed). Mine works just fine. Just trying to save you the money for engaging a contractor (£75 just to visit?) - check again for household causes.

The buzzing in the casing - if it doesn't come out of the speakers, you can get that from the ring main (Naim stuff is especially prone) - hi-fi power from a spur can help a lot.

If you've turned all the phones and chargers off, have you thought the tuner might be at fault? - some kind of electircal component 'leaking' current? (I really have no idea what I'm talking about now). Could you borrow a mate's tuner and run it from your aerial to check?

Just a few thoughts

Mick 

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Re: "pulsing" FM interference

Thanks for your thoughts Mick.


 I've got an Arcan tuner in another room and the reception is fine from the same FM aeriel.


 I think the buzzing from the amp transformers is probably caused by DC on the mains - not so easy to solve unfortunately.  There's a few Units out there that might do the job but very expensive - Alan Clarke at James Audio has been particularly helpful with his advice and has a Unit that he is confident will sort it out but it's about £700 which I just can't afford at the moment.

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RE: Digital and analogue radio

Thought I'd just add, some 3 years later, that I bought the James Audio power conditioner unit shortly after the last post and it has been working very well indeed.  The buzz was reduced to a virtually inaudible level - it's certainly not a problem now.

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RE: Digital and analogue radio

Steven Wilcox wrote:
Thought I'd just add, some 3 years later, that I bought the James Audio power conditioner unit shortly after the last post and it has been working very well indeed.  The buzz was reduced to a virtually inaudible level - it's certainly not a problem now.

 

So a 'mains conditioner' had the effect of reducing audible noise?

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