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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 2nd Aug 2006, 5:00 pm   #1
radio1932
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Question EKCO A22, induced LW noise.

Hi,

I have an EKCO A22, which I have restored to working order.
I have replaced all of the wax paper caps-(all bad), and out of spec resistors and inserted a fresh set of valves.

I have realigned the set using a Leader 3216 RF alignment set and it picks up a good signal, but I get a noisy high frequency whistle on LW, which is less evident on MW and even less so on SW.

On MW it seems that a good strong signal stops the whistle breaking through.

It would appear that the noise is reducing with increasing the reception frequency and signal strength.

Any ideas ??
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Old 2nd Aug 2006, 5:24 pm   #2
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Default Re: EKCO A22 LW noise

Is the audio whistle present irrespective of what frequency the set is tuned to or is it only present when a station is tuned in? Does it vary in frequency?

If the set has an external aerial what happens if you short-circuit the aerial terminal to earth. Don't try this on an AC/DC set.

You need to find out whether the whistle is being generated in the AF or RF stages of the set. If the former it is probably a hetrodyne whistle and should disappear if the oscillator section of the tuning capacitor is short-circuited.
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Old 2nd Aug 2006, 5:26 pm   #3
Steve_P
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Default Re: EKCO A22 LW noise

Well....

1: Check your work again.
2: Is anything in a different place now. It could be pickup.
3: Check round the wavechange switch for leaks.
4: (Unlikely) Are the new valves OK?

Can't think of anything else.

Cheers,

Steve P
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Old 2nd Aug 2006, 5:29 pm   #4
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Default Re: EKCO A22 LW noise

At the risk of stating the obvious, have you eliminated external sources of interference? A TV or computer monitor will produce a very nice LW heterodyne whistle. It doesn't have to be yours, the next door neighbour's telly will do it.

Good luck, Paul
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Old 2nd Aug 2006, 8:41 pm   #5
Phil G4SPZ
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Default Re: EKCO A22 LW noise

Good point about computer interference. My elderly laptop computers produce a whistle emanating from the inverter that powers the screen backlight. It's audible on adjacent vintage radios tuned to long wave, but not present on medium waves.

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Old 2nd Aug 2006, 10:03 pm   #6
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Default Re: EKCO A22 LW noise

Noise on MW and LW has been the subject of many discussions here. I would start by systematically turning off equipment starting with the PC and monitor! Then any low-energy lamps you may have switched on followed by DVD's and any other electronic bits that may be permanently connected...particularly if they have external power supplies...some of these generate so much hash they should be banned!

I used to have a Canon printer that generated a strange pulsing noise all over MW and LW. Recently I discovered that my portable DVD player generates muck when in operation whether connected to the mains or used on it's rechargeable pack. Most of the noise seems to be generated by the inverters driving the backlights for the LCD...even at 20 feet away !


Happy hunting


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Old 5th Aug 2006, 11:06 pm   #7
radio1932
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Default Re: EKCO A22 LW noise

Hello all,

Thank you for your informative input.

Sorry for the delay in responding - I try to avoid spending too much time on my computer at home being stuck behind one at work all day!!

I will try to reply to all your points here !

First of all, yes I have noticed that these sets are excellent at picking up everything from flourescent lamps to a switch being thrown. It is a very good point about nieghbours equipment. I live at the end house in my street, so I must try the radio when next door is out.

I have also noticed that switch mode power supplies provide interesting noises too.

I have made sure that all components are correctly positioned, being careful to accurately change them over one at a time.

I have tried changing the valves over, same thing.

The whistle appears to lock in when picking up a station and seems to be consistant in frequency, Radio 4 LW is most definitely the main problem for me. My cheapy clock radio picks this up as clear as a bell, so it is not signal strength issue.

I have cleaned around the wave change switch, but I will have another go just to see.

G4ILN : I will try connecting the aerial to earth and let you know, (it is isolated on this set). I will also let you know about when the oscillator section of the tuning capacitor is short-circuited.

It may be a few days before I get around to trying these suggestions, so please watch this space. - and thanks again for your inputs to date.

Last edited by Darren-UK; 24th Jul 2007 at 8:36 pm. Reason: Excessive use of emoticons.
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Old 17th Aug 2006, 10:38 pm   #8
radio1932
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Default Re: EKCO A22 LW noise

Hello all,

Finally got round to that pesky problem of whistle.

It turned out to be a number of simple things.

1. There was some pick up from equipment next door.

2. More importantly, A better connection to earth, not just relying on the ring main feed to upstairs.

3. Removal of the plug in circuit breaker had a clear affect.

Cheers
Paul
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