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

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Old 29th Mar 2020, 3:17 pm   #1
cathoderay57
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Default Ferguson 503 Noisy on MW

Afternoon all. I pulled out my Ferguson 503 today to run it up after a few years. It worked very well on USW, SW and LW bands as it did before, having a 6D6 RF amplifier. I also remember that reception was disappointing on MW, and it still is, unsurprisingly. I re-did the RF alignment on MW and it helped a little bit but whereas I am getting 75% deflection on the magic eye for strong signals like R5 Live the background noise is awful. Reception is better at the HF end of the band with local Radio Gloucester (212m) coming in nicely. Looking at the circuit I note that only on MW the aerial is bottom coupled to the aerial coil L4 via C1, C2 and S3 whereas on the other bands the coupling is different. As an experiment I disconnected S3 from C4 and connected it to Grid 1 of V1 (emulating the top coupling used on SW). It wasn't any better but then I was unable to peak C35 whose value would probably have to be changed because of the extra capacitance of the aerial circuit. I didn't feel like opening the can to do that so I put it back the way it was. I've done the obvious things I could think of including testing the continuity of L4 and L9 via the wavechange switch and the dc resistance reads close the values given in Trader #682. I have tried replacement V1 and V2 to no effect. All of the anode and screen voltages are close to the Trader sheet and the cathode voltages are as calculated from the quoted anode and screen currents and cathode resistors. The local/distant switch is in the down position (open circuit). I have tried other radios on the same longwire aerial and reception is much less noisy. Any ideas, or is it just a feature of bottom coupling? Cheers, Jerry
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Old 29th Mar 2020, 3:32 pm   #2
ms660
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Default Re: Ferguson 503 Noisy on MW

According to this article (mag. page 389) the voltage gain across the band is more constant with bottom end coupling:

https://www.americanradiohistory.com...ld-1975-08.pdf

Not saying that's a definite advantage, as you will see by reading the rest of the article.

Lawrence.
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Old 29th Mar 2020, 4:04 pm   #3
cathoderay57
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Default Re: Ferguson 503 Noisy on MW

Thanks Lawrence, that's interesting. The Trader sheet mentions the potential divider function of C1, C2 and C4 which by my calcs gives Vout/Vin of about 0.06 times the potential at the receiver end of the aerial. I suppose for completeness I should remove and test C1 and C2 as it looks like any serious change in value could be a problem on MW. Unlikely though since they are cased mica. C4 has been replaced but I will check a 0.002uF has been fitted.
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Old 29th Mar 2020, 9:17 pm   #4
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Default Re: Ferguson 503 Noisy on MW

C1& C2 ware supposed to be 250pF. C1 measured 300pF & C2 340pF. Not expecting any Improvement, I replaced both with new mica 220pF, and there wasn't. C4 is s brand new 0.0022uF poly film cap. There is generally a lot of noise here on the AM bands since I'm in the middle of a housing estate. With everyone at home there must be lots of appliances on with switch mode power supplies which won't help? Maybe the Ferguson is more sensitive to the background noise, perhaps a more wideband front end, than my other radios. I'll live with it. When I do get a decent signal the push-pull 42 valves and large speaker sound really good. Cheers all.
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Old 31st Mar 2020, 1:31 pm   #5
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Default Re: Ferguson 503 Noisy on MW

The 503 was the radio we used in the 1950’s, worked extremely well. In the second half of the 50’s when I was a little older I used it for SW listening when it was not used for more normal entertainment stations, such as Luxembourg, Hilversum etc. I think those stations were listened to by my parents more the the BBC.
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Old 31st Mar 2020, 9:36 pm   #6
cathoderay57
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Default Re: Ferguson 503 Noisy on MW

Hi Frank, yes, it's a nice set with its spectacular aeroplane style dial. I'll post a photo tomorrow. The cabinet has a few old worm holes but no livestock any more. The chassis has some light surface rust and I had to replace the speaker cloth so It will never be concourse condition but it's a keeper. When I got it I had to replace the AF output transformer and all of the usual capacitor suspects, plus a couple of new AF output valves were needed as one of the 42 pair was very low emission and the other one mediocre. I think this example maybe had a history of poor MW reception because the RF amplifier MW coil had been disconnected, and an attempt made to feed the aerial straight to the 6A7 frequency changer. The alignment had also been messed with. It might not be perfect now but it works a whole lot better than when I first got it. Cheers, Jerry
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Old 31st Mar 2020, 9:50 pm   #7
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Default Re: Ferguson 503 Noisy on MW

Sorry for stating what may be the obvious but, if a radio is picking up noise then it is probably receiving noise.
If the noise reduces when you disconnect the aerial then look for the source of the noise external to the radio.
If you are suffering from excessive interference then the AGC may be limiting the gain of the set making it seem insensitive.

Mike
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Old 1st Apr 2020, 12:01 pm   #8
cathoderay57
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Default Re: Ferguson 503 Noisy on MW

Thanks Mike, the noise is definitely external to the set. I suspect there's little I can do short of moving house . Here are some pics. Cheers, Jerry
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Old 1st Apr 2020, 3:09 pm   #9
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Default Re: Ferguson 503 Noisy on MW

Quote:
Originally Posted by cathoderay57 View Post
there's little I can do short of moving house
The big question would be - where do you think you could move to to get away from the interference that nearly everyone suffers from these days?

I have to say that I've personally noticed an increase in RF noise since the current lockdown situation has started to really take hold, with everyone being at home during the day - I was absolutely obliterated with it a couple of days ago, although not quite so bad today, probably now the novelty of it all has worn off a bit!

All the same, that's a very attractive radio - shame it's AM only, which it has to be with it's age and model type.
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Old 1st Apr 2020, 4:17 pm   #10
cathoderay57
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Default Re: Ferguson 503 Noisy on MW

Some time ago I built a basic active loop aerial using the simplified circuit in Gary Tempest's article referred to here https://www.vintage-radio.net/forum/...d.php?t=137089 . I didn't build the Full Monte version, as I say, just the simplified circuit on Page 44 of the article (BVWS Bulletin Aug 2016). Using two BC547 was disappointing so I substituted two 2N5109. I put the loop in the loft and connected to the radio room (small bedroom below) via coax. On LW and MW it works better than the long wire, but progressively worse as you head up the SW bands. But here's the thing - on LW and MW the signal to noise performance is significantly better than the long wire, even using the 2 transistor version that I build on stripboard, and without any attempt to match the output to the receiver. Well worth the effort to build if you are getting noise problems. Cheers, Jerry
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