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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 24th Nov 2022, 3:26 pm   #101
electronicskip
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Default Re: 2nd November - UK CB anniversary

Quote:
Originally Posted by SiriusHardware View Post
I won't hold you to it but it would be great if you could lay hands on one.

Doesn't even have to work as I have at least one coffin-pattern microphone with a no-name brand like 'Sharmans' on it, so I could make a Frankenmike out of two if necessary - the main thing is that York badge in the little panel below the microphone grille.
Had a rummage through my mic box but no branded York ones I'm afraid , and the only one I have is attached to my own York CB, but will keep my ear to the ground for you in case one turns up.
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Old 24th Nov 2022, 3:30 pm   #102
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Default Re: 2nd November - UK CB anniversary

Appreciated, thanks. This thread has bounced me into having a look to see if there are any in the usual places - there are a couple but they have matching radios attached and are priced accordingly.

If I bought a spares or repairs radio just for the microphone I'd end up fixing that radio as well, so I'd still be short one microphone.
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Old 28th Nov 2022, 5:55 pm   #103
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Default Re: 2nd November - UK CB anniversary

I've tested the Fidelity mic on the Fidelity 1000 and at first it didn't work as it had obviously been wired for a different radio - I think it just keyed it on to transmit as soon as it was plugged in and a quick plug into a Cybernet radio proved it had been wired to work on one of those sets. It looks like the next Fidelity radio in the series is the 2000, a Cybernet chassis radio, but this model doesn't use this style of microphone. The next Fidelity set is the 3000 base station model, which is another user of the 'Great' made chassis, similar, but not the same as the one used in the 1000 model. This 3000 model base station again uses the same style mic as the 1000 model, so the mic could have come from one of these, although the chap did say that it had come from a 1000. I think the bit that had probably been forgotten was that on the demise, or whatever, of the original 1000 radio, the mic had been re-used with another radio and wired accordingly, perhaps when the end of the cable was shortened.

I rewired the mic plug to the Fidelity 1000 standard and the microphone worked. Using another radio as a monitor I compared the Fidelity with Sharman's microphone and it sounded about the same as far as I could tell, although I thought that perhaps I could detect some small difference. I've since had a radio check with someone using both microphones and they said they sounded about the same - 'about' perhaps meaning that there was some difference, but probably nothing worth bothering about, so it sounds like the insert is still good.

Out of interest I measured the DC resistance of both microphone inserts from the plug when in TX and the Fidelity measured around 390 ohms, the Sharmans measured just over 450 ohms. I then measured a couple of other hand mics of both styles and an old Sharmans mic of the same style as the Fidelity measured just over 500 ohms and a more recent CRT coffin style mic measured around 460 ohms. The newer Sharman's and CRT mics, which are of the 'coffin' style measured within 10 ohms of each other. The older mics being the original Fidelity and the old Sharman's, both of the same case style measured over 110 ohms apart. I don't know what we can deduce from this, probably nothing. So the good news is that we have an original Fidelity badged microphone that appears to work well.
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Old 28th Nov 2022, 6:33 pm   #104
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Default Re: 2nd November - UK CB anniversary

I'm not sure why a dynamic microphone would be expected to degrade over time, unless there is the possibility of the permanent magnet losing strength? I suppose the diaphragm which is usually plastic / mylar could stiffen or even disintegrate over time.

The Fidelity 1000 style microphone was also widely used on Uniden (Particularly Cobra, Superstar) radios so if you are unhappy with the way the microphone works or measures for some reason you could always transplant an insert from a modern that-shape microphone into the original Fidelity microphone shell - provided the internal mouldings / receptacle for the microphone insert are identical.

I have sometimes been disappointed to find that they weren't when I have bought, say, a non-brand coffin microphone with the intention of harvesting its element to replace the element in an original branded coffin microphone, only to find that the inserts and the internal mouldings meant to contain them are a completely different physical shape. That being the case the one remaining option might be to carefully lift the Fidelity badge from the original microphone and put it on the clone microphone.

But anyway, you seem happy with it. I would say that having the correct matching microphone will have increased the value of the radio a little bit, I might also be tempted to transplant the intact (never shortened) cable from the Sharmans clone microphone onto the Fidelity microphone as well.

So, next step - 10.7MHz filter, whether active or passive?
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