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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 25th Jul 2014, 2:23 pm   #101
G6Tanuki
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Default Re: Activity on 80 metres?

Or rather than a big MOSFET, you could undoubtedly use one of the high-voltage switching transistors from a dead compact-fluorescent lamp as the modulator stage.

I recall back in the 1980s building 2-stage 'high voltage class-A' transistor amplifiers using a standard valve-type output transformer and something like a MJE340 plastic power TO220 transistor or whatever could be scavenged from dead 'hybrid' TVs . DC stabilisation was by taking the voltage across the MJE340's emitter-resistor as bias for the driver stage (which was usually something like a 2N3053). Gain/power/quality was as good as the likes of an ECL86 and the component-count was lower.
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Old 25th Jul 2014, 6:03 pm   #102
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Default Re: Activity on 80 metres?

Here's an article from 1986. It's a transceiver for topband, but could probably be modified for 80 without too much difficulty. The IFTs in the receiver are a but rare now, but all other components should still be obtainable.

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Old 25th Jul 2014, 6:06 pm   #103
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Default Re: Activity on 80 metres?

Here's the last two.
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Old 25th Jul 2014, 6:24 pm   #104
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Default Re: Activity on 80 metres?

They were talking about top band nostalgia in 1986. (A mere 28 years ago!)

Actually, I'd like an AT5 as I still have a T28 receiver.
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Old 26th Jul 2014, 3:31 pm   #105
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Default Re: Activity on 80 metres?

One post moved to a new thread: https://www.vintage-radio.net/forum/...d.php?t=107966
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Old 26th Jul 2014, 4:02 pm   #106
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Default Re: Activity on 80 metres?

Hi Aub,

Worth noting that there's an error on the modulator circuit. There should be a capacitor between the first anode of the ECC83 and the slider of the gain potentiometer - otherwise the second triode is not going to be very happy! (In fact I would also have put the pot the other way round, i.e. slider to grid, to avoid changes to the roll-off frequency with mod level setting). You wonder sometimes whether the authors ever build and test their own circuits...
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Old 26th Jul 2014, 5:25 pm   #107
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Default Re: Activity on 80 metres?

Hi Keith,

Oh yes. I hadn't noticed that or, at least, I can't remember noticing it. I've had those magazines since they were new and I never built the thing, although I always fancied making the receiver and moding it for 80. I have the IFTs, from when they started making them again, briefly, in the late nineties.

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