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Old 18th Sep 2021, 4:17 pm   #1
G6Tanuki
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Default Valve MF pantry transmitter.

I got bored... And built a MF pantry transmitter using an ECL80.

The triode is an xtal oscillator which feeds the output stage which is screen modulated using a backwards connected transistor radio 'LT44' driver transformer to connect to the high impedance headphones output of the ancient Nokia phone I use for streaming.

Feeding audio to my Roberts R707 it sounds rather good. Currently listening to a bunch of Dusty Springfield tracks through ithough.... The R707 has some serious punch and really handles Dusty's wide open vocal style well.

Play loud and forget about the neighbours!!
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Old 18th Sep 2021, 4:47 pm   #2
Electronpusher0
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Default Re: Valve MF pantry transmitter.

Sounds good, any chance of posting the schematic?

Peter
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Old 18th Sep 2021, 6:28 pm   #3
G6Tanuki
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Default Re: Valve MF pantry transmitter.

Quote:
Originally Posted by Electronpusher0 View Post
Sounds good, any chance of posting the schematic?

Peter
Sure - Ii'll post a schematic and suggested component-values [hand-drawn, I no longer have an Autocad license] in a couple of days.

It really does seem to work well, it's great to be hearing Dusty's wonderfullyfully full-on vocals resonating round the summerhouse.

[Historic sidenote: I'm using a 1.333MHz carrier crystal that first did duty as the clock-oscillator in a 1970s |D|I|G|I|T|A|L| PDP8E.]
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Old 18th Sep 2021, 6:49 pm   #4
paulsherwin
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Default Re: Valve MF pantry transmitter.

The usual caution applies: you should watch the range, depending on your domestic circumstances. Even a weedy ECL80 can chuck out quite a bit of power with a half decent aerial.
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Old 18th Sep 2021, 6:59 pm   #5
Electronpusher0
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Default Re: Valve MF pantry transmitter.

Thanks Paul, noted. I certainly do not want to go outside the boundary of the house.
Peter
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Old 18th Sep 2021, 7:16 pm   #6
G6Tanuki
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Default Re: Valve MF pantry transmitter.

For reference, the 'output' part if my ECL80 panty-transmiter consumes 10mA at 220V.

It's not in in any way coupled to any of my 1.8/3.5/5.5MHz "cloudwarmer "NVIS ham-radio antennas.

Though part of me wonders just if there's anys sort of "DXCC" certrificate for MW pantry-transmitters or their Band-II FM equivalents.
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Old 18th Sep 2021, 7:54 pm   #7
turretslug
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Default Re: Valve MF pantry transmitter.

Reception report from OFCOM?
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