ARC5 GO-GO Modulator

My old 75M AM/CW ARC-5 Mobile station setup drew some interest, and I wanted to explain the Solid State Modulator. I get around the safety issue of putting HV on a backwards 6.3V Filament transformer by using the Modified Heising system.

[@tennesseered586]

Now that is old timey ham radio, by golly.

[@docfoot316]

Greet to see this arc 5 equipment ,a very handy circuit Mike ,i will try this ,many thanks.

[@MIKROWAVE1]

Not used much this way nowadays!

[@mikebracey8832]

Mike, thanks for the modulator video.

[@W1RMD]

Great Mike! Thanks for sharing and explaining the circuits so well. All you need now is a yellow car to put it in!

[@MIKROWAVE1]

I had a buddy who was promised a free paint job for his Volvo from a guy doing fleet cars. Next time I saw it, I thought it was a state vehicle - bright orange yellow!

[@W1RMD]

@@MIKROWAVE1 Ha ha! But it's free!

[@olafelsberry420]

Doing a little bit of reading 75 m radio is on shortwave radio.

[@W4BIN]

The MOSFETs type IRF840 have integral reverse connected diodes, the 1N4001s should not be necessary. Ron W4BIN

[@SergiuCosminViorel]

what is that "keep alive" circuit?

[@playitlouder451]

Why not run the 120 V winding to the audio plate inputs on the modulation transformer, getting rid of the cap? I guess you had a reason?

[@MIKROWAVE1]

Good question! The modulation transformer might well have worked in this way to some advantage due to the ratio, but it adds another variable. The choke idea is quite forgiving.

[@K1OIK]

Can you use this in the afternoon (PM)?

[@MIKROWAVE1]

AM only - In the PM, we let the LIDS er I mean kids, leave class for the day.

[@gretalaube91]

But Mike, where's the XYL gonna sit? 73 es gb, W3IHM

[@MIKROWAVE1]

Truth! Problem solved with my old 1966 Belair I had in College!

[@Dazzwidd]

Now that is game, using that mobile 😅
I would be expecting a short circuit to gate crash the party

[@MIKROWAVE1]

AH yes. Very possible.

[@stevenbliss989]

I must be blind or something, because the circuit as shown would cause continuous conduction from +13.8 through the transformer and through the body diodes in the IRF840 (odd choice for low V btw) to ground????? What am I missing????? And why use 500V mosfet for a low voltage stage????? The diodes IN4001 parallel with the mosfet for a two way diode pair (the other being the mosfet body diode, so what is that about???? That part of the circuit makes no sense to me, again, what am I missing??????

[@MIKROWAVE1]

The body diodes and the redundant protection diodes are the same polarity and should be reverse biased to the +.

[@SergiuCosminViorel]

Reviewed this, and discovered it is not as good solution/idea as you believe.
It is good for the transformer on the audio part, but no good for the big inductor on the supply part for the radio amplifier.
This ARC-5 Go-Go is not some genius idea, it is a surrogate, with no better performance than the simple one transformer idea.

[@AdamosDad]

✋73's🎙KD9OAM🎧