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Hopefully back at it




 
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KQ6F
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« Reply #25 on: November 16, 2020, 07:11:40 PM »

Pat -

If I understand correctly, what you intend is to rework the transformer to get about a 7 ohm load resistance and apply about 60 volts to the RF deck.  That would cause 8.6 amps to flow - way beyond the capability of your power supply.

Rod
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N4LTA
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« Reply #26 on: November 17, 2020, 01:33:27 PM »

No, I was thinking 15 ohms, but I will probably remain at 7 ohms as Wayne and run at a lower voltage. My amps that were lost in the fire ran at 125 volts or a little more as did Nigels.

Pat
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vk3alk
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« Reply #27 on: November 17, 2020, 05:32:35 PM »

Hi Pat....

If it was my Transmitter would leave it at 7R .....
With your Power Supply levels you should achieve a comfortable power level of around 200 Watt carrier and fully modulate it....

Just a question .... is your 125 volt power supply variable and is it regulated ?
Wondering how you will tune up or check SWR and those things which are normally done at lower safe levels ....

Build your TX first before the Modulator so you know what the loading is and then you can design your PWM LPF accordingly etc:

It will end up a being a good AM Transmitter.... Cool


Wayne
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« Reply #28 on: November 17, 2020, 05:41:46 PM »

Yes - variable and current limited and I have a variable 0-60 volt 10 amp supply that I just got to replace some burned up stuff.

Both are nice current limited linear supplies.

The replacement cost insurance left me with some nice choices.

Pat
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vk3alk
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« Reply #29 on: November 17, 2020, 05:44:30 PM »

Ohhh it seems to be one of those weeks...
I'm speaking without thinking through things...
Your Power Supply is only 120 volts at 3 Amps....

You will not be able to fully modulate your TX at 200 Watts ....

You may have to run at a lower power level or better still build another HV Supply...



Wayne
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vk3alk
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« Reply #30 on: November 17, 2020, 05:49:12 PM »

Hi Pat...

I was posting as you were posting......

Ok on the variable supply .... great....

Just built it up and run at a power level that is comfortable for your supply etc: and maybe higher power can come at a later date  Smiley Smiley



Wayne
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