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Old 1st Sep 2021, 1:41 pm   #21
Ian - G4JQT
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Default Re: AM Conversion for CW TX

This is very closely based on the Codar AT5 - I've just changed the VFO for a crystal oscillator. The significant bit for you is probably the audio amp and the modulation transformer which just uses the mains side (with centre tap) of a 15 VA transformer with the secondary windings unused.

(Posting the whole article was easier than explaining the circuit!)
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File Type: pdf AT60b Signal_Issue_51.pdf (567.3 KB, 60 views)
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Old 1st Sep 2021, 3:06 pm   #22
AdrianH
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Default Re: AM Conversion for CW TX

Just a thought, how about an audio and modulator stage from the TR1998, it has valves and modulation transformers on it, drives a TT15 valve with anode mod. There is a compete stage for sale elsewhere or I could well have the mod transformer on it's own if I can find it.

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Old 1st Sep 2021, 6:51 pm   #23
John M0GLN
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Default Re: AM Conversion for CW TX

There is also this way of doing it,

John

http://ekladata.com/ddX2c-NG42DyDMPd..._cq_jun_56.pdf
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Old 19th Sep 2021, 11:01 am   #24
AndyWright
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Default Re: AM Conversion for CW TX

There is also a complete high level AM modulator available on ebay from time to time. It's from the PTR175 transmitter, and has 2 X 2E26 valves in it complete with mod transformer and audio preamp.

Andy
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