Homebrew AM transmitter

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w3jn:
As I said, Bill, there's nothing wrong with that at all.  I once built a pretty fair copy of a Squires Sanders SS-1 receiver  :P

He asked a question, I gave an opinion.  Sumpin like this, there is no right or wrong - my opinion, based on experience, is just as valid as anyone else's.  If he didn't want an opinion he shouldnta asked.

Mike, is this gonna be a single band xmitter, multi bands, what.  If it's just gonna be 75 meters, dispense with all the mixing and just run a straight VFO.  It's prolly easier to build a 160 VFO and multiply it up with a single class C doubler.  The trouble with homebrewing mixers is you gotta take a lot of care in shielding and bypassing or unwanted signals will sneak thru.  Not to say it can't be done but not a great plan for a first project.

The SB400 iron definitely will NOT handle 100W AM plate mudulated (remember your PEP is gonna be 400W or so).  It's made for SSB where the average power is very low.  My SB-400 is good for about 20W of AM and the power tranny gets pretty warm at that.  Given the crummy efficiency of the linear finals in the SB-400, and let's take into account the power needs of the mudulator tubes in your planned xmitter, I'd SWAG that the SB-400 iron isn't good for any more than 40W or so plate modulated.

w5rkl:
I agree, the 400's power transformer is not going to work. I honestly don't know why I even
thought of using it.

The xmtr would initially be single band.

Right now, it's just an idea, something I thought would work and work well.
This hobby is about learning, experimenting, trying different things, and even falling on one's face
to only get back up and try again. One never learns a thing without trying. Whether I would
succeed or not I don't know. I do know I am willing to try. :)

73's
Mike

w3jn:
You have the right attitude for sure.  I've found the best way to learn is to build something that doesn't work  ;)

Anyway there's no reason why you couldn't build up something using the stuff you have; perhaps a pair of 6L6s mudulating a single 6146 using the iron you have.  Build up a VFO for 75, buffer it with a 6AU6, driver would be a 6CL6 or 12BY7.

I'd be willing to bet, though, that Tom K1JJ's Tesla 360 pair a 813s mudlated by a pair might just about fit in that Apache cabinet, sans power supply though  ;D

WD8BIL:
Mike.... just try to get a bigger transformer for the final plate supply. I'd hate to see you go thru all that work for a 25 watt carrier.


Quote

Thanks WD8BIL and W3JN for your "colorful" and "unsupportive" comments, they were really uncalled for....




Considering this is our first encounter... I'll forget you said this. No harm done.
Give us 6 weeks..... we'll grow on ya  :)

The Slab Bacon:
Time for my 2 cents worfh:  Dont forget that the plate tank circuit ib those SB series radios is too close spaced to take plate modulation at 800V. It will most likely zorch over. It wuz designed to run as a 100w PEP leenyour amplifier.
     
                                                             The Slab Bacon                                 
                       

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