[hffenninger]

Built the Tubes and More AM transmitter kit and am enjoying learning the little fella's capabilities. Anyone else who has built this kit, please give me some pointers to optimize it's performance.

thanks
Frank

[Video: https://youtu.be/Bjh_hoSWQV8]

[KCMike]

 Sounded pretty good to me Frank and your radio looks good also. I have an SSTran AMT 3000 I built couple of years
ago. It does a good job. I don't know about the one you built but someone on here probably does and can make suggestions about tweaking it for best performance.

[Radioroslyn]

Found one in the box that I picked up at an auction a yr or so ago. Knew it was a broadcaster but didn't know it was an AES product till I saw it in there catalog a  month ago.
Did try it out. Has great coverage with no ground and just an antenna. No ground loop hum. The only issue is the audio quality could be a bit better.
With this type of transmitter(using a pentagrid tube) there can be some interaction between the oscillator and modulator causing frequency shift with the audio (part of the signal is AM but there can be some FM component to the signal too) which is undesirable.
I did play with it a little added a transformer the match the impedance from the computer out (low Z) to the input grid (high Z) and some loading. Wanted to try adding a little bias to the input to see if that will improves the audio but can't seem to find my little adjustable power supply.

Terry

[Mondial]

You can try changing the value of the cathode resistor to improve the modulation quality. This will effectively change the grid bias and locate the operating point of the tube on a more linear part of the curve. This graph is for the 6BE6, but the 6SA7 is very similar

[Image: http://www.wa2ise.com/radios/6be6g3.jpg]


I read somewhere that changing the resistor from 1 K to 500 ohms results in improved audio, or you can substitute a 1K pot and adjust for best output and quality.

This site goes into a lot of detail on the basic circuit and how it can be improved with negative feedback, etc.

http://www.wa2ise.com/radios/amxmit.html

[Radioroslyn]

Tnx for the link. Will give it a try.
Will we get a chance to have an
eyeball in a week and a half??

Terry

[hffenninger]

Tnx for the link. Will give it a try.
Will we get a chance to have an
eyeball in a week and a half??

Terry

??

[Ron Ramirez]

I think Terry was talking to Mondial.

[Radioroslyn]

+1

Terry

[Mondial]

Hi Terry,

I guess you are referring to Kutztown. Sorry to say I will not be there. Its the same weekend my daughter is coming home from college. 

[hffenninger]

I think Terry was talking to Mondial.

Hijackers...Thanks for the replies though.