Saturday, March 1, 2014

CHN 80-20 tranceiver continued

I fixed the problem with the RIT. It was wired incorrectly.

The TX/Rx leds now work for both 80 and 20 meter. These too were wired incorrectly.

Somehow I made shortcircuit somewhere. This blew a BD137 power transistor.
Fortunately I had a few more in the junk box.

At 80 meters I was able to get a bit more than 10 Watts CW. SSB however was at 3 Watt max.
I have checked all circuits. They seem ok. I fixed it by making a small mar 4 based amplifier. Now I get 10 Watt PEP out. Current is 3 Ampere at 13.8 Volt

On 20 meter it does not work that well. Output is 3 Watt PEP. The input signal is according to spec.
Looking at the signal levels in the PA module it seems that I cannot input more signal.
More signal will cause an distorted output signal. It should be possible to get 10 watts at 20 meter though. I have another power module without transistors. I will try 27 MHZ transistors instead of the BD137. I hope that does the trick.

One of the remaining problems is the enclosure. I need to make a cover for the top left right and the bottom. I hope I can get some aluminum cheap.