开云体育

Thanks for the info.? Looks like an easy way to bring the ubitx up a notch!!

Joe

VE1BWV

On Wed, May 16, 2018 at 3:51 PM, robert_kross via Groups.Io <robert_kross=yahoo.com@groups.io> wrote:

Good Afternoon,

Finally received and housed my ubitx. On receiving the PCB, I replaced the IRF 510 outputs with IRF 530's. These tend to run a little cooler and are just as inexpensive. I tested the output on 40 meters as it was at 25 watts at 14v drawing about 1.9 a. I also replaced driver transistors Q92,93,Q96 and 97 with 2 2N3553's.? I socketed the drivers so I could plug in various types. You can try 2N2219a but they tend to run a little warmer.? You also want to short the 22 ohm resistors off the emitters. I used Q93 and Q96 as they were furthest away from each other and provided space for a heatsink if needed. Lastly, parallel R961(2.2 ohm) with a 1 ohm 1/2 watt.? Be careful to shield the toroids with aluminum foil when soldering so as not to short them out (like I did). After removing C261 and C262 in the feedback circuit, I came up with at 14v: 27.16 watts at 20 meters, 31.78 watts at 40, and 36 watts at 80 meters. I am running a 7812 voltage regulator for the receive and transmit drive, leaving raw B+ for the outputs.? I am also running a microphone compressor. I have made 2 contacts (one 300 miles away and the other roughly 700 miles away).? Both contacts were impressed at the level of power I was using.? I must have a reasonable attic shortened dipole antenna.? Anyway, the 2N3553's barely get warm after keying up the microphone.? I calculated that the 2N3553's were only driving the outputs with 460mw.? I was planning to drive a linear amp with it, but now I will use it as a stand alone radio.? I have not heard of anyone doing this, so I thought I would throw this one out for consideration.

Regards,

Bob KD9ITL