DTB Radio in Carlisle, PA

He's definitely mentally ILL No doubt.... I don't get that S--T NEVER WILL.LOOKING AT PICTURES OF NOT EVEN A FULLY DEVELOPED WOMAN.... #### I CAN'T FIND MY GUN

 

It looks like DeVry University forgot to teach their students the importance of keeping their RF test equipment calibrated.
This radio was sent in by one of David Bupp customers.
Definitely better work than most.


This is what it looks like when a radio sounds good but has a very short transmitting range.


Hopefully Dave sees this so he can make the necessary corrections to his bench to improve the consistency of his work.

 

Not the 1st i have been told about commin from DTB..

 

Believe it or not that work is better than most of what's out there. That's a perfect example of a radio that sounds just fine but would disappear quickly out of my receiver within the first eight miles.

 

Just curious, the service manual says the 98vhp should be set for 65 watts dk and the voltage regulators on the amp board set to 4.0 volts, since this radio uses the 520 mosfets. What I'm wondering is what should the driver and finals be set for? My new 959b had both the driver and final bias set for 4.20v right out of the box. If I set them to 3.5 and 3.75, I couldn't get dk over 3 watts. Set back to 4.20 on both I could turn it up to 10 watts. Looks to me like the 520 mosfets should be biased at 4.0 to 4.20.
Comments?

 

Each radio requires different bias voltages due to sloppy tolerances. Adjustment should be made to bring all the stages into linearity.
Here we see three nonlinear stages.


Sometimes it's necessary to replace all the finals to eliminate IMD as seen here with a problem mosfet which Dave seems to have overlooked. The service manual is completely useless for that particular radio and anyone who follows the service manual is going to have serious problems and blame the manufacturer for the dirty signal. It's critical to adjust bias voltage using a scope until you see the curve of the different stages superimposed on each other working in unison with zero IMD.