On Thu, 17 Feb 2005 11:37:30 -0500, Me wrote:

I took this radio and put it in my car (it's my only radio). When I connect it
directly to the Wilson 1000 barefoot, I get the same problem on SSB. However,
when I go thru the amp, it works perfectly, no power unless I modulate. This is
also true if the amp is turned on or off. It appears to be an impedance
mismatch. Since the amp input is a perfect match, the problem goes away, whether
or not the amp power is on or off. Here is the kicker. The SWR on my home
antenna is about 1.3-1.5 across the band.

Any suggestions?



Vinnie S.


Hi Vinne,
Over the years, I have seen this problem a number of
times, and I found one of the wire wound coils in the back of the
radio was overcoupled, and causing the nasty parasitic you speak of.
You key the mike on SSB, and, after you unkey, there is a full scale
carrier being transmitted...

Exactly.

Resetting the bias didn't help, however,
streching the coil, reducing the inductance always worked.
Unfortunately, Its been a few years since I have worked on a HR-2510,
but can tell you it is the coil is all the way in the back, near the
middle, right by the heat sink, and as I remember, parallel to the
rear panel, and has a ceramic cap in front of it, making it a little
hard to strech the coil. After you take the top off, key the mike on
ssb, and when the parasitic shows up, strech the coil until the RF
power meter drops back down to zero. After you do this, the parasitic
will go away forever. I have fixed at least 10 HR-2510s in this
manner, and never had a problem again. One more point worth mentioning
though. As I recall, I had at least one or two that the parasitic
"went away" when you took off the covers.. You still strech the coil,
and this will fix it, however, a little harder to identify the coil...
I'm sorry I can't recall off the top of my head which coil it is
exactly, but its not hard to find.. If I had a 2510 in front of me, I
could look and tell you, but I don't... As there are just a few coils
that you can strech, you can do it trial by error, and if you choose
the wrong coil, just push the windings back. Anyway, best luck! es 73
Tony..


I will take a look. Togerbird also emailed me, and said to put a mica insulator
between the final and chassis. Since the transistor was not using the chassis as
common, having it ground to the chassis causes this problem.

Here is his comment:

"You need to add an insulator between the final and the Heatsink.
Simply unscrew the final mounting screw, and you should be able to slide a mica
insulator between the final and heatsink.


Make sure to use heatsink compound on both sides of the insulator.


Now for the reason: Uniden chose not to use an insulator. The mounting tab of
the final is Power ground. (emitter)
The heatsink is Chassi Ground. Connecting the final emitter to chassi ground (at
the mounting Screw) can sometimes cause an RF Ground loop."

Anyway, I will take a look at your solution too. Thanks.


Vinnie S.