[Heathkit] SB-300 Question

[Ron Youvan]

>> I just  received an SB-300 with a small problem. Before I dig into it, I 
>> figured I  would ask for hints.

>> Unit works pretty well as long as you leave the  outer jacket of the coax 
>> disconnected. When its connected the receiver goes  deaf.

> Great question, because I have an SB301 that does the same thing. The coax  
> is not shorted, and it happens even without the coax shield being grounded  to 
> earth. The unit receives fairly well with only the center conductor  
> connected. I also note that the chassis has a slight voltage on it. I get  weak sparks 
> when connecting or disconnecting the ground wire. I connected a  voltmeter 
> between the chassis and earth ground, and a voltage slowly swings  about plus 
> then minus 80 millivolts in a six second cycle. This might be normal,  I don't 
> know. But, I think the problems could be related because the  receiver blanks 
> out stronger from the coax shield effect when the chassis  is grounded. 
> Something is slowly charging and discharging,  but that's as far as I got.

   Try the same test using a gud receiver or transceiver with that antenna.  If you get
much more receive signal on the gud receiver while using the shield of the coax as part
of the antenna, (not grounded to the chassis) the SB-300/SB301 have a low sensitivity problem.
-- 
    Ron