[TenTec] Scout 555 garbled SSB TX.

[James Griffith]

I have a Scout that has developed what " I " think is a problem with the radio it self.
I have used the Scout on a "stiff" well regulated power supply. I noticed no real problems with it, in fact, I liked the radio.
Then one day my power supply developed a problem in the current regulator, and would not allow the proper amount of current to be delivered. 
I had another radio with a built in power supply and used that radio until I sold it, and went back to the Scout. I put the Scout on a Sears Die Hard Deep Cycle battery. That's when my problems started.
I noticed that I could now here myself in the Scout speaker on SSB. Other stations told me I was garbled. In playing with the mic gain on transmit I noted that the I could put the radio into oscillation by raising the mic gain to high. I also noted that the mic gain was very sensitive and to get the ALC light only just flash on voice peaks I had to have the mic gain so far down, (9 O'clock position manual suggests was to high) so far that it was almost off.

OK. So I put the radio on a nice 50 ohm load. Mic and mic cable were like new. My idea here was to make sure no RF was getting back into the radio. Cable to load was only two foot long. No change. Radio was still bad. Could here my self in speaker, and mic gain was very sensitive. 

I called Ten Tec. The tech. there told me it was very common to hear you self in the speaker on the Scout. But I did not remember every hearing myself in it before. He also said the Scout is voltage sensitive. That there could not be more that .2 volts drop between the power supply connection and the cable connection on the back of the radio. The Scout was a computer controlled radio and voltage sensitive. 

My own thoughts were, that with the size of the wire on factory supplied DC cable, at ten amps one could easily get more than .2 volts drop across the cable. I did not fell like I found out anything. He did say I could send it in and they would check it out, which is the very reason I bought TT in the first place, "service".

I went back and measured the voltage drop at the back of the radio by putting the radio in "tune" and looking at the drop without full power. The thing dropped from 12.2 to 10 Volts. What the #$%^%&*.  I put that battery on charge and measured it on a regular bases until I knew the battery was fully charged. In this case with my charger and meter the best I could do was about 12.7 volts DC which is a good charge.

On "tune" now the voltage drop was about .5 volts across the cable. We I talked to my friends on the air they said I was understandable, but that I still had a garble to my voice. I have and Autotuner between the radio and a resonate dipole antenna. I have separate dipole for 80, 40, and 20. 

The mic gain is still very sensitive, but does not go into oscillation when turned up now with not modulation. 
I have a hard time believing that this radio is that voltage sensitive. I have ran 100 watt radio of a battery for weeks at a time before charging with no problems. I will probably send the radio to TT, but was wondering if there are some other Scout owners out there that have had similar problems, that are now cured.

The only thing I have not done it get another "stiff" AC supply back on the Scout. But I plan to take it mobile, and if I am having problems now they won't get better mobile. I think something's wrong with the radio myself. What do you think.
Power does not seem to be affected. 20 watts on tune and 50 with the mic.

Jim, WA7NDD


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