[TenTec] Interesting problem and solution

[Ken Brown]

Hi All,

I have an Omni VI and a Titan. I recently changed the key out to tx 
enable cable to what I thought was a better cable, even though it was 
working fine. The origninal cable, that worked, was just a plain ten 
foot long skinny stereo audio phono plug to phono plug cable ( using 
only half of the cable ) and the "better" cable is a six foot Radio 
Shack "Gold Series" Audio/Video cable, which appears to be made from 75 
ohm coax.

With the "better" cable on 160 meters the transmitter would lock up 
whenever the amplifier was putting out more than 500 watts. The watt 
meter would indicate power output, and the side tone was gone, unless I 
continued to intentionally key the transmitter. Reducing drive from the 
Omni, or detuning the amplifier to reduce output to below about 500 
watts, would unlock the system. Same thing either to a good dummy load 
or to an antenna.

Putting back the cheapo, skinny, longer cable made the problem go away. 
At one point I tried a couple of turns of the "better" cable through a 
split ferrite core. That did not fix it.

I'm sticking with the cable that works for now. I am interested in 
opinions about what is wrong with the "better" cable. Lower capacitance? 
Would some additional bypass capacitors on the tx enable in the Omni 
make it work with either cable? I have the amplifer and radio grounds 
connected with RG-8 outer sheild braid, and am using 1/4 inch Andrew 
Superflex Heliax between the Omni and the Titan. It did the same thing 
with RG-58. I just used the overkill heliax cable just because it was handy.

Thanks,

Ken N6KB