[TenTec] Trading Radio's

[Jim Brown]

On 5/31/2014 3:44 PM, Robert wrote:
> First I was not in Dayton.

I was the guy who looked at the radios and identified what are very 
likely Pin One Problems in every one of them. The definition of a Pin 
One Problem is a connector whose shield contact (for example, the shell 
of an RCA or 1/8-in connector) does not contact the chassis directly, 
but goes to the circuit board, wanders around the PC board, and 
eventually gets to the chassis. This usually happens because it's 
cheaper to mount connectors to the circuit board, then poke them through 
a hole in the chassis. Virtually all of the rigs (Ten Tec, Kenwood, 
ICOM, Yaesu) are built this way. Elecraft is a partial exception, but 
they have some Pin One Problems too.

The "very likely" hedge is that it is entirely possible that the 
connector shells are actually bonded to the chassis by a mounting screw. 
This is not usually done, both because it costs more to build, and 
because most engineers don't understand (or even know about) the problem.

>Second, the pin 1 problem doesn't exist.

Bob, as much as I love you, you're dead wrong. :)

It's quite easy (although tedious) to test for Pin One Problems. All the equipment you need is a modulated RF signal generator. I use an HP that has built-in AM and FM 1 kHz tones. Set it for full output, connect the "hot" side of the generator output to the shield connection you're testing, turn on the 1 kHz modulation, sweep the generator from DC to daylight, and listen to the device under test for the 1 kHz tone. If you hear the tone, you have a Pin One Problem. Whether you hear it in RX or TX mode, and the frequency(ies) at which you hear it will depend on how the shield connection wanders around the PC board to find the chassis.

I used exactly this test to diagnose the RF feedback in my FT1000MPs, which showed up on the high end of 75M and on 15M. Injecting the RF at the mic connector, I heard the tone in transmit mode (listening on another radio), peaking around 5 MHz and around 21 MHz. The reference below is a paper I presented to the AES on this method.

http://audiosystemsgroup.com/AESPaperNYPin1-ASGWeb.pdf

John Henry was, as expected, quite busy in the booth, so I very quickly 
dragged him over to show him the problem, and suggested that he have his 
engineering people fix it. And, of course, he knows where to find me via 
email. :)

73, Jim K9YC