[TenTec] Trading Radio's

[Bob McGraw - K4TAX]

Older radios did not offer the high speed inputs and outputs being used for 
data.  These high speed circuits work in the RF range if one considers the 
data rates where analog circuits had limited frequency response.  There's 
also new high speed solid state devices that are more susceptible to RFI 
issues.  It just takes a lot more precaution when using this type of 
equipment.

73
Bob, K4TAX





----- Original Message ----- 
From: "Carter" <k8vt at ameritech.net>
To: <tentec at contesting.com>
Sent: Saturday, May 31, 2014 6:53 PM
Subject: Re: [TenTec] Trading Radio's


> 1) My apologies to you and Bob for the mix up.
>
> 2) Thanks for the interesting test outlined below.
>
> 3) The question begs to be asked: How come the older solid state radios 
> (like my TR-7) did not exhibit this problem using the same (close) antenna 
> in the same shack? More micro electronics today then back then? Older 
> radios built with proper grounding of the connectors? Same amount of RF in 
> the shack then and now, but apparently the RF was not finding its way into 
> the radio back then.
>
> 73,
> Carter   K8VT
>
> On 5/31/2014 7:08 PM, Jim Brown wrote:
>> 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
>
>
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