On 10/27/2010 5:26 AM, Rob Atkinson wrote:
>> The next AES Convention will be held in San Francisco
>> next weekend. If you have time, we can walk the show floor together and
>> I can show you some Pin 1 Problems. :)
>
> Jim, what method do you employ to find the Pin 1 problem on a piece
> of equipment out on a trade show floor? I assume it must be a fairly
>
> simple check I can employ in my ham shack. tnx
On the show floor, it is often easy to spot them with a visual
inspection. What you're looking for is a shield connection that goes
directly to the shielding enclosure. If it does NOT, but goes to the
circuit board and then to the enclosure, it's a pin 1 problem.
Connectors that are mounted to the circuit board and sticking through
holes in the enclosure without making contact are almost certainly Pin 1
Problems.
There's an AES paper on my website that shows how to use a signal
generator to test for Pin 1 Problems. In ham gear, you inject the
signal between the shield contact and the chassis, and listen to the
transmitted output. If you hear the generator in the transmitted
output, you have a Pin 1 Problem. You can do this with an audio
generator to look for hum/buzz susceptibility, and with an AM modulated
RF generator to look for RFI susceptibility.
When I bought an FT1000MP several years ago, I had RF feedback on 75M
and 15M. I used my HP8657A to drive between the shield of the mic
connector and the chassis, running the rig at flea power, and listening
on another RX. The generator was set for AM with it's internal 1 kHz
tone. I found susceptibility that peaked in the 5 MHz region and around
20 MHz. A multi-turn ferrite choke on the mic cable killed the RFI. At
one point, I owned two MPs, and they both exhibited the same problem.
In this test, it doesn't matter what frequency you're transmitting on,
because you're injecting RF with the generator, and because you're TX at
very low power.
The website is http://audiosystemsgroup.com/publish.htm Links to the
AES papers are near the bottom of the page. There are also several
tutorials that discuss the Pin 1 Problem, some written for audio folks
and some for hams.
73, Jim K9YC
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|