Point On. Well stated.
73 Steve - W5JK
On Apr 28, 2010, at 8:52 PM, Gary Hoffman wrote:
> I have to say that the mere existance of a "pin one problem" (sic) is
> neither a necessary nor a sufficient condition for
> having Radio Frequency Interference (or even hum on the signal) in the
> shack.
>
> If it were a sufficient condition, then almost every shack - and certainly
> most all Ten Tec equipped shacks - would have serious
> RFI problems that would require remediation. This is self-evidently not the
> case. Most shacks do NOT have RFI problems.
> Some do of course.
>
> If it were a necessary condition, then no device NOT having a "pin one
> problem" (sic) would ever have RFI. This, self-evidently is not
> the case either.
>
> My point is only this. The problem of radio frequency interference is very
> broad, and covers a very wide range of causes and
> effects. If one does not take a wide view of this matter, one will have a
> very hard time solving RFI problems.....or, in fact, in
> understanding why they DON'T have RFI problems when they "should."
>
> Hence my reference earlier to the "old saw." I won't bother to list my
> educational background, my published papers, my experience in
> aerospace and electrical engineering, my patents, or anything else....since
> none of that would be productive, nor would it solve the
> original poster's (and many others too) technical problems. Responding to
> that kind of stuff just leads to flame wars and takes ones
> attention away from solving real problems.
>
> 73 de Gary, AA2IZ
>
>
> ----- Original Message -----
> From: "Jim Brown K9YC" <k9yc@audiosystemsgroup.com>
> To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
> Sent: Wednesday, April 28, 2010 10:46 AM
> Subject: Re: [TenTec] Orion II 15 m CW Transmit Power Fluctuation
>
>
>> On Wed, 28 Apr 2010 07:54:19 +0000 (GMT), QUENTIN COLLIER wrote:
>>
>>> Sorry to be a pain guys, but as someone who has recently joined this list,
>> can you please explain what the "pin 1 problem" is ?
>>
>> It is the improper connection of the shields of external cables where they
>> enter the rig. The only proper connection is the CHASSIS. Most rigs
>> connect
>> them to the circuit board on insulated connectors that are insulated from
>> the chassis. This causes any current flowing on the cable shield to flow
>> on
>> "ground" or "earth" busses, which then couples that current (noise, hum,
>> buzz, RF) into the rig, where it is amplified and/or detected.
>>
>> This defect was named "the pin 1 problem" because it was described in a
>> reasearch paper presented by Neil Muncy, ex-W3WJE, to the Audio
>> Engineering
>> Society in 1994, and subsequently published in the Journal of the AES in
>> June 1995. Largely as a result of that work, Neil was elected a Fellow of
>> the AES. The connector most used for pro audio is an XLR, and the
>> designated shield contact is pin 1. I'm told that the guy who first called
>> it "the pin 1 problem" was Berhard Weingartner, the founder and president
>> of Neutrik, the excellent connector mfr based in Lichtenstein, who was an
>> active member of the Standards Committee at that time. He has since
>> retired, but both management and engineering of that company are still
>> quite active in AES Standards work.
>>
>> In some bar conversation at technical meetings, Neil said that "most RFI
>> is
>> coupled by pin 1 problems." Between 2003 and 2005, I did some research
>> that
>> proved him entirely correct. My work is also published as several AES
>> papers. My papers, as well as several tutorials on RFI and other topics of
>> interest to hams, are on my website.
>>
>> http://audiosystemsgroup.com/publish.htm
>>
>> Our work led to several new AES Standards on EMC -- AES48, AES54-1, AES54-
>> 2, and AES54-3. They can be purchased from the AES website.
>>
>> It's quite easy for cable shields to carry RF currents if they are near a
>> ham transmitter or broadcast antenna -- those cables are simply acting as
>> receiving antennas. They will also carry leakage current from the AC mains
>> when connected between two pieces of equipment that are connected to
>> different mains outlets. That current is what we hear as hum and buzz. We
>> call it a ground loop, but it is really mains leakage current. A second
>> coupling mechanism for this leakage current is as IR drop in the shield of
>> unbalanced wiring.
>>
>> Most "RF in the shack" is coupled into equipment by a pin 1 problem. When
>> you kill RFI by placing a ferrite choke on wiring, you are killing the RF
>> current on that cable.
>>
>> 73,
>>
>> Jim Brown K9YC
>>
>>
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>
>
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