[TenTec] Orion II 15 m CW Transmit Power Fluctuation

[QUENTIN COLLIER]

Many thanks to Jim for taking the time out to provide a detailed explaination for me!

73,



Quin G3WRR



----- Original Message ----
From: Jim Brown K9YC <k9yc at audiosystemsgroup.com>
To: Discussion of Ten-Tec Equipment <tentec at contesting.com>
Sent: Wednesday, 28 April, 2010 15:46:18
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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