[TenTec] Super feedback on using Yamaha CM-500 with TT Orion II/any ideas about getting rid of RF pickup on electret elements?

[Jim Brown]

Hi Steve,

The amount by which you needed to increase the gain in the Orion is 
approximately the attenuation of the pad. I strongly recommend against 
using such a pad external to the radio on a microphone. A pad IS usually 
needed when we feed a Line Level signal to a mic input. I don't know 
anything about the Orion, so can't help with adjustment of controls or 
the pin-out of connectors. You've got to look that up in the manuals.

I know that K8JHR wrote a QST article recommending it. Nothing personal, 
but I'm an EE and audio engineer by profession. He's not. :) Last I 
heard, material for QST is not reviewed for accuracy, and I cringe every 
month at least once.

As to RFI -- carefully look at where the shields on the mic cable are 
connected at the rig. The ONLY proper connection of a cable shield is 
the CHASSIS. Many (most?) rigs screw up and connect it to the PC board 
instead. They call it "mic ground." Such a failure to connect the shield 
to the chassis is a MAJOR cause of RFI.  In my rigs, if the connector 
shell is bonded to the chassis, that's where I connect the mic shield. 
If you are able to connect these shields to the chassis (DIRECTLY), it 
will likely solve your RFI issues. Both mic and headphone cables can 
couple RFI via this design error.

Neil Muncy, ex-W3WJE (SK) is generally credited with discovering and 
publishing about this in the Journal of the Audio Engineering Society in 
1995. Because Pin 1 of the XLR connectors is the designated shield 
contact, he named it "The Pin One Problem."

All the radios I looked at in Dayton booths last year appeared to have 
Pin One Problems at most of their accessory connectors. The tell-tale 
clue is a connector mounted to a PC board poking through a hole in the 
chassis.

There's a lot of tutorial material on my website about The Pin One 
Problem. k9yc.com/publish.htm

73, Jim K9YC