I use a Shure SM-58 mike with my K3S. It is a balanced dynamic mike.
It has an XLR at the mike and the 8 pin Foster connector at the radio.
I use good quality, 2 conductor, shielded mike cable.
It is wired as follows:
XLR pin #1 to Foster pin #8 {shield}
XLR pin #2 to Foster pin #1 {black}
XLR pin #3 to Foster pin#7 {white}
Operating 160M - 6M at 500 watts or less, I find no issues with the
wiring convention as it works very satisfactory.
73
Bob, K4TAX
On 6/11/2020 8:15 AM, Rich wrote:
Interesting stuff here. Since the original post was regarding the
Rear Mic jack. Would this method also be recommended for the Front
Panel Mic Jack also?
My guess is yes
Rich
K3RWN
On 6/9/2020 22:50 PM, Don Wilhelm wrote:
Joe,
I did not say anything to the contrary. The 'dongle' that I was
referring to is the connection to pin 1 which should be connected to
the outside of the K3/K3S enclosure.
73,
Don W3FPR
On 6/9/2020 9:13 PM, Joe Subich, W4TV wrote:
On 2020-06-09 8:14 PM, Don Wilhelm wrote:
So --- make an adapter so that pins 2 and 3 are connected to the tip
and ring of the mic jack,
No, no, no! The ring of the K3/K3S rear panel mic jack *IS FLOATING*.
Pins 2 and 3 of the XLR *MUST BE* connected to tip and *SLEEVE*.
73,
... Joe, W4TV
On 2020-06-09 8:14 PM, Don Wilhelm wrote:
So --- make an adapter so that pins 2 and 3 are connected to the
tip and ring of the mic jack, then add a one wire 'dongle' exiting
from the XLR plug that is connected to XLR pin 1. Connect that
wire to a screw on the chassis of the K3/K3S/KX2/KX3.
Noise, hum and buzz are then conducted from the shield onto the
"outside" of the radio enclosure where it should be - avoiding the
"pin 1" problem that K9YC often refers to.
For those not familiar with the "pin 1" problem, it is caused by
the jacks in the transceiver (or other gear) being connected to the
circuit board ground plane where it can couple into sensitive
circuits and cause coupling problems. Proper bonding between
enclosures following the path of audio or coax lines can minimize
that problem by keeping some of the noise, hum and buzz mostly on
the outside of the enclosure rather than injecting it into the
circuits on the board ground plane.
We did not have this problem when we mounted the jacks on the
enclosure rather than mounting them on the boards, usually isolated
from the outside of the enclosure.
73,
Don W3FPR
On 6/9/2020 7:47 PM, Joe Subich, W4TV wrote:
Correcting *ALL* the typos <G> ....
So which is correct?
They are electrically equivalent.
Pin 2 of the XLR connection is Mic+
Pin 3 of the XLR connection is Mic-
Pin 1 of the XLR connection is the cable shield (ground).
Mic audio is present between pins 2 and 3.
Pin 1 is nothing more than a shield and should be independently
connected to the *chassis at the jack*.
Good quality XLR cables use a *TWISTED PAIR* for pins 2 and 3.
That twisted pair is shelf shielding - particularly good for
rejecting hum. Connecting a shield in parallel with the wire
for pin 3 "unbalances" the twisted pair and makes it much
more susceptible to hum and RFI - particularly when the shell
of the 3.5mm plug/jack is not tied to the chassis/case of the
transceiver.
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