KX3 need microphone help

[Jim Kutsch, KY2D-2]

I'm running a KX3 and KXPA100 here. Both are very early units but with the
latest firmware. All is fine with the Elecraft hand mic but I want  to use a
boom mic and foot switch. However, I'm having problems with two different
mics. In both cases, when power is set to more than 50W, the audio is
distorted. This happens with the Carolina Windham, the hex beam, and even on
a dummy load. I added a common mode choke but it didn't help.

 

The mic with the problem is an Electrovoice RE15 on a boom with its XLR
connection going into a HOSA splitter cable, TRS on the KX3 side and two XLR
connectors on the other. Thinking this old Electrovoice might be the
problem, I also tried a non-amplified D104 upgraded with a Heil HC5 element.
It's connected with a TRRS patch cable cut and hard wired into the D104
base.

 

The problem remains regardless of mic bias on or off and mic buttons on or
off. Anyone have any ideas? Or, can anyone recommend a mic and cabling
solution I can buy?

 

Thanks and 73, JIM, KY2D

 

 

 

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[Don Wilhelm-4]

Where did you add the common mode choke?  What is the choking impedance
of that common mode choke?  Take a look at the writings of Jim Brown
K9YC for effective common mode chokes.

The fact that you do not have the problem with the MH3 microphone
strongly suggests that there is not a problem with the KX3 or KXPA100.
Both microphones you mentioned are dynamic type and should have Bias
turned off.

You might check the coax connections and your coax jumpers.  PL-259
connectors should be fully seated and be given just a bit more
tightening than "finger tight" to make an effective connection to the
coax shield.  Use pliers to snug them up a bit after making them finger
tight.
Try different coax jumpers - it is not uncommon to have the connection
to the shield fail.

73,
Don W3FPR

On 12/30/2015 7:31 PM, Jim Kutsch, KY2D wrote:

> I'm running a KX3 and KXPA100 here. Both are very early units but with the
> latest firmware. All is fine with the Elecraft hand mic but I want  to use a
> boom mic and foot switch. However, I'm having problems with two different
> mics. In both cases, when power is set to more than 50W, the audio is
> distorted. This happens with the Carolina Windham, the hex beam, and even on
> a dummy load. I added a common mode choke but it didn't help.
>
>  
>
> The mic with the problem is an Electrovoice RE15 on a boom with its XLR
> connection going into a HOSA splitter cable, TRS on the KX3 side and two XLR
> connectors on the other. Thinking this old Electrovoice might be the
> problem, I also tried a non-amplified D104 upgraded with a Heil HC5 element.
> It's connected with a TRRS patch cable cut and hard wired into the D104
> base.
>
>  
>
> The problem remains regardless of mic bias on or off and mic buttons on or
> off. Anyone have any ideas? Or, can anyone recommend a mic and cabling
> solution I can buy?
>
>  
>
> Thanks and 73, JIM, KY2D
>
>  
>
>  
>
>  
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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[Bob McGraw - K4TAX]

Also splitting audio at mike levels can be a real problem as one "split"
can appear as an input to the other side.   Mikes should be connected
direct to one radio only.

As Don stated, PL-259 connectors need to be more than finger tight. I've
found many good looking PL-259 connectors which are exactly that, "good
looking" but found to be poor conductors offering poor RF path and
connections.

73
Bob, K4TAX

On 12/30/2015 6:47 PM, Don Wilhelm wrote:

> Where did you add the common mode choke?  What is the choking
> impedance of that common mode choke?  Take a look at the writings of
> Jim Brown K9YC for effective common mode chokes.
>
> The fact that you do not have the problem with the MH3 microphone
> strongly suggests that there is not a problem with the KX3 or KXPA100.
> Both microphones you mentioned are dynamic type and should have Bias
> turned off.
>
> You might check the coax connections and your coax jumpers. PL-259
> connectors should be fully seated and be given just a bit more
> tightening than "finger tight" to make an effective connection to the
> coax shield.  Use pliers to snug them up a bit after making them
> finger tight.
> Try different coax jumpers - it is not uncommon to have the connection
> to the shield fail.
>
> 73,
> Don W3FPR

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[Jim Brown-10]

On Wed,12/30/2015 4:31 PM, Jim Kutsch, KY2D wrote:
> The mic with the problem is an Electrovoice RE15 on a boom with its XLR connection going into a HOSA splitter cable, TRS on the KX3 side and two XLR connectors on the other.

I suspect it's a wiring problem. The RE15 is a dynamic pro mic and is
balanced; pin 1 is the shield, Pins 2 and 3 are the signal pair. To
connect any balanced dynamic mic to an unbalanced input (virtually all
ham rigs) connect either side of the pair to the shield and to the
sleeve of the Elecraft mic connector, connect the other side of the pair
to the "high" side of the Elecraft mic connector. It's easy to make an
adapter cable. Start with a female XLR3 connector and a male plug that
mates with the KX3. A piece of RG58 or miniature coax like RG-174 work
fine as a mic cable.

Turn BIAS OFF.

73, Jim K9YC


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