Author Topic: Mic audio Noise from K3/0 to Control RRC problem resolved.  (Read 5124 times)

W1AN

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I'm currently setting up another K3/0 (non-mini) twin system and experienced ground loop or noise ingress through the interconnecting mic cable. I've determined I could eliminate the noise by using a 600/600 ohm transformer directly at the rear mic jack on the K3/0 to supply the RRC control. This might have been my final solution but you cannot pass DC mic bias through a transformer if you need to use a condenser mic. My initial setup is thru the front K3/0 8 pin connector using the Heil Proset with a much lower audio level.

Close inspection of 2 of the "factory" AUX/MIC cables show no conformity to the schematic provided in the manual! The cables provided are lengthy CAT5/6 4 pair cable with short breakouts at the end with the PTT RCA connector and 1/8" mic connector. This factory cable is unshielded. Wires used for mic audio and mic return are from separate pairs, not from one twisted pair. Consequently, shielding is close to non-existent. PTT wiring is similar. Making up my own cables with longer shielded wires connected to a very short piece of CAT 5/6 at the RJ45 work much better! Leaving a long length of exposed mic wire is not good practice. This may work OK with high level signals and the majority of installs, but is a no-no for low level mic signals. A shielded piece of CAT 5/6 might also work for a starting point. If you are experiencing noise ingress you may wish to look at the cables.

73, John W1AN
« Last Edit: 2016-02-04, 20:06:06 by W1AN »

K1IKE-Joe

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Re: Mic audio Noise from K3/0 to Control RRC problem resolved.
« Reply #1 on: 2016-02-06, 16:06:23 »
The E850511 cable used to connect the RRC1258 AUX/MIC connector to the Elecraft MIKE MONO & PTT IN connectors can cause microphone digital noise.  We found this a problem when using a Heil headset on a K3/0 setup.  We have two of the  E850511 that are wired the same way.

The problem is caused by a "split pair" in the E850511 cable.  Pins 3&4 of the CAT5 cable that is used to make the E850511 is not a pair of twisted wires.  (See attached photos)  This is how the stock cable is made:

RJ45 pin      Nomenclature
3-GREEN/WHITE   MIC
4-BLUE         MIC GROUND
5-BLUE/WHITE      PTT
6-GREEN      PTT GROUND

In order to keep the MIC leads on the same twisted pair, this is how I rewired the RJ45 on the cable:

RJ45 pin      Nomenclature
3-BLUE         MIC
4-BLUE/WHITE      MIC GROUND
5-GREEN      PTT
6-GREEN/WHITE   PTT GROUND

I then rewired the 1/8" plug and the phono jack accordingly.  This solved the digital noise problem on the microphone audio.  Others that have a noise problem might try this fix.

It appears that if a stock CAT5 or CAT6 is used to make a cable for any other radio that uses the RRC1258 AUX/MIC connector for audio, this problem may happen.  I opted to keep the strapping in the RRC1258 standard for clarity.

Joe, K1ike
« Last Edit: 2016-02-06, 16:08:30 by K1IKE-Joe »

sm2o

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Re: Mic audio Noise from K3/0 to Control RRC problem resolved.
« Reply #2 on: 2016-02-08, 13:10:31 »
I will just clarify that this is not the cables delivered by Remoterig.

73 de mike

K1IKE-Joe

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Re: Mic audio Noise from K3/0 to Control RRC problem resolved.
« Reply #3 on: 2016-02-08, 16:54:34 »
Interesting.  I was under the impression that these cables came from HRO and that they sourced them from Remoterig.  I will try and see where they obtained the cables from.  My apologies if you took this as a fault of Remoterig.  I was just trying to alert the group of a possible problem.

The problem seems to be that the diagrams from Remoterig show pins 3&4 as the mike audio leads.  This in itself is not an error on the part of Remoterig.  The problem is when someone uses a standard CAT5/6 cable to make the cable for the AUX/MIC jack.  When one of the CAT5/6 cable connectors are cut off and the cable is used, pins 3&4 end up being a split pair.  Now this does not always cause a problem, but did with the Heil headset.

Does Remoterig have a cable available that is wired the proper way?

Joe

sm2o

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Re: Mic audio Noise from K3/0 to Control RRC problem resolved.
« Reply #4 on: 2016-02-09, 12:33:02 »
Hi
To me it looks like the cable Elecraft produce. We do not have exactly those cables. We have a cable kit for K3 twin but it's different cables designed to connect to the front mic connector.

http://shop.microbit.se/webshop/catalog/product_info.php?cPath=24&products_id=72

73 de mike