[Elecraft] Background Noise with Mike Plugged in to Rear, Mike Jack

[David Herring]

I don’t disagree with K4TAX.  It’s up to the operator to work out RFI at one’s station.

But for the sake of clarity to those that may read this thread later…

The rigs in question in this part of the thread are the K4.

Every component of my station is bounded and grounded per K9YC’s publications. My antennas are effectively common mode choked both at the feed point and at the entry point to the shack (the latter demonstrably reduces received noise at my noisy QTH).

I am unaffected by RF at the operating position in the sense that I don’t get burned and none of my peripherals (such as a PC and monitors, for example) display any evidence of RF at all. The only issue here is what appears to be RF feedback getting into the audio when using a CM-500 plugged into the rear panel mic jack and, as I discovered later, a D-104 plugged into the front jack. Neither mic is shielded and neither uses twisted-pairs in their cables, so it is possible that at least some of the problem lies not with the station but the mics themselves.  Quite interestingly, another mic didn’t exhibit the problem here at this same station.

So is there RF at my operating position?  Well to state the obvious, I guess there must be at least a little or else this would not happen.  But until I find where it’s coming from, a "band-aid” (common mode choke) is an appropriate way to continue safe operation.  This band-aid may also be appropriate to augment components that can’t readily be fixed otherwise.

My comment about Elecraft looking at the radio for RFI issues was solely in response to another post in this thread where it was stated that Elecraft was ALREADY looking into the rear panel mic jack for RFI, which made me wonder if there was a known problem. IF that is true, then maybe looking at the front panel jack may be advisable. Otherwise I agree it’s not up to Elecraft to work out RFI issues at an individual’s station.

73,
Dave - N5DCH




> On Nov 24, 2021, at 8:11 AM, Bob McGraw <rmcgraw at benlomand.net> wrote:
> 
> Running my K3S, KPA500 and working 160M - 6M at 500 watts, using either a mike into the front of the radio, or my headset into the back, I experience NO RFI issues.  I don't have any toroids on any cables either.   I also run digital modes with a single USB cable between the computer and the radio.  All of these inputs/output stay connected all of the time.
> 
> As to using toroids, refer to the work that Jim, K9YC has written and published.   If you experience RFI and use toroids to resolve the issue, you have only put a band-aid on the wound.   I suggest looking at the antenna system, feed line system, and bonding of equipment cabinets to reduce RF at the operating position.
> 
> I don't see this as a need for Elecraft to look at the radio for RFI issues.  To many hams use the K3 series successfully without RFI issues.
> 
> 73
> 
> Bob, K4TAX
> 
> 
> On 11/23/2021 9:28 PM, elecraft-request at mailman.qth.net wrote:
>> I also had RF problems with the CM-500 plugged into the rear mic jack.  The solution I?ve implemented so far was to wrap about 13 turns of the CM-500?s cord around a #31 toroid. It both shortened the cord which was way too long for my shack and eliminated the RF problem. A two-for-one solution.;-)
>> 
>> On rare occasions I like to use my D-104 mic in the front panel jack.  It too is adversely affected with RF issues.  As soon as I get a moment I?m going to try wrapping it?s cord around a #31 toroid and hope it works as well there as with the CM-500.
>> 
>> I hope Elecraft is looking at the front panel mic jack as well as the rear when looking at solving the RF issue.
> 
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