[Elecraft] K3: 6M SSB audio hash

[James C. Hall, MD]

Good thought, Phil. Actually I have an external speaker plugged in, a NCS 8
ohm, and I did try unplugging the speaker to see what would happen. Same
story - no change in hash. The answer has got to be in the cable itself. If
it's verified with a solution, I can actually have another cable made.

73, Jamie
WB4YDL

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Phillip Buckholdt
Sent: Saturday, June 07, 2008 7:34 AM
To: Jim Brown; Elecraft List
Subject: Re: [Elecraft] K3: 6M SSB audio hash

Do you have anything plugged into the rear headphone jack ?  I have a pair 
oof Bose powered  speakers plugged in  and at higher power levels, I get 
severe RFI,
. With the same speakers on my K-2/100 or my IC-7000 I have no trouble. When

I had a IC-746 I had no RFI in the speakers.

     Just a thought.

     Phil K8MBY


----- Original Message ----- 
From: "Jim Brown" <jim at audiosystemsgroup.com>
To: "Elecraft List" <elecraft at mailman.qth.net>
Sent: Saturday, June 07, 2008 12:45 AM
Subject: RE: [Elecraft] K3: 6M SSB audio hash


> On Fri, 6 Jun 2008 21:22:41 -0400, Joe Subich, W4TV wrote:
>
>>There is a significant problem in using balanced input with any
>>"amateur mic" - including Icom, Kenwood, Yaesu and Heil.  Yaesu,
>>Kenwood and Heil connect the shield of the mic cable to the mic
>>return and not chassis (ground).  Icom uses the shield as the
>>mic return.
>
>>When the shield of the mic cable is tied to the low side of a
>>balanced input, RF that SHOULD go to ground/chassis is forced
>>through the mic preamp instead.   With the shield tied to the
>>mic return there is effectively a 10' piece of wire (antenna)
>>connected to the mic input unless the mic return is tied to
>>the chassis and the chassis is connected to a solid RF ground.
>
> This is not correct. There is nothing wrong with connecting an
> unbalanced mic to a balanced input -- you simply unbalance the
> input by grounding one side of the input. You lose the benefit of
> the balanced circuitry's ability to reject noise, but the input
> will work fine. The correct wiring is simply hot to one side,
> shield to the other side AND the chassis.
>
> I do have a serious quarrel with the W2IHY equalizer though -- it
> is FAR more complex and expensive than needed to get great audio
> from a pro mic with a ham rig. All you really need for an
> equalizer is a good quality capacitor of suitable value in series
> between the mic and the mic input of the radio. The capacitor is
> chosen to provide a low frequency rolloff fairly high in the
> audio passband. See
>
> http://audiosystemsgroup.com/HamInterfacing.pdf
>
> I have used a circuit like this with an EV RE16 and several rigs.
> Total cost about $0.50. It would work equally well with any good
> low-Z dynamic mic. I've also changed values in coupling
> capacitors in the K2 to achieve the same result, and that works
> quite well too. You don't need the capacitor with a K3, of course
> -- the equalizer in DSP does the job.
>
> Pro dynamic mics are easily connected to ham rigs -- since
> they're balanced, one side of the balanced output goes to the mic
> input, the other side goes to audio return, and the shield goes
> to the chassis. I've done this quite successfully with an Omni V,
> a TS850, and FT1000MP. By successfully, I mean that I get VERY
> competitve, clean, contest-quality audio that cuts through QRM
> and noise.
>
>
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