[Elecraft] RS232 Noise

[Ken K3IU]

Oops. I responded to the wrong email. Looks like this has already been 
addressed.
73,
Ken K3IU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Ken K3IU wrote:
> Mike:
>  From Release Notes
> MCU 2.45 / DSP 1.92, 9-29-2008
>
> * TRANSMIT NOISE GATE ADDED:  The TX noise gate can be used to suppress
> transmitted audio below a certain level, e.g. a noisy fan (not the one 
> on the K3, of
> course). To use the noise gate, locate CONFIG:TX GATE, tap '1' to turn 
> it ON,
> then use VFO A to set the desired threshold. Since there's no visual 
> indication that
> transmit audio is below the threshold, you should adjust it using the 
> transmit voice
> monitor (MON), ideally using headphones. Set the threshold high enough 
> to cut off
> transmit audio due to shack noise, but not so high that it causes your 
> voice to drop
> out too frequently. The TX GATE threshold can be adjusted in TX TEST mode.
>
>
>
> Mike Harris wrote:
>   
>> G'day,
>>
>> Finally got around to making a replacement RS232 rig control cable using 
>> CAT6 patch cable, about three metres long.  Method used was as detailed in 
>> the reference below.
>>
>> Results; spectacular!  Noise on 6m increases approx 1dB when the cable is 
>> connected to the K3 (no antenna).  Using the old cable the noise jumps up 
>> approx 9dB and was 6dB up on the noise floor when the antenna is 
>> connected.
>>
>> I can no longer hear the CRT monitor updating when the seconds tick over 
>> in WSJT.  This was audible even when the old cable was disconnected from 
>> the K3 so it was probably being radiated from the cable and picked up by 
>> the antenna.
>>
>> Regards,
>>
>> Mike VP8NO
>>
>> ----- Original Message ----- 
>> From: "Jim Brown" <jim at audiosystemsgroup.com>
>> To: "Reflector Elecraft" <Elecraft at mailman.qth.net>
>> Sent: Thursday, April 23, 2009 10:10 AM
>> Subject: Re: [Elecraft] RS232 Noise
>>
>>
>> | On Wed, 22 Apr 2009 19:11:51 -0400, Mike Harris wrote:
>> |
>> | >This extra noise vanished when I removed the "RS232" cable from the
>> | K3.
>> | >The cable is actually the one I made up for the K2.
>> |
>> | There are several problems in the setup. First, the K3 connector shells
>> | are not properly bonded to the chassis, so the cable shield is useless.
>> | Second, the cable Elecraft sold with the K2-series products used
>> | parallel conductors, not twisted pairs. That's a recipe for noise and
>> | RFI.
>>
>> <snip>
>>
>> | 1) Build the serial cable shown in my RFI application note.
>> | http://audiosystemsgroup.com/RFI-Ham.pdf  It uses CAT5 cable. When VHF
>> | noise is a concern, shielded CAT5 may offer further improvements.
>> |
>> | 3) Fix the pin 1 problem in the K3 by bonding the DB-connectors to the
>> | chassis. Pin 1 problems couple RFI in both directions -- that is, they
>> | let RF into equipment and they put RF onto cables that radiate it.
>> |
>> | 73,
>> |
>> | Jim Brown K9YC
>>
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>>   
>>     
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