[Elecraft] Cable length for KPA/KAT100 remote; importance of KPA100 upgrade

[Don Wilhelm]

Jim,

While you may be correct about the noise pickup, there is also concern 
about timing issues - if only because the performance has not been 
tested at longer lengths by observing the bit timings on the AUUXBUS.

Some time back I had discussions with Jack Brindle about about extending 
the cable length to the KRC2.  He did indicate that there could be 
timing issues on the AUXBUS.  Being a single wire interface, when a 
command is sent, the sending device waits for the expected response, and 
if it is not received in time, an error condition will be declared.
Those are the facts as I know them, and I  recall that 6 feet was 
considered an OK length because it had been tested - longer lengths had 
not been tested.
Of course, this applies to the K2.  The K3 may or may not be different.

73,
Don W3FPR

On 3/23/2012 6:04 PM, Jim Brown wrote:
> On 3/23/2012 12:21 PM, Don Wilhelm wrote:
>> I don't think you will get any smoke, but if you get "strange
>> happenings" - like the KPA100 is not recognized, or doesn't give a
>> response back to the K2 in sufficient time (command flow over the
>> AUXBUS) and things get "mixed up" or you get ERR 080, the cure will be
>> to shorten the cable.
> I would not expect timing problems, but parallel wire cables are recipe
> for noise and RFI problems, and making them longer makes that worse. I
> don't understand why, but Elecraft seems still not to have gotten the
> message that TWISTING is FAR more important than shielding in providing
> immunity from RFI and noise.
>
> There are simple instructions on my website for using CAT5 cable for
> this sort of application.
> http://audiosystemsgroup.com/HamInterfacing.pdf   The specific wiring
> instructions are given for RS232 connections, and your cable is NOT, but
> if you will be in good shape if you follow the conceptual instructions
> of using one twisted pair for each signal circuit with the "colored"
> conductor used as the numbered pin and all four "white/color striped"
> conductors twisted together and tied to the connector shell.  If you
> have shielded CAT5, tie those four striped whites to the designated
> return pin and tie the shield to the connector shells.
>
> 73, Jim Brown K9YC
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