Can Bluetooth be used to replace link between K2 and remote KPA100+KAT100

[harry weston]

Hello. I am assembling KPA100 and KAT100 into an EC2 case, and intend to use the K2 indoors, where I can keep snug and warm, with the amplifier and tuner in a shed outside, less than ten metres away, and close to the antenna. Can I use a Bluetooth RS232 serial replacement pair for this communication link? I am concerned because we are warned against using a standard RS232 cable to link them, and the Bluetooth modules are rather expensive to buy for an experiment, unless I am pretty sure it will work. Thanks, Harry Weston M0SOP
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[Don Wilhelm-4]

Harry,

First, the signals required to operate the KPA100/KAT100 remotely are
*not* RS-232 signals.They are 'hard-wired' signals to and from the base
K2.  Note that the connector is labeled AUX I/O - the fact that there is
a DE-9 connector on any piece of equipment does not denote RS-232 unless
explicitly stated, and the K2 is no different.

Secondly, I believe you will encounter timing problems on the AUXBUS
signal (the one wire K2 signalling line between the firmware ICs in the
Elecraft gear.  It will likely work up to 2 meters, but 10 meters is
stretching it a lot.  You would have to do extensive testing to
determine that 10 meters of cable will work with no problems.  The
AUXBUS carries data that requires a response in a certain period of time
and that timing is critical.

The other internal signals used to connect the KPA100/KAT100 are not
likely to cause problems unless the cable resistance is a problem. Those
signals are:
+12CTRL - this is a 12 volt line that is active whenever the K2 is
powered on.
8R ---- this signal controls the transmit/receive switching, Whether
propagation delay would prove troublesome over a great cable distance
remains to be tested.
VRFDET -- This carries the measured power output from the KPA100
wattmeter back to the base K2 so power output control can be
maintained.  Again the resistance of the wire may be a factor in correct
operation.

Better to bring your KPA100/KAT100 inside in the warmth of the shack and
just run the output coax(s) to the shed and antenna field.

73,
Don W3FPR


On 1/26/2013 12:16 PM, harry weston wrote:
> Hello. I am assembling KPA100 and KAT100 into an EC2 case, and intend to use the K2 indoors, where I can keep snug and warm, with the amplifier and tuner in a shed outside, less than ten metres away, and close to the antenna. Can I use a Bluetooth RS232 serial replacement pair for this communication link? I am concerned because we are warned against using a standard RS232 cable to link them, and the Bluetooth modules are rather expensive to buy for an experiment, unless I am pretty sure it will work. Thanks, Harry Weston M0SOP
>

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[harry weston]

Thank you Don for that, a very useful reply. There is obviously a lot more to it than I expected, and your explanation will help me to understand the way the link works. A rethink now needed on the whole thing, 73, Harry M0SOP

--- On Sat, 26/1/13, Don Wilhelm <[hidden email]> wrote:

From: Don Wilhelm <[hidden email]>
Subject: Re: [Elecraft] Can Bluetooth be used to replace link between K2 and remote KPA100+KAT100
To: "harry weston" <[hidden email]>
Cc: [hidden email]
Date: Saturday, 26 January, 2013, 18:01

Harry,

First, the signals required to operate the KPA100/KAT100 remotely are *not* RS-232 signals.They are 'hard-wired' signals to and from the base K2.  Note that the connector is labeled AUX I/O - the fact that there is a DE-9 connector on any piece of equipment does not denote RS-232 unless explicitly stated, and the K2 is no different.

Secondly, I believe you will encounter timing problems on the AUXBUS signal (the one wire K2 signalling line between the firmware ICs in the Elecraft gear.  It will likely work up to 2 meters, but 10 meters is stretching it a lot.  You would have to do extensive testing to determine that 10 meters of cable will work with no problems.  The AUXBUS carries data that requires a response in a certain period of time and that timing is critical.

The other internal signals used to connect the KPA100/KAT100 are not likely to cause problems unless the cable resistance is a problem. Those signals are:
+12CTRL - this is a 12 volt line that is active whenever the K2 is powered on.
8R ---- this signal controls the transmit/receive switching, Whether propagation delay would prove troublesome over a great cable distance remains to be tested.
VRFDET -- This carries the measured power output from the KPA100 wattmeter back to the base K2 so power output control can be maintained.  Again the resistance of the wire may be a factor in correct operation.

Better to bring your KPA100/KAT100 inside in the warmth of the shack and just run the output coax(s) to the shed and antenna field.

73,
Don W3FPR


On 1/26/2013 12:16 PM, harry weston wrote:
> Hello. I am assembling KPA100 and KAT100 into an EC2 case, and intend to use the K2 indoors, where I can keep snug and warm, with the amplifier and tuner in a shed outside, less than ten metres away, and close to the antenna. Can I use a Bluetooth RS232 serial replacement pair for this communication link? I am concerned because we are warned against using a standard RS232 cable to link them, and the Bluetooth modules are rather expensive to buy for an experiment, unless I am pretty sure it will work. Thanks, Harry Weston M0SOP
>

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