When all else fails, start at the beginning.

Found the problem. Cold solder joint on the PL-259 failed in the feedline -
obviously due to temperature swings, since I solder perfect connections
every time. Yeah, and the pope's Protestant...

Fixed it and now it works - almost. Twice now, a few minutes after it tuned,
my radio by itself would key the transmit - both times while I was not even
near it! I had to shut down power to kill it! Oh well, one more problem to
troubleshoot!


"Jon KB1HTW" wrote in message
...
I need to extend the control cable for my AH-4 tuner. I have lots of Cat 5
Ethernet cable. The four leads to the tuner are Key, Start, +13.8Vdc, and
Ground. I initially hooked up each to each of the four pairs in the
Ethernet cable (i.e., Key to Blue/Blue-White). My thinking was parallel
each pair so I have less current loss, but I think I blew the capacitance
out of the water and the Key/Start pulses are getting smeared along the
100+ foot run.

What's the best way to wire things up so to the twisted pairs so any RFI
gets nulled out? Ground to each of the 4 White leads, and Key to say Blue,
Start to Green, and +13.8V to Orange? That way each twisted pair would
have a "signal" and ground. Or I could use the Brown for Ground, and
connect the AH-4 factory cable's shield to the four white leads. Which is
the preferred route for minimizing RFI or cable capacitance affecting the
Start/Key pulse signals?

Jon - KB1HTW

Jon,

I bet what you experiencing now is stray RF triggering either the tuner or
the radio. Because 706 has CMOS at its control circuits, this does not have
to be a strong RF signal, may be your local broadcast station or your 802.11
router will induce enough energy into the cable to trigger the circuit.
If you removed the ferrite beads from your cable, put them back on. To
improve noise suppression make a turn or two through the beads. If the hole
diameter is not big enough, put one more bead. Locate the beads near the
unit. If you can not replace your TP cable with a shielded one, I would
suggest to connect one wire of each TP to the ground. You asked how come the
Ethernet works fine with TP - you can not compare these things. Ethernet
transciever may use differential input amplifiers which supress common mode
noise by design, noise-immune modulation and different voltage swing. In
your case it is a single ended control wire, so all induced noise will get
inside the radio. If you can, put 0.01 uF bypass capacitors from the control
wires to the ground at the transciever side. I read AH-4 has chokes inside,
so concentrate youe efforts on the transciever side. The transciever may
also have some noise supressors inside, but people's experience with the
remote head control cable shows they are not effective enough. Sometimes
Icom does weird things. One of them is about the remote head control cable,
First, at the remote head side its shield is not connected to anything.
Second, at the transciever side, its shield is electrically connected to the
enclosure through a black oxidized screw, which , if not tightened enough,
works as an insulator, because it is made of an oxideized material. Look at
yours by the way. I replace that screw with a stainless steel one. This is
the thing to look at if you use the head remotely. When the head is sitting
at the unit, it works OK. Sorry for a bit of an off-topic..

Good luck with your troubleshooting,
Ivan
--


"Jon Gauthier (KB1HTW)" wrote in message
...
When all else fails, start at the beginning.

Found the problem. Cold solder joint on the PL-259 failed in the
feedline -
obviously due to temperature swings, since I solder perfect connections
every time. Yeah, and the pope's Protestant...

Fixed it and now it works - almost. Twice now, a few minutes after it
tuned,
my radio by itself would key the transmit - both times while I was not
even
near it! I had to shut down power to kill it! Oh well, one more problem to
troubleshoot!


"Jon KB1HTW" wrote in message
...
I need to extend the control cable for my AH-4 tuner. I have lots of Cat
5
Ethernet cable. The four leads to the tuner are Key, Start, +13.8Vdc, and
Ground. I initially hooked up each to each of the four pairs in the
Ethernet cable (i.e., Key to Blue/Blue-White). My thinking was parallel
each pair so I have less current loss, but I think I blew the capacitance
out of the water and the Key/Start pulses are getting smeared along the
100+ foot run.

What's the best way to wire things up so to the twisted pairs so any RFI
gets nulled out? Ground to each of the 4 White leads, and Key to say
Blue,
Start to Green, and +13.8V to Orange? That way each twisted pair would
have a "signal" and ground. Or I could use the Brown for Ground, and
connect the AH-4 factory cable's shield to the four white leads. Which
is
the preferred route for minimizing RFI or cable capacitance affecting
the
Start/Key pulse signals?

Jon - KB1HTW