I just bought an Icom PW-1 solid state kilowatt amplifier.
On my tower, I have an HF multiband antenna that is rated for 1200W, but
8' above it on the top of the same mast is my triband (2m/70cm/23cm)
vertical.

My question (being new to the kilowatt club) is what proximity concerns
might I have? I have a 2nd roof mounted mast about 30' away from the
beam with a discone and a 6m-70cm log antenna on it.

To put it simply, is there a minimum distance I should keep other
antennas away from the main HF array? I would prefer to not burn out the
front end of any of my other radios.

Any experiences or advice on this one?

Thanks,
Pat, VE3PMK

"Pat MacKinnon" wrote
I just bought an Icom PW-1 solid state kilowatt amplifier.
On my tower, I have an HF multiband antenna that is rated for 1200W, but
8' above it on the top of the same mast is my triband (2m/70cm/23cm)
vertical.

If the other antenae are directly above your HF vertical you should have no
problems. The radiation pattern is a toroid (donut) shape and antennae
above and below are in the 'hole'. I use a 6m/2m/70cm vertical above a
pair of 40/75m inverted 'Vs' driven by 600 watts and haven't smoked anything
yet. However RF is magic and YMMV.

My HF antenna is a Beam, not a vertical.
Sorry, I should have better articulated that.

The 6 band HF beam is 1' above the thrust bearing, and ~ 8' above the beam
is the triband vertical (at the very top of the mast.)
That said, there will definitely be a significant RF field above and below
the beam, as well as to the obvious front and back of the beam.

So, is there a danger of inducing destructive voltages to the vertical
above? What about other antennas on my roof near the tower?

My beam is well above the roof line, but as I have two tripods on the roof,
each with assorted verticals and beams {6m - 70cm LogP, two discones, a 902
yagi, and 902 vertical, and a 220MHz vertical.) These are each 25 to 30
feet away from the HF beam. There's also a distorted G5RV (aka: has a 90
degree turn near the end of the long leg as to stay on the property) running
off the roof to some trees along the back fence.

So you see my concern about having a 1KW RF source in proximity to all the
other antennas.

'73, VE3PMK

Pat:

It's a horrible problem, and there's nothing you can really do about it
except put it back in the box and ship it to me in Hawaii. That'll put it
far enough away you won't have to worry about cooking any of the other front
ends....

hi hi hi....

On a serious note, you probably don't have much to worry about due to the
difference of frequencies between various rigs. I have two HF rigs in my
shack (Icom 751A and 746Pro) and with one on the X9 Beam and the other on
the Carolina Windom (that uses the tower for support of one end) I do get
some significant bleed through, but not enough energy to cause damage to
either one.

If you typically work on a single band, you can put band traps (coax stubs
cut to block a given band) on the radios you are worried about... Another
choice is to make up a good antenna switch center that grounds the inputs to
other (hf at least) rigs when you are pushing 1KW on HF. I'm working
through the control logic for one right now... Want to be able to switch
any of 5 antennas into choice of the two radios, with ground blanking for
the receiving rig when transmitting on the other. The logic to do the
grounding is trivial, but am still thinking about how I'm going to guarantee
I don't get two rigs on the same antenna, and ground all unused antennas.
746 Pro will have priority if both rigs select the same antenna, and want to
put other rig into dummy load if antenna selection conflict exists... Once
I get past doing my income taxes, I'll actually start thinking about how to
implement the logic.

Good Luck!

--Rick AH7H

Pat MacKinnon wrote:

I just bought an Icom PW-1 solid state kilowatt amplifier.
On my tower, I have an HF multiband antenna that is rated for 1200W, but
8' above it on the top of the same mast is my triband (2m/70cm/23cm)
vertical.

My question (being new to the kilowatt club) is what proximity concerns
might I have? I have a 2nd roof mounted mast about 30' away from the
beam with a discone and a 6m-70cm log antenna on it.

To put it simply, is there a minimum distance I should keep other
antennas away from the main HF array? I would prefer to not burn out the
front end of any of my other radios.

Any experiences or advice on this one?

Thanks,
Pat, VE3PMK