KX-1 antenna matching

[Rick Dwight]

Stan,
     I have used a kx 1 for thousands of QSO’s many in the field on 40, 30, and 20 meters.  My usual field antenna is a 26 ft piece of wire and one or two 17 counterpoise wires.  If the counterpoise (radial) wires are laying directly on the ground, usually I get a very good match on all 3 bands.  If part or all of the counterpoise/radial wire is elevated, then sometimes I clip on an extension of about 8 feet to get a better match if the SWR is higher than about 2:1 (probably only necessary on 40 meters sometimes).  Occasionally for 40 meter elevated counterpoise operation I have even used a single 34 ft counterpoise wire if I happen to have one available….not likely when backpacking.  I would just use your 16 or 17 ft counterpoise for 20 meters…it might improve your 1.6:1 SWR, however I still have my original PA transistor and have often operated with SWR’s around 2:1 or higher, however my goal is to try not to exceed about 2:1. Usually I can get SWR down somewhere between 1:1 and and perhaps 1.9:1 (just a guess) on 40 meters, and often about the same or even slightly better on 20 and 30 meters.  I always carry a 8 ft piece of wire with a big clip on the end.  Often clipping it to a metal picnic table, guard rail, chain link fence, or car body either instead of a radial, or in addition to one and get satisfactory performance.  If I use an elevated counterpoise…then I clip the 8 ft wire onto the end of my 17 ft counterpoise for better matching on 40 and possibly 30 meters.  I see no reason to just use a 8 ft counterpoise or radial wire for 20, a 16 or 17 wire should be better on all the bands. Occasionally I lay down two 17 ft radial wires on the ground if I have them and there is room.  Some of my attempts at modeling showed slightly improved performance.  If I have a preferred direction I often lay them down in roughly that quadrant.  The theory is it may slightly help in that direction, but more important it may eliminate a very slight null opposite to the desired direction.  This is my unproved theory only since it would be nearly impossible to measure something like a dB or so.
           This is usually the only antenna I carry for backpacking, or travel around the US or Europe.  Something like a linked dipole (usually set up as an inverted V) will often perform significantly better, however I much prefer something like the 26 ft wire….5 minutes to set up and lots of time to operate vs. an hour set up and less operating time.
            Rick  KL7CW   Palmer, Alaska  

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[stan levandowski]

Rick, thanks for your input from way up there in Alaska!  The KXAT1
manual suggested (actually "stated") 1/8 wavelength minimum
counterpoises per band and that's where the 8 foot wire for 20M came
from.  Also, my counterpoises have not always been on the earth;
sometimes raised by a foot or so. 


I think I'll scrounge up some wire, some alligator clips and make up
some "extensions" like you described and do some testing tomorrow.  I
also like your idea about clipping it to a metal picnic table.  Today, I
was operating from a very large (8 foot) and heavy wrought iron picnic
table on my rear deck.  Never thought about trying that!  I've got a
nice large central air compressor nearby also but that might introduce
RFI.  Still, might be worth a quick clip-up to see.


Thanks, Stan WB2LQF


On Fri, Jun 09, 2017 at 07:22 PM, Frederick Dwight wrote:

> Stan,
>      I have used a kx 1 for thousands of QSO’s many in the field on
> 40, 30, and 20 meters.  My usual field antenna is a 26 ft piece of
> wire and one or two 17 counterpoise wires.  If the counterpoise
> (radial) wires are laying directly on the ground, usually I get a very
> good match on all 3 bands.  If part or all of the counterpoise/radial
> wire is elevated, then sometimes I clip on an extension of about 8
> feet to get a better match if the SWR is higher than about 2:1
> (probably only necessary on 40 meters sometimes).  Occasionally for 40
> meter elevated counterpoise operation I have even used a single 34 ft
> counterpoise wire if I happen to have one available….not likely when
> backpacking.  I would just use your 16 or 17 ft counterpoise for 20
> meters…it might improve your 1.6:1 SWR, however I still have my
> original PA transistor and have often operated with SWR’s around 2:1
> or higher, however my goal is to try not to exceed about 2:1. Usually
> I can get SWR down somewhere between 1:1 and and perhaps 1.9:1 (just a
> guess) on 40 meters, and often about the same or even slightly better
> on 20 and 30 meters.  I always carry a 8 ft piece of wire with a big
> clip on the end.  Often clipping it to a metal picnic table, guard
> rail, chain link fence, or car body either instead of a radial, or in
> addition to one and get satisfactory performance.  If I use an
> elevated counterpoise…then I clip the 8 ft wire onto the end of my 17
> ft counterpoise for better matching on 40 and possibly 30 meters.  I
> see no reason to just use a 8 ft counterpoise or radial wire for 20, a
> 16 or 17 wire should be better on all the bands. Occasionally I lay
> down two 17 ft radial wires on the ground if I have them and there is
> room.  Some of my attempts at modeling showed slightly improved
> performance.  If I have a preferred direction I often lay them down in
> roughly that quadrant.  The theory is it may slightly help in that
> direction, but more important it may eliminate a very slight null
> opposite to the desired direction.  This is my unproved theory only
> since it would be nearly impossible to measure something like a dB or
> so.
>            This is usually the only antenna I carry for backpacking,
> or travel around the US or Europe.  Something like a linked dipole
> (usually set up as an inverted V) will often perform significantly
> better, however I much prefer something like the 26 ft wire….5 minutes
> to set up and lots of time to operate vs. an hour set up and less
> operating time.
>             Rick  KL7CW   Palmer, Alaska
> Sent from Mail for Windows 10
>
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[stan levandowski]

Thank you to all who offered suggestions, all of which helped me solve
this nagging problem.


I bought a 33' tape measure from Harbor Freight.  I scrapped off the
paint at the end, drilled a 3/16" hole and put a bolt, a couple of
washers and a two nuts on it.  Then I cut a 5' piece of wire and
attached one end to the tape measure and the other end to the black BNC
terminal on the KX1.


I did not fiddle around with the 25 foot radiator.


I laid the tape measure right on the grass.


By adjusting the tape measure - now I knew exactly how much counterpoise
was being deployed and it was infinitely adjustable - I was able to get
1:1 SWRs on 40, 30 and 20 meters.


I found that 31 feet on the tape measure + the 5 foot connecting wire
worked best as a single compromise counterpoise length for all three
bands -- with this 36 foot length I got 1:1 on 40M, 1.3 on 30M and 1.2
on 20M.


73, Stan WB2LQF







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