KX1 Antenna Idea

[Dan Romanchik KB6NU]

Hi again--

Last night, I worked a guy who also is a KX1 owner, and we
got to talking about antennas. I mentioned that while the
antenna suggested in the antenna tuner manual (24-28-ft.
driven element with a 16-ft. counterpoise) tunes up OK, I
was kind of disappointed in the performance. The other guy
mentioned that he uses a 40-meter doublet, usually in an
inverted vee configuration, fed with ladder line, and that
it tunes up well on all three bands.

I asked him whether or not he used a balun, and he said no,
he just fed it directly into the radio. I suppose his
antenna could be fairly well-balanced or that the KX1 is
able to tolerate a fair amount of imbalance.

Whatever the case, I was thinking that it shouldn't be too
difficult to build a small balun--and it really could be a
small one since the maximum power level it needs to handle
is just 5W--into a small plastic project box. On one end,
the box would have two binding posts to connect the ladder
line, and a panel-mount male BNC (if they make such a thing)
on the other.

Does this seem reasonable to do or is it overkill?

73!

Dan KB6NU
===================================================
President, ARROW Comm. Assn. (www.w8pgw.org)
ARRL MI Section Affiliated Club Coordinator
Candidate for GL Division Vice Director, Fall 2005
Read my ham radio blog at www.kb6nu.com

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[Steven Pituch]

Hi Dan,
I would just use the dipole.  If you want a balun just coil up about 5 turns
of the coax (use RG-8x) near the "T" of the antenna in about a six inch
diameter and tape the coil together.  I think that’s what Louis Varney (Mr.
G5RV) recommended for his antenna.  I have a picture of it on my 40 meter
dipole at:
http://users.ev1.net/~spituch/Steve's%20Page/Radio/Antenna/Antenna.htm

Regards,
Steve, W2MY

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[Don Wilhelm-3]

Dan,

Actually, in my experience, the tuner could care less whether the load is
balanced or unbalanced, it will just do its best job of matching the
impedance it sees regardless of balance.

OTOH, if you are concerned about radiation patterns, or 'RF-in-the-shack',
it would be prudent to install a balun.  For most situations (multiband
use), I recommend a 1:1 balun over a 4:1 because it and the tuner will
handle a greater variety of loads compared to the 4:1.  The only important
parameter that you need in a blaun is the ability to reduce or eliminate RF
on the outer side of the coax shield (common mode current), and a simple
choke made by coiling up a length of coax will do the job fine, as will the
type with a ferrite beads on the coax (W2DU type).  One thing that is
certain, use a current type balun, the voltage type balun will not handle
reactive feedpoint impedances very well, where the current type
(particularly the 1:1 balun) will handle it much better (note that
everything is a compromise when multiband antennas are addressed).

73,
Don W3FPR

> -----Original Message-----
> Hi again--
>
> Last night, I worked a guy who also is a KX1 owner, and we
> got to talking about antennas. I mentioned that while the
> antenna suggested in the antenna tuner manual (24-28-ft.
> driven element with a 16-ft. counterpoise) tunes up OK, I
> was kind of disappointed in the performance. The other guy
> mentioned that he uses a 40-meter doublet, usually in an
> inverted vee configuration, fed with ladder line, and that
> it tunes up well on all three bands.
>
> I asked him whether or not he used a balun, and he said no,
> he just fed it directly into the radio. I suppose his
> antenna could be fairly well-balanced or that the KX1 is
> able to tolerate a fair amount of imbalance.
>
> Whatever the case, I was thinking that it shouldn't be too
> difficult to build a small balun--and it really could be a
> small one since the maximum power level it needs to handle
> is just 5W--into a small plastic project box. On one end,
> the box would have two binding posts to connect the ladder
> line, and a panel-mount male BNC (if they make such a thing)
> on the other.
>
> Does this seem reasonable to do or is it overkill?
>
> 73!
>
> Dan KB6NU
>

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[KK7P]

> ... One thing that is
> certain, use a current type balun, the voltage type balun will not handle
> reactive feedpoint impedances very well, where the current type
> (particularly the 1:1 balun) will handle it much better (note that
> everything is a compromise when multiband antennas are addressed).

Then there is the hybrid balun described in this month's issue of QEX
which tries to cover both cases...

Lyle KK7P

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[Charles Greene-2]

Dan,

Here's another idea.  Use a short length of coax like 1' or less of RG-58
or better RG-174, and put some ferrite beads around the coax to make a 1:1
balun.   On the antenna side it is balanced, so solder this to the ladder
line.   I hope you are at least using the small 300 ohm ladder line for 5
watts.   If the feedline is small enough; #22 or smaller twisted pair, you
can use the beads right over the feedline as a 1:1 balun.  I have made up
some feedline using #28 teflon insulated solid wire wrap wire held together
with heat shrink tubing.  The characteristic impedance is not important and
it is low loss.  I measured some #26 twisted pair once and it's impedance
is about 180 ohms.

In this application, a 1:1 balun works as well as a 4:1 balun.  A 1:1 balun
can be made up using a pair of #28 magnetic wire and a F-50-43 1/2" ferrite
tordal core.  Wind 10 turn of the wire pair on the core and secure both
ends with wire wrap ties.  Alternatively, you can use RG-174 instead of the
wire.  It usually takes a somewhat larger core, like a F-82-43 .825" core
in order to get enough turns to work well on 40; or use a F-50B-43 core and
fewer turns.  I have made lots of these small 1:1 baluns and my favorite is
one using a F-82-43 core and as many turns of RG174 as you can get on it.

On my KX1, I use a 8' length of RG-58 soldered directly to one side of a
42' antenna and a 8' counterpoise soldered to the coax shield for a
portable antenna.  The other end has a BNC plug for the KX1.  Works well
for a portable.  Doesn't beat an inverted V at 30' though, so you are on
the right track.

At 09:08 PM 9/9/2005, Dan Romanchik wrote:

>Hi again--
>
>Last night, I worked a guy who also is a KX1 owner, and we got to talking
>about antennas. I mentioned that while the antenna suggested in the
>antenna tuner manual (24-28-ft. driven element with a 16-ft. counterpoise)
>tunes up OK, I was kind of disappointed in the performance. The other guy
>mentioned that he uses a 40-meter doublet, usually in an inverted vee
>configuration, fed with ladder line, and that it tunes up well on all
>three bands.
>
>I asked him whether or not he used a balun, and he said no, he just fed it
>directly into the radio. I suppose his antenna could be fairly
>well-balanced or that the KX1 is able to tolerate a fair amount of imbalance.
>
>Whatever the case, I was thinking that it shouldn't be too difficult to
>build a small balun--and it really could be a small one since the maximum
>power level it needs to handle is just 5W--into a small plastic project
>box. On one end, the box would have two binding posts to connect the
>ladder line, and a panel-mount male BNC (if they make such a thing) on the
>other.
>
>Does this seem reasonable to do or is it overkill?
>
>73!
>
>Dan KB6NU

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[Martin Gillen]

Hi, Chuck.

I have a question about your feedline:

> I have made up some feedline using #28 teflon
insulated
> solid wire wrap wire held together with heat shrink
> tubing. The characteristic impedance is not
important and
> it is low loss. I measured some #26 twisted pair
once and
> it's impedance is about 180 ohms.

I know that coax can be looped around 5 times to
create
a balun near the dipole feedpoint.  Can twisted pair
be looped around to create a balun also?  Also, what
was
the distance between the twists?  I'm interested in
making one to feed a dipole for my KX1 field kit :)

How can you measure that a balun is being effective?

Thanks,
Martin.
[hidden email]


       
       
               
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[John Harper AE5X]

>How can you measure that a balun is being effective?
>
>Thanks,
>Martin.


That's a very good question. BTW, I'm the guy Dan worked the other night
when we had this conversation on 40m - good to work you, Dan.

There are 3 reasons I've never used a balun with my standard "field kit"
consisting of the KX1 and a 40m inverted V fed with ladder line or twinlead:
1. The KX1's autotuner tunes all 3 bands with this antenna; contacts,
including DX, are easily made. (http://www.ae5x.com/charon.htm)
2. The main advantage of the KX1 is the integration of so many things that
previously were seperate items: batteries, paddles, tuner and all the
interconnecting cabling associated with them. The KX1 leaves not only less
to take but less to forget to take - been there, done that... ;-)
3. An external balun is one more item to pack (or to forget to pack) and, if
I bring it, how can I tell if it's doing me any good? Would the guy in Spain
give me a 579 instead of a 569? I doubt it. If there were a measurable way
to quantify the advantage, I'd consider packing one along but the advantage
would have to be practical, not merely theoretical.

John Harper AE5X
Portable QRP: http://www.ae5x.com


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[Leigh L. Klotz Jr WA5ZNU]

I sometimes carry a balun, either the BL1 or the K5OOR binocular core
one, and the test I use is simple enough: if I find signals get better
when I put my hand on the KX1 I use it, but only when I use twinlead,
not with the wires directly connected.  If you have to bring the
feedline with you then weight of the balun isn't much, but if you don't
have a feedline, then you don't need it.

Right now I am out with my KX1 and listening to QSOs on 40m, just the
wire in a tree and one or two on the ground.
Leigh / WA5ZNU
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[Charles Greene-2]

Martin,

I went up in my attic with a ruler and this is what I found for some feed
lines I made:

#24 stranded, silver plated teflon insulted, with about one twist per inch.

#26 , same type, about two twists per inch.

#28 solid, silver plated teflon insulated wire wrap wire about one twist
per inch plus a heat shrink tube about every two inches.

All are close spaced.

I also have about 1000' of #26 solid as above that would work too, or I
could use if for a near invisible antenna.

A good source of similar wires to above is eBay.

GL

73, Chas

At 10:58 AM 9/10/2005, Martin Gillen wrote:

>Hi, Chuck.
>
>I have a question about your feedline:
>
> > I have made up some feedline using #28 teflon
>insulated
> > solid wire wrap wire held together with heat shrink
> > tubing. The characteristic impedance is not
>important and
> > it is low loss. I measured some #26 twisted pair
>once and
> > it's impedance is about 180 ohms.
>
>I know that coax can be looped around 5 times to
>create
>a balun near the dipole feedpoint.  Can twisted pair
>be looped around to create a balun also?

I don't see why not.  You probably would want to use a plastic juice bottle
as a form, which I do anyway for coax.

>  Also, what
>was
>the distance between the twists?  I'm interested in
>making one to feed a dipole for my KX1 field ki


>How can you measure that a balun is being effective?

Measure impedance with an impedance meter.  the Z should be roughly 10
times the impedance of the feed line.  Or else check antenna handbook and
use the dimensions they give.  Note that the handbook is for coax, and a
higher impedance feed line will take more turns.  Impedance is proportional
to N^2.


>Thanks,
>Martin.
>[hidden email]

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[Bob Cunnings NW8L]

On 9/10/05, Martin Gillen <[hidden email]> wrote:
>  
> I know that coax can be looped around 5 times to
> create
> a balun near the dipole feedpoint.  Can twisted pair
> be looped around to create a balun also?

Sure, a 1:1 choke balun can be made with twinlead as well as coax feedline.
 
I've been having good results lately with a speaker wire doublet
antenna cut for 30 meters, which my KX1 tunes up nicely on all 3 bands
with a feedline length of 40'. I made 9 turns with the last 18" or so
of the (twinlead speaker wire) feedline through a T140-43 ferrite
toroid to create a 1:1 choke balun. A couple of nylon tie wraps bind
the feedline to the toroid securely. A 4" pigtail was left over which
I terminated with a cheap RS BNC connector for attachment to the KX1.
No enclosure, no connectors, nice and simple, not as bulky as an
airwound balun, but admittedly a bit heavier.
 
 Bob NW8L
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