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The K2 and Random Antennas

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tom.w3qs

The K2 and Random Antennas

Good Morning, Group,

I'm about to order my K2 and I have a load of questions, but just one for
now.

I am presently restricted to a random wire (perhaps 60 feet or so - OK,
about 20 meters) sloping up to the top of a tree. I am feeding this with 50
feet of RG-8 and have a ground system consisting of two 1/4 wave wires for
40 through 10.

Will the K2 and the KAT2 tuner handle this antenna? Anyone have similar
setups?

Thanks es 73

Tom, W3QS

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Ron D'Eau Claire-2

RE: The K2 and Random Antennas

Tom W3QS wrote:

I'm about to order my K2 and I have a load of questions, but just one for
now.

I am presently restricted to a random wire (perhaps 60 feet or so - OK,
about 20 meters) sloping up to the top of a tree. I am feeding this with 50
feet of RG-8 and have a ground system consisting of two 1/4 wave wires for
40 through 10.

Will the K2 and the KAT2 tuner handle this antenna? Anyone have similar
setups?

--------------------
How are you feeding the wire, Tom? At the end or the center?

Since you are using coax, I'm guessing you are planning on center feed. That
is, you are erecting a "doublet" fed with coax.

If so, then you will experience very high relative losses in your coax. The
antenna will show a lot of reactance on all bands except maybe 40 and 15
meters if you can get 66 feet of wire up. A 66 foot wire is self-resonant at
40 meters. That is, it will show very little reactance. The impedance at the
center will be resistive and somewhere in the vicinity of 50 ohms - a good
match for 50 ohm coax. It will show another resonance at about 21 MHz (15
meters) where it will again show a decent match for coax.

On the other bands the SWR will be very high and so your coaxial line losses
will be very high. Most operators using a non-resonant doublet like that
will choose open wire line or 450 ohm ladder line to minimize these losses.
Those lines have much, much lower losses than coax primarily because of the
lower SWR on the line. For example, if you have a 60-something foot radiator
fed at the center, on 20 meters it will be close to two half waves,
presenting a very high impedance at the center feed point. In the practical
world, the impedance will probably be something on the order of 2000 or 2500
ohms, maximum. If you connect 50 ohm coaxial line to the center, the SWR
will be >40:1. If you use 450 ohm ladder line the SWR will be about 5:1.
That's a huge difference that will save you a lot of RF being wasted as heat
in the coax.

If you simply cannot run the ladder line or open wire line all the way to
the rig, use a short piece of coax for the final few feet, but keep it as
short as possible. Connect one side of the ladder line to the center
insulator and the other to the braid. The coax simply makes a shielded wire
to run the last few feet.

If your feed line is "in the clear" running up to the antenna, I'd not
bother one bit about trying to "balance" it with a balun. Baluns are
unpredictable and often lossy in lines with high SWR. Just hook one side of
the feeder to the center pin of the antenna connector and the other side to
the ground. If you want to try a balun, put it at the end of the open wire
section of your feed line. I'd recommend using a 1:1 balun although
sometimes if you have a very high impedance at the end of the open wire
feeder, a 4:1 balun will bring the value down into the range for the tuner.

If you are feeding your 60-something foot wire at one end, don't use coax at
all. Just bring the end to the center pin at the ATU output. Avoid running
the line any distance inside the house. It may cause RFI and pick up noise
from wiring and appliances. To 'ground' your rig effectively, connect a 1/4
wave long wire to the case of your rig for each band you are operating on.
The ground wires must be insulated at the far end. They will be hot with RF
at the ends. You can run them indoors (along baseboards, etc) or outside.
Just be careful to keep the ends insulated and away from people and pets.
They can inflict an RF burn if touched while transmitting.

You mentioned 40-10. If you can put up 60+ feet of wire, you'll find that it
will work FB on 80 meters as well, either center fed or end fed.

The Elecraft tuners have excellent matching ranges, with the exception of
perhaps the built-in KX1 ATU. The KX1 ATU
was designed to fit in a tiny space, so it doesn't offer the wide range of
the other Elecraft tuners. It is possible to arrange an antenna they can't
match on one or more bands because of the impedance extremes. The usual way
to deal with that is to change the length of your feedline.

Ron AC7AC

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Don Wilhelm-3

RE: The K2 and Random Antennas

In reply to this post by tom.w3qs

Tom,

The KAT2 should adequately match the antenna system that you have, but I
would recommend that you scrap the coax and feed it with open wire line
because the feedpoint impedance on 40 meters and above should be a lot
greater than 50 ohms - the line losses and SWR on the feedline should be
rather high.

BTW, you could add a couple radials cut for 80 meters and use it on that
band too - the 60 ft wire is almost a quarter wave on 80 and it should
behave similar to a 60 ft high vertical (with some horizontal radiation too
depending on how much it slopes)

73,
Don W3FPR

> -----Original Message-----
>
> I'm about to order my K2 and I have a load of questions, but just one for
> now.
>
> I am presently restricted to a random wire (perhaps 60 feet or so - OK,
> about 20 meters) sloping up to the top of a tree. I am feeding
> this with 50
> feet of RG-8 and have a ground system consisting of two 1/4 wave wires for
> 40 through 10.
>
> Will the K2 and the KAT2 tuner handle this antenna? Anyone have similar
> setups?
>
> Thanks es 73
>
> Tom, W3QS
>
>

--
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Hank Kohl K8DD-2

Re: The K2 and Random Antennas

Tom ....

I would agree with Don! The K2 & KAT2 should match it great ..... with
or without the radials.
When I was a young General in about 1959 or 60 I had great luck on 80 &
20 AM with a 60 - 65' longwire from the second floor window out to a
tree. The shack was on the first floor with about 40 ft of coax of
questionable quality, and I used a tuner. (WRL Globe Chief 90, homebrew
cathode modulator, WRL tuner and an SX-99 and a homebrew TR switch).
The more OT's that told me it shouldn't work, especially with no ground,
the better it seemed to work!
Give it a try and be sure to report back when you put the K2 & KAT2 on it.

72 73 Hank K8DD

W3FPR - Don Wilhelm wrote:

>Tom,
>
>The KAT2 should adequately match the antenna system that you have, but I
>would recommend that you scrap the coax and feed it with open wire line
>because the feedpoint impedance on 40 meters and above should be a lot
>greater than 50 ohms - the line losses and SWR on the feedline should be
>rather high.
>
>BTW, you could add a couple radials cut for 80 meters and use it on that
>band too - the 60 ft wire is almost a quarter wave on 80 and it should
>behave similar to a 60 ft high vertical (with some horizontal radiation too
>depending on how much it slopes)
>
>73,
>Don W3FPR
>
>
>
>>-----Original Message-----
>>
>>I'm about to order my K2 and I have a load of questions, but just one for
>>now.
>>

--

'Never argue with an idiot. They drag you down to their
level then beat you with experience.' -anon

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tom.w3qs

RE: The K2 and Random Antennas

Thanks for all the replies. Leaves me with a lot of questions.

My shack is located in the basement, and the only way to get RF out is by a
rather circuitous route through a couple of walls, so I don't think open
wire line is possible. The antenna wire is then fed at the ground end. If
I shorted braid-to-center at the rig and fed the whole thing as a wire I
have a problem with where to put the counterpoise. I don't have room for
radials attached to the case of the rig, and don't have direct access to
earth-ground.

I gather mismatch at the feed point is the major concern, so do ya think
something like the par electronic end-fed 'dipole' would be better?

Bennie, any idea when the DLRDLL-EndFedZ will be available?

Tom

-----Original Message-----
From: Hank Kohl K8DD [mailto:[hidden email]]
Sent: Sunday, June 12, 2005 4:42 PM
To: [hidden email]
Cc: tom.w3qs;
Subject: Re: [Elecraft] The K2 and Random Antennas

Tom ....

I would agree with Don! The K2 & KAT2 should match it great ..... with or
without the radials.
When I was a young General in about 1959 or 60 I had great luck on 80 & 20
AM with a 60 - 65' longwire from the second floor window out to a tree. The
shack was on the first floor with about 40 ft of coax of questionable
quality, and I used a tuner. (WRL Globe Chief 90, homebrew cathode
modulator, WRL tuner and an SX-99 and a homebrew TR switch).
The more OT's that told me it shouldn't work, especially with no ground, the
better it seemed to work!
Give it a try and be sure to report back when you put the K2 & KAT2 on it.

72 73 Hank K8DD

W3FPR - Don Wilhelm wrote:

>Tom,
>
>The KAT2 should adequately match the antenna system that you have, but
>I would recommend that you scrap the coax and feed it with open wire
>line because the feedpoint impedance on 40 meters and above should be a
>lot greater than 50 ohms - the line losses and SWR on the feedline
>should be rather high.
>
>BTW, you could add a couple radials cut for 80 meters and use it on
>that band too - the 60 ft wire is almost a quarter wave on 80 and it
>should behave similar to a 60 ft high vertical (with some horizontal
>radiation too depending on how much it slopes)
>
>73,
>Don W3FPR
>
>
>
>>-----Original Message-----
>>
>>I'm about to order my K2 and I have a load of questions, but just one
>>for now.
>>

Ron D'Eau Claire-2

RE: The K2 and Random Antennas

Tom wrote:
My shack is located in the basement, and the only way to get RF out is by a
rather circuitous route through a couple of walls, so I don't think open
wire line is possible. The antenna wire is then fed at the ground end. If
I shorted braid-to-center at the rig and fed the whole thing as a wire I
have a problem with where to put the counterpoise. I don't have room for
radials attached to the case of the rig, and don't have direct access to
earth-ground.

--------------------

Sounds like the way to go is to center fed a dipole with coax. Even if you
have to fiddle around with the path of the coax so it runs parallel with the
antenna for a while to get to the center, just keep it as far from the
radiator as possible before running up to the center point of the radiator.

Now, you must keep the SWR within reason. There's a couple of ways to do
this that work pretty well and don't need to cost much, will provide you
with coverage of at least 40/20/15 and 10, and, perhaps, some of the other
bands in between as well.

First, if you can get 66 feet of wire up there (even if the ends have to
droop down or run off a an angle from the insulators for a bit to make the
length) you are all set. That's a 1/2 wave on 40 and 3/2 waves on 15. That
provides a decent match to minimize feeder losses on 40 and 15. Now you can
connect in parallel with that dipole two more dipoles: one is 33 feet long
and one 16 feet long. If you don't have other attachment points, just let
them droop below the 66 foot dipole and, after the end insulators, tie them
off to the 66 foot radiator. An easy way to do that is to use monofilament
fishing line at the ends of each radiator. It's a great, lightweight
insulator.

The three antennas will interact somewhat, but the system will show a usably
low SWR on 40,20,15 and 10 meters. Your ATU will probably load them up on
the WARC bands as well, although the SWR may be fairly high there.

Ron AC7AC

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tom.w3qs

RE: The K2 and Random Antennas

In reply to this post by tom.w3qs

Some interesting ideas, Stuart. I may have to try them. My two biggest
problems, now, are getting the RF out of the shack and feeding antenna
anywhere other than at the end. I am seriously thinking of getting a
trapped vertical which would solve both problems. I was trying to do this
on the cheap, and guess that isn't a good idea.

Anyone have any experience with the Hustler 6 band vertical?

73, Tom

-----Original Message-----
From: Stuart Rohre [mailto:[hidden email]]
Sent: Tuesday, June 14, 2005 3:54 PM
To: tom.w3qs
Subject: Re: [Elecraft] The K2 and Random Antennas

Tom,
You can always find a way to run balanced line to a good center fed doublet,
(dipole).

You can put it on electric fence 5 inch plastic standoffs across a wall or
ceiling, then inside pvc conduit as you pass thru a wall. Use Wireman's 300
ohm ladder line, which is narrow. An alternate way thru a wall is to mount
two "all threads" rods in shrink tubing on each; in a pair of drilled holes
spaced about the spacing of your feeder.

Use PVC conduit larger than the ladder line by a factor of 2X and space the
ladder line by cutting some foam spaces to slip over the line. Make these
circular and spaced every 18 inches.

Twisting a ladder line also helps keep it equally spaced from unbalancing
conductors, in that any coupling will be equally received by the parallel
wires as they change direction in the twist. The twist is every 18 inches
or more at HF.

73,
Stuart
K5KVH

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Lars Edwards

Re: The K2 and Random Antennas

Tom

I had some very good experience with a Hygain trap vertical (40-10m). I had
it set up in a ground plane configuration with 4 radials per band.

The base of the antenna was no more than 20 ' high at most and I had 4 sets
of "bundled radials" that I had staked out ~ every 90 degrees around the
antenna. Each "bundle" had one radial cut for each band. I also used guys
near the top that kept the antenna pretty stable in some high winds.

I actually operated with the antenna at heights as low as 10 -15 ft. and
still had reasonably good results. All of this running from < 2watts to ~
10 watts.

I've been using a GAP Titan with the K2 and running ~ 10 watts max have
worked over 180 countries in the past year or less using this set up.

Lars

WB2ORD

----- Original Message -----
From: "tom.w3qs" <[hidden email]>
To: <[hidden email]>
Sent: Tuesday, June 14, 2005 4:24 PM
Subject: RE: [Elecraft] The K2 and Random Antennas

> Some interesting ideas, Stuart. I may have to try them. My two biggest
> problems, now, are getting the RF out of the shack and feeding antenna
> anywhere other than at the end. I am seriously thinking of getting a
> trapped vertical which would solve both problems. I was trying to do this
> on the cheap, and guess that isn't a good idea.
>
> Anyone have any experience with the Hustler 6 band vertical?
>
> 73, Tom
>
> -----Original Message-----
> From: Stuart Rohre [mailto:[hidden email]]
> Sent: Tuesday, June 14, 2005 3:54 PM
> To: tom.w3qs
> Subject: Re: [Elecraft] The K2 and Random Antennas
>
> Tom,
> You can always find a way to run balanced line to a good center fed

doublet,
> (dipole).
>
> You can put it on electric fence 5 inch plastic standoffs across a wall or
> ceiling, then inside pvc conduit as you pass thru a wall. Use Wireman's
300
> ohm ladder line, which is narrow. An alternate way thru a wall is to
mount
> two "all threads" rods in shrink tubing on each; in a pair of drilled
holes
> spaced about the spacing of your feeder.
>
> Use PVC conduit larger than the ladder line by a factor of 2X and space
the

> ladder line by cutting some foam spaces to slip over the line. Make these
> circular and spaced every 18 inches.
>
> Twisting a ladder line also helps keep it equally spaced from unbalancing
> conductors, in that any coupling will be equally received by the parallel
> wires as they change direction in the twist. The twist is every 18 inches
> or more at HF.
>
> 73,
> Stuart
> K5KVH
>
>
>
>
>
>
>
> _______________________________________________
> Elecraft mailing list
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>
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>
>

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