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Random wire lengths for antennas

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Emory Schley

Random wire lengths for antennas

My KX2 Owner's Manual, page 10, says "A length of about 25 feet for each wire, matched to the KX2's output using an antenna tuner (see ATU, pg. 11) will typically provide good performance on 40-10 m. (Without an ATU, resonant lengths are required for each band.) This antenna is ideal for outings where all gear must fit into a small bag (e.g., our model CS-40)."

I just bought my KX2 in late November/December 2016, so I presume this is the latest edition of the Owner's Manual.

Emory Schley
N4LP
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murphy

Re: Random wire lengths for antennas

True enough, so I initially used about 25 feet (actually 29 feet) but it failed on 60 and 80 meters. I wanted to work all the covered bands. So my recommendation is to use 58, 29 feet to cover them all. Maybe something shorter will also work, but I will let others cut more wire first

On 01/28/2017 08:38 PM, Emory Schley wrote:

My KX2 Owner's Manual, page 10, says "A length of about 25 feet for each wire, matched to the KX2's output using an antenna tuner (see ATU, pg. 11) will typically provide good performance on 40-10 m. (Without an ATU, resonant lengths are required for each band.) This antenna is ideal for outings where all gear must fit into a small bag (e.g., our model CS-40)."

I just bought my KX2 in late November/December 2016, so I presume this is the latest edition of the Owner's Manual.

Emory Schley
N4LP

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Matt Zilmer-3

Re: Random wire lengths for antennas

In reply to this post by Emory Schley

What Rev do you see on the front cover?

73,

matt W6NIA

On 1/28/2017 5:38 PM, Emory Schley wrote:

> My KX2 Owner's Manual, page 10, says "A length of about 25 feet for each wire, matched to the KX2's output using an antenna tuner (see ATU, pg. 11) will typically provide good performance on 40-10 m. (Without an ATU, resonant lengths are required for each band.) This antenna is ideal for outings where all gear must fit into a small bag (e.g., our model CS-40)."
>
> I just bought my KX2 in late November/December 2016, so I presume this is the latest edition of the Owner's Manual.
>
> Emory Schley
> N4LP
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--
Always store beer in a dark place. - R. Heinlein

Matt Zilmer, W6NIA
[Shiraz]

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Thorpe, Jeffrey

Re: Random wire lengths for antennas

Look here:

http://www.hamuniverse.com/randomwireantennalengths.html

Jeff -kg7hdz

On Jan 28, 2017, at 7:16 PM, Matt Zilmer <[hidden email]<mailto:[hidden email]>> wrote:

What Rev do you see on the front cover?

73,

matt W6NIA

On 1/28/2017 5:38 PM, Emory Schley wrote:
My KX2 Owner's Manual, page 10, says "A length of about 25 feet for each wire, matched to the KX2's output using an antenna tuner (see ATU, pg. 11) will typically provide good performance on 40-10 m. (Without an ATU, resonant lengths are required for each band.) This antenna is ideal for outings where all gear must fit into a small bag (e.g., our model CS-40)."

I just bought my KX2 in late November/December 2016, so I presume this is the latest edition of the Owner's Manual.
Emory Schley
N4LP
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--
Always store beer in a dark place. - R. Heinlein

Matt Zilmer, W6NIA
[Shiraz]

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wayne burdick

Re: Random wire lengths for antennas

Administrator

In reply to this post by Emory Schley

Generally something in excess of 50' for both wires will provide adequate on 80 meters and up.

Wayne
N6KR

On Jan 28, 2017, at 5:38 PM, "Emory Schley" <[hidden email]> wrote:

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Tim Seed

Re: Random wire lengths for antennas

In reply to this post by Emory Schley

You can download some code I wrote for this at https://github.com/timseed/rnd_Wire.git <https://github.com/timseed/rnd_Wire.git>

For those people who just would like “some data” this is the output of the program listed above. I have not tried this data in EzNEC etc. The Spectrum I was checking against from 160m to 10m including full 80m/40m as well as 30m and 60m bands.

Possible good length at 6.0M 19.69Ft
Possible good length at 6.99M 22.94Ft
Possible good length at 8.26M 27.09Ft
Possible good length at 10.1M 33.14Ft
Possible good length at 12.01M 39.39Ft
Possible good length at 13.99M 45.89Ft
Possible good length at 18.01M 59.08Ft
Possible good length at 20.2M 66.28Ft
Possible good length at 24.01M 78.77Ft
Possible good length at 24.77M 81.27Ft
Possible good length at 27.75M 91.06Ft
Possible good length at 29.56M 96.98Ft
Possible good length at 33.03M 108.36Ft
Possible good length at 34.97M 114.72Ft
Possible good length at 40.41M 132.56Ft
Possible good length at 44.34M 145.47Ft
Possible good length at 45.46M 149.13Ft
Possible good length at 48.95M 160.61Ft

Hope this helps,
Regards

Tim A45WG

> On Jan 29, 2017, at 4:08 PM, James Rodenkirch <[hidden email]> wrote:
>
> Emory - before you cut any wire, go to the below url and peruse all of the info - unless you desire to operate have a 1/2 wavelength antenna (not a bad thing) and have a 1/2 wavelength tuner for the band of interest, mgo to the below url for recommended wire lengths that avoid 1/2 wave antenna lengths for the your bands of interest.
>
> http://www.hamuniverse.com/randomwireantennalengths.html
>
> 71.5/72 de Jimm Rodenkirch K9JWV
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Tom McCulloch

Re: Random wire lengths for antennas

In reply to this post by Thorpe, Jeffrey

I guess we need an alternate definition of "random" ;-)

Tom

wb2qdg

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ktalbott

Re: Random wire lengths for antennas

Indeed we do. And not just "random" but
all flavors of end-fed antennae. I get
chastised for calling my
end-fed-tuned-multi-band-trapped-wire-an
tenna (actually it is an LNR MTR) an
EFHW. EFHW is simple to send. Should I
send EFTMBTWA? Perhaps some smart
people on the list will recommend a
succinct, unambiguous naming convention
for all flavors of end fed wire
antennae.
Ken - ke4rg

-----Original Message-----
From: Elecraft
[mailto:[hidden email]
] On Behalf Of Tom McCulloch
Sent: January 29, 2017 10:55
To: [hidden email]
Subject: Re: [Elecraft] Random wire
lengths for antennas

I guess we need an alternate definition
of "random" ;-)

Tom

wb2qdg

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Augie "Gus" Hansen

Re: Random wire lengths for antennas

Hi Ken,

How about EFRW (End Fed Random Wire). It shouldn't matter whether it is
just a piece of wire or one with traps, loading coils, or any other
lumped reactance. And it's also "simple to send".

73,
Gus Hansen
KB0YH

On 1/29/2017 9:13 AM, Ken Talbott wrote:

> Indeed we do. And not just "random" but
> all flavors of end-fed antennae. I get
> chastised for calling my
> end-fed-tuned-multi-band-trapped-wire-an
> tenna (actually it is an LNR MTR) an
> EFHW. EFHW is simple to send. Should I
> send EFTMBTWA? Perhaps some smart
> people on the list will recommend a
> succinct, unambiguous naming convention
> for all flavors of end fed wire
> antennae.
>

wayne burdick

The "Kinda Random Antenna" (was: Random wire lengths for antennas)

Administrator

In reply to this post by Tom McCulloch

I'd call an ad-hoc antenna that works on multiple bands with an ATU a "Kinda-Random Antenna" (KRA). (Apologies to linguistic purists.)

A simplified definition might be:

A. long enough to work within the maximum limits of the ATU's L-network on the lowest band used
B. presents a reasonably low impedance on all bands used (e.g., doesn't look like an end-fed half-wave)

ATUs have limited monotonicity and granularity, as well as stray impedances, so in practice there is a third criteria:

C. tunable on each band used despite specific L-network idiosyncrasies

This third criteria is the hardest one to predict for a given ATU design, as the idiosyncrasies vary with PCB layout and actual component values. They may only impact the highest bands, or for a particular antenna, the bands on which Q is the highest. For our ATU designs, we try to minimize strays and keep the network monotonic by using tightly toleranced capacitors and toroidal inductors.

While a wide range of wire lengths will meet the requirements of a "KRA" in the field, we've found from experience that something in the 25'-28' range works on all bands from 40 meters up, and roughly twice this for 80 meters up. Since it's impossible to predict the effect of ground losses, obstructions, deployed wire angles, etc., you may occasionally need to add or remove wire to obtain resonance on all bands used.

73,
Wayne
N6KR

On Jan 29, 2017, at 7:55 AM, Tom McCulloch <[hidden email]> wrote:

> I guess we need an alternate definition of "random" ;-)
>
> Tom
>
> wb2qdg

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Charlie T, K3ICH

Re: Random wire lengths for antennas

In reply to this post by ktalbott

OK, How about only Two types,
by definition:

#1 EFHW (End Fed ½λ resonant wire)
#2 NRW (Non-Resonant wire)

Chas

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Ken
Talbott
Sent: Sunday, January 29, 2017 11:14 AM
To: [hidden email]
Subject: Re: [Elecraft] Random wire lengths for antennas

Indeed we do. And not just "random" but all flavors of end-fed antennae. I
get chastised for calling my end-fed-tuned-multi-band-trapped-wire-an
tenna (actually it is an LNR MTR) an
EFHW. EFHW is simple to send. Should I send EFTMBTWA? Perhaps some smart
people on the list will recommend a succinct, unambiguous naming convention
for all flavors of end fed wire antennae.
Ken - ke4rg

-----Original Message-----
From: Elecraft
[mailto:[hidden email]
] On Behalf Of Tom McCulloch
Sent: January 29, 2017 10:55
To: [hidden email]
Subject: Re: [Elecraft] Random wire
lengths for antennas

I guess we need an alternate definition
of "random" ;-)

Tom

wb2qdg

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Michael Babineau-2

Re: Random wire lengths for antennas

In reply to this post by Emory Schley

I use an 84 to 86 feet (W3EDP length) of #26 AWG Wire on a plastic camping clothesline reel
and it matches quite easily with the KAT2 (K2 internal tuner) or the Elecraft T1. This will match
(and work reasonably well) from 80m through 10m as it is not close to a multiple of a half wave
on any of the ham bands so it presents a reasonable impedance that can be matched by an autotuner.

I use 5 X 16 foot radials on the ground as a minimum or Google “W3EDP" if you prefer to use an
elevated “counterpoise”.

Cheers

Michael VE3WMB

>From: Wayne Burdick <[hidden email] <mailto:[hidden email]>>
>Subject: Re: [Elecraft] Random wire lengths for antennas
>Date: January 29, 2017 at 12:01:14 AM GMT-5
>To: "Emory Schley" <[hidden email] <mailto:[hidden email]>>
>Cc: Elecraft <[hidden email] <mailto:[hidden email]>>

>Generally something in excess of 50' for both wires will provide adequate on 80 meters and up.

>Wayne
>N6KR
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Barry K3NDM

Re: The "Kinda Random Antenna" (was: Random wire lengths for antennas)

In reply to this post by wayne burdick

Wayne,
I know what you are saying and agree. In very simple terms, if you
can load it, it will radiate. That was a position that a writer with the
nom de plume of Kurt N Sterba too in a book he wrote. By the physical
law of conservation of energy, it all has to go somewhere. And, that
could be heat or radiation. In his book he claims to have loaded a
shopping cart and talked to people.

Yes, you can do these things as long as you make good connections
and the tuners can handle it. All of the discussion is how to pick a
length that the tuner will accept. Once there, physics takes over. And
just to prove my point, and yours, I just worked the CQ 160 CW contest.
My antenna was a vertical 20 meter dipole center fed with open wire. My
radio is a K3s. I worked across this country, Canada, and some DX with
this 33' wire antenna that by all rights should have been over 200'. I
would have done better, but my local power company added another
handicap, line noise. Bottom line: Throw some wire up and see if it can
be loaded. If yes, go for it.

73,
Barry
K3NDM

------ Original Message ------
From: "Wayne Burdick" <[hidden email]>
To: "Tom McCulloch" <[hidden email]>
Cc: "Elecraft Reflector" <[hidden email]>;
"[hidden email]" <[hidden email]>
Sent: 1/29/2017 12:40:58 PM
Subject: [Elecraft] The "Kinda Random Antenna" (was: Random wire lengths
for antennas)

>I'd call an ad-hoc antenna that works on multiple bands with an ATU a
>"Kinda-Random Antenna" (KRA). (Apologies to linguistic purists.)
>
>A simplified definition might be:
>
> A. long enough to work within the maximum limits of the ATU's
>L-network on the lowest band used
> B. presents a reasonably low impedance on all bands used (e.g.,
>doesn't look like an end-fed half-wave)
>
>ATUs have limited monotonicity and granularity, as well as stray
>impedances, so in practice there is a third criteria:
>
> C. tunable on each band used despite specific L-network
>idiosyncrasies
>
>This third criteria is the hardest one to predict for a given ATU
>design, as the idiosyncrasies vary with PCB layout and actual component
>values. They may only impact the highest bands, or for a particular
>antenna, the bands on which Q is the highest. For our ATU designs, we
>try to minimize strays and keep the network monotonic by using tightly
>toleranced capacitors and toroidal inductors.
>
>While a wide range of wire lengths will meet the requirements of a
>"KRA" in the field, we've found from experience that something in the
>25'-28' range works on all bands from 40 meters up, and roughly twice
>this for 80 meters up. Since it's impossible to predict the effect of
>ground losses, obstructions, deployed wire angles, etc., you may
>occasionally need to add or remove wire to obtain resonance on all
>bands used.
>
>73,
>Wayne
>N6KR
>
>
>On Jan 29, 2017, at 7:55 AM, Tom McCulloch <[hidden email]> wrote:
>
>> I guess we need an alternate definition of "random" ;-)
>>
>> Tom
>>
>> wb2qdg
>
>
>______________________________________________________________
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Lynn W. Taylor, WB6UUT

Re: Random wire lengths for antennas

In reply to this post by Tom McCulloch

Not an alternate definition, but we have to recognize that just any old
random length won't work.

If the wire is near 1/2 wavelength on a band, the impedance at the end
will be very high, and the tuner may not be able to match it.

In truth, we're really talking about non-resonant antennas, so numbers
like 53' keep coming up.

It was easier before 60m and 30m and 17m and 12m because all of the ham
bands were harmonically related, and the math was simpler.

73 -- Lynn

On 1/29/2017 7:55 AM, Tom McCulloch wrote:
> I guess we need an alternate definition of "random" ;-)
>
> Tom
>
> wb2qdg
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Hank Garretson

Re: Random wire lengths for antennas

In reply to this post by Emory Schley

On Sun, Jan 29, 2017 at 1:01 PM, Lynn W. Taylor, WB6UUT <
[hidden email]> wrote:

> If the wire is near 1/2 wavelength on a band, the impedance at the end
> will be very high, and the tuner may not be able to match it.
>

Why is that? A quick heuristic to help understand.

The current at the far end of a random wire is zero. One-quarter wavelength
from the far end, the current is maximum. Another one-quarter wavelength
along (total of one-half wavelength from far end) the current is zero.

I = E / Z >> Z = E / I

So, one-half wavelength from the far end, Z is going to be whatever E is
divided by a very small number >> VERY HIGH and hard to match.

This also explains why the impedance at the center of a half-wave dipole is
reasonable. Current at either end of the dipole is zero and high at the
center. Voltage at either end of the dipole is high and low at the center.

Z = E / I

At half-wave dipole center, low voltage at center divided by high current
at center gives a low impedance, easy to match.

It's all basic physics. There is no magic magic number or formula. Despite
what some antenna manufactures will tell you.

Ham Exuberantly,

Hank, W6SX
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k6dgw

Re: The "Kinda Random Antenna"

In reply to this post by Barry K3NDM

N6BT famously set up a "phased array" of 3 light bulbs in a V-beam
configuration and achieved WAC. He called it "The Illuminator." Kurt N.
Sterba [a regular in the old WorldRadio] is correct, the power will go
somewhere. My home antenna is a 136' wire strung along the wood fence
on electric fence insulators. Fed at the end, no overt counterpoise
[the outside of the coax shield handles that]. Not spec'd for 160 but
the KAT3 matches it fine. Invisible to HOA. NVIS on 160 and 80,
semi-NVIS on 40.

One thing to remember: feeding electrically long wires results in
complicated radiation patterns. The higher in frequency you go, the
more it's going to squirt your RF in different directions, not all of
which point at the DX. But, mine works very well considering it's about
1.8 m off the ground.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 1/29/2017 10:26 AM, Barry wrote:

> Wayne,
> I know what you are saying and agree. In very simple terms, if you
> can load it, it will radiate. That was a position that a writer with
> the nom de plume of Kurt N Sterba too in a book he wrote. By the
> physical law of conservation of energy, it all has to go somewhere.
> And, that could be heat or radiation. In his book he claims to have
> loaded a shopping cart and talked to people.
>
> Yes, you can do these things as long as you make good connections
> and the tuners can handle it. All of the discussion is how to pick a
> length that the tuner will accept. Once there, physics takes over. And
> just to prove my point, and yours, I just worked the CQ 160 CW
> contest. My antenna was a vertical 20 meter dipole center fed with
> open wire. My radio is a K3s. I worked across this country, Canada,
> and some DX with this 33' wire antenna that by all rights should have
> been over 200'. I would have done better, but my local power company
> added another handicap, line noise. Bottom line: Throw some wire up
> and see if it can be loaded. If yes, go for it.
>
> 73,
> Barry
> K3NDM

Barry K3NDM

Re: The "Kinda Random Antenna"

Skip,
Great idea for an antenna. I gotta try that one sometime.

Kurt N. Sterba was correct. Textbook antennas aren't always
possible, or even needed. If the situation is difficult, any radiator is
better than none. However, hams in general are anal animals on the
subject of antennas. My attitude has always been what's a db or two
among friends, and quite often that is the number we are sweating. But,
if you can't make it exactly like Kraus writes, get as close as you can
and let your antenna tuner worry about the match and don't think about
that extra db.

73,
Barry
K3NDM

------ Original Message ------
From: "Fred Jensen" <[hidden email]>
To: [hidden email]
Sent: 1/29/2017 6:10:29 PM
Subject: Re: [Elecraft] The "Kinda Random Antenna"

>N6BT famously set up a "phased array" of 3 light bulbs in a V-beam
>configuration and achieved WAC. He called it "The Illuminator." Kurt
>N. Sterba [a regular in the old WorldRadio] is correct, the power will
>go somewhere. My home antenna is a 136' wire strung along the wood
>fence on electric fence insulators. Fed at the end, no overt
>counterpoise [the outside of the coax shield handles that]. Not spec'd
>for 160 but the KAT3 matches it fine. Invisible to HOA. NVIS on 160
>and 80, semi-NVIS on 40.
>
>One thing to remember: feeding electrically long wires results in
>complicated radiation patterns. The higher in frequency you go, the
>more it's going to squirt your RF in different directions, not all of
>which point at the DX. But, mine works very well considering it's
>about 1.8 m off the ground.
>
>73,
>
>Fred ["Skip"] K6DGW
>Sparks NV DM09dn
>Washoe County
>
>On 1/29/2017 10:26 AM, Barry wrote:
>>Wayne,
>> I know what you are saying and agree. In very simple terms, if you
>>can load it, it will radiate. That was a position that a writer with
>>the nom de plume of Kurt N Sterba too in a book he wrote. By the
>>physical law of conservation of energy, it all has to go somewhere.
>>And, that could be heat or radiation. In his book he claims to have
>>loaded a shopping cart and talked to people.
>>
>> Yes, you can do these things as long as you make good connections
>>and the tuners can handle it. All of the discussion is how to pick a
>>length that the tuner will accept. Once there, physics takes over. And
>>just to prove my point, and yours, I just worked the CQ 160 CW
>>contest. My antenna was a vertical 20 meter dipole center fed with
>>open wire. My radio is a K3s. I worked across this country, Canada,
>>and some DX with this 33' wire antenna that by all rights should have
>>been over 200'. I would have done better, but my local power company
>>added another handicap, line noise. Bottom line: Throw some wire up
>>and see if it can be loaded. If yes, go for it.
>>
>>73,
>>Barry
>>K3NDM
>
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Nr4c

Re: Random wire lengths for antennas

In reply to this post by Charlie T, K3ICH

Since when is an EFHW a Random wire? It's not random, it's a half wavelength on a given frequency.

A Random wire is a wire of any length not resonant on the frequency desired. But it's a Half Wave on SOME frequency!

Sent from my iPhone
...nr4c. bill

> On Jan 29, 2017, at 12:53 PM, Charlie T, K3ICH <[hidden email]> wrote:
>
> OK, How about only Two types,
> by definition:
>
> #1 EFHW (End Fed ½λ resonant wire)
> #2 NRW (Non-Resonant wire)
>
> Chas
>
> -----Original Message-----
> From: Elecraft [mailto:[hidden email]] On Behalf Of Ken
> Talbott
> Sent: Sunday, January 29, 2017 11:14 AM
> To: [hidden email]
> Subject: Re: [Elecraft] Random wire lengths for antennas
>
> Indeed we do. And not just "random" but all flavors of end-fed antennae. I
> get chastised for calling my end-fed-tuned-multi-band-trapped-wire-an
> tenna (actually it is an LNR MTR) an
> EFHW. EFHW is simple to send. Should I send EFTMBTWA? Perhaps some smart
> people on the list will recommend a succinct, unambiguous naming convention
> for all flavors of end fed wire antennae.
> Ken - ke4rg
>
> -----Original Message-----
> From: Elecraft
> [mailto:[hidden email]
> ] On Behalf Of Tom McCulloch
> Sent: January 29, 2017 10:55
> To: [hidden email]
> Subject: Re: [Elecraft] Random wire
> lengths for antennas
>
> I guess we need an alternate definition
> of "random" ;-)
>
> Tom
>
> wb2qdg
>
>
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wayne burdick

Re: [KX3] The "Kinda Random Antenna" (was: Random wire lengths for antennas)

Administrator

In reply to this post by wayne burdick

Have you tried this with a low-power balun mounted right at the antenna jack? That will often help with RFI issues.

Wayne
N6KR

On Jan 29, 2017, at 6:03 PM, Jeff Crilly <[hidden email]> wrote:

> So I tried this out... using a ~26 foot wire ...
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Dean L

Re: Random wire lengths for antennas

In reply to this post by Nr4c

I believe that is why Jeff, kg7hdz, provided a link to an excel chart that
has lengths of NO half waves in US ham bands. Saves a bunch of math.

Making the Antenna " End fed non halfwave( in the ham bands )wire" or the
EFNHWW.
Whew....
73 all
Dean K2WW
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