Elecraft

A Good Antenna Length?

Classic

List

Threaded

33 messages Options

Jim GM

A Good Antenna Length?

What antenna lengths are you using on 160M with your KX3 or KXPA100
internal tuner? What is best for 160-6 meters? I like making my own
antennas with wire.

I usually have to give up one band or another cause it just would not tune
up on a certain band.

I have tried to stay with in these guide lines.

--
Jim K9TF
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Don Wilhelm-4

Re: A Good Antenna Length?

Jim,

Having one antenna to cover 160 meters through 6 meters is asking a *lot*.
But I would suggest starting with a halfwave on the lowest frequency band.
If that is a half wave on 160, then the pattern will begin to break into
multiple lobes beginning at 20 meters and up. Whether those lobes will
be in a favorable direction for you is a different question.

Of course, you would feed such an antenna with open wire line or ladder
line because those are relatively low loss and losses will increase as
the SWR increases. The feedline will have a high SWR on some bands.

The length of the feedline makes a big difference in the ability of any
given tuner to resolve the impedance at the shack end. A few sessions
with the TLW (Transmission Line for Windows) may be helpful in
determining the best feedline length compromise that ends up with a
usable impedance at the shack end for all bands considered. Of course
it will be necessary to know the antenna feedpoint for each band to know
how to find the impedance transformation that will be present at the
shack end. Antenna modeling can answer that antenna feedpoint impedance
question.

If the feedpoint impedance at the shack end is out of range of the tuner
being used, some additional capacitance or inductance placed either
across the feedline or in series with it may be necessary to bring the
impedance into a range that the tuner can handle.

Thirdly, you need a good current mode choke (balun) to keep RF out of
the shack and to provide a balanced to unbalanced transformation. Its
impedance must be at least 10 times (more is better) the highest line
impedance seen at the place that current mode choke is placed.

All the above must be taken into consideration for any antenna.

Yes, there is much more to your question than just the lengths of the
radiator. Any answers that do not also include the type and length of
the feedline may not be able to be duplicated given your particular
physical situation. Antennas and feedlines are just like that. Of
course an antenna whose feedpoint impedance is matched to the
transmission line characteristic impedance can use any length of that
feedline, but that is not the usual case for multiband antennas.

You will likely have better luck with 2 antennas - one for the low HF
bands and another for the upper HF bands - those are normally easier to
deal with. The ideal is a resonant antenna for each band, or fan
antennas covering multiple bands (I restrict those to 3 bands because
the interaction makes tuning frustrating).

Good luck on finding that "magic" length - many have tried over the
years and all are compromises.

73,
Don W3FPR

On 7/4/2014 5:21 PM, Jim GM wrote:
> What antenna lengths are you using on 160M with your KX3 or KXPA100
> internal tuner? What is best for 160-6 meters? I like making my own
> antennas with wire.
>
> I usually have to give up one band or another cause it just would not tune
> up on a certain band.
>
> I have tried to stay with in these guide lines.
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Jim GM

Re: A Good Antenna Length?

In reply to this post by Jim GM

I have tried a 6:1 balun at the feed point of the inverted L. How ever it
presents a significant loss while QRP with 5 W. Just does not have enough
isolation from ground. yet it presents a good match. Go figure.

--
Jim K9TF
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Don Wilhelm-4

Re: A Good Antenna Length?

Jim,

A lossy balun will provide a good match - just the same as a dummy load
resistor provides a good match (that is a near 100% loss if you are
considering the radiation capability).

Everything that loads does not make a good radiator.

73,
Don W3FPR

On 7/4/2014 6:16 PM, Jim GM wrote:
> I have tried a 6:1 balun at the feed point of the inverted L. How ever it
> presents a significant loss while QRP with 5 W. Just does not have enough
> isolation from ground. yet it presents a good match. Go figure.
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Kurt Cramer-3

Re: A Good Antenna Length?

In reply to this post by Jim GM

Why not consider a fan dipole. 160, 40, and 17 ?????? Model it on an antenna program. You're still going to need a tunner .

Sent from my iPhone

> On Jul 4, 2014, at 2:21 PM, Jim GM <[hidden email]> wrote:
>
> What antenna lengths are you using on 160M with your KX3 or KXPA100
> internal tuner? What is best for 160-6 meters? I like making my own
> antennas with wire.
>
> I usually have to give up one band or another cause it just would not tune
> up on a certain band.
>
> I have tried to stay with in these guide lines.
>
> --
> Jim K9TF
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

mcduffie

Re: A Good Antenna Length?

In reply to this post by Jim GM

> Just does not have enough
> isolation from ground. yet it presents a good match. Go figure.

A dummy load presents a good match. It just doesn't get out well.

Trying to have one antenna do 160-6 meters is just too much if you care about
getting out. One antenna can do a fair job on two bands, sometimes, three if
done right. But if you expect to have more than a dummy load on multiple bands,
you need to plan on having multiple antennas.

Gary
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Don Wilhelm-4

Re: A Good Antenna Length?

In reply to this post by Kurt Cramer-3

Why do you need a tuner with a well designed fan dipole. The lengths of
each set of wires can be trimmed to allow coax feed.

I have 2 fan dipoles here, one for 20, 15, and 10 and another for 30,
17, and 12 meters. Each fed with a single coax.
Restricting them to 3 bands simplifies the tuning difficulties
associated with interaction. Keeping the wires about 1 foot apart
reduces that interaction.

I do not mix bands that are 3rd harmonic related on the same coax, it
just complicates things - in other words, I do not mix radiators for 80
and 30 on the same coax, the same for radiators for 40 and 15 meters.

The KISS principle applies.

73,
Don W3FPR

On 7/4/2014 6:22 PM, Dad wrote:

> Why not consider a fan dipole. 160, 40, and 17 ?????? Model it on an antenna program. You're still going to need a tunner .
>
> Sent from my iPhone
>
>> On Jul 4, 2014, at 2:21 PM, Jim GM <[hidden email]> wrote:
>>
>> What antenna lengths are you using on 160M with your KX3 or KXPA100
>> internal tuner? What is best for 160-6 meters? I like making my own
>> antennas with wire.
>>
>> I usually have to give up one band or another cause it just would not tune
>> up on a certain band.
>>
>> I have tried to stay with in these guide lines.
>>
>> --
>> Jim K9TF
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

wayne burdick

Re: A Good Antenna Length?

Administrator

On Jul 4, 2014, at 3:34 PM, Don Wilhelm <[hidden email]> wrote:

> Why do you need a tuner with a well designed fan dipole. The lengths of each set of wires can be trimmed to allow coax feed.
>
> I have 2 fan dipoles here, one for 20, 15, and 10 and another for 30, 17, and 12 meters. Each fed with a single coax.
> Restricting them to 3 bands simplifies the tuning difficulties associated with interaction. Keeping the wires about 1 foot apart reduces that interaction.
>
> I do not mix bands that are 3rd harmonic related on the same coax, it just complicates things - in other words, I do not mix radiators for 80 and 30 on the same coax, the same for radiators for 40 and 15 meters.
>
> The KISS principle applies.
>
> 73,
> Don W3FPR
>
> On 7/4/2014 6:22 PM, Dad wrote:
>> Why not consider a fan dipole. 160, 40, and 17 ?????? Model it on an antenna program. You're still going to need a tunner .
>>
>> Sent from my iPhone
>>
>>> On Jul 4, 2014, at 2:21 PM, Jim GM <[hidden email]> wrote:
>>>
>>> What antenna lengths are you using on 160M with your KX3 or KXPA100
>>> internal tuner? What is best for 160-6 meters? I like making my own
>>> antennas with wire.
>>>
>>> I usually have to give up one band or another cause it just would not tune
>>> up on a certain band.
>>>
>>> I have tried to stay with in these guide lines.
>>>
>>> --
>>> Jim K9TF
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>> Message delivered to [hidden email]
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Nr4c

Re: A Good Antenna Length?

In reply to this post by Jim GM

Oops,

Jim
I use two antennas here at my place.
For 80 and 160 I use a 170 foot long wire running from just over my feed line entry to a point 40 ft below a branch on a 75 ft pine, up to to the branch and over to another tree ( kinda like a "Z"). This is fed to an "L Match" made from a section of coil and a variable capacitor for 80 and I add an additional fixed cap for 160.

For higher bands I have a 40-20-10 meter "fan" dipole that my K-Line (& my KX3-Line") will tune on 40-20-17-15-12-10-6 meters. Many will say "it can't work" but please don't tell my radios! The Elecraft tuners can tune anything!
I once worked a friend who'd just moved and was using a "GutterTron" ant in the CQWW. Yeah, the gutter and downspout fed against a ground-rod.

Another friend loaded up the liner in his chimney, called a GutterTron.

Have fun. Try anything. It just might work. You can make a lot of antennas from a $45.00 spool of THHN and plastic "cutting" board from Walmart. About 2/3rds the price of a G5RV.

Sent from my iPhone
...nr4c. bill

> On Jul 4, 2014, at 5:21 PM, Jim GM <[hidden email]> wrote:
>
> What antenna lengths are you using on 160M with your KX3 or KXPA100
> internal tuner? What is best for 160-6 meters? I like making my own
> antennas with wire.
>
> I usually have to give up one band or another cause it just would not tune
> up on a certain band.
>
> I have tried to stay with in these guide lines.
>
> --
> Jim K9TF
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

wayne burdick

Re: A Good Antenna Length?

Administrator

In reply to this post by Jim GM

Jim,

Try 102 feet (or so) for each leg of a dipole fed with twinlead or open-wire line. This is not a close multiple of a half-wave on any band from 160-6 meters, so it stands a chance of providing a reasonable match on all bands.

If the internal tuners can't find a match on one or two bands, adjust the length of one or both sides by a couple of feet experimentally. It'll be slightly imbalanced if it ends up off-center-fed, but this won't have much practical impact.

At my QTH I use a 4:1 balun (Elecraft BL2) right at the radio to feed this antenna. The BL2 also has a 4:1/1:1 switch. I use the 4:1 setting for all but one band, where the 1:1 setting makes it easier on the ATU. Note that if you don't get to a low SWR when you first tap ATU TUNE, tap again within 5 seconds and the tuner will try more LC combinations. This will nearly always provide a 2:1 or better match unless the antenna presents a very high impedance.

The KXAT3 will match a wider range than the KXAT100. For safety reasons, our QRO ATUs put limits on the SWR they will try to match.

Use a good ground at the station. If in your installation you experience any RFI at higher power, drop back to a lower level.

73,
Wayne
N6KR

On Jul 4, 2014, at 2:21 PM, Jim GM <[hidden email]> wrote:

> What antenna lengths are you using on 160M with your KX3 or KXPA100
> internal tuner? What is best for 160-6 meters? I like making my own
> antennas with wire.
>
> I usually have to give up one band or another cause it just would not tune
> up on a certain band.
>
> I have tried to stay with in these guide lines.
>
> --
> Jim K9TF
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

wayne burdick

Re: A Good Antenna Length?

Administrator

In reply to this post by Nr4c

On Jul 4, 2014, at 4:01 PM, Nr4c <[hidden email]> wrote:

> I once worked a friend who'd just moved and was using a "GutterTron" ant in the CQWW. Yeah, the gutter and downspout fed against a ground-rod.
>
> Another friend loaded up the liner in his chimney, called a GutterTron.

I worked all over the country on 10 and 15 meters recently using a large metal window frame (5' x 8' picture window) as the antenna. I used alligator clips directly from the KX3 to two spots on the frame, experimenting with spacing. This is not described in the literature, but it worked. The ATU tuned up the window frame to ~1.0:1 on 20-6 meters.

Wayne
N6KR

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Nate Bargmann

Re: A Good Antenna Length?

In reply to this post by Jim GM

A few years ago I took a cue from a usenet posting by Walt, W2DU, that
stated that the 102 foot doublet of the G5RV is a good antenna on 80m
when fed with twin/window lead and a tuner as it is 3/8 of a wavelength
on that band. I carried it further and have a 204 foot doublet fed with
450 ohm window lead and a Palstar AT1500DT tuner and the apex around 40
feet above ground level and the ends around 20 feet.. It may or may not
work with the K3's internal tuner as I've not tried feeding it with
coax. It works very well for me on 160m, 80m, and 40m. At the moment I
am also feeding it on the higher bands until I get dedicated wires up
for those bands.

As I understand it, the 3/8 wavelength on the lowest band avoids
feeding it at the voltage loop so matching is easier. Having a 3/4
wavelength 80m and 1.5 wavelengths on 40m also matches easily in my
experience.

73, Nate N0NB

--

"The optimist proclaims that we live in the best of all
possible worlds. The pessimist fears this is true."

Ham radio, Linux, bikes, and more: http://www.n0nb.us
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Dr. William J. Schmidt, II

Re: A Good Antenna Length?

In reply to this post by wayne burdick

That's what I use... about 103 feet... and gives reasonable match on all
bands.

Dr. William J. Schmidt - K9HZ / J68HZ/ 8P6HK/ ZF2HZ/ PJ4HZ/ VP5HZ

Owner - Operator
Big Signal Ranch
Staunton, Illinois

email: [hidden email]

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Wayne
Burdick
Sent: Friday, July 04, 2014 6:15 PM
To: Jim GM
Cc: Elecraft
Subject: Re: [Elecraft] A Good Antenna Length?

Jim,

Try 102 feet (or so) for each leg of a dipole fed with twinlead or open-wire
line. This is not a close multiple of a half-wave on any band from 160-6
meters, so it stands a chance of providing a reasonable match on all bands.

If the internal tuners can't find a match on one or two bands, adjust the
length of one or both sides by a couple of feet experimentally. It'll be
slightly imbalanced if it ends up off-center-fed, but this won't have much
practical impact.

At my QTH I use a 4:1 balun (Elecraft BL2) right at the radio to feed this
antenna. The BL2 also has a 4:1/1:1 switch. I use the 4:1 setting for all
but one band, where the 1:1 setting makes it easier on the ATU. Note that if
you don't get to a low SWR when you first tap ATU TUNE, tap again within 5
seconds and the tuner will try more LC combinations. This will nearly always
provide a 2:1 or better match unless the antenna presents a very high
impedance.

The KXAT3 will match a wider range than the KXAT100. For safety reasons, our
QRO ATUs put limits on the SWR they will try to match.

Use a good ground at the station. If in your installation you experience any
RFI at higher power, drop back to a lower level.

73,
Wayne
N6KR

On Jul 4, 2014, at 2:21 PM, Jim GM <[hidden email]> wrote:

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Hank Garretson

Re: A Good Antenna Length?

102 feet.

There is nothing magic about 102 feet if you feed it with open-wire line.
Having a decent match at the feed point doesn't mean squat because
feed-point impedance is transformed by the feed line and what you get at
the transmitter end won't be the same as at the feed point unless feed-line
length is an even multiple of a half wavelength.

What IS important is the total length of one half of your dipole plus your
open-wire feed.

For whatever frequency/frequencies you want an easy match on, make half of
your dipole plus feed length as close to an odd multiple of a quarter
wavelength as you can.

This can be problematic if you want to operate on multiple bands. Don't
despair--it's not that hard. You can adjust flat-top length or feed-line
length or both to get something you can match on all your bands of
interest.

Bottom line. Your ability to match is affected by both dipole length and
(open-wire) feed-line length.

73,

Hank, W6SX
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Dick, K2ZR

Re: A Good Antenna Length?

In reply to this post by Nr4c

Hi All,

When in Key West I have little space for antennas. I built a simple Off
Center Fed 40M Windom [ 67/33 or about 44' & 22' ]. The long element is a
15' off of the ground while the short element that is not much higher goes
up to the peak of my QTH and back down to the other side of my deck.

My K2/100 - KAT100 generally runs 75W & I've had great success with this
antenna on every band 40-10. For 80M and 160M I alligator clip an 8' piece
of wire from the end of the short element to my gutter system with provides
another 80' of metal to the antenna. Do I burn up 160 & 80, not big time no
but, I make contacts on both bands.

In addition, if you ask me what I do for a ground: It's a 40' piece of #14
wire connected to a 2' piece of copper ground rod. Key West is a rock and
it's tough to get down any further.

Is my 40M Windom Gutter/Rube Goldberg Contraption a dummy load, no! I have
the K2ZR/4 contest wallpaper and logs full of contacts to prove it.

It 'taint perfect but you do what ya gotta do. And, if the bands are in
lousey shape I ride my bike 5 minutes to my shady spot at Fort Zachory
Taylor Beach and play some tunes on my Taylor Big Baby guitar. Life is good!

73,

Dick

K2ZR

Niagara County, NY

Mid-May to Mid December

Ricardo en Cayo Hueso

K2ZR/4

Key West, "The End Of The Road" IOTA NA-062

Mid-December - Time to go to Dayton

The Southernmost Ham Shack In The Continental USA

-----Original Message-----
From: Elecraft [mailto:[hidden email]] On Behalf Of Nr4c
Sent: Friday, July 04, 2014 7:01 PM
To: Jim GM
Cc: Elecraft
Subject: Re: [Elecraft] A Good Antenna Length?

Oops,

Jim

I use two antennas here at my place.

For 80 and 160 I use a 170 foot long wire running from just over my feed
line entry to a point 40 ft below a branch on a 75 ft pine, up to to the
branch and over to another tree ( kinda like a "Z"). This is fed to an "L
Match" made from a section of coil and a variable capacitor for 80 and I add
an additional fixed cap for 160.

For higher bands I have a 40-20-10 meter "fan" dipole that my K-Line (& my
KX3-Line") will tune on 40-20-17-15-12-10-6 meters. Many will say "it can't
work" but please don't tell my radios! The Elecraft tuners can tune
anything!

I once worked a friend who'd just moved and was using a "GutterTron" ant in
the CQWW. Yeah, the gutter and downspout fed against a ground-rod.

Another friend loaded up the liner in his chimney, called a GutterTron.

Have fun. Try anything. It just might work. You can make a lot of antennas
from a $45.00 spool of THHN and plastic "cutting" board from Walmart. About
2/3rds the price of a G5RV.

Sent from my iPhone

...nr4c. bill

> On Jul 4, 2014, at 5:21 PM, Jim GM < <mailto:[hidden email]>
[hidden email]> wrote:

>

> What antenna lengths are you using on 160M with your KX3 or KXPA100

> internal tuner? What is best for 160-6 meters? I like making my own

> antennas with wire.

>

> I usually have to give up one band or another cause it just would not

> tune up on a certain band.

>

> I have tried to stay with in these guide lines.

>

> --

> Jim K9TF

> ______________________________________________________________

> Elecraft mailing list

> Home: <http://mailman.qth.net/mailman/listinfo/elecraft>
http://mailman.qth.net/mailman/listinfo/elecraft

> Help: <http://mailman.qth.net/mmfaq.htm> http://mailman.qth.net/mmfaq.htm

> Post: <mailto:[hidden email]> mailto:[hidden email]

>

> This list hosted by: <http://www.qsl.net> http://www.qsl.net Please help
support this email

> list: <http://www.qsl.net/donate.html> http://www.qsl.net/donate.html
Message delivered to

> <mailto:[hidden email]> [hidden email]

______________________________________________________________

Elecraft mailing list

Home: <http://mailman.qth.net/mailman/listinfo/elecraft>
http://mailman.qth.net/mailman/listinfo/elecraft

Help: <http://mailman.qth.net/mmfaq.htm> http://mailman.qth.net/mmfaq.htm

Post: <mailto:[hidden email]> mailto:[hidden email]

This list hosted by: <http://www.qsl.net> http://www.qsl.net

Please help support this email list: <http://www.qsl.net/donate.html>
http://www.qsl.net/donate.html Message delivered to <mailto:[hidden email]>
[hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Jim Sheldon

Re: A Good Antenna Length?

In reply to this post by Jim GM

Been there, done that one too. Hamfest in Concordia, KS back in the
early 80's just after I retired from the Army. Used an old Ten-Tec
Argonaut and loaded the entire gutter system at the motel the hamfest
was held at. There was so much corrosion in the joints that even the 5
watt Argonaut wiped out TV reception throughout the whole motel. Worked
a whole bunch of stations on 20 meters too. Good thing they never
figured out where the problem was coming from - LOL!

Jim - W0EB

------ Original Message ------
From: "Wayne Burdick" <[hidden email]>
To: "Nr4c" <[hidden email]>
Cc: "Elecraft" <[hidden email]>; "Jim GM"
<[hidden email]>
Sent: 7/4/2014 6:20:40 PM
Subject: Re: [Elecraft] A Good Antenna Length?

>
>On Jul 4, 2014, at 4:01 PM, Nr4c <[hidden email]> wrote:
>
>> I once worked a friend who'd just moved and was using a "GutterTron"
>>ant in the CQWW. Yeah, the gutter and downspout fed against a
>>ground-rod.
>>
>> Another friend loaded up the liner in his chimney, called a
>>GutterTron.
>
>
>I worked all over the country on 10 and 15 meters recently using a
>large metal window frame (5' x 8' picture window) as the antenna. I
>used alligator clips directly from the KX3 to two spots on the frame,
>experimenting with spacing. This is not described in the literature,
>but it worked. The ATU tuned up the window frame to ~1.0:1 on 20-6
>meters.
>
>Wayne
>N6KR
>
>
>______________________________________________________________
>Elecraft mailing list
>Home: http://mailman.qth.net/mailman/listinfo/elecraft
>Help: http://mailman.qth.net/mmfaq.htm
>Post: mailto:[hidden email]
>
>This list hosted by: http://www.qsl.net
>Please help support this email list: http://www.qsl.net/donate.html
>Message delivered to [hidden email]

David Cutter

Re: A Good Antenna Length?

In reply to this post by Jim GM

You might consider an off-centre-fed dipole with appropriate balun and
choke. A dual core balun that gives good cancellation of common mode
currents at the feed point is essential and some folks add another choke on
the ground with ground spike on the house side to drain off residual cmc.
If you are particularly prone to local noise pickup on your long runs of
coax, then another choke at the entry to your house is a good move.

Coverage of 160 to 6 is possible but the baluns and chokes need attention to
cover that range, especially if suspended and running power unless sturdily
supported. Inverted V is easiest. You might not get all the coverage you
want in one wire but you can join another ocfd onto the original to get more
coverage on difficult bands.

The ocfd gives your matching unit an easier time, ie reduced losses.
Running your radio without a linear means you can have a lightweight aerial
with small balun on fibreglass pole.

These gents have done a huge amount of work: http://hamwaves.com/cl-ocfd/
and here http://www.dj0ip.de/off-center-fed-dipole/
http://www.dj0ip.de/off-center-fed-dipole/80m-ocf/
and try the user group: [hidden email]

73
David
G3UNA

----- Original Message -----
From: "Jim GM" <[hidden email]>
To: "Elecraft" <[hidden email]>
Sent: Friday, July 04, 2014 10:21 PM
Subject: [Elecraft] A Good Antenna Length?

Jim Brown-10

Re: A Good Antenna Length?

On 7/5/2014 2:05 AM, David Cutter wrote:
> You might consider an off-centre-fed dipole with appropriate balun and
> choke.

Not if you're going to run power. An off center fed antenna generates
high common mode voltage, which will fry even the best choke when
running power. I wouldn't consider such an antenna at greater than 100W.

73, Jim K9YC
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

LA7NO

Re: A Good Antenna Length?

Hello,

I can recommend reading the following:

http://hamwaves.com/cl-ocfd/index.html

The high common-mode signals are apparently well attended to.

Per-Tore / LA7NO

On 5 July 2014 16:24, Jim Brown <[hidden email]> wrote:

> On 7/5/2014 2:05 AM, David Cutter wrote:
>>
>> You might consider an off-centre-fed dipole with appropriate balun and
>> choke.
>
>
> Not if you're going to run power. An off center fed antenna generates high
> common mode voltage, which will fry even the best choke when running power.
> I wouldn't consider such an antenna at greater than 100W.
>
> 73, Jim K9YC
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

73,

Per-Tore / LA7NO

Dave-5

Re: A Good Antenna Length?

In reply to this post by Jim Brown-10

I tried a 40M OCFD for a while. I gave up on it and went back to a centre
fed dipole instead.

Even on 40M it didn't seem very good and I was plagued with RF getting into
PCs and them shutting down or periferals stopping working. Plus, despite
the hype, it didn't really seem to work well on other bands. The Antenna
analyser was very dismissive, showing resonances outside of the Amateur
bands and, on some that it was supposed to work on, no sign of any resonance
at all.

Dave (G0DJA)

----- Original Message -----
From: "Jim Brown" <[hidden email]>
To: <[hidden email]>
Sent: Saturday, July 05, 2014 2:24 PM
Subject: Re: [Elecraft] A Good Antenna Length?

> On 7/5/2014 2:05 AM, David Cutter wrote:
>> You might consider an off-centre-fed dipole with appropriate balun and
>> choke.
>
> Not if you're going to run power. An off center fed antenna generates high
> common mode voltage, which will fry even the best choke when running
> power. I wouldn't consider such an antenna at greater than 100W.
>
> 73, Jim K9YC
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]