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The use of a doublet

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Tom Brereton

The use of a doublet

I have long been an advocate of the center fed doublet.
I have put them up in numerous state and even in Germany.
Of course I have used different tuners. Folks here in this
write about of all kinds of external tuners.

May I make a radical suggestion? Use the internal K3
antenna tuner! Now I know that most transceivers have
internal tuners that will operate well only up to 3:1 swr.
The K3 tuner is rated much higher than that. Indeed,
I was very surprised how well it works here in my station
with my 135' foot dipole with 450 ohm ladder line and a
balun.
I highly recommend that one should consider the K3 tuner.
It's a winner.

Tom Brereton, W0TOM
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Dave Van Wallaghen

Re: The use of a doublet

I'm using a 66' doublet fed with homebrew ladder line for portable
operations in my yard. I have it flat top up in a tree about 35' up. I
made a small adapter to go from the ANT1 connector from my KAT3 to a
couple of banana sockets. I then bring the ladder line straight into
that adapter.

I wound up with a feedline length of around 55' and the KAT3 tunes up on
this arrangement 80m-10m FB. It is obviously very short for 80m and I
don't use it on that band, but the KAT3 did tune up on it (I'm sure not
very efficiently).

I've been running 5 watts out there and worked a number of states. I
worked Italy on 5 watts last summer on 20m.

I hooked the doublet directly to the KAT3 at the urging of Ron (AC7AC)
and Don (W3FPR) here on the list and have been very happy with it.

73,
Dave W8FGU

THOMAS BRERETON wrote:

> I have long been an advocate of the center fed doublet.
> I have put them up in numerous state and even in Germany.
> Of course I have used different tuners. Folks here in this
> write about of all kinds of external tuners.
>
> May I make a radical suggestion? Use the internal K3
> antenna tuner! Now I know that most transceivers have
> internal tuners that will operate well only up to 3:1 swr.
> The K3 tuner is rated much higher than that. Indeed,
> I was very surprised how well it works here in my station
> with my 135' foot dipole with 450 ohm ladder line and a
> balun.
> I highly recommend that one should consider the K3 tuner.
> It's a winner.
>
> Tom Brereton, W0TOM
> ______________________________________________________________
> 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
>
>

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Don Wilhelm-4

Re: The use of a doublet

In reply to this post by Tom Brereton

Tom (and all others who have commented),

Please pass along the length and type of your feedline when making
statements of the effectiveness and ease of tuning for your antenna.
With a resonant halfwave dipole fed with coax (or any line matched to
the antenna impedance), the feedline length is not important, but most
multiband antennas are not like that and the feedline length is a very
important parameter.
The feedline is a part of the antenna system, and when not matched to
the antenna feedpoint impedance, it will act as an impedance transformer.
Your particular antenna and feedline may work just fine, but the same
antenna with a different feedline length may not work out well.
So for others to duplicate your experiences (or attempt to), please add
the length and type of feedline.

73,
Don W3FPR

THOMAS BRERETON wrote:

Joe Planisky

Re: The use of a doublet

For those who might be a little mystified by this discussion of
feedlines and antennas, I can recommend the series of articles titled
"Another Look at Reflections" by M. Walter Maxwell (W2DU/W8HKK)
published in QST between 1973 and 1976. The whole series is available
as a single PDF file at http://www.arrl.org/members-only/tis/info/pdf/Reflect.pdf
(for ARRL members only, sorry.) It's a very thorough treatment of
the subject of transmission lines and impedance matching. Easy
reading in some places and a bit tougher in others, it's well worth
close and careful study if you want to understand transmission lines
and matching.

73
--
Joe KB8AP

On Jul 15, 2009, at 4:34 PM, Don Wilhelm wrote:

...

> The feedline is a part of the antenna system, and when not matched to
> the antenna feedpoint impedance, it will act as an impedance
> transformer.
> Your particular antenna and feedline may work just fine, but the same
> antenna with a different feedline length may not work out well.
...
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David Cutter

Re: The use of a doublet

In reply to this post by Tom Brereton

I use mine with a 2 x 88ft doublet fed straight in and it works on all
bands.

David
G3UNA

----- Original Message -----
From: "THOMAS BRERETON" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Sent: Wednesday, July 15, 2009 11:44 PM
Subject: [Elecraft] The use of a doublet

>I have long been an advocate of the center fed doublet.
> I have put them up in numerous state and even in Germany.
> Of course I have used different tuners. Folks here in this
> write about of all kinds of external tuners.
>
> May I make a radical suggestion? Use the internal K3
> antenna tuner! Now I know that most transceivers have
> internal tuners that will operate well only up to 3:1 swr.
> The K3 tuner is rated much higher than that. Indeed,
> I was very surprised how well it works here in my station
> with my 135' foot dipole with 450 ohm ladder line and a
> balun.
> I highly recommend that one should consider the K3 tuner.
> It's a winner.
>
> Tom Brereton, W0TOM
> ______________________________________________________________
> 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

Russ Tobolic

Fw: The use of a doublet

In reply to this post by Don Wilhelm-4

You can go straight to www.W2DU.com to get thePDF's.

Russ, N3CO

----- Forwarded Message ----
From: Joe Planisky <[hidden email]>
To: Elecraft Reflector <[hidden email]>
Sent: Wednesday, July 15, 2009 10:28:32 PM
Subject: Re: [Elecraft] The use of a doublet

For those who might be a little mystified by this discussion of
feedlines and antennas, I can recommend the series of articles titled
"Another Look at Reflections" by M. Walter Maxwell (W2DU/W8HKK)
published in QST between 1973 and 1976. The whole series is available
as a single PDF file at http://www.arrl.org/members-only/tis/info/pdf/Reflect.pdf
(for ARRL members only, sorry.) It's a very thorough treatment of
the subject of transmission lines and impedance matching. Easy
reading in some places and a bit tougher in others, it's well worth
close and careful study if you want to understand transmission lines
and matching.

73
--
Joe KB8AP

On Jul 15, 2009, at 4:34 PM, Don Wilhelm wrote:

...

> The feedline is a part of the antenna system, and when not matched to
> the antenna feedpoint impedance, it will act as an impedance
> transformer.
> Your particular antenna and feedline may work just fine, but the same
> antenna with a different feedline length may not work out well.
...
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list1

Re: The use of a doublet

In reply to this post by Joe Planisky

Joe,
Thank you for thst wonderful reference.
Steve, W2MY

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]]On Behalf Of Joe Planisky
Sent: Wednesday, July 15, 2009 9:29 PM
To: Elecraft Reflector
Subject: Re: [Elecraft] The use of a doublet

For those who might be a little mystified by this discussion of
feedlines and antennas, I can recommend the series of articles titled
"Another Look at Reflections" by M. Walter Maxwell (W2DU/W8HKK)
published in QST between 1973 and 1976. The whole series is available
as a single PDF file at
http://www.arrl.org/members-only/tis/info/pdf/Reflect.pdf
(for ARRL members only, sorry.)
73
--
Joe KB8AP

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Ralph Tyrrell

Re: The use of a doublet

In reply to this post by Tom Brereton

I use the K3 internal tuner then to a BL2. Most bands are good with the 1:1 ratio. That little switch is handy to go to 4:1 for some bands.

I have a 85 m loop and have worked 160 to 6 meters with good results.
On 160 I do have to tie the 450 Ohm line wires together and feed it against ground. A DPDT knife switch does that for me.

73, Ty, W1TF, K3 #696

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AC7AC

Re: The use of a doublet

In reply to this post by David Cutter

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