[Elecraft] OT: G5RV's antenna

2012-03-09 Thread Ken G Kopp
I have Varney's (G5RV) original article.  The antenna was designed
for -only- 20M .  Since then it's taken on the proverbial "life of it's
own" and become somewhat of a "cult" antenna, as is the case with
the "Carolina Windom".

Why would one start with a perfectly good balanced-line fed Zepp,
cobble a piece of "special-length" coax onto the end of that balanced
line so that the antenna becomes something else, and then have to
use an antenna tuner to make the thing work?

Since the antenna requires a tuner, why not connect the balanced line
to a balanced tuner ... or one with a balun ... and enjoy all the virtues
of a classic Zepp?

73!

Ken Kopp - K0PP
elecraftcov...@gmail.com
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Re: [Elecraft] OT: G5RV's antenna

2012-03-09 Thread Don Wilhelm
Ken,

I will agree with all until I got to the end of your post - "classic zepp"
The original (and classic)  Zepp antenna was a 1/2 wave wire fed through 
a 1/4 wave transmission line connected to the end that was trailed 
behind lighter-than-air aircraft (Zepplin).  If you look at the J-pole, 
and turn it horizontally, you will see exactly the same thing - a 1/4 
wave transmission line with one side connected to a 1/2 wavelength radiator.

I am not sure how the "Zepp" term became associated with any kind of 
center fed dipoles, but it has in ham circles, and I find it confusing - 
there is the Center Fed Zepp (2 halfwaves in phase) antenna, and then 
there is the Extended Center Fed Zepp (5/8 wavelength each side of 
center), and then there is the "classic Zepp" that is the antenna 
designed for trailing the aircraft.  So we must be careful to explain 
which kind of Zepp antenna we are referring to when we write "Zepp"  
There is a lot of difference.

73,
Don W3FPR

On 3/9/2012 9:53 PM, Ken G Kopp wrote:
> I have Varney's (G5RV) original article.  The antenna was designed
> for -only- 20M .  Since then it's taken on the proverbial "life of it's
> own" and become somewhat of a "cult" antenna, as is the case with
> the "Carolina Windom".
>
> Why would one start with a perfectly good balanced-line fed Zepp,
> cobble a piece of "special-length" coax onto the end of that balanced
> line so that the antenna becomes something else, and then have to
> use an antenna tuner to make the thing work?
>
> Since the antenna requires a tuner, why not connect the balanced line
> to a balanced tuner ... or one with a balun ... and enjoy all the virtues
> of a classic Zepp?
>
> 73!
>
> Ken Kopp - K0PP
> elecraftcov...@gmail.com
> __
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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Re: [Elecraft] OT: G5RV's antenna

2012-03-09 Thread Ken G Kopp
Yes Don, I knew when I used the term "classic Zepp" that I was taking
a bit of liberty with the term.  The original Zepp was indeed end-fed from
the cabin of a Zepplin.  I've often wondered how long the feeder actually
was.  They may have been closer to a simple end-fed wire.

I'd also noted the concept repeated in the J-pole.

We "old ops" have certain advantages ...

73!  Ken

On Sat, Mar 10, 2012 at 3:23 AM, Don Wilhelm  wrote:
> Ken,
>
> I will agree with all until I got to the end of your post - "classic zepp"
> The original (and classic)  Zepp antenna was a 1/2 wave wire fed through
> a 1/4 wave transmission line connected to the end that was trailed
> behind lighter-than-air aircraft (Zepplin).  If you look at the J-pole,
> and turn it horizontally, you will see exactly the same thing - a 1/4
> wave transmission line with one side connected to a 1/2 wavelength radiator.
>
> I am not sure how the "Zepp" term became associated with any kind of
> center fed dipoles, but it has in ham circles, and I find it confusing -
> there is the Center Fed Zepp (2 halfwaves in phase) antenna, and then
> there is the Extended Center Fed Zepp (5/8 wavelength each side of
> center), and then there is the "classic Zepp" that is the antenna
> designed for trailing the aircraft.  So we must be careful to explain
> which kind of Zepp antenna we are referring to when we write "Zepp"
> There is a lot of difference.
>
> 73,
> Don W3FPR
>
> On 3/9/2012 9:53 PM, Ken G Kopp wrote:
>> I have Varney's (G5RV) original article.  The antenna was designed
>> for -only- 20M .  Since then it's taken on the proverbial "life of it's
>> own" and become somewhat of a "cult" antenna, as is the case with
>> the "Carolina Windom".
>>
>> Why would one start with a perfectly good balanced-line fed Zepp,
>> cobble a piece of "special-length" coax onto the end of that balanced
>> line so that the antenna becomes something else, and then have to
>> use an antenna tuner to make the thing work?
>>
>> Since the antenna requires a tuner, why not connect the balanced line
>> to a balanced tuner ... or one with a balun ... and enjoy all the virtues
>> of a classic Zepp?
>>
>> 73!
>>
>> Ken Kopp - K0PP
>> elecraftcov...@gmail.com
>> __
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Elecraft@mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
> __
> Elecraft mailing list
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> Help: http://mailman.qth.net/mmfaq.htm
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> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
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Re: [Elecraft] OT: G5RV's antenna

2012-03-09 Thread Ron D'Eau Claire
The feeder was exactly 1/4 wavelength long so it transformed the very high
impedance at the end of the radiator to a very low impedance at the rig in
the Zeppelin, minimizing "RF in the Shack" issues. 

Since the radiator was 1/2 wavelength long, very little current flowed from
the feeder into the radiator. It was a voltage "loop". That meant that,
although the other side of the feeder was terminated in an insulator, the
currents along the feed line were well balanced. Most radiomen of the time
considered that the leakage current into the insulator closely matched the
current into the radiator so the balance was very good indeed. 

The next step, coming back to Don's comment, was to connect two Zepps back
to back for some additional gain. Extending the radiators beyond 1/2
wavelength enhanced this effect and, since it was now a center fed antenna,
feedline imbalance was no longer a danger, hence the popularity of the
"extended double Zepp".

I am always careful to call my center fed wires a "doublet" to avoid
confusion but many Hams today incorrectly call any wire fed at the center
with open wire line a "Zepp". 

Feeding a traditional Zepp only minimizes feed line radiation when the
radiator is exactly 1/2 wavelength. (The feeder can be any length if you can
deal with the feed point impedance at the rig end.) However, many Hams have
reported excellent results with Zepps with not-1/2-wave long radiators. In
those cases the feed line is also part of the radiating antenna. That can be
good when the feeder is in the clear and less so if it's not. The same is
true of most off center fed antennas.

73,  

Ron AC7AC

-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Ken G Kopp
Sent: Friday, March 09, 2012 7:34 PM
To: d...@w3fpr.com
Cc: elecraft@mailman.qth.net
Subject: Re: [Elecraft] OT: G5RV's antenna

Yes Don, I knew when I used the term "classic Zepp" that I was taking a bit
of liberty with the term.  The original Zepp was indeed end-fed from the
cabin of a Zepplin.  I've often wondered how long the feeder actually was.
They may have been closer to a simple end-fed wire.

I'd also noted the concept repeated in the J-pole.

We "old ops" have certain advantages ...

73!  Ken

On Sat, Mar 10, 2012 at 3:23 AM, Don Wilhelm  wrote:
> Ken,
>
> I will agree with all until I got to the end of your post - "classic zepp"
> The original (and classic)  Zepp antenna was a 1/2 wave wire fed 
> through a 1/4 wave transmission line connected to the end that was 
> trailed behind lighter-than-air aircraft (Zepplin).  If you look at 
> the J-pole, and turn it horizontally, you will see exactly the same 
> thing - a 1/4 wave transmission line with one side connected to a 1/2
wavelength radiator.
>
> I am not sure how the "Zepp" term became associated with any kind of 
> center fed dipoles, but it has in ham circles, and I find it confusing 
> - there is the Center Fed Zepp (2 halfwaves in phase) antenna, and 
> then there is the Extended Center Fed Zepp (5/8 wavelength each side 
> of center), and then there is the "classic Zepp" that is the antenna 
> designed for trailing the aircraft.  So we must be careful to explain 
> which kind of Zepp antenna we are referring to when we write "Zepp"
> There is a lot of difference.
>
> 73,
> Don W3FPR

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Re: [Elecraft] OT: G5RV's antenna

2012-03-10 Thread Kim Bottles
I am with Ken on this one. 

I use a 130 foot classic Zepp with 600 ohm ladder line to a balun and then a 
short coax line to the K-3 with internal tuner. It tunes very nicely on all HF 
bands 160 to 10. (Yes, even 160.)

Kim - K7IM

-Original Message-
From: Ken G Kopp [mailto:kengk...@gmail.com] 
Sent: Friday, March 09, 2012 6:54 PM
To: elecraft@mailman.qth.net
Subject: [Elecraft] OT: G5RV's antenna

I have Varney's (G5RV) original article.  The antenna was designed for -only- 
20M .  Since then it's taken on the proverbial "life of it's own" and become 
somewhat of a "cult" antenna, as is the case with the "Carolina Windom".

Why would one start with a perfectly good balanced-line fed Zepp, cobble a 
piece of "special-length" coax onto the end of that balanced line so that the 
antenna becomes something else, and then have to use an antenna tuner to make 
the thing work?

Since the antenna requires a tuner, why not connect the balanced line to a 
balanced tuner ... or one with a balun ... and enjoy all the virtues of a 
classic Zepp?

73!

Ken Kopp - K0PP
elecraftcov...@gmail.com

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Re: [Elecraft] OT: G5RV's antenna

2012-03-10 Thread Kim Bottles
OK, I amend my post to say 130 foot doublet.

Kim - K7IM

-Original Message-
From: Ron D'Eau Claire [mailto:r...@cobi.biz] 
Sent: Friday, March 09, 2012 8:09 PM
To: 'Ken G Kopp'; d...@w3fpr.com
Cc: elecraft@mailman.qth.net
Subject: Re: [Elecraft] OT: G5RV's antenna

The feeder was exactly 1/4 wavelength long so it transformed the very high 
impedance at the end of the radiator to a very low impedance at the rig in the 
Zeppelin, minimizing "RF in the Shack" issues. 

Since the radiator was 1/2 wavelength long, very little current flowed from the 
feeder into the radiator. It was a voltage "loop". That meant that, although 
the other side of the feeder was terminated in an insulator, the currents along 
the feed line were well balanced. Most radiomen of the time considered that the 
leakage current into the insulator closely matched the current into the 
radiator so the balance was very good indeed. 

The next step, coming back to Don's comment, was to connect two Zepps back to 
back for some additional gain. Extending the radiators beyond 1/2 wavelength 
enhanced this effect and, since it was now a center fed antenna, feedline 
imbalance was no longer a danger, hence the popularity of the "extended double 
Zepp".

I am always careful to call my center fed wires a "doublet" to avoid confusion 
but many Hams today incorrectly call any wire fed at the center with open wire 
line a "Zepp". 

Feeding a traditional Zepp only minimizes feed line radiation when the radiator 
is exactly 1/2 wavelength. (The feeder can be any length if you can deal with 
the feed point impedance at the rig end.) However, many Hams have reported 
excellent results with Zepps with not-1/2-wave long radiators. In those cases 
the feed line is also part of the radiating antenna. That can be good when the 
feeder is in the clear and less so if it's not. The same is true of most off 
center fed antennas.

73,  

Ron AC7AC

-Original Message-
From: elecraft-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Ken G Kopp
Sent: Friday, March 09, 2012 7:34 PM
To: d...@w3fpr.com
Cc: elecraft@mailman.qth.net
Subject: Re: [Elecraft] OT: G5RV's antenna

Yes Don, I knew when I used the term "classic Zepp" that I was taking a bit of 
liberty with the term.  The original Zepp was indeed end-fed from the cabin of 
a Zepplin.  I've often wondered how long the feeder actually was.
They may have been closer to a simple end-fed wire.

I'd also noted the concept repeated in the J-pole.

We "old ops" have certain advantages ...

73!  Ken

On Sat, Mar 10, 2012 at 3:23 AM, Don Wilhelm  wrote:
> Ken,
>
> I will agree with all until I got to the end of your post - "classic zepp"
> The original (and classic)  Zepp antenna was a 1/2 wave wire fed 
> through a 1/4 wave transmission line connected to the end that was 
> trailed behind lighter-than-air aircraft (Zepplin).  If you look at 
> the J-pole, and turn it horizontally, you will see exactly the same 
> thing - a 1/4 wave transmission line with one side connected to a 1/2
wavelength radiator.
>
> I am not sure how the "Zepp" term became associated with any kind of 
> center fed dipoles, but it has in ham circles, and I find it confusing
> - there is the Center Fed Zepp (2 halfwaves in phase) antenna, and 
> then there is the Extended Center Fed Zepp (5/8 wavelength each side 
> of center), and then there is the "classic Zepp" that is the antenna 
> designed for trailing the aircraft.  So we must be careful to explain 
> which kind of Zepp antenna we are referring to when we write "Zepp"
> There is a lot of difference.
>
> 73,
> Don W3FPR


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