Gamma fed or folded dipoles?
 

I am going to build an array of 4 stacked dipoles for operation on 2 metres.
I would like to know whether the gamma fed dipole has any advantage over the
folded dipole, apart from the folded dipole being a tad more difficult to
make.

I have heard that the gamma fed dipole has a skewed radiation pattern in
comparison to the folded one.

Any thoughts and advice?
Many thanks
John
VK2KC

Gamma fed or folded dipoles?
 

On Fri, 21 May 2010 05:22:34 GMT, "VK2KC" wrote:

I have heard that the gamma fed dipole has a skewed radiation pattern in
comparison to the folded one.

Hi John,

You could have heard the same thing said for the opposite design - and
they would BOTH be true.

The devil is in the details, such as how much skew would it take to
bother you? Then there is the question, how much skew before it would
it matter anyway? Some folks sweat over things they couldn't possibly
measure. Worse yet, they would pay more to change things than they
would get back in improvement.

73's
Richard Clark, KB7QHC

Gamma fed or folded dipoles?
 

VK2KC wrote:
I am going to build an array of 4 stacked dipoles for operation on 2 metres.
I would like to know whether the gamma fed dipole has any advantage over the
folded dipole, apart from the folded dipole being a tad more difficult to
make.

I have heard that the gamma fed dipole has a skewed radiation pattern in
comparison to the folded one.

Any thoughts and advice?
Many thanks
John
VK2KC

Richard Harrison has posted a number of times the comment that systems
using folded dipoles are much more robust with respect to lightning and
static discharges due to the low impedance path for DC and most of the
RF components they contain.

Roy Lewallen, W7EL

Gamma fed or folded dipoles?
 

In message , VK2KC
writes
I am going to build an array of 4 stacked dipoles for operation on 2 metres.
I would like to know whether the gamma fed dipole has any advantage over the
folded dipole, apart from the folded dipole being a tad more difficult to
make.

I have heard that the gamma fed dipole has a skewed radiation pattern in
comparison to the folded one.

Any thoughts and advice?
Many thanks

The Clemens match is a variant of the gamma match that gets round that
problem. I tried them on 6m and 4m.

Http://www.qsl.net/yt1vp/THE%20CLEMENS%20MATCH.htm

You need to watch the losses in the coax dielectric. I vaporised UR67
and had to go to PTFE.

Brian GM4DIJ

--
Brian Howie

Gamma fed or folded dipoles?
 

On 22 mayo, 07:05, Brian Howie wrote:
In message , VK2KC
writes

I am going to build an array of 4 stacked dipoles for operation on 2 metres.
I would like to know whether the gamma fed dipole has any advantage over the
folded dipole, apart from the folded dipole being a tad more difficult to
make.

I have heard that the gamma fed dipole has a skewed radiation pattern in
comparison to the folded one.

Any thoughts and advice?
Many thanks

The Clemens match is a variant of the gamma match that gets round that
problem. I tried them on 6m and 4m.

Http://www.qsl.net/yt1vp/THE%20CLEMENS%20MATCH.htm

You need to watch the losses in the coax dielectric. I vaporised *UR67
and had to go to PTFE.

Brian GM4DIJ

--
Brian Howie

Hi Brian:

When dipoles are mounted to the side of a tower or metallic support,
the gamma match allows the impedance matching to a 50 ohms
transmission line at the optimal distance from the mast to obtain the
typical diagram of the "ofsset." configuration.
To adapt the folded dipole impedance only appealing to a 4:1
transmission line balun it is necessary to bring them near enough to
the tower or conductive mast and so the radiation diagram is no longer
the one that habitually we imagine (+9 dB front, 3 dB back).

Miguel Ghezzi LU6ETJ

Gamma fed or folded dipoles?
 

On 24 mayo, 17:36, lu6etj wrote:
On 22 mayo, 07:05, Brian Howie wrote:





In message , VK2KC
writes

I am going to build an array of 4 stacked dipoles for operation on 2 metres.
I would like to know whether the gamma fed dipole has any advantage over the
folded dipole, apart from the folded dipole being a tad more difficult to
make.

I have heard that the gamma fed dipole has a skewed radiation pattern in
comparison to the folded one.

Any thoughts and advice?
Many thanks

The Clemens match is a variant of the gamma match that gets round that
problem. I tried them on 6m and 4m.

Http://www.qsl.net/yt1vp/THE%20CLEMENS%20MATCH.htm

You need to watch the losses in the coax dielectric. I vaporised *UR67
and had to go to PTFE.

Brian GM4DIJ

--
Brian Howie

Hi Brian:

When dipoles are mounted to the side of a tower or metallic support,
the gamma match allows the impedance matching to a 50 ohms
transmission line at the optimal distance from the mast to obtain the
typical diagram of the "ofsset." configuration.
To adapt the folded dipole impedance only appealing to a 4:1
transmission line balun it is necessary to bring them near enough to
the tower or conductive mast and so the radiation diagram is no longer
the one that habitually we imagine (+9 dB front, 3 dB back).

Miguel Ghezzi LU6ETJ- Ocultar texto de la cita -

- Mostrar texto de la cita -

SRI, my post was to John question, not to Brian answer :)

Miguel

Gamma fed or folded dipoles?
 

On 21 svi, 07:22, "VK2KC" wrote:
I am going to build an array of 4 stacked dipoles for operation on 2 metres.
I would like to know whether the gamma fed dipole has any advantage over the
folded dipole, apart from the folded dipole being a tad more difficult to
make.

I have heard that the gamma fed dipole has a skewed radiation pattern in
comparison to the folded one.

Any thoughts and advice?
Many thanks
John
VK2KC

The folded dipole with 1:4 baloon is best solution for maching
yagis .

Gamma fed or folded dipoles?
 

On May 27, 3:54*pm, jure wrote:
On 21 svi, 07:22, "VK2KC" wrote:

I am going to build an array of 4 stacked dipoles for operation on 2 metres.
I would like to know whether the gamma fed dipole has any advantage over the
folded dipole, apart from the folded dipole being a tad more difficult to
make.

I have heard that the gamma fed dipole has a skewed radiation pattern in
comparison to the folded one.

Any thoughts and advice?
Many thanks
John
VK2KC

*The folded dipole with 1:4 baloon is best *solution for maching
yagis .

Over the last few years a I have started preferring using the folded
dipole for the driven element also. I dont understand your need for
4:1 BALUN though.

Jimmie

Gamma fed or folded dipoles?
 

On May 27, 8:13*pm, JIMMIE wrote:
On May 27, 3:54*pm, jure wrote:



On 21 svi, 07:22, "VK2KC" wrote:

I am going to build an array of 4 stacked dipoles for operation on 2 metres.
I would like to know whether the gamma fed dipole has any advantage over the
folded dipole, apart from the folded dipole being a tad more difficult to
make.

I have heard that the gamma fed dipole has a skewed radiation pattern in
comparison to the folded one.

Any thoughts and advice?
Many thanks
John
VK2KC

*The folded dipole with 1:4 baloon is best *solution for maching
yagis .

Over the last few years a I have started preferring using the folded
dipole for the *driven element also. I dont understand your need for
4:1 BALUN though.

Jimmie

another robust one is the T match as used in old telrex yagis. it is
dc grounded and needs no capacitor, but it does use a 1/2 wave 'balun'
or phasing line between the halves of the T.

Gamma fed or folded dipoles?
 

On 27 svi, 22:13, JIMMIE wrote:
On May 27, 3:54*pm, jure wrote:



On 21 svi, 07:22, "VK2KC" wrote:

I am going to build an array of 4 stacked dipoles for operation on 2 metres.
I would like to know whether the gamma fed dipole has any advantage over the
folded dipole, apart from the folded dipole being a tad more difficult to
make.

I have heard that the gamma fed dipole has a skewed radiation pattern in
comparison to the folded one.

Any thoughts and advice?
Many thanks
John
VK2KC

*The folded dipole with 1:4 baloon is best *solution for maching
yagis .

Over the last few years a I have started preferring using the folded
dipole for the *driven element also. I dont understand your need for
4:1 BALUN though.

Jimmie

You must put the balun to have 50 Ohm . http://users.belgacom.net/hamradio/schemas/14balun.gif