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

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