Eric Schumacher wrote:
Hi Group

Can anyone give me a brief explanation of the theory of operation of a
commerical FM broadcast antenna. Specfically the Jampro JMPC (picture
at )http://www.jampro.com/fma/jampjmpc.htm It looks to me like a couple of
1/2 wave dipoles each folded into V and fed in phase using two gamma
matches.

Looks like a lindenblad antenna
(http://www.amsat.org/amsat/articles/w6shp/lindy.html)
with a original feeding.


Thierry
F4DWV

"hello" wrote in message
...
Eric Schumacher wrote:
Hi Group

Can anyone give me a brief explanation of the theory of operation of a
commerical FM broadcast antenna. Specfically the Jampro JMPC (picture
at )http://www.jampro.com/fma/jampjmpc.htm It looks to me like a couple
of
1/2 wave dipoles each folded into V and fed in phase using two gamma
matches.

Looks like a lindenblad antenna
(http://www.amsat.org/amsat/articles/w6shp/lindy.html)
with a original feeding.
Thierry F4DWV

Not to me. It looks like the lindenblad elements are fed IN phase, right?

Differences
JMPC Lindenblad
-two bent half waves -four straight half waves
-Elements in two planes -elements in four planes
-symmetry around the -symmetry around the center
center of the two of the four antennas
elements for 180 for every 90 degrees
degrees of rotation of rotation

similarities
circular polarization
Perhaps fed in phase elements
Weird.

--
Steve N, K,9;d, c. i My email has no u's.

Thanks for the insight guys. There were some pearls in there.

Eric


"Steve Nosko" wrote in message
...

"hello" wrote in message
...
Eric Schumacher wrote:
Hi Group

Can anyone give me a brief explanation of the theory of operation of a
commerical FM broadcast antenna. Specfically the Jampro JMPC (picture
at )http://www.jampro.com/fma/jampjmpc.htm It looks to me like a
couple
of
1/2 wave dipoles each folded into V and fed in phase using two gamma
matches.

Looks like a lindenblad antenna
(http://www.amsat.org/amsat/articles/w6shp/lindy.html)
with a original feeding.
Thierry F4DWV

Not to me. It looks like the lindenblad elements are fed IN phase, right?

Differences
JMPC Lindenblad
-two bent half waves -four straight half waves
-Elements in two planes -elements in four planes
-symmetry around the -symmetry around the center
center of the two of the four antennas
elements for 180 for every 90 degrees
degrees of rotation of rotation

similarities
circular polarization
Perhaps fed in phase elements
Weird.

--
Steve N, K,9;d, c. i My email has no u's.

Thierry, F4DWV, writes:

Looks like a lindenblad antenna
(http://www.amsat.org/amsat/articles/w6shp/lindy.html)
with a original feeding.

I think there is definitely a kinship there. Folding
back the dipole "legs" makes the dipoles less directive
and it becomes possible to use only two dipoles rather
than the four of the Lindenblad.

Of course, when I look at a Lindenblad in a certain
way, it appears to be a highly truncated, half-wave
section of a quadrifilar helical antenna radiating
in the normal (radial) mode. You have to tilt your
head just right to see it.

Jim, K7JEB