BKR:

Reg has " There is a 3-phase transmitter feeding a 3-phase antenna..."

Does this mean the transmitter is powered off 3-phase 60 cycle (if so,
really doesn't affect the antenna) or is the transmitter final somehow
constructed with a tank supplying 3-phase rf???

Then the "3-phase antenna", is each monopole, dipole fed though different
lengths of feedline, with one 0 degree length, one 120 degree length, and
one 240 degree--electrical lengths?

Those brits can be tricky yanno! grin

John

On Fri, 19 Aug 2005 21:05:28 -0600, BKR wrote:


Just a hint:
Think of how a turnstile antenna works. That one works in the
horizontal plane with 90 degree phasing. Check the radiation patern.


Reg Edwards wrote:
There is a 3-phase transmitter feeding a 3-phase antenna via a 3-wire
transmission line.

The antenna consists of three 1/4-wave horizontal radiators spaced at
120 degee intervals.

Is the radiation pattern in the horizontal plane perfectly
omni-directional?
----
Reg.

I think he was providing a simplified model by eliminating phasing
lines. As I understood it he meant that there 3 outputs from the TX
with 3 equal length feedlines or a special feedline, and that all are in
a rotating 120 degree progression.



John Smith wrote:

BKR:

Reg has " There is a 3-phase transmitter feeding a 3-phase antenna..."

Does this mean the transmitter is powered off 3-phase 60 cycle (if so,
really doesn't affect the antenna) or is the transmitter final somehow
constructed with a tank supplying 3-phase rf???

Then the "3-phase antenna", is each monopole, dipole fed though different
lengths of feedline, with one 0 degree length, one 120 degree length, and
one 240 degree--electrical lengths?

Those brits can be tricky yanno! grin

John

On Fri, 19 Aug 2005 21:05:28 -0600, BKR wrote:


Just a hint:
Think of how a turnstile antenna works. That one works in the
horizontal plane with 90 degree phasing. Check the radiation patern.


Reg Edwards wrote:

There is a 3-phase transmitter feeding a 3-phase antenna via a 3-wire
transmission line.

The antenna consists of three 1/4-wave horizontal radiators spaced at
120 degee intervals.

Is the radiation pattern in the horizontal plane perfectly
omni-directional?
----
Reg.

On Fri, 19 Aug 2005 20:21:38 +0000 (UTC), "Reg Edwards"
wrote:

Is the radiation pattern in the horizontal plane perfectly
omni-directional?

No (and begs the question, what IS perfect?).

On Fri, 19 Aug 2005 22:00:33 +0000 (UTC), "Reg Edwards"
wrote:

What is the radiation pattern in the horizontal plane?

Just like for the two lobes of a dipole, three lobes for a tripole.

Also what is the equivalent load impedance between each of the line
wires.

35 Ohms.

Hardly comes to the class of pageantry in:
On Tue, 16 Aug 2005 16:15:10 +0000 (UTC), "Reg Edwards"
wrote:

Is there anybody about who still imagines that an SWR meter, located
... on the other side of the tuner, indicates
SWR on the transmission line between transmitter and the antenna?

Anybody indeed? Name someone else other than yourself, Reg. Jeesh....

Time to throw in the last spade of earth and say Amen.

73's
Richard Clark, KB7QHC

With a delta connection the line wires would have to opened out at
their ends and would radiate just as much as the triangular antenna
itself.

With either delta or Y connection there is no 4th neutral wire. As the
whole system is balanced there would be zero current in the neutral
anyway.
----
Reg.

"Richard Clark" wrote
What is the radiation pattern in the horizontal plane?

Just like for the two lobes of a dipole, three lobes for a tripole.

Also what is the equivalent load impedance between each of the line
wires.

35 Ohms.

===================================
Richard,
Would you care to divulge how you obtained these two answers?
----
Reg.

"Reg Edwards" wrote in message
...
With a delta connection the line wires would have to opened out at
their ends and would radiate just as much as the triangular antenna
itself.

You are describing the Y connection. With delta connection the load is
between adjacent wires of the feedline. Look at any two wires of what you
describe, and there is a 1/2 wave dipole, center fed, formed by two of the
1/4 wave radiators. But, instead of the two halves of the dipole being fed
180 degrees out of phase, they are 120 degrees. Each 1/4 wave radiator is
part of two different dipoles. Each dipole is bent 60 degrees at the feed
point.

As for the feeedline, I presume what you have is like a twisted pair, but
there are 3 wires, not 2 You could not use a flat transmission line because
it would not be symmetrical.

Tam

With either delta or Y connection there is no 4th neutral wire. As the
whole system is balanced there would be zero current in the neutral
anyway.
----
Reg.

On Sat, 20 Aug 2005 08:51:12 +0000 (UTC), "Reg Edwards"
wrote:


"Richard Clark" wrote
What is the radiation pattern in the horizontal plane?

Just like for the two lobes of a dipole, three lobes for a tripole.

Also what is the equivalent load impedance between each of the line
wires.

35 Ohms.

===================================
Richard,
Would you care to divulge how you obtained these two answers?

Hi Reg,

Sure. Why don't you first confirm them?

On the other hand - how could it be otherwise?

73's
Richard Clark, KB7QHC

On Fri, 19 Aug 2005 20:21:38 +0000 (UTC), "Reg Edwards"
wrote:

There is a 3-phase transmitter feeding a 3-phase antenna via a 3-wire
transmission line.

The antenna consists of three 1/4-wave horizontal radiators spaced at
120 degee intervals.

Is the radiation pattern in the horizontal plane perfectly
omni-directional?
----
Reg.

No. Effectively you are feeding two legs with a -120 degree phase
and that will make it directional.

For Omnidirectional operation ALL legs will have to be fed in phase.
If the three sources are laggin in phase then the feed system will
have to correct the phase till all are in phase.

Many years ago, there was a CB (USA 27mhz 11m) that used three
vertical dipoles with phasing to get directionality or omnidirectional
gain.


Allison

nospam:

That cb antenna (with the 3 dipoles arranged so as to go omni/directional)
was called a "scanner", made by antenna specialists I believe (reed
switches in a relay box control the elements.)

I cut one down, along with the phasing harness to the center of the 10
meter band, works great! And you are correct, the three 120 degree spaced
vertical dipoles are fed in phase for omni-pattern.

John

On Sat, 20 Aug 2005 18:22:29 +0000, nospam wrote:

On Fri, 19 Aug 2005 20:21:38 +0000 (UTC), "Reg Edwards"
wrote:

There is a 3-phase transmitter feeding a 3-phase antenna via a 3-wire
transmission line.

The antenna consists of three 1/4-wave horizontal radiators spaced at
120 degee intervals.

Is the radiation pattern in the horizontal plane perfectly
omni-directional?
----
Reg.

No. Effectively you are feeding two legs with a -120 degree phase
and that will make it directional.

For Omnidirectional operation ALL legs will have to be fed in phase.
If the three sources are laggin in phase then the feed system will
have to correct the phase till all are in phase.

Many years ago, there was a CB (USA 27mhz 11m) that used three
vertical dipoles with phasing to get directionality or omnidirectional
gain.


Allison

In article .com,
wrote:

Us Amateurs don't have a lot of experience

That's why they call you "Amateurs".....the Professional Radio Engineers
understand perfectly what the OP was talking about, and exactly why, and
how, this type of antenna system is used in the real world of
communications, both fixed and mobile.

Me who has been around the biz, since almost before Moses.....