W. Watson wrote:
A standing wave is the sum of an incident added to the reflective wave.
Isn't it possible to send two incident waves down an xline with
different frequences, and produce two different standing waves by having
some multiplicative relationship between the two incident waves and the
xline length?

Sure, it's possible but one wonders about the application.

2. Matched impedances give ideal power transfer; mismatched
impedances give high SWR and reduced power transfer.

A middle ground - Conjugately matched impedances give ideal power
transfer in the presence of high SWR. A feedline doesn't have to
be flat to be "matched". All that is required is that maximum
available power (actually energy) be transferred.
--
73, Cecil http://www.qsl.net/w5dxp

To anybody who may be reading -

(1) There's far too much importance attached to standing waves on
transmission lines. But see (4).

(2) There are colossal standing waves on antennas which are seldom
taken any notice of.

(3) Anyway, of what use does anybody make of standing waves after
taking the trouble to measure them. And the measurements themselves
are the most inacurate in the field of radio engineering.

(4) And to cap it all, the common or garden SWR meter does NOT
measure standing waves on the feedline to the antenna where they might
conceivably be of interest. It's all a gigantic hoax!
----
Season's Greetings from Reg, G4FGQ.

..
"Cecil Moore" wrote in message
om...
W. Watson wrote:
A standing wave is the sum of an incident added to the reflective wave.
Isn't it possible to send two incident waves down an xline with different
frequences, and produce two different standing waves by having some
multiplicative relationship between the two incident waves and the xline
length?

Sure, it's possible but one wonders about the application.

Cecil:

Think about a 6 MHz wide analog TV channel. Those antennas aren't flat, and
there are 2 transmitters, visual and aural. Putting an analog TV station on
the air the first time, particularly low VHF, is a real interesting
exercise. Or at least it was back in the stone (vacuum tube) age, the last
time I did one.

73,
George
W5VPQ
My real address is my ham call atARRL.NET The ATTGlobal is a SPAM trap


snip

Crazy George wrote:
Those antennas aren't flat, and
there are 2 transmitters, visual and aural.

The audio is not mixed with the main carrier?
--
73, Cecil http://www.qsl.net/w5dxp

On Sun, 25 Dec 2005 22:31:09 GMT, Cecil Moore wrote:

Crazy George wrote:
Those antennas aren't flat, and
there are 2 transmitters, visual and aural.

The audio is not mixed with the main carrier?
It can be either way.

If you choose to use separate transmitters the demands on antenna
bandwidth are greatly reduced.
John Ferrell W8CCW

John Ferrell wrote:

Cecil Moore wrote:
The audio is not mixed with the main carrier?

It can be either way.

If you choose to use separate transmitters the demands on antenna
bandwidth are greatly reduced.
John Ferrell W8CCW

Thanks John, my IC-706 will receive the TV frequencies, but since
I have never heard any audio, I assumed the audio and video were
mixed to an IF frequency and then mixed to the TV frequency. (I
have a reference book on TV but haven't looked at it in a long
time).
--
73, Cecil http://www.qsl.net/w5dxp

No. They are separate. Audio is FM and video is AM. Dan

Cecil Moore wrote:
John Ferrell wrote:

Cecil Moore wrote:

The audio is not mixed with the main carrier?


It can be either way.

If you choose to use separate transmitters the demands on antenna
bandwidth are greatly reduced. John Ferrell W8CCW


Thanks John, my IC-706 will receive the TV frequencies, but since
I have never heard any audio, I assumed the audio and video were
mixed to an IF frequency and then mixed to the TV frequency. (I
have a reference book on TV but haven't looked at it in a long
time).

dansawyeror wrote:
No. They are separate. Audio is FM and video is AM. Dan

I can receive the commercial FM band just fine on my IC-706.
Why can't I receive TV audio on it?
--
73, Cecil http://www.qsl.net/w5dxp

"John Ferrell" wrote
Crazy George wrote:
The audio is not mixed with the main carrier?
It can be either way.

TV aural uses a separate transmitter from TV visual, because the visual
amplifier in a TV tx is not linear enough to amplify both the aural and
visual waveforms while maintaining r-f intermods sufficiently low (to FCC
spec). The aural and visual signals are combined with mutual isolation of
the txs, and radiated by a single antenna, typically.

In an emergency, TV stations sometimes combine A&V at exciter level and pipe
them through the visual PA, which is operated at reduced power to minimize
r-f intermods. Typically the TV station is not meeting spec then, however.

If you choose to use separate transmitters the demands
on antenna bandwidth are greatly reduced.

Reducing antenna bandwidth needed also would require separate antenna
systems for the aural and visual transmitters. That is done, occasionally -
but not often. This doesn't reduce the bandwidth needed by the visual tx by
very much, however. Generally it's more cost-effective to use a single
antenna to radiate both A&V.

RF (RCA Broadcast systems field engineer, 1965-1980)

"Cecil Moore" wrote in message
om...
W. Watson wrote:
A standing wave is the sum of an incident added to the reflective wave.
Isn't it possible to send two incident waves down an xline with
different frequences, and produce two different standing waves by having
some multiplicative relationship between the two incident waves and the
xline length?

Sure, it's possible but one wonders about the application.


Some repeaters use one antenna for two repeaters on 144 and 440 mhz.
Comercial transmitters do this all the time. Usually the transmitters are
in the same band.