Standing Waves (and Impedance)
 

Owen Duffy wrote:
Is the sound subcarrier supposed to be at 65.75MHz for your Ch3?

I think that's a valid assumption. It's possibly a cockpit
error of some kind. I will have to try again.
--
73, Cecil http://www.qsl.net/w5dxp

Standing Waves (and Impedance)
 

Dave Platt wrote:
It's possible that your IC-706 isn't willing/able to lock onto a
carrier with such a high deviation, perhaps? or perhaps it needs to
be switched manually to a "wide FM" mode to do so in this frequency
range?

It's also possible that I am senile and need to try again.
--
TNX & 73, Cecil http://www.qsl.net/w5dxp

Standing Waves (and Impedance)
 

Dave Platt wrote:
It's possible that your IC-706 isn't willing/able to lock onto a
carrier with such a high deviation, perhaps?

I just drug out the IC-706 manual. It receives channel 2
on the HF antenna and channel 3 on the VHF antenna. :-)
--
73, Cecil http://www.qsl.net/w5dxp

Standing Waves (and Impedance)
 

"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)

Standing Waves (and Impedance)
 

US TV aural is frequency modulated, with +/-25 kHz deviation defined as 100%
modulation. Pre-emphasis of 75 microseconds is applied to program audio.

It is transmitted as a discrete r-f waveform about 250 kHz below the upper
edge of the TV channel. TV receivers typically demodulate it using an FM
detector tuned to the 4.5 MHz intercarrier product present in the output
signal of its video detector. Therefore if the TV visual carrier (only)
goes off the air, no audio will be heard at the TV set, either.

Any communications-type receiver capable of tuning to, and demodulating the
TV aural carrier will enable listening to it. Even some little "pocket"
AM/FM radio receivers have that ability.

RF

Standing Waves (and Impedance)
 

"Reg Edwards" wrote
Who cares what is the SWR on the transmission line provided the
transmitter is loaded with its correct load resistance?
____________

Probably most people who don't want to destroy their transmission line.

Apparently this does not include your esteemed self.

RF

Standing Waves (and Impedance)
 

In article ,
Cecil Moore wrote:

It's possible that your IC-706 isn't willing/able to lock onto a
carrier with such a high deviation, perhaps?

I just drug out the IC-706 manual. It receives channel 2
on the HF antenna and channel 3 on the VHF antenna. :-)

#splorf#

Well, I suppose it does make sense in a way, but it sorta seems to
violate the Law of Least Astonishment!

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Standing Waves (and Impedance)
 

In article ,
(Dave Platt) wrote:

For what it's worth, I'm able to use my Kenwood TS-2000 to tune in the
audio carrier of our local Channel 2 station. According to my cheat
sheet, 2's video carrier is at 55.25, with audio carrier 4.5 MHz
higher... hence 59.75 MHz. It seems to tune in best on my radio at
59.745.

Your channel 3 audio carrier ought to be at 61.25 + 4.5 = 65.75 MHz.

The normal video carrier frequency for US TV stations is 1.25 MHz above
the low frequency end of the channel, and the audio carrier frequency is
4.5 MHz higher than that. But some station assignments specify that the
video carrier should be a small number of kHz above or below the
frequency described above, with the audio carrier still 4.5 MHz above
the (displaced) video carrier so that when the TV receiver is properly
(mis)tuned, both carriers will be converted to the expected intermediate
frequencies. Perhaps your channel 2 station has been moved downhill 5
kHz. In any case the +/- 25 kHz deviation for 100% modulation would make
the audio sound pretty ugly on a narrow band ham receiver.

David, ex-W8EZE

--
David Ryeburn

To send e-mail, use "ca" instead of "caz".

Standing Waves (and Impedance)
 

65.75 is the magic frequency. It does appear the WFM mode can not be used on
this frequency on the 706 MKIIG I have. In the FM position, while distorted
it is copyable. The radio shows WFM mode, but it certainly isn't in the wide
mode.

Now I have to get in the circuitry and see why the WFM is not operable on
this band.

"Cecil Moore" wrote in message
et...
Fred W4JLE wrote:
You can if you tune to the audio offset.

I have run the IC-706 all up and down the channel 3
60-66 MHz frequencies while in College Station, TX
and cannot hear the audio anywhere.
--
73, Cecil http://www.qsl.net/w5dxp

Standing Waves (and Impedance)
 

Fred W4JLE wrote:
65.75 is the magic frequency. It does appear the WFM mode can not be used on
this frequency on the 706 MKIIG I have. In the FM position, while distorted
it is copyable. The radio shows WFM mode, but it certainly isn't in the wide
mode.

My original problem was with an original IC-706 which I sold.
I'm now mobile with an IC-706MKII with DSP. But my mode switch
switches from FM to AM to FM ... and never shows WFM at all,
not even when tuned to 88-108 MHz so commercial FM or TV is not
worth listening to. I have a Sony Walkman that does receive VHF
TV audio and my CCRadio+ does also.
--
73, Cecil http://www.qsl.net/w5dxp