-ex- wrote:
Doug Smith W9WI wrote:

Andrew VK3BFA wrote:

thats interesting - us in OZ had the same VHF output system years ago,
but when we got UHF broadcasting, all the VCR's went to UHF output.
Most (if not all) are tunable over a narrow range,(via a trimmer cap on
the rear panel) some of the more exotic ones (even from dumpster
diving) have user settable(sp) output with the actual RF frequency on
screen - makes a crude UHF sig gen.


UHF in the States long predates the VCR. But that may be why we stuck
with VHF output -- because early UHF tuners were pretty bad and many
Americans had experience with their poor stability and difficult tuning.

For the most part, USA VCRs or cable boxes have always had a switch for
ch 3/4, or to a lesser extent, 2/3. The way the channel allocations are
done in the US you won't find adjacent channels broadcasting in a given
area so one or the other is supposed to work. Guys halfway between
Philadelphia and New York City will of course explain why thats not
always workable.
Nowadays they have dropped in the digital channels, yes in VHF too, with
no need to regard adjacent channels which turns the cake upside down.
Given the capabilities of modern tuners it makes much more sense to have
selectable UHF channel outputs on consumer gear. There's still some
free slots in the most crowded metro areas...although the "digital data"
people are lobbying hard to get access to those unused frequencies.


-Bill

Hi Bill,
digital here has been a mixed bag - where I am, its line of sight to
the hills which is full of UHF translators - thats not so bad for
analog, as you can "see" the QRM underneath the ch you have chosen as a
RF out. Digital, well, you dont get nothing on screen, so it looks like
the front end of the VCR has died. Took me a while to twig to that one
- even the local agents for a very well known brand didnt know it and
were trying to sell me a new front end to fix the problem!

Hitachi have had OSD of RF frequency out for a while now - Philips also
in some of their tv;s, and TEAC as well, so it will pretty well be
universal before long. The Chinese are really gearing up - they do make
some pretty sophisticated gear, but will happily sell us rubbish if we
want it as well!

We also have a FM broadcast channel on the same tower as the VHF
transmitters - it QRM's TV ch 10 depending on how good the tuner front
end is. - Funnily enough, (well, it isnt really, more obvious) the
older style rotary UHF tuners with ganged RF and LO tuning dont seem to
have any trouble, only the varactor tuned ones. But then, they are the
sweepings of the factory floors of Asia - bought on price rather than
performance. Try telling the customer this tho....

Andrew VK3BFA

Andrew VK3BFA wrote:


-ex- wrote:


We also have a FM broadcast channel on the same tower as the VHF
transmitters - it QRM's TV ch 10 depending on how good the tuner front
end is. - Funnily enough, (well, it isnt really, more obvious) the
older style rotary UHF tuners with ganged RF and LO tuning dont seem to
have any trouble, only the varactor tuned ones. But then, they are the
sweepings of the factory floors of Asia - bought on price rather than
performance. Try telling the customer this tho....

Andrew VK3BFA

The Keyword here is how 'bad' the tuner front end is Its probably a
tossup if there's a harmonic being received instead of a mixing beat but
at least tunable sets have a chance of getting away from it.

Here in the US, gear usually has options of off-air, cable, cable HRC
(harmonically related channels) or cable IRC (incrementally related
channels) . Depending on the freq of the FM station *sometimes* you can
force the set away from the FM harmonic by selecting one of the
oddballs. But if its beating with the video there's no cure.

Do you still have folks with rotary tuner sets down there? I haven't
seen one in a customer's home for 30 years on this side!

-Bill

-ex- wrote:
Andrew VK3BFA wrote:


-ex- wrote:


We also have a FM broadcast channel on the same tower as the VHF
transmitters - it QRM's TV ch 10 depending on how good the tuner front
end is. - Funnily enough, (well, it isnt really, more obvious) the
older style rotary UHF tuners with ganged RF and LO tuning dont seem to
have any trouble, only the varactor tuned ones. But then, they are the
sweepings of the factory floors of Asia - bought on price rather than
performance. Try telling the customer this tho....

Andrew VK3BFA

The Keyword here is how 'bad' the tuner front end is Its probably a
tossup if there's a harmonic being received instead of a mixing beat but
at least tunable sets have a chance of getting away from it.

Here in the US, gear usually has options of off-air, cable, cable HRC
(harmonically related channels) or cable IRC (incrementally related
channels) . Depending on the freq of the FM station *sometimes* you can
force the set away from the FM harmonic by selecting one of the
oddballs. But if its beating with the video there's no cure.

Do you still have folks with rotary tuner sets down there? I haven't
seen one in a customer's home for 30 years on this side!

-Bill

Hi Bill, nope, not many left with rotary tuners (on UHF) - but I still
get called in to fix them occassionally, and even more so that some of
them still have good tubes in them!

Andrew VK3BFA