How far away from viewers are VHF signals typically broadcast?
(i.e. up to 1000 miles)

wrote:
How far away from viewers are VHF signals typically broadcast?
(i.e. up to 1000 miles)
Pretty much line of sight is the rule at VHF and above. The line of
sight is baaed on the curvature of the earth, and modified by the
respective heights of the two stations.

A nice little on-line calculator is at:

http://www.qsl.net/kd4sai/distance.html

enter the heights of the two antennas, and it will calculate the
distance that you can expect to cover.


Sometimes there are propagation effects that will dramatically extend
the range, but these are the exception not the rule, and although
amateurs have a lot of fun with the effect, it isn't reliable for any
length of time.

- 73 de Mike KB3EIA -

Mike Coslo wrote in
:

wrote:
How far away from viewers are VHF signals typically broadcast?
(i.e. up to 1000 miles)
Pretty much line of sight is the rule at VHF and above. The line of
sight is baaed on the curvature of the earth, and modified by the
respective heights of the two stations.

A nice little on-line calculator is at:

http://www.qsl.net/kd4sai/distance.html

enter the heights of the two antennas, and it will calculate the
distance that you can expect to cover.


Sometimes there are propagation effects that will dramatically
extend
the range, but these are the exception not the rule, and although
amateurs have a lot of fun with the effect, it isn't reliable for any
length of time.

Yep...and tropo scatter, the only RELIABLE long-haul VHF mode is way too
weak for TV broadcasting, though it does work great on CW or SSB with
good antennas and equipment. When I had a 19el antenna at 85 feet in
Nova Scotia, I could reliably work Cape Cod, 500 miles away, on 2m CW.
But it took high selectivity, and a good preamp even with that antenna
and both stations running about 600 watts out. About 60db overall path
gain over a 1w signal. Plus the bandwidth gain from TV to CW is about an
additional 48db.


--
Dave Oldridge+
ICQ 1800667

In article ,
Dave Oldridge wrote:

Yep...and tropo scatter, the only RELIABLE long-haul VHF mode is way too
weak for TV broadcasting,

Oh, I wouldn't class Wideband TropoScatter in the unreliable folder.
The AirForce built the White Alice System in Alaska in the 50's and it
had some 300 to 400 mile shots that ran 24/7 with 5 Mhz bandwidth or
more. Yea, it took 60 foot high Parabolic Antennas, and 20Kw feeds, but
it worked at 900 Mhz and was very reliable, with uptimes in the 99.7%
range.

Me one of the older guys who can actually remember
he hardware involved.......

Hard to rely on the RX end of broadcast to put up sufficient antennas
to hear troposcatter signals...

Maybe with lots and lots of power on the TX end and a robust digital
mode you could do troposcatter broadcasting to the general public, but
it's a lot easier for point to point links..

Dan

Me wrote:
In article ,
Dave Oldridge wrote:

Yep...and tropo scatter, the only RELIABLE long-haul VHF mode is way too
weak for TV broadcasting,

Oh, I wouldn't class Wideband TropoScatter in the unreliable folder.
The AirForce built the White Alice System in Alaska in the 50's and it
had some 300 to 400 mile shots that ran 24/7 with 5 Mhz bandwidth or
more. Yea, it took 60 foot high Parabolic Antennas, and 20Kw feeds, but
it worked at 900 Mhz and was very reliable, with uptimes in the 99.7%
range.

Me one of the older guys who can actually remember
he hardware involved.......

wrote:
How far away from viewers are VHF signals typically broadcast?
(i.e. up to 1000 miles)


Well the exact answer to the exact question is: As far away as they can be!!
[I'm in New Hampshire and I'm sure somewhere in Europe VHF signals are being
transmitted. But, I surely can't hear them :-)

Allowing for the ambiguous wording and hopefully moving to the intent of the
question A 1000 feet high tower will have about a 50 mile radius range.

A 2000 feet high tower will have about a 70 mile range.

a 200 feet high tower will have about a 20 mile range.

wrote in message
oups.com...
How far away from viewers are VHF signals typically broadcast?
(i.e. up to 1000 miles)


I'm guessing you are asking about "DX" or "DX'ing," the art, science and
hobby of long-distance communications. One good TV DX website is
http://www.w9wi.com/.

1000 miles is unlikely but not impossible. 100 miles is quite reasonable I
am 124 miles south of Mt Wilson, the transmitter site for Los Angeles TV,
and I get them more or less reliably with antennas about 30 feet above
ground. At that distance, the problem is not signal strength,
but it is being behind the "bump" caused by the curvature of the earth. Mt.
Wilson does me a big favor by being about a mile high.

Some years ago in Norfolk, Virginia, I watched a late-night movie from a
station in Buffalo NY, over 400 miles away. The picture was snowy, but good
enough to permit enjoying the movie. That was a rarity, as most nights
after that I saw little or nothing of that station.

The best TV DX I have ever had was one night in the winter (Jan. or
Feb.) back about 1992. I was living in far Northern Wisconsin and I got
the news from a New Orleans TV station (Ch. 3 I believe) and the video
was very good with full sound. I had the TV running in the other room
and didn't even suspect that it was not my normal channel out of Duluth,
MN until the weather forecast came on and said the high temp expected
was going to be in the low 80s (that would be VERY unusual Wisconsin
weather for the middle of winter)!!

Scott


Sal M. Onella wrote:


Some years ago in Norfolk, Virginia, I watched a late-night movie from a
station in Buffalo NY, over 400 miles away. The picture was snowy, but good
enough to permit enjoying the movie. That was a rarity, as most nights
after that I saw little or nothing of that station.