[BC] Commercial Station Feeding A Commercial Translator Question

[Mark Humphrey]

According to a July 1945 article in "FM and Television" magazine,
General Electric's early TV station WRGB in Schenectady originally
used a rhombic antenna to receive NBC programs from WNBT, transmitting
on the former Channel 1 (video carrier 51.25) from the Empire State
Building in New York at a distance of 129 miles.   Although this
receive site was up in the Helderbergs at 1800' AMSL, a profile graph
shows the antenna was still 6767 feet below an unobstructed optical
"line of sight" path.   The rhombic was 180 feet on a side and
supported by four 128 foot towers, with a gain of 20 dBd.

The story reports that, "over a period of a year, good picture signals
are received without interference at least 85% of the time.
Unsatisfactory signals, marred by static sources, are received about
10% of the time, and poor reception during the remaining 5% is due to
fading.  During the winter months practically no fading is
experienced; in general, the only interference comes from diathermy
machines or precipitation static."

It's also interesting to see that this early relay system avoided
demodulation.  The receive site was a couple of miles away from the
Schenectady transmitter, so GE used a 10 watt direct conversion VHF
link (with video carrier at 163.25) to hop the WNBT signal over this
short distance, then it was heterodyned down to WRGB's original
carrier frequency of 67.25 and amplified to 40 kW.

I believe a few of the early low-band FM stations in the
Albany/Schenectady market -- perhaps WRGB's sister WGFM -- also
attempted to take off-air feeds from New York, but probably
encountered similar fading problems.

Mark



On 10/17/07, WFIFeng at aol.com <WFIFeng at aol.com> wrote:

>
> Correction: *Could* work. You're talking about 90 miles. Someone else
> mentioned a distant site where it only worked reliably in winter. This is because in
> the warmer weather, the atmosphere is much more active, and there are "layers"
> of differing temperatures and humidity levels. These will all wreak havoc
> with VHF.
>
> You also will have the flutter effect caused by all types of aircraft within
> range... and at 90 miles spacing, that's a LOT of room for a LOT of aircraft!
>
> Willie...
>
>