[BC] Commercial Station Feeding A Commercial Translator Question

[R A Meuser]

I looked after a cable operation where one of the head ends used a 
rhombic to receive channels 2 and 4 Buffalo over a distance of a few 
hundred miles At another there was a ground mounted semi parabolic 300 
feet across which also pulled in stations from over the horizon. Other 
similar systems were known to have parabolics up to 1000 feet. One site 
had a pair of 1000 footers, phased to suppress a somewhat local channel 
3 while receiving chs 2 and 4. Those parabolics were really troposcatter 
systems. The could bring in stunning pictures, but when they faded, the 
fades were very deep slow fades.

All these systems worked better in Winter than summer, skip being one of 
the reasons.  However UHF is the opposite, especially over large bodies 
of water. You could pull in stations that looked local all summer long 
only to have them disappear completely by late November or December.







Mark Humphrey wrote:
> 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.