Radio-Electronics - July 1957 - pg 79

Transoceanic TV-DX
Calvin R. Graf, W5LFM

With the 11-year sunspot cycle expected to hit its peak in late 1957, the possibility for
transoceanic television reception becomes more likely as the sunspot number increases.  European TV
stations, especially the BBC, have been received as far south as southern Texas and west to
California beginning in October and continuing the rest of the year.  In San Antonio, Tex., reception
of England, Northern Ireland, France, Switzerland and Germany have been almost daily occurrences.
Best and most often reception is in the frequency range of 41 to 50 mc.

As the sunspot number increases, the F2 layer of the ionosphere, because of increased ionization,
is better able to reflect high-frequency signals for longer paths and longer periods of time.
During a sunspot minimum the maximum usable frequency for long-distance paths might be as low as
10-20 mc, but at the sunspot peak, it might rise as high as 50-70 mc for certain paths.  And the
sunspot cycle maximum ex- pected in late 1957 might be the highest experienced in our lifetime!
It has been reported that KPRC-TV, channel 2, Houston, Tex., has been received in South Africa, a
distance of nearly 9,000 miles.

The accompanying chart lists locations, frequencies, lines per picture, video antenna power and
antenna polarization of many TV stations which can easily be received.  Remember that in most
countries the number of scanning lines which form the picture are different from those of the United
States.  Except for the United States, Canada and a few South American countries which use 525 lines,
most countries use 405, 625 or 819.  This means the pictures cannot be locked in on a receiver
designed for 525 lines without modifying the receiver circuit.  Moreover, since our TV receivers have
fixed channels which are different from other countries almost none of the frequencies will coincide.
Most other countries use amplitude modulation for the sound carrier while we use frequency modulation.
A shortwave receiver covering 40 to 50 mc or a converter is desirable.

                Frequencies Mc   video     antenna
Station         Video   Audio   ERP kw  polarization  sound  lines
Great Britain
 London          45.0    41.5      34         V        AM     405
 Belfast, N.I.   45.0    41.48     20         H        AM     405
 Holme Moss      51.75   48.25    100         V        AM     405
 N. Hessary Tor. 51.75   48.23     16         V        AM     405
 Kirk o'Shotts
   Scotland      56.75   53.25    100         V        AM     405
 Norwich         56.75   53.25     10         H        AM     405
France           52.4    41.25     50         H        AM     819
Switzerland      48.25   53.75     30         H        FM     625
Australia        64.25   69.75    100                  FM     625
Russia           49.75   56.25     40         H        FM     625

German audio has been received on 45.625 and 48.8 mc (50 kc/swing FM).  Russian programs are on from
1100-1500 EST, with the stations closed down Thursdays for maintenance.

Reception of European stations is best between mid-morning and noon.  Australia should be best from
mid-afternoon to evening.  Since propagation is by the F2 layer, the sun should be near noon at the
mid-path point.

Most of the European stations received in south Texas have been heard from 0830 to 1230 CST, with the
lower frequencies lasting the longest.  During the months of November and December, 1956, BBC TV audio
on 41.5 me was received almost every day and BBC video on 45 mc was received about three-fourths of
the time.  Occasionally, frequencies as high as 53 mc are received.

When conditions are good, it doesn't require much of an antenna to receive transoceanic TV.  A simple
300-ohm vertical folded dipole cut to 41.5 mc has picked up TV signals from five European countries.
Signal strength is so great at times that the BBC has been heard using a pocket screwdriver for an
antenna inside a concrete building!  It doesn't take much - give it a try.

END
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Personal Comments

This was the month that I arrived in San Antonio, completely ignorant of the historic nature of
Solar Cycle 19 (though deeply into astronomy) or its VHF radio propagation effects!  I would not
catch the British and French audios, etc until October 1978 - Cycle 21.  By then Germany had given
up on those 45-48 MHz audios cited.

The article neglects to mention that the BBC video modulation was positive - that is the whiter the
image the deeper the modulation - just the opposite of US NTSC.  This would only be of consequence
to someome trying to render their 405-line video on a CRT.

Also, this predates the introduction of Australian Channel 0 (46-52 MHz) in 1964 so the 64-MHz listed
for them was their then-lowest TV frequency (and, as higher than the other "targets", a much-less
chance of F2 affecting it).

WA5IYX