XPost: rec.radio.amateur.moderated

EI7GL....A diary of amateur radio activity

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More information about the proposed Amateur TV experiments at 29.250 MHz &
51.7 MHz

Posted: 08 Dec 2021 12:06 AM PST https://ei7gl.blogspot.com/2021/12/more-information-about-proposed-amateur.html


In a previous post in August of 2021, I outlined how some radio amateurs in Europe plan to experiment with digital ATV (Amateur TV) on the 10-metre
band in the Summer of 2022. That post generated quite a bit of interest.
On Monday the 6th of December 2021, the BATC streamed a YouTube
presentation about current Amateur TV techniques and activity as part of
the RSGB Tonight at 8 series.
While the video is about 75 minutes in length, the piece I found really interesting was about the proposed ATV experiments at 29.250 MHz and 51.7
MHz. They refer to these as the 'lower ATV bands'.
Amateur TV up to now has normally been used on the UHF and microwave bands. This new development at 29 MHz and 51 MHz will potentially allow ATV
signals to be sent on frequencies which will achieve much greater distances
via the ionosphere - i.e Sporadic-E and F2 layer.
I find it amazing that there is the potential of sending amateur TV signals between say Europe and North America on the 10-metre band.
The presentation with time guides are shown below...
Video guide...
03:35: Introduction starts
05:15: G8GTZ begins his presentation
06:55: What is ATV - Amateur TeleVision / Why amateur television? / ATV is going digital12:00: Analogue V Digital ATV / Reduced bandwidth (RB-TV) / 80
kHz RBTV16:30: UK ATV activity and repeaters
20:45: ATV on the air - 1 The lower ATV bands22:45: ATV on the air - 2 Low
cost 5.6 GHz FM ATV with example contact29:45: ATV on the air 3 - DATV on
QO100 (Geostationary satellite)38:20 - DATV equipment / Getting started /
Ryde DATV receiver / Portsdown DATV transceiver / DATV receive system /
DATV transmit system / 57:55: Info about British Amateur Television Club (BATC)1:01:00 Q &A session
I am told that the numbers involved are likely to be small with perhaps something like 20-30 stations taking part. Special boards are being
developed at present and no doubt, these will be be got ready for the Sporadic-E season next May.
It would be very interesting if some radio amateurs in North America got interested in this project.Links...
1) BATC website... https://batc.org.uk/

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Skewed propagation path on 28 MHz between Australia & South America - Dec
2021

Posted: 06 Dec 2021 10:57 PM PST https://ei7gl.blogspot.com/2021/12/skewed-propagation-path-on-28-mhz.html



Recently, Scott VK4CZ reported a skewed path on 28 MHz between Australia
and South America.
The image above shows what happened. The direct and shortest path from
VK4CZ to CE2SV is 11,800kms and is shown in Green. The beam heading from eastern Australia is 142 degrees.
VK4CZ however found that the FT8 signals from CE2SV peaked at about 70
degrees, a skewed path that was about 70 degrees off the direct path.
Scott mentions that the skewed path opening was from 21:00 - 22:00 UTC and
I believe at that time period, the sun was directly over the centre of the Pacific.
VK4CZ was using an ICOM IC-7600 with a 5-element monoband Yagi for 28 MHz
at 20 metres above ground level.

Scott, VK4CZ writes... "It's been amazing to see the scatter path to South America out of the North Pacific available again on 10m yesterday and again this morning. This path was a consistent feature through the peak of last cycle, and with digital modes it's becoming available now!
Worked/seen this morning were HK (Columbia), LU (Argentina) and CE (Chile)
all peaking at a QTF of 70. Direct QTF for CE 145... so well off a direct
path.
It's an interesting propagation mode that I regularly observe across the Pacific. As I understand, it's trans-equatorial scatter.The same path
should be available to Africa in the afternoon/evenings from here.
The likelihood of it also being available at 50MHz is high.... we'll just
need the cycle to progress towards the peak to be sure.
A couple of cycles back, I heard Peter PY5CC in Brazil on 6m CW using the
same path (albeit late afternoon when TEP peaked to KH6 / Hawaii)."
Analysis... This is my understanding of what happened and I'm open to correction. Directly under the sun near the equator, the solar radiation is
at it's highest and the F layer of the ionosphere is highly ionized with a
high maximum usable frequency (MUF).This is usually split into two zones of high electron density either side of the geomagnetic equator but in
December, the southern one is much larger.This can be thought to be like a
tube like structure that is stretched out east-west.
The above graphic is a bit rough but you can get the general idea of the
signal hitting the F layer from the side.Skewed paths are a fascinating
subject and are allow serious DXers and contesters to exploit paths when
the direct path isn't possible. This is especially true on the higher HF
bands like 28 MHz where the shortest east-west paths are often closed.I
suspect these skewed paths happen a lot more often than we realise
especially now that so many people are using weak signal modes like FT8.

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