XPost: rec.radio.amateur.moderated

EI7GL....A diary of amateur radio activity

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Explosion from Tonga volcano detected in Ireland (Non Radio Post)

Posted: 16 Jan 2022 02:39 AM PST https://ei7gl.blogspot.com/2022/01/explosion-from-tonga-volcano-detected.html



This is an interesting scientific observation and I thought it might be
nice to keep a record of it. I tried to work a radio angle into this post
but I failed! 😂
At 04:10 UTC on the 15th of January 2022, a huge underwater volcano near
Tonga in the Pacific exploded and sent a shock wave around the world. It
was so big that the sound was heard as a rumble 9000kms away in Alaska.


The video clip above shows the explosion and you can see the shock wave
being sent outwards.
What I find really amazing is that this pressure wave was detected at the
other side of the planet in Europe.
Cormac, EI4HQ and Alan, EI3EBB both have their own weather stations and are located near the city of Cork on the south coast of Ireland.

At roughly 18:44 to 18:50 UTC, both Cormac and Alan detected the change in pressure on their weather stations.
EI4HQ in Cobh...
When I made the above image, I wasn't sure if it was the Tonga event or
not. It later turned out that it was.
EI3EBB in Watergrasshill observed the same spike..

You'll notice that there is also a drop in pressure as the pressure wave passes.
Due to the shortcomings and distortion on the Mercator flat map, the
pressure waves from Tonga actually came from the north-west and not from
the south-west as the map might suggest.

It was interesting to see that the pressure wave arrived in Cork about 15 minutes or so before it reached weather stations in Essex and Suffolk in
the south-east of England.

Short Path & Long Path... Just like in radio, there are two paths for a
signal to travel on a globe. The short path is shown above and the long
path as shown below.

And sure enough just before 02:00 UTC, the long path pressure wave arrived
in Cork.
The distance for the long path signal was in the region of 24,000 kms.
It's amazing to think that a volcano in the Pacific could cause a change in
air pressure at the other side of the planet.
Questions... Like any unusual event, it often raises more questions...
Q. Could the sudden change in air pressure cause a rain shower somewhere in Europe? Was the change enough?
Addendum... This is a more detailed chart from EI4HQ showing the air
pressure changes...



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Custom made beacons for the 28 MHz band from AA7DJ

Posted: 15 Jan 2022 10:12 AM PST https://ei7gl.blogspot.com/2022/01/custom-made-beacons-for-28-mhz-band.html





I recently came across this beacon for the 28 MHz band and it thought it
might be of interest to others.
While most beacons are built from modified CB radios or home built from
parts, there is an option to buy a 'ready to go' beacon from Vlad, AA7DJ in
the USA. The beacon is shown above and it runs with an output power of 10
watts on the 28 MHz band although this can be reduced.
The frequency and callsign are given to AA7DJ and he then builds the
beacon. Upon arrival, all a station needs to be do is to supply power to
the unit and plug in an antenna.

The interior of the beacon is shown above with the frequency synthesizer
inside the metal cage on the left and the power amplifier stage with low
pass filter on the right.
On his QRZ page, AA7DJ writes..."The synthesizer board has PLL chip, VCO, crystal reference and microcontroller. The last one produces frequency code
for PLL. Also it generates CW message and keying sequence for the amplifier board. "
Frequency stability is claimed to be about 10-50 PPM as determined by used crystal.

The spectrum output with the level of harmonics is shown above. If
additional suppression is required then another low pass filter could be
added.
Permits... From my understanding, a special license is required to operate
a beacon on the 28 MHz band in most parts of the world. In the USA however,
the FCC allows radio amateurs to operate beacons on 28 MHz and the VHF
bands.
This is specifically for the purpose of ...'observation of propagation or
other related experimental activities'. The power limit of 100 watts by the
FCC is quite generous in this regards.
In conclusion... While many may want to build their own beacon, there are others who will just want to order a ready built unit and put it on the air. There is a small but active group of 28 MHz beacon enthusiasts in the USA
and many speak highly of this unit built by Vlad, AA7DJ. I don't know how
much a unit costs but several have mentioned that it is reasonable.
If anyone is interested in buying a unit then they should contact AA7DJ via
his QRZ page.

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