I have a question about MS propogation and duration.
I often monitor the VK6RSX 50Mhz beacon (the 2m beacon seems to be dead) as an iindicator of possible propogation paths to the north of Perth.
There are no active 6m stations who utilise MS within >>2100km of Perth. So, watching VK6RSX is my only exposure to MS.
I occasionally see traces lasting for well over one minute, as opposed to the more frequent short duration pings.
Could these longer "traces' be MS or low level SpE ?
Ive attached a couple of screen grabs - VK6RSX is the trace at ~970 Hz. The other trace at 1000 Hz is a birdie from somewhere in the neighbourhood.
Welcome your comments.
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attachment=570]
Im guessing this is clearly MS - Initially bright then very diffuse/scattered
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attachment=571]
This one is more consistant , although possibly slight doppler shift at commencement of trace. Is this likely to be MS or low level SpE?
Hi Nigel,
It is perhaps uncommon, but not impossible, for the propagation you've observed to be MS; it is not "sporadic E" - at least, not as I've known it, having experienced Es propagation and researched the phenomena over decades since the late-1960s. I've certainly heard 6m MS signals lasting more than a minute in the era when Wally VK5ZWW (later VK4DO) ran tests from his home in Adelaide.
Cheers.
We now have a WebSDR on my Men's Shed building here in Western Sydney, somewhat more 6m beacons here.
www.nepeanshed.org.au:8073
At last, Telstra have given this a fixed IP address again after going NBN from ADSL.
(Three months no service, NBN up, then three monthly IP address changes and this is a Business Service!!)
Based on OpenWebRX s/w so is similar to KiwiSDR, one thing, resets every hour back to 160m. just set your band again.
Antenna: 9m pole then 10m of RG214 to a SDRplay RSP1 in 10bit mode.
The 'regular' E layer only works to 25Mhz. So if you hear shortskip at higher frequencies
you know it is propagation by the Es layer. The height in the E layer at which a MS reflection
occurs depends on the speed of the meteor (since showers have different speeds, some are good
for longer distances, some for shorter distances).
Es means two things; the layer of ionosphere or a propagation by means unknown via the Es layer.
So while MS involves the Es layer, it is NOT Es propagation since the means of propagation is
known (the extra ionization required to allow the E layer to function above 25Mhz came from the
meteor).
Years ago, this 'propagation by something at E layer height by means unknown' was called 'SpE'.
A current identification* of Es (propagation) might be 'very strong constant signals lasting over
10 minutes'.
Perhaps your question involves the duration of bursts? This could be overdense/underdense
(differences in signal strength, keep agc off or the difference seen on waterfall). Or the
direction and duration of trail. Or the difference in lengths of nighttime/daytime bursts.
I hope to read your explantion of what you observed...
'agx
*And more recently, as noted on cluster, Es means a dx contact made by digital burst
The strongest & longest bursts from meteors result from the overdense situation; a reflection.
I have attached a drawing that shows the overdense return to 70seconds (66Mhz data?).
The photo is from the '50s and shows common underdense return. If you watch these waterfalls,
unless you have a wideband system, you are missing half the picture; see the other attachment
(143Mhz, QRO).
Here's some more:
The relative length of meteor burst is related to a square.
The relative strength of meteor burst is related to a cube.
So since 144/50 is 2.9, the burst on 6m is 2.9*2.9 or 8 times longer on 6m than 2m, and
since 144/50 is 2.9, the burst on 6m is 2.9*2.9*2.9 or 24 times stronger on 6m than 2m.
There are also about 2.9 times as many bursts on 6m than 2m.
A table, with initial 2m burst length 50mS and strength 0db (a 6db increase perhaps one "S" unit)
frequency length strength
144Mhz 50mS 0dB <= reference levels
50Mhz 410mS +13.7db +2 "S"
40Mhz 648mS +16.7db +2½ "S"
29Mhz 1230mS +20.8db +3 "S"
This is all relative to same power level; if the transmitted power* is 6dB greater on 50Mhz than
144Mhz, then the 50Mhz level would be 13.7+6=19.7dB better than the lower power 144Mhz signal.
clearly, lower frequencies are best, so how about 40m?
7Mhz 20sec +40dB +6 "S"
The "regular" E layer is present on 40m during daylight hours, so to be sure that your 20second
burst really is MS, best to try at night for a contact within the skip zone...
Now, take off angle is an important thing here;
600km 18°
800km 15°
1200km 8°
1600km 4°
take off angle is related to the height of antenna above ground (unless you live on the side
of a hill, in which case it is the height of the hill that is important).
But wait, there's more. And that is background noise level. This background noise level consists
of galactic noise, atmospheric noise (QRN) , solar noise and the background QRM (electrical noise) level.
So considering background QRM only:
frequency strength background dB above noise
144Mhz 0dB 0dB 0dB <= reference levels
50Mhz +13.7db 10dB 3.7dB
40Mhz +16.7db 12dB 4.7dB
29Mhz +20.8db 20dB 0.8dB
7Mhz +40dB 40db 0dB (for 40m the summer QRN level can exceed background QRM)
This is an approximation; the actual background noise level depends on your situation; the rural
noise level is more than 20db lower than the urban noise level. That means that a MS signal (or
any) received at S3 in a rural area can be below the noise when received in the city. If you
are in a rural area, this improved signal to noise allows direct FSK for MS data. FSK allows
for faster data rates and rejects amplitude variations (most noise). Effective FSK matches the
transmit modulation index with the receive IF bandwidth.
*adding more elements is not the same thing because going beyond 5 elements reduces the meteor
'capture area' too much.
overdense.jpg underdense.jpg echoes.jpg
Technically, you could call a meteor signal Sporadic E, because its activating the E layer sporadically in the surrounding area of the Ionospheric E layer where the meteor passes.
(17-05-2023, 11:15 AM)VK2KRR Wrote: [ -> ]Technically, you could call a meteor signal Sporadic E, because its activating the E layer sporadically in the surrounding area of the Ionospheric E layer where the meteor passes.
Yes. Activating the Es layer.