Unusual propagation, VHF?

[Skywave]

Listening to Classic FM this afternoon (June 3rd., 13:30 hrs.) on my Sony portable radio / cassette (with its telescopic whip aerial), on the ground floor. The reception was subject to rapid fading, sometimes quite deep and very variable in its repetition rate. At first, I suspected aircraft flutter, but as this phenomenon continued for at least half an hour, I ruled that possibility out. I listen to this radio (Classic FM) in this room a lot: never noticed this effect before. Of course, may be a fault in this radio, but I doubt it.

Next, I went upstairs to the workshop. There I have a Sony tuner-amplifier which is fed from a 3-element beam on the roof. Tuned to Classic FM: no fading whatsoever.


Considering the time of the year, current 'clock time' and current weather (warm, blue sky, some cumulus clouds), I suspect sporadic-E. But - and if so - why only the one radio affected? I appreciate that the roof aerial will deliver a much stronger signal, but surely the effects of sporadic-E (or whatever) will affect the strength of the received signal to a very similar degree, irrespective of the magnitude (and phase) of that signal.

Your thoughts, please.

Al.

[Refugee]

Your roof aerial will be directional so there will be no problem.
I have had a Dutch station come in over radio 4 FM at times on both valve and transistor radios. It is indeed down to the weather.

[Skywave]

Thank you.

Al.

[Biggles]

Haven't heard any lifts on this year on domestic VHF but a few times last year while listening on my car radio on the way to work, Radio 2 has been totally wiped out by strong Scandinavian and even Spanish stations with full RDS station idents. I normally pull over and have a quick scan around the band to see what comes up. A few minutes later and they are all gone. I wonder if this would happen with digital broadcasting too, even though they operate on twice the frequency? Amazing stuff, RF.
Alan.

[PJL]

Reflection? We get terrible tidal fading on TV here to the extent I abandoned terrestrial TV.

[Nymrod121]

Sporadic E propagation at Band III ? - that *would* be interesting

Tropospheric is more likely (I've seen perfectly decoded teletext services from Westdeutsche Rundfunk UHF TV received at Holme Moss - (granted there was a very good antenna support pole and the site location has significant height advantages - so tropo enhancement of DAB broadcasts (while rare) is possible, especially if an atmospheric temperature inversion event ("ducting") occurs between transmitter and receiver locations.

It might be worth asking Todd Emslie (Australian DX enthusiast/expert) if he's noted anything like this over there in the auntypodes

Best wishes
Guy

[michamoo]

I had Chaine 3 Algeria (RDS identified) fighting with Radio 2 one evening last week here in Cambridgeshire plus a few unknown Italian stations.

[Nymrod121]

That's very impressive DX Did you research the possible transmitter site from knowledge of your R2 frequency in use at the time?
Best wishes
Guy

[Skywave]

Today is June 4th.; time is 23:45 local. Just had a tune around on the AmRad HF bands: the 14 MHz, 21 MHz and 28 MHz bands are wide open. In the last 15 minutes on 10 meters, copied several stations from the USA at reasonable strength and many EU stations coming in at 5 & 9+. Haven't witnessed this sort of reception on those bands (especially 10 meters) for a very long time - and especially at this hour, too; very unusual.
At least I now know that the RA-17 is up to scratch . . . I was beginning to wonder.

Al.

[Jeremy M0RVB]

Last night (4th June) 50MHz looked like 20MHz usually does - FT8-wise anyway - absolutely full of it. 28 was good too. I had to sleep so didn't go further down the dial.

[michamoo]

Hello Guy...The Chaine 3 signal was on 88.4 Mhz so seems it was the 10Kw Chr'ea transmitter which it seems is located in mountains close to the city of Algiers.

http://www.elahcene.co.uk/algeria/chrea.htm

[Skywave]

Update: today is June 5th,; time is 20:50.

Have spent the last half-hour listening to the 10 m. AmRad band: it's wide-open with some exceptionally strong signals coming in from many places in Europe. I copied a station in Vienna who was putting in a signal here of well above S9 + 20 dB - but with severe fading right down to inaudibility and with a very variable fade rate. (At his loudest, probably an aerial input to the RA-17 well into the mV region ). Much same with many other signals. Most of the activity seems to be between 28,400 and 28,550 kHz using SSB and judging by the level of the QRM, you'd think that there was a contest on!

It's been decades since I've received signals like these on the AmRad 10 m. band: it's almost spooky!

Al.

[Hybrid tellies]

At this time of year you can get a mix of tropo and SpE enhanced conditions on the FM band which can affect the reception of some local stations.
I live in between Bristol and Bath where the reception of the national stations from Wenvoe and the low powered relays at Bristol Illchester Cresent and Bath are all weak and variable especially during the summer months when all the trees and bushes are in full leaf.
On the positive side listening to the weak BBC R2 FM signal can act as an alarm to any openings and have sometimes heard Radio 2 being totally swamped out by Italian or Iberian stations.

[Refugee]

We have been listening to radio4 on FM and today it has been fading up and down like an overseas MW station. A dutch station has been known to swamp radio4 in this location.

[Nymrod121]

Positive ident of SAM FM on 106.0 MHz here in N. Worcestershire - Chillerton Down on the Isle of Wight.
(Fuba UKA 8 - bearing roughly SE - & Hitachi FT3500L)
AtB
Guy

[Nymrod121]

Originally Posted by michamoo

Hello Guy...The Chaine 3 signal was on 88.4 Mhz so seems it was the 10Kw Chr'ea transmitter which it seems is located in mountains close to the city of Algiers.

http://www.elahcene.co.uk/algeria/chrea.htm

[crusher19860138]

I have heard Irish stations on FM also, Lyric, Today FM, RTE R1 & R2.

[Nymrod121]

Further to my post #06, Todd Emslie has kindly responded to my enquiry email and has given his permission for me to quote from his replies:

(1)

"Hello Guy,

Good to hear from you.

Compared to analog band 2 FM, DAB band III tropo DX is generally more difficult to decode. The task becomes even more difficult with band III sporadic E. When 100 kW (nominal) power analog band 3 TV stations were running some years back, a TV DXer was doing well to receive them once for 2 minutes on average every Es season. It is rare to have Es at 176 MHz, but even rarer at circa 190 MHz. I suggest this effectively precludes band 3 sporadic E DX in practice.

I wonder if you have ever received Israel FM via 2Es. There are some high power Israel channels located toward the low end of the 88 to 108 MHz band."


(2)

" Hello Guy,

Someone once told me that a general rule for average Es occurrence is doubling the RF (MHz) reduces by a factor of 10. For example, suppose there is 1,000 hours of sporadic E at 28 MHz over June to July, there would be 100 hours at 56 MHz, 10 hours at 112 MHz, and 1 hour at 224 MHz. In practice it doesn't work quite the same, but you get the basic idea re sporadic E occurrence vs. freq . In a poor Es season, there is no Es at 175 MHz. Even 144 MHz 2 metre ham band openings are minimal, or don't even occur.

Morocco and Algeria north Africa FM are generally within single-hop Es range of southern and central UK. The low end of the band starting at 87.5 MHz to 90 MHz is where reception seems to be more common.

The main challenge for FM DXers in Europe (especially Italian DXers who have local stations every 100 KHz), is extreme FM band congestion. Some DXers use RF phase cancellation in order to null unwanted signals on the same frequency. Others use dedicated tuners that feature digital signal processing technology IF stages such as the Sony XDR series tuners. Another interesting avenue is PC software used in conjunction with a dedicated outboard RF tuner. The outboard tuner handles RF selectivity and sensitivity, which is connected to the PC via a USB cable. The software handles demodulation, tuning, AGC, and IF.

Variable phase cancellation within the IF stage (455 KHz or 10.7 MHz) is another potential method of reducing 100 KHz or 200 KHz adjacent channel interference at band 2 FM.

Regards,

Todd"


Hope this is of interest.
Guy

[colourking]

Originally Posted by Skywave

Listening to Classic FM this afternoon (June 3rd., 13:30 hrs.) on my Sony portable radio / cassette (with its telescopic whip aerial), on the ground floor. The reception was subject to rapid fading, sometimes quite deep and very variable in its repetition rate. At first, I suspected aircraft flutter, but as this phenomenon continued for at least half an hour, I ruled that possibility out. I listen to this radio (Classic FM) in this room a lot: never noticed this effect before. Of course, may be a fault in this radio, but I doubt it.

Any large wind turbine(s) nearby?, signal reflections off the rotating blades can cause 'rapid fading' on FM reception.

The effect can be quite noticeable in hilly areas if the receiver location has terrain shadowing resulting in a weakened reception, but with the wind turbine(s) having line-of-sight with both the transmitter (and receiver) and so can have significant reflections.

The effect would come-and-go depending on the direction of the wind and therefore the turbine swiveling to face different directions.

A directional aerial of course could avoid such reflections provided it has a poor response in the direction of the reflections

If only the blades could be made of a non-conductive/reflective material ! (the varying multipath effects caused by the rotating blades (unlike stationary multipath) is a problem for digital terrestrial TV )