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Manx Radio oddness?

Posted: 08 Feb 2018, 20:14
by Andy
Anyone out there in range of Manx Radio with an SDR? I wonder - could you take a look at Manx Radio on 1368? It seems to have a big lower sideband splashing right out to the next lower channel, and the waterfall display shows a strange 'sweeping' effect of stripes. I've attached a screenshot which shows it up quite well. The big signal from Asian Sound on the HF side stops me seeing if there's a matching upper sideband. I'd be surprised if there wasn't.
I can hear it also on my analogue RX and as far as I can tell it isn't a mix or overload effect.
It's been there for a few nights now, but due to the poor daytime signal I can't see it during daylight hours.

Re: Manx Radio oddness?

Posted: 09 Feb 2018, 07:53
by grafter
It looks like propagation effects to me with selective fading of the sidebands. I grabbed a couple of images this morning taken a few minutes apart. The first is using a MW flag antenna hence the lack of other Euro signals, the second is with a Wellbrook loop. Anyway, you can see the difference in the sidebands on each one.
1368.jpg
I see that effect on ionospheric prop even FM via Sporadic E and F2, I made this some time ago of an OTHR on 10m, you can see the effect as well as hear how it effects the sound of the SSB signal.

https://www.youtube.com/watch?v=piunB8pTQwQ

Re: Manx Radio oddness?

Posted: 09 Feb 2018, 09:08
by Andy
Thanks for taking a look, Grafter. Yes, I did think it may be selective fading, but it looked too neat and steady to me. You're probably right.
What do you think of the extent of the sidebands? They seem to extend out to +/-8 KHz which seems a bit bold to me. Around 5 (sometimes 6) KHz is the norm. Apparently the spec is 7.5KHz @-20dB and 9KHz @-40dB. I didn't get chance to note what it was last night, and on real modulation it would only be an estimate. It sure *looks* a bit pushy. Maybe I should get out more...

Re: Manx Radio oddness?

Posted: 09 Feb 2018, 09:28
by Clipper

Re: Manx Radio oddness?

Posted: 09 Feb 2018, 14:54
by grafter
I think the current spec of digital audio processors have such a steep roll off at HF they can put the bandwidth to the max without splashing over. Caroline's DSPX-AM unit used on 648 is one such device and they do squeeze every last drop out of it.

Does IOM come under Ofcom jurisdiction, like who's going to tell them off if they push it a little bit too hard sometimes? FWIW nothing will beat the audio quality of Radio Caroline back in the 80s using the old 963kHz TX and Orban Optimod, some of the recordings I have (plus others online) sound very close to processed studio recordings, dread to think what the sidebands looked like on that!

Re: Manx Radio oddness?

Posted: 09 Feb 2018, 15:36
by Andy
I don't think Ofcom have any power over them, it's down to the IOM CC I think. I have let the station know they are almost completely overlapping the upper sideband of the station on the LF side of them and they have acknowledged my post. I can't see them doing anything about it though!

Re: Manx Radio oddness?

Posted: 09 Feb 2018, 18:43
by grafter
Just as a point of interest and nothing really to add to the thread but Manx radio have potentially gained quite a few new anorak listeners since the BBC locals have switched off. We've lost Surrey and Manx is available on demand pretty much all the time using the flag antenna.

Re: Manx Radio oddness?

Posted: 07 Sep 2018, 18:50
by Sparkgap
Are they doing what Atlantic 252 did and using (I think) single sideband + carrier? Apparently it's supposed to help under poor propagation conditions.

Re: Manx Radio oddness?

Posted: 14 Sep 2018, 08:02
by Andy
Sparkgap wrote:
07 Sep 2018, 18:50
Are they doing what Atlantic 252 did and using (I think) single sideband + carrier? Apparently it's supposed to help under poor propagation conditions.
No, both sidebands are there and a bit better look at them shows they are equal. But overall it is definitely W-I-D-E.

Re: Manx Radio oddness?

Posted: 14 Sep 2018, 09:25
by Tigersaw
Funny enough I put up a 80m loop the other day and had a browse in the MW band. I get radio devon S9 and very clear, Manx is just as strong but sounds 'wierd' with washing and mutter type effects

Re: Manx Radio oddness?

Posted: 14 Sep 2018, 22:14
by LeakyFeeder
Not long back from the IOM but only used VHF for 2m and secure DMR for bike to bike comms