[cma-l] RF Link Fault

Wed Nov 2 08:06:01 GMT 2011

Gordon
I'm not aware of the nature of the complaint from the amateur rado operator, but your antenna being defective would be most unlikely to cause an intereference problem.
If your equuipment shows correct spectral occupancy, which Ofcom will and possibly already has determined, then any perceived intrusion into his operational part of the spectrum would be a result of inadequate bandwidth control in his equipment.
I'd be interested to know how the complaint was worded and what was Ofcom's response.

------------------------------------
Ian Hickling
Partner
transplan UK

> From: cmalist at tmcrfm.co.uk
> To: lists at philedmonds.info
> Date: Tue, 1 Nov 2011 18:45:21 +0000
> CC: cma-l at mailman.commedia.org.uk; hospitalradio at hospitalradio.dns2go.com
> Subject: Re: [cma-l] Streaming audio problem
> 
> Hi Phil,
> 
> I'm on the onelist too - but haven't put the question there as it's been 
> very quiet for a while.
> 
> Yes, we're JFMG licensed for the link and have been since 2006. The schedule 
> specified direction anetanna and that's what we have, 3 element Yagi's at 
> each end. The antenna don't need to be CE marked, but the transmitter has to 
> be. It is part of the JFMG agreement.
> 
> Ofcom had a report of interference to a radio ham and, when they did a site 
> visit, they were the ones who saw the antenna was broken. It is on those 
> grounds they want to come back and check it complies once the repairs have 
> been carried out. The antenna was fixed yesterday, the transmitter is back 
> on today and Ofcom will visit shortly, date to be arranged.
> 
> It was a temporary 'fix' so we're not looking at spending money on anything 
> at this time. The FM link works fine for us when it's active, but maybe not 
> for the radio ham. The old PC we had never had these issues, so we suspect 
> we've not set something up properly. The router is prime suspect at present 
> and we'll try swapping that out shortly.
> 
> In the meantime, the problem is solved by virtue of having the link back in 
> service. Having said that, we could save a bob or three by taking the link 
> out and using the ADSL at both sites. I should note that we are mono only, 
> as in 'AM', so we don't pay for a stereo license on the link, which makes it 
> a quarter of the stereo annual cost at £208.50. The shoutcast stream bit 
> rate is low, 56 Kbps at 22.1Khz in mono.
> 
> I hadn't thought of using VLC, having tried Windows Media Player and Winamp 
> and getting similar problems I took it that any media player would suffer in 
> a similar fashion. Just to test this out I'm installing at rtight now (good 
> job we have VNC installed) and will let it run overnight. Nobody on site so 
> the listeners will hear the audio from the FM link. I'll see how that goes. 
> Winamp fell over every few minutes and was forever showing the [Buffer: 0%] 
> message. WMP would run for a couple of hours, then stop without warning.
> 
> If this stops/starts I'll try the Ping trick - although I'm probably going 
> to put that in a batch file I can hide rather than leave a command prompt 
> open.
> 
> Connecting anything to the NHS system is a big No. We've been warned not to 
> even contemplate it. A bit daft as they have as dedicated microwave link 
> between the two sites that was put in years ago.
> 
> Just to pick up on the ISP dropping the connection, the audio was being 
> restarted due to silence of over 16 seconds every 2-3 minutes at times 
> during the day, but not overnight and not when something else is connected, 
> so there's a possibility that's the reason.
> 
> While I've been typing this, VLC has remained active for almost 18 minutes - 
> hmmm. No, I didn't stay connected, so can't be that. I need a darkened room 
> now.
> 
> Gordon
> 
> 
> ----- Original Message ----- 
> From: "Phil Edmonds" <lists at philedmonds.info>
> To: <cma-l at mailman.commedia.org.uk>; "Hospital Radio Discussion List" 
> <hospitalradio at hospitalradio.dns2go.com>
> Sent: Tuesday, November 01, 2011 5:13 PM
> Subject: Re: [cma-l] Streaming audio problem
> 
> 
> Hi Gordon,
> 
> I've took the liberty of including the "Hospital Radio Onelist" into
> this reply as there will probably be some technically knowledgeable
> people who subscribe to that list that aren't on the CMA mailing list.
> 
> See below for my comments
> 
> On 31/10/2011 20:19, Gordon Sharpe, TMCR 95.3 FM wrote:
> > Guys, I have an issue with hospital radio, rather than community, but
> > hope someone can help as it may solve another issue for me.
> > */Trust AM/* serves the Bassetlaw (Worksop in N Notts, if you need to
> > ask) and Doncaster hospitals. It's main base is Bassetlaw and from there
> > there has been a Band 1 FM link for the last 6 years to feed audio to
> > the remote hospital in Doncaster, a tad over 13 miles as the crow flies.
> > Except it broke last week, the antenna fell apart. Thats been fixed but
> > now Ofcom want to check the link transmitter and it could be a while
> > before service can be restored.
> 
> That's interesting - in my experience of JFMG licenced "Programme Making
> and Special Event" links Ofcom have not been interested in checking the
> equipment - though they do often specify use of directional tx aerials
> (I assume that any new kit would have to be CE type approved - but that
> would only apply to the transmitter not the antenna?)
> It would be interesting to know on what grounds they want to check the
> link system before you can put it on-air - after all I assume you've
> already paid the £800+ annual licence fee for the privilege.
> 
> 
> > So, to try and make sure the patients could still listen I set up a PC
> > to use Winamp to listen to streaming audio feed sent out from Bassetlaw
> > using Shoutcast. It works fine for me at home, I could listen all day -
> > and have done. Not so at the Doncaster studio though. It's been breaking
> > up very badly, stop/start and sometimes showing [Buffer: 0%]
> > I've read up about adjusting this that and the other settings and have
> > tried just about everything I could find on the topic, it still does it.
> > Except, when I connect via VNC to have a look at the log files or
> > whatever. As long as there's a connection the stream remains stable. The
> > stream is 'private' and had a password, which I took off to allow it to
> > reconnect during these troubles. I often listen from home, to check that
> > everything is up and running as I live in Doncaster too and can't hear
> > the AM signal.
> 
> I'd try a different playback client - such as VLC.
> 
> Maybe TalkTalk do have some sort of traffic management in place which is
> not seeing any upload traffic from your remote site - seems unlikely,
> perhaps something on your local machine or router is dropping the
> connection?
> 
> Try opening a Command Prompt Window (Start ->Run -> cmd) on the remote
> end machine and running the following command:
> 
> ping -t google.com
> 
> this will run a continuous string of ping commands - which will keep the
> connection live. This is a trick I use when using mobile broadband to
> keep the connection open - as I find my provider often seems to 'drop'
> my connection if I don't do anything for a few minutes.
> 
> 
> > The router has already been set to a 'nailed up' connection, it's on
> > TalkTalk Business. Checking the speed via ThinkBroadband.com says
> > they're getting roughly 4.6 down and 0.7 up . I'm on a Virgin Cable 10Mb
> > connection at home (9.6/1.0).
> > I have a silence detector module running on the PC itself, it triggers
> > after 16 seconds of silence. It kills Winamp and restarts it, taking it
> > that the program itself has got stuck. Any blip in the meantime resets
> > the counter, so the stop/start issue isn't always being detected. The
> > resets are being logged at 4-5 per hour, except between 11pm and 7am
> > when it seems to run smoothly ?
> > I have had an active connection via VNC for the last hour and a half and
> > the stream has remained up and stable during that time. Having noted the
> > 11pm to 7am window when all runs with no problem I had suspected some
> > sort of blocking by TalkTalk, but by having something else connected it
> > sorts itself out...?
> > Ideally I want to use the stream to feed the audio to the Doncaster
> > studio 24/7, rather than have the FM link. OK, so the audio would be 40
> > seconds behind real time but who's bothered about that when you're laid
> > up in a hospital bed?
> 
> If you go down the replacing the FM link route I'd recommend not using
> PC's and get a pair of Barix codecs (you'll recoup the cost in 1 year of
> no JFMG licences) - though in my experiences it will drop occasionally
> over ADSL links. Fine for non 24/7 purposes such as I have it in use
> for. However cue Ian Hickling who I believe has had success doing this
> on a 24/7 basis in Wales.
> 
> 
> If both hospitals are the same NHS Trust you may be able to negotiate a
> link over their LAN/WAN - I know of Chorley Hospital Radio and Roch
> Valley Radio who do this - the former with Barix units the later with
> more expensive Comrex codecs - but the principle is the same. I believe
> Nick Beer at Westcountry Broadcast is your man who set-up Roch Valleys
> system so give him a shout for some advice.
> 
> 
> > I had planned to have a haircut later this week, I just hope I've got
> > some left by then as this one has me puzzled.
> > Any ideas?
> > Gordon Sharpe, TMCR FM
> >
> 
> 
> Regards,
> Phil Edmonds.
> 
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