Linking

Discuss UK-based Radio outside the South East of England
e.g. Birmingham, Bristol, Leeds & Manchester
'Legal' radio topics often go here too.
Post Reply
TGillies
ne guy
ne guy
Posts: 8
Joined: Sat Feb 14, 2015 1:28 pm

Linking

Post by TGillies » Sun Jul 08, 2018 11:42 pm

what is the best way to set up a link these days from tx site to studio? i have a shoutcast server on the go but unsure of how it would be set up exactly, ie having constant connection at site etc

OldskoolPirate
no manz can test innit
no manz can test innit
Posts: 103
Joined: Thu Feb 18, 2016 9:32 pm

Re: Linking

Post by OldskoolPirate » Mon Jul 09, 2018 12:35 pm

Don’t use shoutcast it’s too slow. 30s to a minute lag time.

MC Spanner
big in da game.. trust
big in da game.. trust
Posts: 80
Joined: Thu Mar 23, 2017 12:01 pm

Re: Linking

Post by MC Spanner » Mon Jul 09, 2018 4:00 pm

Not an easy question really - there are so many variables involved.

My 1st thoughts in order of increasing price/difficulty. I'm assuming either you know what you're doing technically or have access to an engineer.
  • Cheapest/easiest is an analogue radio STL offering increasing security/difficulty/expense with rising frequency. You get to keep all your processing / stereo / RDS gear at the studio but there's a significant risk your studio will be found especially with low STL frequency (e.g. Band I)
  • Microwave link, benefits are as above plus greater security but harder to implement and the components are getting scarce these days.
  • Internet or LAN based link - tons of configuration options here. Ask yourself what spec you want from your broadcast e.g. what processing, stereo, RDS and that will help shape hardware spec at the TX site. As you say, you will need access to IP at the site. Security will depend on your link configuration, your understanding of WANs and ability to code and configure systems to make reverse engineering of your link as difficult as possible. If you know what you're doing, you can do this cheaply and reliably with relatively little equipment.
  • Finally a digital RF STL - expensive and you risk losing a pricey receiver at your TX site / midpoint.
Somewhere in the middle are niche schemes like irregular programme data uploads via the net or other data broadcast schemes, swapping SD cards, etc. Do you need to be real-time live?

There's probably something really obvious I've missed of course.

You could have a multi stage link using more than one of the above.

So first up ask yourself some questions. How many source sites are there? Presenters linking in from home generally means internet at least up to a midpoint. What band are you targeting? Do you want stereo, RDS? Do you want more than one TX site? Will the site move regularly? How far is the link to the TX site (either from a single studio or midpoint), is it line of sight, can you get access to the net there and how? You potentially need to consider data allowances and how you connect to your rig, or how it connects to you ;-), are you prepared to return to your TX site (some computer configurations are likely to be less than 100% reliable) and of course, what's the real risk of being raided in your location/choice of frequency, how much cash have you got and how much are you prepared to lose when someone nicks your rig.

There's way more to it than this and loads of solutions but hope this gets the ball rolling.

Albert j
who u callin ne guy bruv
who u callin ne guy bruv
Posts: 34
Joined: Mon Jul 02, 2018 5:22 pm

Re: Linking

Post by Albert j » Mon Jul 09, 2018 6:00 pm

Raspberry pi easy cheap and works great. Linking to a studio in 2018 is crazy it's the same as texting offcom the location!

TGillies
ne guy
ne guy
Posts: 8
Joined: Sat Feb 14, 2015 1:28 pm

Re: Linking

Post by TGillies » Mon Jul 09, 2018 10:28 pm

MC Spanner wrote:
Mon Jul 09, 2018 4:00 pm
Not an easy question really - there are so many variables involved.

My 1st thoughts in order of increasing price/difficulty. I'm assuming either you know what you're doing technically or have access to an engineer.
  • Cheapest/easiest is an analogue radio STL offering increasing security/difficulty/expense with rising frequency. You get to keep all your processing / stereo / RDS gear at the studio but there's a significant risk your studio will be found especially with low STL frequency (e.g. Band I)
  • Microwave link, benefits are as above plus greater security but harder to implement and the components are getting scarce these days.
  • Internet or LAN based link - tons of configuration options here. Ask yourself what spec you want from your broadcast e.g. what processing, stereo, RDS and that will help shape hardware spec at the TX site. As you say, you will need access to IP at the site. Security will depend on your link configuration, your understanding of WANs and ability to code and configure systems to make reverse engineering of your link as difficult as possible. If you know what you're doing, you can do this cheaply and reliably with relatively little equipment.
  • Finally a digital RF STL - expensive and you risk losing a pricey receiver at your TX site / midpoint.
Somewhere in the middle are niche schemes like irregular programme data uploads via the net or other data broadcast schemes, swapping SD cards, etc. Do you need to be real-time live?

There's probably something really obvious I've missed of course.

You could have a multi stage link using more than one of the above.

So first up ask yourself some questions. How many source sites are there? Presenters linking in from home generally means internet at least up to a midpoint. What band are you targeting? Do you want stereo, RDS? Do you want more than one TX site? Will the site move regularly? How far is the link to the TX site (either from a single studio or midpoint), is it line of sight, can you get access to the net there and how? You potentially need to consider data allowances and how you connect to your rig, or how it connects to you ;-), are you prepared to return to your TX site (some computer configurations are likely to be less than 100% reliable) and of course, what's the real risk of being raided in your location/choice of frequency, how much cash have you got and how much are you prepared to lose when someone nicks your rig.

There's way more to it than this and loads of solutions but hope this gets the ball rolling.
Wow, really appreciate you going to the effort to highlight the various possibilites.

So here is where i stand atm..

Was initiallly thinking of going down the web route as it would require less equipment and like you say, would probabley be the cheapest option. however as another poster stated above, you would have that 30s delay in transmission which for me is a big factor. also taking into consideration the fact that you would need a realiable, stable and secure internet connection, which, lets be honest in some cases isnt as easy as it sounds.

so now thinking of going down the band I route (or similar) as it would be reasonably doable price wise and (hopefully) easier to set up. now i know there is a risk, but as someone who has always run direct, it cant get any riskier than that and would be a vast improvement. i know a lot of you will be thinking.. direct wtf! but too be honest, its pretty much how all pirates north of the english borders has operated, past and present. i can only think of one station up here that tried linking a few years back (flexx fm), but didnt last very long.

so yeah i want to try turn the tide up here a bit, but as you can imagine, very inexperienced in this area of the game.

any information on STL linking at this stage would be highly appreciated.

cheers in advance.

MC Spanner
big in da game.. trust
big in da game.. trust
Posts: 80
Joined: Thu Mar 23, 2017 12:01 pm

Re: Linking

Post by MC Spanner » Tue Jul 10, 2018 12:05 am

OK so for analogue STLs, the most common which have been used in London over the years are Band I and 10GHz using Gunn modules (Solfan, C&K etc) and a "satcan" receiver plus LNB. If you want to keep the cost down, you're probably going to end up putting your own system together. Microwave gear is getting harder to come by but does appear on ebay from time to time, and with an average setup you can get a quality link over 2 or 3 miles line of sight pretty easy. Beware though, it's not trivial to stop either end of the link drifting for various reasons and some people do report trouble with alignment of the Gunn modules. As for Band I, the equipment is very similar to the Band II stuff you'll be more familiar with and the relationship between your required power and link quality will be same ball park. Most links I've seen use dipoles or 2-element beams and horizontal polarisation and a couple of Watts will probably get you a mile or so give or take. There's band I info on here in other threads.

Less commonly I've seen gear for bands III and IV used but the higher the frequency there are subtle differences in technology needed which may trip you up. Generally it's all a balance. Band IV is great as you can use lower power and ordinary looking TV aerials and hide your link close to other signals in the band, but there's not much gear around and it will almost certainly have to be made specifically for you.

As regards the internet and delay. More recently I've seen setups using 3G/4G mobile networks, using dongles or whatever. The networks are pretty good these days, you can run for hours at 128kbps with no problems. That's with an icecast2 server and like Albert J said, a Pi or similar at the main TX decoding the stream. A Pi model 3 has enough grunt to handle the pre-emphasis, stereo coding and RDS, with a £5 DAC based on ES9023, PCM5102/12 etc (you need 192KHz for decent stereo + RDS). You've also got GPIO to remote control the TX and do other stuff. I'm intrigued as to why a 30 second delay is a problem, I'd say it's more like 15 secs but depends on various factors. But a delay is a delay.

Really all a basic STL gives you is the facility to have your TX somewhere else, not so much security as they're easy to trace and OK it's better these days but even North of the border the authorities still do give a toss. You know about Flexx, Allusion etc. If you keep it up they will get you eventually especially if you use an analogue STL below Band IV and without other precautions (judicious placing of link antennae, warning systems etc).

TGillies
ne guy
ne guy
Posts: 8
Joined: Sat Feb 14, 2015 1:28 pm

Re: Linking

Post by TGillies » Tue Jul 10, 2018 12:23 am

The Rasberry Pi idea intrigues me. only problem is, ive never used one, pretty confident i could get my head round it fairly quickly tho, would go as far to say the setting up of the tx side would be easier than setting up the pi itself.

is there any reliable tuts around for setting up stream through the pi?

Albert j
who u callin ne guy bruv
who u callin ne guy bruv
Posts: 34
Joined: Mon Jul 02, 2018 5:22 pm

Re: Linking

Post by Albert j » Tue Jul 10, 2018 3:17 pm

TGillies wrote:
Tue Jul 10, 2018 12:23 am
The Rasberry Pi idea intrigues me. only problem is, ive never used one, pretty confident i could get my head round it fairly quickly tho, would go as far to say the setting up of the tx side would be easier than setting up the pi itself.

is there any reliable tuts around for setting up stream through the pi?
Setting what up? You plug it in and it comes on! Not much too set up all you do is put your stream into it beforehand but you can order it with it all on there already!

MC Spanner
big in da game.. trust
big in da game.. trust
Posts: 80
Joined: Thu Mar 23, 2017 12:01 pm

Re: Linking

Post by MC Spanner » Wed Jul 11, 2018 12:21 am

TGillies wrote:
Tue Jul 10, 2018 12:23 am
is there any reliable tuts around for setting up stream through the pi?
I can't find it now but I was convinced one of the forum members created a script which would handle connection & streaming of audio on a Pi, and posted a link to it. I think it was radio-berlin. Anyone else remember this?

Again, the config you need for your Pi will depend on lots of factors, e.g. if you want decent audio/stereo/RDS you'll need an external DAC which may need a device tree overlay and/or other tweaks. To stream your audio the Pi will need the stream address and if the stream isn't well known, you may want to make arrangements to obfuscate it in case the machine falls into the wrong hands. If you're using mobile 3G or 4G to connect to the internet and you want to log on to your Pi (e.g. to power the TX up or down, re-point your stream, play pre-recorded audio etc) you'll most likely need to set up a reverse tunnel (again, you should obfuscate the address) plus the fairly complicated provisions to make sure it doesn't fail. The solution is as simple or as complicated as you need for whatever you want to do.

nrgkits.nz
no manz can test innit
no manz can test innit
Posts: 142
Joined: Fri Oct 17, 2014 10:35 am

Re: Linking

Post by nrgkits.nz » Fri Aug 31, 2018 11:19 pm

I would be more inclined to use a pair of ubiquiti nano beams, and create a link to another location nearby where you can tap into the internet over adsl/wifi or similar (not expensive data limited 4g) then just feed the site using a icecast/shoutcast server hosted offshore out of reach. Ofcom will trace the link to the adsl/wifi connection but can go no further because they'll need to access the streaming server to get the source IP address of the studio. Here in NZ telcos require a police/court warrant to give up any customer info related to a particular adsl connection.

Albert H
proppa neck!
proppa neck!
Posts: 1026
Joined: Tue Apr 05, 2016 1:23 am

Re: Linking

Post by Albert H » Sat Sep 01, 2018 1:21 pm

I still prefer 50cm Band IV using ordinary TV Yagis at each end. You can link tens of miles at low power, and the gear isn't too expensive.

The transmitter is quite easy - Lecher Bars for resonant circuits and TSA5511 for the PLL. I use a J310 FET for the VCO, an MMIC for the buffer and some gain, feeding a BFG135 for about 500mW output. With the gain provided by big Yagi aerial, we're getting about 20 Watts ERP in a very tight beam.

The receiver is simplified by use of a TV receiver front end. The Philips UV616 was a particular favourite, because it could be used on any frequency from 45MHz (Band I) right up to around 900MHz, using the same IF setup. The first IF, coming out of the tunerhead can is at 35 MHz, which gets mixed with a crystal oscillator to give 10.7MHz to feed a conventional CA3189 IF strip. The sensitivity is spectacular, and the receiver doesn't suffer from de-sensing due to proximity to big rigs.

I've linked as far as 40 miles (LOS) using cheap Band IV gear, with a fully noise-quietening signal good enough for stereo and RDS! I used this type of technique to get up to my solar and wind powered rig in the Hollywood Hills.
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

Post Reply