Technical Description

Introduction

Although the bulk of this writeup describes our setup for RSL2 we have recently recommissioned our studio at the YMCA during April 2010 to allow us to make our own recordings in situ and in due course go back to making live broadcasts as opposed to the current situation where we make all our programmes off-line. This writeup is in the process of being updated to reflect our current studio arrangement but is reassonably accurate. There are some updates towards the bottom of the page.

For RSL1 Vintage Radio (VR) had the use of two rooms in the YMCA building in Birkenhead. For RSL2 in November 2009 we have had the use of the same two rooms. The "studio" is on the top floor and houses the mixing desk, internet streamer and OFCOM recorder and is the centre for the actual broadcasting. The "Green Room" is used for guest reception, off-air programme preparation and monitoring of the transmitted audio by both FM and Internet.

The two rooms are kept in contact by "on screen messaging" - software Yellow Stickies plus two way radios which are used in both “setting up” and “real time”.

The VR studio is built from a range of equipment, some purchased, some loaned from various members of the technical team and the Flame Radio community radio station. The equipment is not brand new and in most cases has seen a lot of use but works and does what we want.

The studio was built and commissioned by our own technical team.

Gordon from the Wirral Amateur Radio group set up the VHF FM transmitter and aerial system that was supplied by Flame Radio. A spare back-up transmitter is available from 7 Waves.

To see an update of where we now are technically as of 2010 click here.

How is this all connected together?

We put the studio together in this configuration.

(Just click on the image to expand it into your screen)

 

 

 

Mixing desk

The mixing desk is a 16 channel Alice Soundtech Series A desk purchased from a ArrowSound hospital radio. We believe it is about 20 years old and had been unused for a few years and required quite a lot of attention to clean up the desk and the audio faders which were electrically very noisy. A number of faders could not be cleaned but we had sufficient channels that worked to make a working desk. The makers of the desk provided us with a user manual with all the circuit diagrams free of charge for which we are very grateful. Unfortunately some of the electronics also required repairing. It was not the latest equipment and despite the odd hiccup has generally generally worked well.

Each channel could be trimmed for level and the microphone channels, of which we had three, had pan controls to get the stereo positioning correct.

The desk had one audio bus. In addition there was a monitoring bus that fed into a pair of monitor speakers (one of the technical teams cast off 'ghetto blasters') and three sets of headphones for studio presenter and guests connected via a dedicated multi-channel headphone amplifier. The monitor speakers are set to mute when a microphone went live although they will still play the audio from the desk.

We have audio feeds from:

• Three microphones
• Two CD players with auto start from the desk
• IRN news feed (as of April 2010 not used for our internet streaming service)
• An audio channel from the RS Player audio jukebox
• An auxiliary audio channel to connect laptops etc.

Source equipment

Numark MP302 CD 19” rack mounted players, with autostart, triggered by the desk faders going off zero, are used. The fader start electronics was built by our technical team as the desk was incompatible with Numark players. Numark were very helpful and their technical team supplied the circuit diagram so we could build the interface. We had to make some minor modifications to the circuit as we had some problems with contact bounce from the mixing desk which used a dry relay contact to drive the interface circuit.

In addition to the three studio microphones and an IRN news feed we also use the RS Player jukebox software (http://www.rsplayer.co.uk/standard.htm) running on a home built Windows XP PC with one audio channel connected via the appropriate desk fader. At the time of writing our experience of it has been very positive.

The main microphone is an Audio Technical AT804 dynamic microphone. The two guest microphones are loaned from one of the technical team members and were good quality phantom powered condenser microphones.

RS Player playout software

The main audio feed was a PC running the RS Player Audio playout software (http://www.rsplayer.co.uk/standard.htm). We looked at a number of packages but this was generally well regarded, easy to use and a fraction of the price of the MYRIAD software. It cost around £70 and the MYRIAD software is several thousand. As we were running on a shoestring it was not a difficult decision. So far all who have used it were very pleased with it even though most presenters had been trained on the MYRIAD system and generally found the familiarisation took a few minutes.

The RS player software ran on a Windows XP PC with a 17” LCD monitor.

The RS Player is a high capacity audio player database that contains copies of thousands of music tracks. Our pre-recorded Vintage Radio tracks and programmes could also be loaded onto the database. The audio was presented to the desk via an individual channel fader. We also created a backup copy of the database on a separate external hard disc.

The RS Player system could also be used for constructing individual play lists of music for individual presenters just like the MYRIAD system. These play lists allowed tracks to be selected and played in sequence or selected from a screen display in any order. These Play lists were very useful as we built a number of them to create programmes for overnight runs when the station was unmanned.

The RS Player also can produce play list logs that may be required for copyright and licensing purposes.

Audio processing

When transmitting it was important to ensure that the quality of the audio is optimum. This we achieved by compressing the audio feed slightly which had the effect of reducing the high volume peaks and increasing the low volume peaks slightly and adjusting the audio frequency response (a bit like adjusting the treble and bass controls on your Hi-Fi). We use a Triple C multi-band audio processor. On this occasion we also use the built in level limiters on the desk.

We were mindful that adjusting the audio response enhanced the listening experience for the over 50’s and those people who may not necessarily be listening to the programmes on the highest of quality radios. In other words we achieve a compromise.

Transmitter and Aerial

We used a transmitter made by the Alice company and borrowed from Flame Radio. Due to the OFCOM Restricted Service Licence we were limited to a maximum height above sea level for the aerial and a maximum power of 10 watts. We used a vertically mounted (polarised) folded dipole, with a 10m long (approx.) downlead to the transmitter.

The transmitter and aerial was tuned to give the optimum performance which was very important given that we were restricted to a 10 watts output into an omni-directional vertically polarised aerial. The aerial was borrowed from the 7 Waves Community Radio station and was actually cut to different frequency than the 87.7MHz we are required to transmit on. This meant that the transmission performance we could achieve is slightly less than optimum.

A professional aerial erector installed the transmitter aerial. The transmitter was set-up by a radio engineer to ensure that the power was within the OFCOM licence conditions and that the transmission performance is optimised.

A remote control kill switch is set up so that the transmitter could be ‘killed’ at a moments notice from the studio. A standard wireless remote control mains switch was purchased from a large DIY retailer and found to have an adequate range.

The picture also shows the satellite dish that we used for the IRN news feed.

Radio Coverage

By clicking on this map, it will expand into your screen and show the predicted coverage of the transmission on the allocated frequency of 87.7MHz.

By clicking on this map, it will expand into your screen and show the predicted coverage of the transmission on the allocated frequency of 87.7MHz.

Whilst the Wirral is relatively flat and is not more than a few tens of metres above sea level it does have a sandstone ridge down its spine plus a number of high rise buildings in the Birkenhead area which adversely affected the transmission coverage.

As we indicated previously the transmitter is limited by OFCOM to 10 watts and the aerial was a vertically polarised omni-directional dipole which would give minimal antenna gain. These factors tend to limit the range for a good received signal to around four miles radius of the transmitter. In practice the effects of reflection and other propagation effects enables some listeners as far as Southport to the north and Thornton Hough to the south to hear the transmissions.

Station Failure

When doing the unmanned overnight transmissions it was essential that if the audio signal (from the RS Player) or the mixing desk failed, that some form of programme and station identification is still transmitted. We use a piece of equipment from Flame Radio, that detected any gaps in the audio feed from the studio of more than a two to three minutes and then switched over to an pre-corded programme on an MP3 CD player. This then plays some music and station identification at regular intervals.

Internet Streaming

A key requirement of our transmission period on the air was that we also supply a concurrent audio stream over the Internet via our web site. This was important as it allows Vintage Radio to increase its reach beyond the range of its VHF radio transmission which is approximately a four mile radius of the transmitter – centred on Birkenhead in the Wirral.

We take an audio feed from the studio mixing desk and feed this into a PC dedicated to streaming the audio. The PC uses a Windows Media encoder from Microsoft to encode the audio into a WMA format audio stream. This is then fed to Psquared streaming audio server via the YMCA LAN (where the studio is based) and then out over the internet.

We encode the audio as mono at a bit rate of 32kb/s and distribute via a streaming package from Psquared that will support a maximum of 50 concurrent listeners. The costs of streaming are dependant on bit rate and the number of concurrent users. We use WMA format encoding as for RSL1 mainly because the Microsoft encoder is available free with Windows and has proved to be largely stable. The internet streaming PC is enabled for remote management.

The Vintage Radio web site is set up to use an embedded Windows Media player to play the audio from the Psquared streaming audio server. For those listeners who used Apple computers a free Media Player was found that allowed Apple users to play the Windows format audio streams. For our next RSL we expect to use mp3 encoding as this is more widely acceptable.

One issue with the Internet streaming was that the audio encoder introduced a considerable delay of up to 50 secs. This is a known issue and can be easily seen on Cable TV systems where the TV and associated audio is supplied via digital systems and when compared side by side with the terrestrial equivalent shows a very noticeable lag between the two sources.

Update May 2010 - Since RSL2 we are now streaming a pre-recorded service on the Internet using mp3 rather than wma format. This surprisingly caused some compatability problems with Apple computers, a problem we had had for RSL1 and RSL2 but which we had resolved with a free download. This has now been fixed and as of late April 2010 our web site now offers two methods of accessing our audio stream via Flash based player as well as a Windows Media player solution. This has now been tested on Windows XP, Windows Vista, Windows 7, Apple Mac's and Ubuntu Linux systems and found to work well. Our streaming service is now provided via the Community Media Association (www.commedia.org.uk/ )via their Canstream service.

Satellite News feed

One of the key requirements was to be able to supply a national news bulletin on the hour from Vintage Radio, This we did by contracting with Independent Radio News (IRN) for the period of the transmission period. They in turn supply the news feed from Sky.

We use the IRN news feed from the Astra satellite located at 28 degs E. We fastened a 60cm satellite dish onto the roof of the YMCA near the transmission aerial and this is then fed to a satellite receiver in the machinery room.

The audio is fed to the mixing desk via twin screened audio cable on the outside of the YMCA through the window seals which we had determined had enough “give” with the cable so as not to crush the signal pairs.

As the receiver supplies standard audio (unbalanced) and the mixing desk was balanced input we had to create a simple unbalanced to balanced adapter by simply tying one side of the balanced input to earth. We then trimmed the audio level on the desk to ensure the desk audio levels were correct.

Content monitoring

Whilst we are on air (RSL's only) we have to monitor our signal continuously so we could ensure we are actually transmitting and that the technical quality of our transmission is acceptable. We do this in two ways.

Firstly, by the simple expedient of keeping a VHF radio in both our 'green' room and studio at a low background level so that the presenter and studio manager could monitor the signals. It was also a task of the studio manager and the technical support (who were also available at the studio whenever the station was manned during normal broadcasting hours) to check the internet feeds by logging onto the web site and checking the audio was streaming correctly. We also used listener reports as a secondary check. We also encourage all presenters to “keep an eye” on the signal levels on the mixer unit to ensure an adequate audio level.

Secondly, as we were operating under an OFCOM RSL we had to comply with their requirements for monitoring which stipulated that all programme content must be recorded and kept for up to 42 days from the last date of transmission.

The 42 day recording requirement is met by use of yet another PC that was dedicated to the task and used a specific piece of software that took the audio stream from the transmitter audio feed and recorded it into 60 minute duration, time stamped audio files. The format of these files is mp3.

This also has the secondary benefit of being a source of programmes for subsequent re-transmission for our next RSL and also for people who would like a personal copy of their programmes. However, in practice we are using two PC's, one connected to the desk and one connected to a portable FM radio, basically as a 'belt and braces' approach.

Communication with the outside world.

Dedicated Phone number

In addition we wanted to post a publicly accessible telephone local style telephone number on our website. We use the free SIPgate VOIP system and set it up with a small amount of credit to allow outgoing calls. SIPgate gives considerable flexibility as to choice of telephone numbers and we were able to select a Liverpool area 0151 series number. We connected a DECT cordless phone via an ATA box which had an ethernet network interface which was then connected over the YMCA network.

Dedicated e-mail facility

We also offer an e-mail facility whereby listeners could e-mail in their requests and comments. The inbox for the mail system is received from the Internet in the Studio and displayed on a large screen using a PC projector so that the current announcer can address the requests and comments. Web mail is used so we could view the emails from both studio and Green room PC's.

Networking

We had a modest networking requirement which was to connect the two communication PC's plus the streaming PC and the SIPGate phone via the YMCA network. To do this we constructed a mini network using two 10MB/s ethernet hubs plus a powerline adaptor to physically join the studio and green room. The reason for doing this was because the two rooms were connected to two seperate LANs that were not bridged, we had no access to the cable ducts to run Cat 5 ethernet cable and WiFi was unavailable.

Update: Since we we introduced our Internet streaming service in Apil 2010 we have not used Powerline solutions which are the subject of some debate in various standards bodies because of potential issues with RFI. The ones we used were, however, fuilly approved.

Health and Safety

Whilst not operating a commercial station it was important that we operate to the highest possible professional standards and hence it was essential that we had to consider the aspects of health and safety. A risk assessment was undertaken before going on-air to identify potential issues and hazards and made available to our hosts, the YMCA.

In addition appropriate insurance cover is in place to protect studio staff and guests and their belongings and all studio equipment.

Documentation

A number of documents were written for station staff covering topics such as using the IRN news feed, operation of our two way radios used for communications between studio manager and technical support etc. These are laminated and kept in the studio.

The Future

To increase the flexibility of content the technical team are working on a number of projects designed to increase our flexibility in respect of content and a wider embrace of members of the community that may not be able to make the studio in person.

1. An “outside broadcast” unit already constructed by one of our team that will allow “round the table” interviews with live transmission into the studio via the mobile internet facility. Completed and all fits in a small briefcase. Currently being used fro off-site recordings where a simple digital recorder gives insufficient flexibility.

2. Creation of a secure content archive and database. This will allow us to use appropriate previously recorded material if we have a unavoidable shortfall - e.g. a presenter falls ill etc.

3. We have had some minor service outages sinec we have been streaming on the net with our renmote studio solution so we are reviewing solutions to infrom us more quickly to allow us get us back on the air

Studio update May 2010

The studio has been re-installed back in the YMCA buiding. We have been fortunate that we have had some capital grants and donations from various organisations which includes the Riverside Trust and the Media Trust. This has allowed us to purchase new microphones, 22" wide screen monitors for our playout and web browsers systems, re equip our mixing desk with new faders plus A4 document shelf, in addition a new Behringer distribution amplifier, backup hard discs, and new microphone stands. So we more or less have the basics for a complete studio without having to borrow or hire equipment. Of course the largest cost we face, as do most community stations, is funding the day to day running costs and its this problem we are turning our fund raising attention to. If you'd like to make a donation via our secure on-line PayPal system it would be very gratefully received.

Internet Streaming solution between RSL broadcast's - started April 2010

As we were not in a position to broadcast on the airwaves (87.7MHz VHF FM), for a number of reasons, primarily financial as well as regulatory we decided that we would put together a limited internet based service (see our News and Schedules pages for more details) so we could maintain our broadcast presence for our growing listener base and also continue to give an outlet for all our broadcasters and producers.

As all our content for this service is pre-recorded a traditional studio approach was not required. So we decided to design a virtual studio. This used a PC acting as a streaming server located in the YMCA to which we could upload remotely all our content. Click onthe thumbnail to see a block diagram of our solution.

In practice we take an 8GB memory stick once a week to the server rather than uploading the files and plug it in having first removed the previous weeks memory stick. Each memory stick contains a weeks programming. We are currently broadcasting a 3 hour programme which is repeated 4 times daily which is then replaced with a new programme the following day and so on.

Each daily 3 hour programme is a 150MB+ mp3 file which we replicate to create a 675 MB+ file. Each days programme is loaded into a CART on our playout system (RS Player http://www.rsplayer.co.uk/standard.htm). The files are very large at this point which does throw the RS player file size reporting awry but RS Player still works and at the time of writing has been 100% stable since the beginning of April 2010. We cannot recommend RS player more highly. Its a fraction of the price of the MYRIAD software which many of our presenters trained on but most have found that converting from MYRIAD to RS Player has taken about 5 minutes which is a credit to its designers.

Once the CARTs have been loaded with a days programme we use some additional software available from the RS Player team to control the software. This software gives us a command line interface to control RS player from our scheduling software. We then use the free Solways scheduling software (http://www.theabsolute.net/sware/#tasksched) to time schedule when the CARTs are started each day. The Solways scheduler is coonnecetd via RS Send which provides a simple command line interface to teh RS Player software. Our streaming server is then connected over the YMCA LAN to a streaming service operated by the CMA. To remotely control the setting up of the scheduler software etc we use a LogMeIn (www.logmein.com) subscription which allows a secure VPN access to our server at the YMCA.

We are streaming using mp3 format and at very very low bit rate of 32kb/s in mono. We use the Edcast 3 encoder (http://www.oddsock.org/). The reason for streaming at this bit rate was solely driven by the cost of the streaming service.

To avoid the need to go out from teh playout software via the analogue soundcard and keep in the digital domain we used the Virtual Cable software http://software.muzychenko.net/eng/vac.html) to connect the RS Player to the Edcast encoder. The Virtual Cable software like the RS Playersoftware involves a one off purchase fee. The Solways and Edcast software is freeware. The LogMeIn software is subject to small annual charge.

Our virtual studio server is a HP machine running Windows XP with auto update turned off. Surprisingly and possibly tempting fate we have had no downtime that is directly attributable to Windows XP. However, we have had a number of short outages recently which we are investigating. We suspect a mix of heat (due to a poorly ventilated cupboard), PC configuration issues and occasional finger problems.