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The History Fundamentals of Amateur Repeaters Including the Lincolnshire Coast 70cm repeater GB3LC it s future role

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The History Fundamentals of Amateur Repeaters Including the Lincolnshire Coast 70cm repeater GB3LC it s future role

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    1. The History & Fundamentals of Amateur Repeaters Including the Lincolnshire Coast 70cm repeater GB3LC & it’s future role By Roger Wilson G4IPE

    2. What is a repeater? A repeater is a device that performs 3 basic functions: It receives and demodulates an RF signal. It regenerates the audio information. It modulates and retransmits the audio on a new RF carrier.

    3. Some History… Amateurs experimenting with VHF/UHF in the 1930’s discovered that propagation was generally limited to line-of-sight. The limited working range offset the advantages of VHF/UHF gear for mobile/portable operation (small antennas and light equipment) In the 1950’s, widespread availability of WWII surplus electronics led to the creation of the first repeaters on the West Coast of the USA. The repeaters were AM and used frequencies on the 2 meter band. By the 1970’s, standard offsets and FM were introduced. Mainly due to Japanese Black Boxes First repeater in the UK was GB3PI

    4. Early Crystal Controlled FM 2 Metre Radio’s

    5. More Crystal 2 metre Radio’s

    7. Early Synthersised Mobiles

    8. Early Synthesised Portable Radio’s

    9. Early 2 metre multimodes

    10. First UK Repeater The very first radio telephone voice talk-through repeater was developed by the radio amateurs at PYE Telecoms (later to become Philips Telecom), and became licensed as GB3PI in 1971. In May 1972,  it was moved from the PYE factory site, to their aerial mast at Barkway, Hertfordshire to provide a much wider coverage area for mobile and portable users. It is still active over 34 years later

    11. Basic Repeater Block Diagram

    12. Antenna Voice Repeater antennas are almost always vertically polarized and have an omni directional azimuth pattern. Generally the same antenna is used for transmitting and receiving (except for some repeaters such as GB3LC) The antenna is mounted as high as possible in order to have good line-of-sight coverage.

    13. Duplexer A duplexer is a special type of filter that allows a single antenna to transmit and receive simultaneously on two closely spaced frequencies. A typical duplexer consists of two pairs of resonant cavities. Two pass the transmit signal from the transmitter to the antenna while rejecting the received power. The other two pass the receive signal from the antenna to the receiver while rejecting transmitted power. Typical rejection is better than 70 dB, while attenuating the desired signal less than 2 dB

    14. Duplexer Diagram

    15. Duplexer Operation Received Signals

    16. Duplexer Operation Transmitted Signals

    17. Receiver A repeater receiver must have good sensitivity and excellent selectivity, in order to have adequate rejection of the transmitted signal. The receiver will have at least two outputs: Audio output Carrier detect The audio output can contain both audio signals and out-of-band control tones. A signal appears on the carrier detect line when an RF carrier breaks the receiver’s squelch.

    18. Carrier Operated Relay The carrier operated relay turns on the transmitter in response to: 1750Hz Tone Burst &/or CTCSS Tone A Carrier with or without voice

    19. Transmitter The transmitter should meet the following criteria: High spectral purity (to avoid unnecessary receiver interference) Highest possible output power (for greatest coverage within licensing conditions)

    20. ID Timer / logic Controller The ID timer/logic performs basic ID housekeeping tasks: Generating the Repeaters Callsign (in CW) Tracking time between ID transmissions Timeout Timer Decoding of 1750Hz tone burst (if enabled) Decoding/Encoding of CTCSS Tones (if enabled)

    21. Repeater Simulation

    22. Repeater Controller A repeater controller provides (at least) the following capabilities CW callsign of Repeater Transmitter controls Special supervisory tones (courtesy beep, etc.) 1750Hz tone burst decoding CTCSS decoding

    23. CTCSS (Also known as Subaudible tone, Private Line. PL Tone, Tone lock Etc.) CTCSS means “continuous tone coded squelch system” A repeater using CTCSS cannot be accessed unless a user transmits a sub audible tone with his audio information. All new repeaters & Internet Gateways now have to be accessed by CTCSS (no 1750Hz tone burst allowed)

    24. CTCSS TONES USED FOR AMATEUR REPEATERS & GATEWAYS IN THE UK Tone A = 67.0Hz Tone B = 71.9Hz Tone C = 77.0Hz Tone D = 82.5Hz Tone E = 88.5Hz Tone F = 94.8Hz Tone G = 103.5Hz Tone H = 110.9Hz Tone J = 118.8Hz

    26. Important Notes All new repeaters & Internet Gateways on 145Mhz need CTCSS to access They are all licensed for 12.5Khz Spacing N.B. Deviation on your transmitter must be set at 2.5Khz Most modern radio’s can be set to low deviation via the radio’s menu system Incorrect setting can result in your signal being clipped (i.e. Norman Collier) If your radio can not be set via the menu, Please consider having you radio adjusted (dev. pot inside radio)

    27. Some Notes on Repeater Operation All transmission over a repeater should be in accordance with licensing conditions. Amateurs should give priority to mobile & hand portable stations Wait for the courtesy tone!!!! (to reset timeout timer) The repeater should not be tied up by long conversations – use a simplex frequency for a long QSO.

    28. History of GB3LC A local 70cms Repeater was first discussed when the Louth radio club was formed in 1978 Mick G8OOS & Roger G8OOW found a disused communications site at Kenwick Top near Louth (1978). Coverage tests were undertaken using a 60ft trailer tower loaned from Western Electronics. Very good coverage of the Lincs coast was found from this site. Site was originally used to relay TV & Radio into the town of Louth by Radio Rentals (i.e. Cable TV) The site was used from 1957 to the early 70’s. Closed down due to Belmont mast becoming active from 1965 Mick G8OOS & Roger G8OOW (now G4IPE) purchased the site in 1979 Original mast had been removed, Applied for planning permission for 100ft mast. Refused permission for 100ft mast, however was granted permission to erect 50ft mast Western Electronics kindly offered to supply & install 50ft Alumast at cost price.

    29. History of GB3LC (cont.) Applied for a repeater licence (late 1978). Asked for the callsign GB3EL (East Lincolnshire) Callsign GB3EL not available (allocated to East London repeater) therefore was allocated GB3LC (Lincolnshire Coast) Allocated one of the new frequencies (RB13) therefore no problems with co channel interference from other repeaters. Purchased Ex-PMR Base Station, Filters Etc. Made our own Full wave Dipoles from article in Practical Wireless

    30. Mick G8OOS Fitting the Dipoles

    31. The First GB3LC Repeater

    32. Official opening of GB3LC on February 20th 1980

    33. Original Mast & Coverage (1980)

    34. Coverage of GB3LC when first on the air Before the Worksop repeater GB3DS was allocated the same channel !!! as GB3LC, there were regular users working the repeater from Nottinghamshire & Derbyshire etc. Also base stations were working LC regularly from Norfolk & East Yorkshire Since the early 80’s less stations used LC due to co-channel Interference Constant problems with GB3DS on the same frequency (CTCSS Tone the same as well!!!)

    36. Fred the Talking Clock

    37. Fred is now over 24 years old & still working!!!! I believe that the Sharp CT-660 was the first ever domestic talking clock in the World. I think he cost about Ł45. Fred was fitted to GB3LC in 1980 & became well known throughout the UK (and abroad) due to the fact that no one had ever heard computer generated speech on a repeater before. He used to announce the time on the hour with speech & BBC style pips. Fitting Fred to GB3LC caused a lot of confusion to the repeater management group & the DTI as they didn't know if computer generated speech was legal!!! In the end the DTI suggested we remove him until such time they could decide if he was legal or not. We removed him after approx. 6 months & we didn't hear back from the DTI etc. so he was never replaced.

    38. Current Mast of GB3LC

    39. Current Base Station, Storno 9000

    40. The Future of GB3LC Put GB3LC back on the air if there is enough local interest. Coax needs replacing (high loss RG213 being used at the moment) Replace Antenna’s? &/or single antenna working (i.e. purchase or make Duplexer) New base station? Original Storno 9000 released 20 years ago in 1985 Internet Link the repeater to increase activity Enable Emergency Battery Backup for Raynet use etc. Start a group to help finance the upkeep of LC Site rent alone is approx. Ł170 per year without updating equipment etc.

    41. The Future of GB3LC What is Repeater Linking?

    42. What is Repeater Linking? Repeaters may be linked to increase the coverage available to the users. Linking methods: Echolink (Most Popular for Repeaters in Europe) IRLP ,Internet Repeater Linking Project (popular in the USA) WIRES (Yaesu’s own system, mainly USA) EQSO (Not really suitable for Repeaters)

    43. How does it work?

    44. Internet Repeater Linking This type of linking uses VoIP (Voice over Internet Protocol) to connect repeaters via the Internet. The repeater is connected to the Internet via a Radio connected to a PC (Link Station) The software provides A/D conversion and compression for the audio and transceiver control. The repeater may be accessed from the Internet by users who have VoIP capability (except for IRLP & Wires)

    45. Why Connect GB3LC to the Internet? Increase activity of the repeater Access to thousands of amateurs worldwide Access to hundreds of repeaters & links worldwide Enables thousands of amateurs worldwide to access GB3LC & talk to the local amateurs ALL FOR FREE!!!!

    46. Benefits of Internet Linking GB3LC for local users Listen to the latest RSGB News   Listen to the latest Eagle Radio Group news & other local amateur radio news   Listen to the WWV (solar/space news etc.)  Listen to current local weather conditions Listen to the local 7 day weather forecast Plus more features to come!!!

    48. For more information: Look At. WWW.G4IPE.COM Follow the link to the Internet Gateway Also Look at WWW.ECHOLINK.ORG

    49. That’s All Folks! Any Questions?

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