10 metre FM Amateur Repeater VK5RSC

Adelaide South Australia.

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News and Updates

This news was last updated July 01, 2004

The repeater is currently:- On Air

We have moved the repeater to new SCARC sites . The new sites are further south of Adelaide but will still be accessable by most of the Adelaide area. The 10m RX is at Willunga and the Tx site is at Mt Terrible with the new callsign of VK5RSC . Some new features are hoped to be incorporated and a new 2m antenna is being built to improve the 2m gateway performance. Stay tuned .....

Recent activity on the repeater has been from W4, ZL, OE2, VK2, VK6, VK8, VK3, VK4, SP, YJ, JA, VK7.

Keep your ears tuned to 10FM .. US stations are quite regularly comming in on openings in our mornings at about 2030-2300 UTC .. They have been breaking the squelch open on 5RHO regularly but not good enough to work as yet. The MUF's are raised and gradually things are picking up with band openings running all day sometimes from 0600-2030 local time.

Also in the evenings just after local sundown there seems to be some sort of openings happening into Europe even as late as 2230 local. There appears to be ionisation over the Indian Ocean. Heard and worked for 6mins or so on the repeater OE2LXL . The VK6's have been working the Middle East and Europe on our repeater input. We can not hear the VK6 boys but we can hear the other half of the QSO via the repeater at times.
10m has been quiet compared to last solar cycle so far. The F layer does appear to be having a more significant influence as time passes however with better openings over longer distances when it does open.

We also are still developing the control systems to give us some more convenient features including an automatic CTCSS Enable/Disable at the 10m RX site. This will hopefully detect and act on a lot of the spurious traffic that is coming in from our northern neighbours and make listening to the repeater more bearable at peak propagation times. We plan that this will automatically detect the nuisance signals and kick in the 10m CTCSS access . When the band has cleared it will switch back to carrier operated (no CTCSS required).

Tony VK5AH .

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What's a 10 metre repeater ?

A 10 metre repeater is similar to any other Amateur repeater. It allows users to talk to each other over long distances as it is a re-transmits what it hears . The distance is achieved due to the fact that the repeater is placed at higher altitudes (typically on hills and mountains) than the users. The users can be mobiles hand-helds or base stations .

There are some interesting advantages to 10 metres. It is frequently subject to ionospheric propagation which is primarily linked to Solar radiation and the 11 year Solar cycle. This Solar ionisation of the upper atmosphere (ionosphere) allows for long distance communications . This could be say across Australia or even Australia to the United States or Europe . See ionospheric propagation explained

10 metres also carries for a longer distance than say VHF signals. With reasonably effecient antennas on mobiles very good distances can be spanned on direct paths with less problems being encountered from things like buildings and hills. This is due to the longer wavelength involved on 29 Mhz (10 metres) . The repeater 10m signal has been heard near Pt. Lincoln (some 250km direct line of site) repeatedly in mobiles. This does not appear to be a ionospheric phenomenon but rather a ground wave or direct signal.

The Adelaide 10 metre repeater has the added advantage of a 2 metre user gateway. This opens the possibility for mobiles or hand-held units to listen to and communicate with distant stations in other states or countries . The 2 metre band is heavily populated in Adelaide by amateurs so this gives many more amateurs access to the repeater and the 10 metre band .

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Operational Information

Callsign- VK5RHO

10m Frequencies - Output 29.620 Mhz , Input 29.520 Mhz

2m Simplex Gateway- 147.675 Mhz

CTCSS & DTMF Tone Access-

Output Power- 10m =50w , 2m =18w

Antennas- 10m 1/2 wave end fed verticals, 2m 1/2 wave folded dipole.

Timeout- 3 mins

Mobile Range- about 80 Km .

Beep Tones- single beep= 10m access, double beep= 2m access, NO beeps= mains failure

TX Location- 10m TX and 2m TX/RX is at Houghton 410m ASL . Grid locator PF95IE

RX Location- 10m RX is at Anstey hill 400m ASL which is 2.4 km south of TX.

Link- The link between the 2 sites is 70cm UHF horizontaly polarised using CTCSS .

Notes-

It is not necessary to wait for the repeater tail to drop when working in on 10m. This is a 7 second tail. The timeout is reset at the same time as you hear the beep or beeps.

The DTMF 5 access opens the repeater till there is no activity for 10 seconds. Then another DTMF 5 or CTCSS tone is required again for access .

The 2m gateway will not let you access the system whilst it is transmitting as it is a Simplex operation . Also while you are accessing via 2m , 10m audio can mix with yours and both will come out on the 10m output. If you have problems getting in sideways on 2m due to heavy 10m traffic then try anticipating the 10m traffic a bit and transmit just before the 10m squelch closes. Bear in mind the 2m TX will not start up again if the 2m squelch is open at the site . You will now seize control of the system .

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Inside the 10m Repeater

The repeater basically consists of 2 separate sites the 10m Rx site and the main Tx site. So we will treat them as such in this breakdown.

 
The Rx site. A Ranger SRL-1645 comercial radio is used as the receiver on 29.520 Mhz. This radio was originally a 35 Mhz mobile transciever. The squelch opens at about .22uV and closes again at .18uV . The hysteresis is good when band path fade occors. The Ranger is also setup as a transmitter and can double as a spare exciter at the Tx site. As a backup Rx we also have a Hamtronics kit which is a double conversion Rx using a MC3357 IF chip. It has similar characteristics to the Rangers Rx . We also have a exported FM CB converted to 10m which can serve a dual role as a Rx and Tx backup.
 
The 10m Rx is interconnected to a UHF link Tx on 70cm (420Mhz) . This is a Philips T band 828 with the receiver removed. The receiver is reboxed and located at the Tx site. The UHF Tx runs about 1w into a 5 element yagi pointed northward at the Houghton Tx site. The tail is quite long on this UHF Tx (about 2 mins). On some busy days the Tx can be running non stop.
 
The link actually uses a CTCSS (PL) tone of its own. This tone is keyed ON and OFF by the 10m squelch line thus enabling us to get a accutate representation of the 10m receiver squelch at the remote site. A small PIC 16c84 microcontroller also monitors the squelch line from 10m. This is used in conjunction with the CTCSS (PL) detector to determine valid incomming signals. The PIC micro has been setup to decode DTMF tone commands that can be used to do things like disable the UHF link or turn the 10m CTCSS access on and off . The PIC also takes care of the CW ident on the link. This site is backed by a small gell-cell sealed lead acid battery.
 
The TX site. The transmitter site at Houghton is by far the more complex of the sites. It consists of a UHF link receiver a 2m tranceiver and a 10m transmitter as well as a larger degree of control circuitry and larger power supply to run everything. There are 3 antennas involved here also compared with 2 at the Rx site. The UHF link antenna is once again a 5 element yagi pointed south . See the above operational info section for the other antenna details. The UHF link Rx is the other half of the Philips T band radio reboxed into an old A band chassis.
 
The 10m transmitter section consists normally of a converted NRZ-FSK pager Tx wound back to about 3w driving a 50w General electric base station Power Amp. The PA was from a GE 35 Mhz comercial base station. The FSK pager Tx was originally on 40 Mhz and has had a few mods done to it including changing the multiplication stages to 9x up from 3.29 Mhz to 29.620 Mhz and an additional microphone audio type stage to FM the crystal with a varactor. A high SWR detection switch is also included to switch out the PA in the event of a major antenna problem. In this case the 3w driver is left to drive the antenna by itself.
 
The old GE base station power supply also runs all the equipment at this site. It is a curious design to say the least. Surfice to say it is a fero-resonant transformer type power supply. I have added a relay for mains failure detection and a couple of diodes for battery switching/charging. The batteries are 2x 6v 110 A/H stationary wet lead acid types.
The 2m tranceiver is a Motorola Syntrx running about 22w into cavities.
The Audio mixing is relatively simple. Its basically a multiple input adder circuit consisting of LM324 OP AMPs. The available inputs are 2m , 10m (via the UHF link) , a 0dBm line input from external sources and the repeater controller beeps along with the CW ident . The 2m input is switched under the control of the CTCSS decoder (2m -141.3 Hz) so that only 2m audio with the subaudible tone enters the mixer. Also a 10m Delink is possible which disconnects the crossconnect path from 10m to 2m using a remote command . This would only come into use if the repeater operated duplex on 2m instead of simplex. In effect this would be 2 repeaters . One on 10m and one on 2m supporting 2 different conversations with certain limitations.
The control part of the TX site consists of a mixture of components. The CW ident comes from a VK5WA discrete design using no microprocessor. The tails and time out timers are of discrete component design also using 74123 ICs . This was done originally as we did not want to spend time developing microprocessor controllers and code at the expense of getting the repeater on air. At that time things like the PIC NHRC controller were not about and it could potentially have become rather complex with multiple inputs and multiple outputs to and from transmitters/transceivers . Allowance has been made in the design for a microprocessor enhancement in future. The controller design is not dependant upon this being present but when it is more features will become available. Initially a motorola J1 was going to be used but along came the PIC 16c84 chip that seemed to offer more in the line of what was required. This enhancement is not yet fitted or fully developed. It will however allow us to do a few more things remotely like for example :- 2m channel change, 2m tail kill, 2m radio reset, 2m disable, broadcast mode through time out disable and DTMF 5 digit detect as a secondary tone access option on 2m in addition to the CTCSS function.
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The Adelaide 10m Repeater story

During the mid 1980's the idea of a 10 metre repeater was born in Adelaide at the Elizabeth Amateur radio club VK5LZ . This was the first of the repeaters licensed as VK5RLZ by the club. The plan was to site the 10m RX about 2km north of the club rooms and link it via phone line to the club room where the 10m TX was to be located. This never got off the ground for various reasons. The repeater never went to air as VK5RLZ.

In about mid 1994 I picked it up again this time with a new set of ideas. The sites at Elizabeth were no longer viable. The noise levels and costs were making it prohibitive. I found a possible site at Glenside near the City. This involved 2 buildings on a campus only 250m apart but a privately owned phone line was available for the link . VK5RHF went to air running just 2W ERP into a 1/4 wave ground plane in July 1995. It took a lot of fiddling and testing to make this arrangement work at such close proximity and I certainly learned lots of essential things in the process.

The South Coast Amateur radio club took interest at this point with the intention to move the repeater to Chandlers Hill VK5RDX and O'Halloran Hill for the receiver . This would have proved to be a good set of sites . Unfortunately the Chandlers Hill site fell through . Once again we were faced with the dilemma of finding not just one site but two that were reasonably close but not too close to each other . Work was started on the introduction of a 70cm UHF link and this ran at Glenside initially as a test between the two buildings . This made the phone line redundant and opened up the new possibility of relocating the receiver . This is exactly what happened . On about the September 15 1998 the receiver was relocated to Ansteys Hill and beamed the traffic back down to Glenside TX site via the new UHF link . We turned up the power at Glenside for the first time without any receiver desense experienced .

The South Coast club still kept hold of the ball and ran with it till it was officially handed to the WIA . We managed to find 2 new sites in the north east of Adelaide thanks to the Wireless Institute of Australia (South Australian Division) and The North East Radio Club . At Houghton and Ansteys Hill respectively . So the repeater became VK5RHO . It stopped operations from Glenside on April 1 1999 as VK5RHF and recommenced from Houghton VK5RHO on April 2 1999 . There it still resides .

Tony VK5AH

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Acknowledgments

Special thanks to the following local clubs and amateurs for helping to get this project going.

Wireless Institute of Australia (South Australian Division) VK5WI.

North East Radio Club VK5GRC

South Coast Amateur Radio Club VK5ARC

Elizabeth Amateur Radio Club VK5LZ .

Amateurs

VK5'S - EX, HSX, ZWI, KK, KCB, KBJ, ZBR, GRS, UDX, TZX, GH, WA, VK3UR

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Heres a few images from the two sites in the NE Adelaide hills.

The 10m TX , UHF link Yagi and 2m antenna (dipole) up the tower.

View of the 10m repeater cabinet . Controller and UHF link radio center shelf . 2m TRX and 10m exiter bottom shelf with 2m cavities to the left. VSWR protection switching top shelf. 50w 29Mhz PA and Power supply sitting up top.

The Houghton (Tx site) antennas and tower.

The view nearby the Anstey Hill (Rx site) looking westerly towards the city.

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