KE8RV Repeater System

147.285 MHz

London, OH

Operated by the Madison County Amateur Radio Club

Equipment

Coverage

History

Operation

Site Index

INTRODUCTION
These pages will describe the technical aspects of the KE8RV Repeater System on 147.285 MHz. Follow the links above for more information about the indicated topics.
The Repeater System is located in London OH at the Madison County Hospital in central Madison County. There are also three remote receiver sites located in Plain City, West Jefferson, and Mt Sterling at the north, east, and south ends of the county respectively. This enables low-powered handheld coverage throughout the entire county, and mobile coverage over most of the adjoining counties. (See Coverage for more information.) All sites have emergency backup power available.
The Repeater System is operated by the Madison County Amateur Radio Club (MCARC), and is open for all amateurs to use. For more information about our club, click here to visit the club's web site.
Welcome! - You are encouraged to use the system.

WEEKLY "GET TOGETHER" NET
Every Tuesday evening at 8:00 PM we host a very friendly net and all amateurs are welcome and encouraged to check in. Hear about the latest club news and other items of interest from the members.


CURRENT REPEATER STATUS - - 100% Operational
MAINTENANCE HISTORY: June 30, 2009 - The Plain City receive site was hit by lighting on June 19th or early morning June 20th, damaging the power supply, receiver, and controller. The backup battery suffered unrecoverable damage due to complete discharge. A new power supply and backup battery (13A-H) were installed. A dual-gate mosfet for the receiver RF front end and an op-amp on the controller board were replaced. June 27, 2009 - The Mt Sterling receive site link antenna was mis-aligned by strong winds earlier this year. The link antenna has been re-aimed, securely tightened, and is now fully functional. Many thanks to Jim Bingham - KC8ARZ (son-in-law of club members Art & Betty Eberle - K8JBF & N8KPZ) for his work on the tower! January 5, 2009 - The West Jefferson receive site has been updated with the new microprocessor-based controller. All three remote receive sites are now controlled with this new hardware. See the Equipment page for the details. November 30, 2008 - A new microprocessor-based controller has been installed at the Plain City receive site. October 25, 2008 - The South receive site has been installed at the firehouse in Mt. Sterling, providing coverage to the southern parts of Madison County. This new microprocessor-based controller has multiple CTCSS and carrier access modes, several timer modes, and a DSP based CTCSS decoder. September 14, 2008 - Added a backup battery to the main repeater site in London. The controller would sometime malfunction when the AC power glitched during a transfer to the backup generator. The battery will allow the controller to survive these power interruptions. June 30, 2008 - A new dual circulator/isolator was added to the main transmitter in London June 15, 2008 - We did not get permission to install the south receive site at the new firehouse in Sedalia. Plans are being made to move the south site to Mt Sterling. January 25, 2008 - The Sedalia receive site was removed from service and the tower and antennas disassembled because of the pending demolition of the firehouse. The new firehouse is under construction and should be completed by the end of February 2008. Hopefully we'll have the tower and antenna re-installed later this Spring. March 19, 2007 - The West Jefferson receiver site was damaged by lightning this morning, killing the power supply. The backup battery died sometime later. The regulators and diodes in the power supply literally exploded. The backup battery suffered unrecoverable damage due to complete discharge. Receiver and link transmitter were not damaged. The power supply has been repaired and battery replaced on March 20. February 12, 2007 - Fan replacement completed and 100W amplifier is back online. Also, the "kerchunk" filter has been turned off for instant carrier access. February 5, 2007: Routine inspection revealed that the cooling fan on the transmitter's power amplifier has died. Last inspection was June 10, 2006, so it quit sometime in the last 8 months. To avoid risking damage to the amplifier, the amp is off-line and the repeater is running barefoot at 25 watts. A new fan has been ordered and should be installed next week. February 5, 2007: Programming Changes - Due to increasing amounts of DX and other noises hitting the Sedalia and Plain City receivers, the repeater now has the "kerchunk" filter turned on. If the repeater has been idle for more than several minutes, it will take one second of continuous carrier to activate the repeater. Keep this in mind so that the first second of your transmission is not chopped off. Also, the pitch of the CW reset beeps have been changed to make it easier to tell how many receivers you have "hit" during your transmission. The range used to be from 523 Hz to 1046 Hz; now the range is from 350 Hz to 1185 Hz. June 12, 2006: The new and improved Sedalia receiver site is back in service, sporting a new microprocessor-controlled controller and CTCSS decoder. See the Equipment page for more information. June 8, 2006: The main repeater site in London was hit by lightning, damaging the power supply and the Plain City link receiver. Repairs were completed by June 10.



FREQUENTLY ASKED QUESTIONS (FAQ)
Q.	How does the voter work?
A.	At the main transmit site, there are are three receivers that listen to a set of UHF link frequencies in addition to the main 2-meter receiver on 147.885 MHz. Remote receiver sites also listen on 147.885 MHz and transmit what they hear back to the main site on a UHF link frequency. The voter decides which one of the four receivers is receiving the best signal by continuously measuring the signal to noise ratio. The quietest signal (the one with the least amount of high-frequency white noise) will be voted, and its signal is sent to the 147.285 MHz transmitter. The voter may vote different receivers several times a second if the signal is rapidly changing or fluttering. The best signal is always sent to the transmitter, assuring the best possible signal to the transmitter.

Q.	Where are the receivers located?
A.	The main receiver is located at the transmitter site in London, OH, at the Madison County Hospital. The north receiver is located in Plain City, OH at the Pleasant Valley Joint Fire District Firehouse. The south receiver is located in Mt Sterling, OH at the Firehouse. The east receiver is located in West Jefferson, OH near the High School.

Q.	What is the meaning of the CW (Morse Code) at the end of each transmission?
A.	It is the indication of which receiver was voted the most during a user's transmission by sending a specific letter in Morse Code at the end of each transmission: "L" (-) for the London receiver "W" (--) for the West Jefferson receiver "S" (**) for the Mt Sterling (South) receiver "P" (--*) for the Plain City receiver A microcomputer samples the voter output 20 times each second and counts how many times each receiver is voted during a user's transmission. The receiver with the highest vote count determines which letter is sent.
	Also, the pitch of the CW character indicates how many of the receivers you "hit" during your transmission. The lowest pitch indicates only one receiver, and the highest pitch means that you have a strong signal and are hitting all four receivers. The intermediate pitches indicate that two or three receivers are receiving your signal.

Q.	Why am I sometimes voted into a receiver that is not the closest to me?
A.	The voter will always choose the receiver with the best signal. However, if you have a very good signal (full quieting) into more than one receiver, the voter cannot choose which one is best because there is no difference to detect (it's a tie.) In that case, the voter will lock onto the first receiver that comes up. Usually that will be the local London receiver because there are no link delays with that receiver.

Q.	Is an Autopatch available to make telephone calls?
A.	No. The repeater has the necessary hardware, but no telephone line is available at the repeater site.

Q.	How much power is the repeater's transmitter?
A.	100 watts at the transmitter, but with losses in the isolator, duplexer and feedline, there's less than 40 Watts at the antenna. However, the antenna has 6-9dB of gain in its best direction, so the Effective Radiated Power (ERP) is greater than 100 Watts in most directions.

Q.	So, the repeater's antenna is directional?
A.	Yes, sort of. Since the antenna is closely side-mounted to its tower, there is a weak null to the southwest of London.

Q.	Is a subaudible tone (CTCSS, PL, etc.) necessary to access the system?
A.	No. However, the remote receivers are designed to have a higher sensitivity (actually, a looser squelch) if you are using a 82.5 Hz subaudible tone on your signal. If you are out in the fringes with a weak signal, then using 82.5 Hz subaudible tone may improve your signal quality into the repeater.

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This page last updated July 1, 2009