TECHNICAL DESCRIPTION OF RMVHFS 146.76 REPEATER

REPEATERS' STATUS (11/10/03):

146.76 repeater system - transmitter and all receive sites operating normally

224.02 repeater system - operating normally

449.55 repeater - operating normally (repaired 11/09. See picture on right).

220/440 link - operating normally

NØBP displaying defective legacy component from UHF transmitter.

Inputs at 222.42 and 444.55 MHz are usually repeated/translated simultaneously to 224.02 and 449.55 MHz. The 70 cm machine transmits a continuous 100 Hz tone and normally requires a 100 Hz (PL, CG, or CTCSS) tone to key up. A PL decoder is not required by users to hear the 70 cm transmit signal, but if used will eliminate local RF interference and squelch burst noise. The 222.42 MHz input is carrier squelch. Both inputs are open to all users. Linking and other functions are controllable by the authorized control operators via a number of gateways, and some limited linking to the 2-meter repeater is possible for emergency situations.


Gunbarrel Transmit/Local Receive Site	Primary Louisville Remote Receiver Site

The 146.16/146.76 MHz WØIA repeater is the designated emergency repeater for Boulder County. See the BCARES WEB-SITE for information on the services performed and for membership information.

The '76 2-meter amateur repeater is a sophisticated multi-site system based on commercial 2-way radio equipment with some additional custom designed hardware. The primary repeater is a Motorola MSR-2000 rated for 100 watts continuous output. Multiple receive sites and a network of microwave and UHF links provide for coverage from hand held radios throughout the plains and mountain areas of Boulder County. The receive sites and UHF links utilize General Electric Mastr-II equipment. The GE four channel voting comparator is located at the Gunbarrel site. Power at the Gunbarrel and Louisville primary sites is fully backed up with batteries and/or generator equipment, and the other sites may be backed up using computer type UPS equipment.

100 Hz sub-audio tone (PL, CG, or CTCSS) access is not required for the 2 meter system but is recommended for best access to all the receivers. See note below*.

The PRIMARY TRANSMIT SITE is located on Gunbarrel Hill in northeast Boulder County located approximately at an elevation of 5415' MSL. Published coordinates of this repeater is 40.0628ºN, 105.1506ºW datum WGS85 - UTM Zone 13, N 4434527, E 487156.

The antenna at Gunbarrel has 6-dB gain for transmit and receive and is set for an omnidirectional pattern. It is fed with low-loss semi-rigid feed line. The roughly 400 watt ERP signal is adequate to provide usable reception at virtually all locations on the plains and in the mountains of Boulder County.

Three additional receive sites are located within the County to provide for coverage from hand-held 2-meter radios. A receiver in the hills above the town of Lyons provides for good coverage in the northern part of the Boulder mountains and two receive sites on the Davidson Mesa, one permanent and one at a temporary test location, provide for excellent receive coverage in mountain valleys and for improved reception for mobiles due to diversity reception that helps eliminate mobile flutter effects. A voting system ensures that the best receive signal is repeated on a continuous and instantaneously switched basis. The received signals are linked to the transmit site via a network of digital microwave and analog UHF one-way links. All links and the transmit site can be controlled by the authorized control operators in-band and via a number of additional access points. A carefully engineered arrangement of reverse-burst and inhibit tone encoders on the UHF links assures minimal switching delays between receivers and the virtual elimination of transmitted double squelch bursts. This unique system was designed and implemented by NØBP.

A system of ID tones identify the receive site in use at the instant of repeater drop as follows:

RECEIVE LOCATION	TONE	PITCH	PL TONE REQUIRED
Gunbarrel	Single beep	Medium	100 Hz (see Note below)
Louisville Primary	Single beep	Low	carrier squelch
Lyons	double beep	high followed by medium	carrier squelch
Louisville #2 (test location)	double beep	high followed by low	carrier squelch

The ID, WØIA/R T*, is transmitted via modulated CW every 5 minutes. (MCW ID's on the UHF links are transmitted every 9 minutes but are not retransmitted by the VHF repeater output.) The repeater time out timer (to prevent a permanent key up condition) is 2 minutes and is reset whenever the input signal is dropped long enough to allow the "courtesy beep" to be heard. The transmit hang time is 4 seconds. The output carrier continues an additional 500 milliseconds without the 100 Hz PL tone to minimize squelch burst noise being received by the users who have activated their transceiver's tone decoding.

If no courtesy beep is transmitted, the voting system has been temporarily disabled and reception is only via the Gunbarrel local receiver. Likewise, if the "T" suffix is not heard on the ID then the Gunbarrel receiver is operating carrier squelch. See notes below for more details.

The 146.76 repeater transmitter superimposes a 100 Hz audio tone on all transmissions. A PL decoder is not required by users to hear the transmit signal, but if used will eliminate local RF interference and squelch burst noise.

Only the local receive site at Gunbarrel usually requires that you transmit a 100 Hz sub-audio ("PL"). The three additional receivers DO NOT REQUIRE any tone access. The 146.76 repeater system remains an open repeater system for all users. This can be suspended temporarily due to participation in a controlled emergency or training exercise or when formal nets are in operation.

The repeater's transmit WØIA/R modulated tone identification includes an additional "dash" (Morse "T" for TONE) to indicate that the local Gunbarrel receiver is in the tone receive mode. Note that use of the repeater system as a whole never requires tone access as the three remote receivers are operated carrier squelch all the time. Only the local receiver at Gunbarrel requires tone access. Only slightly better coverage is provided if you have 100 Hz capability on your transmitter due to the ability of the additional local receive site at Gunbarrel to be included in the voting system when you transmit. The local tone receiver requirement is necessary to minimize random key-ups due to the heavy multi-band high power transmitter concentration at the Gunbarrel site. Studies are being done to identify and eliminate the sources of the intermittent interference. The tone requirement may be removed in the future. Should this happen an update will be posted on this web page.

The requirement for tone access at the local receive site can be defeated by any user by their transmitting a DTMF (touch-tone) "Ø". For the following approximately 5 minutes the local receiver will operate without the receive tone requirement. The 5 minute timer is reset whenever a Ø tone is received on any of the receivers. Note that this control tone must be received by one of the remote sites if no tone is present on the user's signal for the temporary defeat to occur. In addition, the tone requirement can be disabled for any length of time by the control operators: for example if there is a voter system failure. Note that the tone is required only for the local receiver, one out of four in operation. Full county coverage is usually provided for transmitters without PL even without this site due your being heard by the other three receive sites. Note that the primary Louisville site provides essentially overlapping coverage to that of Gunbarrel and enhanced coverage of southern and eastern Boulder County and of Broomfield.

The recent improvements at the transmit site and the incorporation of additional receivers throughout Boulder County have resulted in a major net improvement to the coverage of the RMVHFS 146.76 repeater--even with the tone access requirement for the one receive site.