Central Idaho Amateur
Radio Club
     
CIARC - Repeaters - 2 Meters
Repeater Network




2m Repeater

A completely new 2m repeater was constructed in the spring of 2012.


2m Repeater Access Parameters
Call
Sign
QTH Input
MHz
Output
MHz
CTCSS
Decode
CTCSS
Encode
Timeout
Timer
Minutes
KC7MCC Brundage Mountain 147.620 147.020 100.0 100.0 10

The 2m repeater, in conjunction with a full-duplex 33cm link, operates as the hub within an extensible repeater network. The repeater consists of a full-duplex 2m repeater, full-duplex 33cm repeater/link, Motorola Micor™ squelch gate, repeater controller, 2m power amplifier, 2m dual-port isolator, 33cm dual-port isolator, 2m duplexer, 33cm duplexer, 2m/33cm diplexer, Andrew LDF4-50 feed-line and antenna system as shown below:



The repeater encodes telemetry beeps on the squelch tail. The beeps, in general, indicate that the transmitting station has completed their transmission and that another station can now transmit. If the transmitting station is noisy then they may have simply fallen out of the receiver and may re-appear momentarily.


   

The 2m repeater is operating on a temporary antenna system consisting of an NGC Comet GP-15 (4.0 dBd) for 2m and an NGC Comet KP-20 (7.0 dBd) on 33cm, and a coax run that exhibits higher losses than the LDF4-50 hard-line that was part of the planned installation. Once a suitable antenna bracket has been fabricated, the NGC Comet GP-15 will be replaced with a Station Master antenna. The temporary 2m antenna has no down-tilt while the Station Master does have down-tilt and offers additional gain. Problems that were observed with the LDF4-50 hard-line when installed on the hilltop are being investigated at ground level and it is hoped that the LDF4-50 will be installed at a later date. When the transition to the Station Master antenna is made, 2m repeater coverage close in should improve. Moving to LDF4-50 hard-line should dramatically improve the 33cm link back-bone performance.

Measured repeater performance and operational settings are as follows:


2m Repeater Performance
Parameter Measurement
Receiver Sensitivity 0.18 µV for -12 dB SINAD
Squelch Threshold 0.05 µV
Receive Duplexer Attenuation 1.6 dB
Effective Receive Sensitivity (Duplexer Loss) 0.23 µV for -12 dB SINAD
TK-705D Transmitter Output Power 4.3 W
KLM PA15-80BL Amplifier Output Power 50.0 W
EMR Isolator Output Power 40.0 W (0.97 dB loss)
Duplexer Output Power 27.5 W (1.62 dB loss)
TK-705D Repeat Audio Deviation 5.0 KHz
TK-705D ID'er Audio Deviation 1.5 KHz

2m Repeater Operational Settings
Parameter Setting
Transmitter Timeout Timer 10 minutes
Transmitter ID Timer 10 minutes
Transmitter Squelch Tail Timer 2 seconds

Note that a re-tune of the EMR isolator is pending as the insertion loss is excessive (loss is specified to be 0.5 dB). With the EMR insertion loss falling within specification, the output power from the duplexer should increase to 31 watts.

The following power measurements were made, with observations in battery power and commercial power modes, at each point along the transmit signal path. No measurable loss was detected at the lightning arrestor so that component has been omitted from the signal chain. All measurements are expressed in watts.


2m Repeater Power Measurements
Power Source Kenwood
TK-705D
Transmitter
KLM
80-Watt
Amplifier
Isolator Duplexer
Commercial 4.3 50.0 40.0 27.5
Battery 4.3 4.3 3.7 2.6

Note that for the ERP calculations below, the transmitter power output that was measured at the end of the signal chain comprised of the isolator, duplexer, diplexer and lightning arrestor. Only the feed-line loss and the antenna gain were required to complete the ERP calculations.


2m Repeater Operating Parameters
Power
Source
Power
Output
Watts
Antenna
Gain dBd
Duplexer Rx
Insertion
Loss dB
Duplexer Tx
Insertion
Loss dB
Isolator Tx
Insertion
Loss dB
Feed-line
Loss dB
Total Tx
Loss/Gain dB
Total Rx
Loss/Gain dB
ERP
Watts
Commercial 27.5 +6.0 -1.5 -1.5 -0.5 -0.4 +3.6 +4.1 165
Battery 2.6 15

The following coverage plots represent a calculated repeater performance for commercial power and battery power modes for the 2m repeater operating from the Mt Brundage repeater site. Since the power level used in the calculation is the power level run into the feed-line, only the pure feed-line loss and antenna gain were included in the transmitter calculations while the duplexer insertion loss was included with the receiver calculations.

Operation on battery power, with a reduced transmitter power level, results in approximately one half of the coverage footprint (expressed in square kilometers) when compared to full power operation on commercial power.

To view the two coverage foot prints, move your cursor on and off of the image below. Note that this web page feature requires a web browser that supports CSS3 (current FireFox, Safari, Google Chrome and IE10 should work).