This co-hosted 2 meter repeater addition to the system has been operational since 2002 and offers decent sensitivy for 5 watt HT's out about 5 miles and 5 watt mobile operation out 10-15 miles and an average 15-20 mile mobile coverage period.
In the beginning there were problems getting the duplexer to work well in the ham band (the WP629B is designed for 130-144Mhz) without desense, however some modifications and fine tuning took care of that.
IRLP is not yet accessible from this repeater, it is however from the co-hosted 447.925 machine.
THE REPEATER:
This system is currently based on a special GE Master II/M PLL mobile transceiver one of a lot that I purchased from an auction in Washington state. These units all have internal amplifiers that do 125 watts and diversity reception with an internal spliter and a factory added BNC 2nd receive antenna port.
The GE Mastr II is generally accepted to be a very solid performing radio and the PLL exciter used is generally 20-25dB quieter with close in white noise than exciters that use multiple stages of multiplication to get from the crystal's 1/12 on channel frequency.
I split this unit into a duplex radio for repeater use. It can be used with either the internal amplifier for low power backup repeater operation with fan cooling or with an external GE amplifier as it is currently. When used with an external amplifier the chassis mounted SO-239 jack is not used and the exciter output is feed to the external PA. This unit will serve as the backup repeater down the road when the normal operation is moved to a GE VHF base with continuous duty PA that I am swapping out the standard exciter with a PLL exciter and re-wiring for repeater operation at which point the entire 2m repeater system will be contained in the GE cabinet and powered by a standard GE ferroresonant 13.8vdc power supply seen in the photo below.
As the receiver on this GE radio just barely meets the book spec of .5uv sensitivity and that is without PL decode and a duplexer, an ARR P144VDG preamp has been added to the system to lower the noise floor and increase the gain. This GaAsFET preamp has a .5db noise factor and 24db rated gain.
REPEATER POWER AMPLIFIER:
I am using an external GE 100w continuous duty cycle PA which was a gift from my good friend Doug, W2UG. At present is just sitting on the radio with a single fan as the power is set low. An attenuator is used between the PLL exciter and the PA as the exciter is 600mw and the PA is designed for standard 250mw exciters. All of this is just sitting on top of the wooden frame for the duplexer at the moment. All of the cables between the duplexer, PA, exciter and receiver and preamp are RG142 doubled shielded teflon jacketed with RG214 interconnecting the duplexer cavities.
REPEATER CONROLLER:
The controller is off to the side sitting atop some Wacom 140-174Mhz pass cavities not currently being used. The power supply is currenlty an Astrom RS-50 sitting on the floor. Later a full full GE Master II repeater with a continous duty amplifier will be used.
The controller currently is a borrowed RC-96 from my friend Kenny, KB2KBD all reprogrammed to brag away with voice messages and get some attention along with a Com-Spec TS-64MSII board being used for CTCSS.
I will soon be changing over to a Com-Spec TP-3200 controller will be used that will support both PL and DPL until the Pacific Research RI-400 controller become available.
PL and DPL:
The primary PL tone will be 127.3hz, this is the only tone that will normally be re-transmitted for use with CTCSS. When the system is fully configured one will also be able to access it using PL tones 127.3, 131.8, 136.5, 141.3, 151.4 and the DPL/DCS code of 031. However, in all those cases 127.3hz will ALWAYS be what is retransmitted. The use of DCS/DPL is very dependant on a number of factors. For full DCS/DPL access with other like configured users you can use DCS code 315. For more inforamtion on Digital Coded Squelch click here.
DUPLEXER:
The duplexer currenly being use is a Wacom WP-629B Bp/Br with optional N connectors that is designed for 130-144Mhz operation. I have been pushing the limit to make it work at 146.730 at a 600Khz split. The WP-639 model which is very a similar that has cavities some four inches shorter and other differences is rated for 144-174Mhz. The WP629B should actually be usable to 150Mhz I have been told by an ex Wacom engineer with some effort.
The WP629B specifications are for 80db of attenuation at a 600Khz split. The unit is rated for 200 watts and easily tunes to pass but has a problem meeting the rejection specificiation up the band for my frequency as the invar rods which are part of the notch capacitor assembly are not the correct size.
The unit was originally tuned for 139.025 transmit and 142.400 receive. This would have likely been some U.S. government user, perhaps Navy related. I bought to sets of these at a good price, I am using one and a friend will be using the other for his repeater down in the 145Mhz part of the band.
ANTENNA:
The antenna is a Celwave Super Station Master antenna. This is the antenna to use for repeater operation. It is some 22 feet long and has true 5.25db gain.
My anatenna is mounted up in an Oak Tree using an IIX pole mount by viirtue of all the in-the-tree work being done by my good friend Bill, KC2CNB.
The particular Station Master being used was factory tuned for 151.250Mhz and was donated to by John, WA2OTP. I have another that is factory tuned for 142Mhz that I was a gift from my good friend Sam, WB2HAE/SK that I plan to open and re-cut onto my frequency as a spring project next year.
My friend Ron, N2FFL and I were able to retune the one in use with the 1/4 wave aluminum reflector method !
Starting with pieces of aluminum foil we determined the location and width of foil that resulted in resonating the antenna at my transmit frequency. The end result that worked the best for my antenna was a piece about twelve (12) inches in length with the center about 18 inches from the bottom of the radome. This resulted in a 1.6:1 VSWR, no better was achieved via any other known metdod. My friend Bill, KC2CNB also applied this method, however on his station master he ended up with the a number of pieces of various widths spaced the lenght of the antenna, which is what I understand is pretty much normal.
Anyhow, mine only worked with one wide reflector. I then re-expocy painted the antenna with two part epoxcy and later added aluminum tape to exactly where and the size previously determined and covered with heavey Andrew labeled electrical tape and wire ties. If you look at the photos above, you will see the black electrical tape above the aluminum base of the antenna.
I have also recently taken a Super Station Master apart that had an intermittent VSWR and repaired and reassembled it, that was to say the least very interesting, see my 1.25m page for more info.
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