This co-hosted 1.25 meter repeater addition to the system has been in operation since September 2002.
IRLP is not yet accessible from this repeater, it is however from the 447.925 machine.
At present it is based on an old Maggiore Hi Pro repeater, however it will be based on a GE Master II conversion once I get that process perfected.
The current configuration is a the Hi Pro exciter/receiver and 15w PA driving a TE Systems 100w amplifer into a TX/RX Vari-Notch 215-250Mhz duplexer with a Bird 4521 metering panel housed in a 6 foot Motorola repeater cabinet using Hustler G7-220 for the antenna.
Although not seen in these photos taken at an early stage of system start up when handy jumper cables were used along with connector adapters to determine eact needed lenghts and connector types as the system uses a combination of BNC, PL-259 and N connectors. At this time all cabling between each point is Mil-C17 double shielded teflon jacket RG-58 type cable (RG-142) with the proper connecter until the output of the duplexer.
A PD220-8B1 220-225Mhz Super Station Master antenna was acquired that exhibuted an intermittent VSWR problem. It has now been repaired and will be installed before the end of spring on an IIX mount as is the 2m repeater station master. The photo below is the PD220 antenna removed from its radome for inspection and repair.
It was interesting taking the antenna apart, it was more interesting see what is actually inside and then repairing it, it was even more interesting getting the thing back together again ! Below is a closeup of the antenna removed from the radome, we found it a lot like a plumbing job when repairing the antenna.
I have now re-tuned, re-epoxcied and repaired the Super Station Master type antenna and I am of the belief that one can probably keep these antenna working for ever as long as a lightening strike does not melt it down !
The system is currently under the control of a modified TP-3200 controller (later the controller will be a Pacific Research model.) in community tone panel configuration supporting PL 127.3hz, 131.8hz, 136.5hz, 141.3hz, 156.7hz and DCS 031/PL 156/.7 and DCS 315/315. There is about a 1.5 second delay on decode using DCS for some reason !
The primary PL tone will be 156.7hz, this is the only tone that will normally be re-transmitted for use with CTCSS. In DCS operation code 031 is decoded and 156.7hz encoded if your radio can just do DCS on transmit or DCS/PL like the Yaesu VX-7R and others.
For full DCS/DPL access with other like configured users you can use DCS code 315, but not interact with PL users.
The use of DCS/DPL is very dependant on a number of factors. For more inforamtion on Digital Coded Squelch click here.
The image above and below is on the back side of the system. In these photos the TE systems amplifer has not yet been installed.
The TX/RX duplexer tuning rods extend forward and prevent the front door of the cabinet from being installed.
The TX/RX model 28-52-02 (215-250 MHz) Duplexer specs are:
Minimum freq. spacing 1.6 MHz
Max. continuous power 250 watts
Tx noise supp. at RX freq. 58db min./90 dB max.
Rx isolation at Tx freq. 90 dB
I also have Celwave dual port ferrite isolators should it be needed and an additional 3 cavity rack mount Wacom passband cavity filter.
GE Master II 220 Repeater:
This effort has been disappointing to date. The receiver has been very problematic, poor sensitivity and unreliable operation have plagued it since day one.
I took on this project as both a technical challenge and as an effort to make more use of the 220Mhz band. Also important is access by the Novice class licensee as 1.25 meters is the only VHF/UHF band below 23cm that a Novice has access.
This repeater will be based on a converted GE Master II/M 150.8-174Mhz PLL based exciter and standard receiver. The challenge here is getting the Master II converted to 220 and working at the 200-300mw from the exciter and the receiver working to begin with !
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
This receiver has an ARR 220Mhz P220VDG 20db gain .5db NF GaAsFET pre-amp for installed. I needed one with the GE based 2 meter repeater as well.
One can buy a converted Master II/M 220 repeater from the renowned Kevin Custer W3KKC or one can build it by following the directions at the following URL links, bear in mind that you must follow the correct directions for the model of Master II radio being use. One of the best sources of information on making repeaters is to be found at the Repeater Builder Technical Reference Page http://www.repeater-builder.com brought to us thanks to W3KKC.
This link pertains to the PLL exciter only.
The following three links discuss the non-PLL exciter and the standard receiver.
Milcom 220Mhz Amplifier:
Rather than creating a 25 to 30 watt repeater using the typical power module or modifying the 35w GE PA, I will be directly driving a converted commercial Milcom/Uniden ARX2125 220Mhz ACSB trunking system 125 watt pep rated linear amplifier.
I bought the Milcom amplifiers (two sets) as a package deal that included the needed power supply for each amplifier from a outfit that took possession of the assets of a defunt commercial venture into the 220Mhz LMR arena that stole the bottom two MegaHertz of the band from Amateur Radio and changed it from the 1.25m to 1.35 meter band technically.
These Milcom ARX2125 28 vold D.C. PA's are built like a "tank" and features 100% VSWR and D.C. power shutdown protection and other monitoring features which will need defeating as they will no longer be used as designed in a bay of multiple amplifiers for redundant operation. As can be seen in the above photo's they mount in a bay of multiple amplifiers in conjuction with a Celwave 220 transmitter combiner and receiver multicoupler for multi channel redundant operation.
These units came complete with the required Astron rack mounted 28 volt 25 amp power supplies from which the 13.8v needed for the Master II exciter and receiver will be derived as well. This PA uses a Motorola CA2832C MMIC (1.5w output rated with maximum gain of 35db) for the first amplification stage followed by a number of PolyFET amplifier modules with an absolute output of 200 watts pep. The PA will be re-biased and driven to about 100 watts of carrier power. The little board on the lid in the photo below is the bias board for supplying the idle condition for linear operation.
This is a complicated amplifer made for a redundant bay of PA's that has a lot of stuff in it that can and must in some cases be bypassed. Many signals are looped through that we do NOT need to loop and combine. A lot of sensing circuitry exists that I have no idea about and don't care about.
There is high VSWR and temperature monitoring and this unit is very well fused internally, these are important factors however.
Conversion details: Preliminary Information -
As to using the amp for repeater use, this is what I have done to make it work, perhaps there is a better way ?
1. I removed the brown D.C. wire from the CA2832C and its white coax output from the input to the 2nd driver stage. (Note driving the first stage only a few miliwatts (about -8dbm) is needed.)
2. I replaced the male chassis connector to SMA with a BMC chassis and wired RG-174 to the input of the 2nd RF stage.
3. I wired in an external source of 28 volt D.C. from the Astron supply and fused it. When 28v is applied, the 28 and 13.8 LEDs on the front panel will lite.
4. I added a new BNC output direct from the output power combiner J1 connection bypassing the next combiner and 220Mhz output filter.
5. Apply 4.5v to red/yellow wire to fan/bias board using a tap off that board. A signal of 5 volts could be applied and will be in the future from the repeater controller so that bias is only applied during transmit. When this line is high, the TX light on the from panel lites.
6. I apply 300mw (1-2 watts is ok) of FM drive to the 2nd driver board for 125w output at 220Mhz. You can by pass the 2nd stage and drive 25 watts direct into the combiner for 125w output at 220Mhz.
However, the amplifier output goes down rapidly as you go above 220Mhz, down to 50 watts at 224Mhz as these are narrow band. I will be next modifying them to work at full output at 224Mhz.
More details to follow including more photo's.
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