Specification for a GE Mastr II receiver is .5 micro volts for 20 db quieting. For approximate check, put an AC volt meter on the speaker with squelch open. For example, if voltage is 1.2 volts and you supply .4 mv on receive frequency to the receiver in order to get the voltage down to .12 (a factor of ten) that means your receiver requires .4 volts for 20 db quieting. Adding a preamp with ban pass cavity in front will give even better results. I always get better results than the specifications.
Duplexer on Bisky Mtn.
60 watts into duplexer 45 watts out
2 meter repeater CURRENTLY ON Bench:
I'm showing 210MW on excitor and 140 Watts output. Set to 78 watts
.500 µv for 20 db quiting into receiver
.14 µv for 20 db quitting into band pass cavity and Pre Amp: 5/26/18
2 Meter Backup Repeater 11/13/17 - CURRENTLY ON BISKY: 4/19/2018
.500 µv for 20 db quitting into receiver
.112 µv for 20 db quitting into band pass cavity and Pre Amp
Specification for exciter - 250MW
1/27/2020
Backup 443.100 on bench. Open squelch .150 mv with no pre amp. With pre amp open squelch at .075 mv
.250 mv for 20 DB using AC volt meter described above.
Notes: Just rambing notes for my information scroll down for latest
The power amplifier is turned on with a NPN transistor with a heat sink tab on the back. To check a NPN transistor using an ohm meter:
1. Put - lead to emitter and + lead to base; it should show a reading. Reverse leads, and it should show open.
2. Put - lead to collector and + lead to base; it should read mega ohms. Reverse leads, and it shoud read open.
3. Emitter and collector should be open either way.
PNP conducts with leads switched.
When PA is active, base has 5 .2 volts. I use another identical transistor to turn the fan on with the 5 volts on the base of the PA transistor.
Notes on Remote Base on 224.48 Repeaters.
I use a TM701, the radios require a reset (Turn on with Mr button pressed) Step must set to 5 KHz after each reset.
Both repeaters are using speaker audio and masurements a made by ear with 1000 Hz on frequency tone. In other words just a guess as to 20 db quitting
224.98 on bench # 1
.5 µv for 20 db quitting into receiver
.15 µv for 20 db quitting into band pass cavity and Pre Amp
224.98 on bench # 2
.38 µv for 20 db quitting into receiver
.15 µv for 20 db quitting into band pass cavity and Pre Amp
I inject signal and use Pin 4 of P904 and DVOM on DC mV to tune. You have to really turn the signal up to use the GE Meter.
Schmetic for Fan controlled by CTCSS
Pre Amp After Band Pass Filter
The pages on this 220 conversion site are copied from a site I did so long ago that the camera I use stored to a 3.5 inch disk. It not an update, just trying to preserve the information and typos.
N4KHQ Bench
GE Mastr II 150.8-174MHz Conversion to 220MHZ
This modification was designed by Dave Ackley W4UWH and will require from 8 to 16 hours of work to completely modify a GE Master II 150.8-174 MHz into a 220 MHz repeater. The PA presents the most challenge and Dave has made the modification by changing one of the power transistors and several capacitors but Dave has a $16,000 IFR Service Monitor and knows how to use the equipment. I am convinced the modification is beyond all but the most knowledge RF specialists. I tried a couple of PA mods I found on the www and none performed well enough to be used for a repeater. After spending $60 for rf power transistors and capacitors, one modification produced 7 watts and the other produced about 40 watts but had a half frequency spurious signal. The solution Dave suggested for me was a $59 RF Parts # M57774 Power Module. I use the web page as my notes. I have updated the Exciter Modification page with directions as to how to tune a modified exciter and added the PTT Fan/ARR protection link
2 Meter removed from my tower at small Bisky site 7/16/22
PreAmp before Filter Can .040µV squelch closes & .050µV Squelch opens
Filter Can Before PreAmp .045µV squelch closes & .056µV squelch opens
Dead Full Quitting .315 by ear zero pops
Good youtube on quitting: https://www.youtube.com/watch?v=9HRALdWXIBQ
Monitor PF 1 key opens speakerfor signal without CTCSS (QT) to test for quiting. Signal does not key repeater when no CTCSS is present.
Update May 2024
NOTES: TKR-D710 Kenwood 2 Meter Repeater
Duplexer -> Band Pass -> AR2 Preamp -> Receiver
Preamp .05 µv opens squelch
.177 40 Db Quitting zero pops
12 watts out from repeater
69 watts from amp
49 watts to Antenna
6.26 DC amps repeater 7.2 DC amps for amplifier
4.17 AC amps for repeater in TX
DB Products 4 cans Duplexer has 1.5 db insertion loss
Update May 2024
NOTES: TKR-D810 Kenwood 443.100 Repeater
Duplexer -> Band Pass -> AR2 Preamp -> Receiver
.177 µv opens squelch without pre amp
.39µv 40 Db quiting to ear zero pops without pre am
.09µv opens squelch with pre amp
.17µv 40 Db quiting to ear zero pops with pre amp
16 watts out from repeater
73 watts from amp
63 watta to antenna
Tx RX 4 cans duplexer has .64 db insertion loss
watts to Antenna
DC amps repeater DC amps for amplifier
AC amps for repeater in TX
Notes on GE repeater Black Mountain using arrow beam
.1 µv In and out like desense
.126 Holds repeater up
My notes on Tuning Duplexers:
The high frequency for plus offset is the frequency the user Tx and goes to RX of repeater. The high for a minus offset is the frequency the repeater is transmitting. The highest frequency of the pair always goes to the high side of the duplexer but you switch sides of TX and RX connections to the repeater when you go from plus to minus offset.
Example: The TX-RX duplexers are marked high frequency on the right side and low frequency on the left, assuming the antenna connect is front and centered. If you have a plus offset, the repeater TX 443.100 and Rx 448.100, The right two cans passes 448.100, the higher frequency and notches 443.100 and connect to the receiver of repeater. The left two cans (low) connect to the TX and they pass 443.100 lower frequency and reject 448.100. If you had a minus 443.100, the repeater would TX 443.100, the high frequency right sided of cans and notch 438.100. The repeater receive would connect to the left side and pass 438.100 and reject 443.100. This would keep the notches on the correct side of the pass frequency.
If duplexers are currently tuned for a different pair, move pass (Knobs) slowly together a short distance. Pass rods also move the notches, therefore, notches must be tuned last. Next move notches a short distance to keep notches together and spacing close. If duplexer are untuned, you may have to tune each can separately. It appears to me there are multiple passes and notches on a single can, probably harmonics. be sure to start on the best notch a pass.
Notes on Backup 2M amp TE Systems Repeater Amp 1512rr 160watts
25 watts in 68 watts out
30 watta in 80 watts out
Notes on 220 repeater
AC amps 6.01 with High power on remote base
AC amps 5.04 with remote base on medium power