Hi All,
I've searched the archives & website for info on this Amp and can't find anything. It's sort of similar to the N1275A or the N1248A convert-a-com amps but for a Motorcycle (I was told). It looks like the back end of a MoCom 70 heat sink. I need more specific schematic or manual info so I can integrate it into the repeater keying control logic. The Amp is working fine on 147 MHz, keys up on RF input and makes rated output. I want to use it in repeater service at reduced (~40 Watts) output, possibly with a small fan for cooling, as needed. Anyone have any history/info using this Amp?
Model N1254A, 150.8 to 162.0 MHz, Mfg Aug 1977.
Max input 7 Watts, Output 60 Watts. FCC # CC 3303.
Power Amp board TLD8922A uses M9622/23/24 & two M9625's for final transistors.
Output directional coupler/power monitor board, TLD8922A.
Input attenuator (-3 dB) & RF sense keying board, NLD7141A.
Input/Output bypass relays are 23C84103B01.
Any info, links, etc. much appreciated.
Tnx, & 73's
George
Motorola N1254A Power Amp for 2M repeater info
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Dan562
- Posts: 533
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- What radios do you own?: Kenwood, Yaesu, ICOM, Motorola
Re: Motorola N1254A Power Amp for 2M repeater info
Hi George,
This N1254A VHF RF Amplifier was probably used with a Convertacom for a HT-220, MX300 or MT500 Handie-Talkie portable radio in a Mobile enviroment to boost the signal. With the string of RF transistors and heatsink, it was a MICOR design that was developed from the Plantation, Florida SP Subscriber Engineering Department for originally the Public Safety Market. The MICOR Series had 60, 90, 100 and 110 Watt RF Power Amplifier designs and the T/R Relays had a UHF (Female) connector on one end and pair of RCA (Jacks) connectors on the opposite end. The Relay coil was Black rectangular plastic with the metal relay body inserted through the coil.
I'm a bit surprised that there's only a -3 dB attenuator feeding the first RF M9622 transistor as the stage only requires 1 Watt of RF drive to the Control Stage. Motorola Parts Department does not supply any more M9625 RF Transistors because they told the Purchasing Agent to tell the former Motorola Semiconductor Group to destroy the M9625 mold before making the last time buy DUH and this was during the 1990s. Another Brillaint Motorola Decision!
The Motorcycle Radio was a MCR-100 so I doubt this RF amplifier was used with that radio. Look for a VHF Micor Service Manual, perhaps on eBay for the schematics of the Power Amplifier stage. If you put this amplifier into a repeater service make sure you've got pleanty of air movement across the heatsink fins (perhaps muffin fans) otherwise you'll burn yourself and possibly decrease the lifetime of the RF devices. The Power Amp was designed for intermittent duty cycle not continuos. You will not need the RF By-Pass Relays in a repeater configuration.
Dan
This N1254A VHF RF Amplifier was probably used with a Convertacom for a HT-220, MX300 or MT500 Handie-Talkie portable radio in a Mobile enviroment to boost the signal. With the string of RF transistors and heatsink, it was a MICOR design that was developed from the Plantation, Florida SP Subscriber Engineering Department for originally the Public Safety Market. The MICOR Series had 60, 90, 100 and 110 Watt RF Power Amplifier designs and the T/R Relays had a UHF (Female) connector on one end and pair of RCA (Jacks) connectors on the opposite end. The Relay coil was Black rectangular plastic with the metal relay body inserted through the coil.
I'm a bit surprised that there's only a -3 dB attenuator feeding the first RF M9622 transistor as the stage only requires 1 Watt of RF drive to the Control Stage. Motorola Parts Department does not supply any more M9625 RF Transistors because they told the Purchasing Agent to tell the former Motorola Semiconductor Group to destroy the M9625 mold before making the last time buy DUH and this was during the 1990s. Another Brillaint Motorola Decision!
The Motorcycle Radio was a MCR-100 so I doubt this RF amplifier was used with that radio. Look for a VHF Micor Service Manual, perhaps on eBay for the schematics of the Power Amplifier stage. If you put this amplifier into a repeater service make sure you've got pleanty of air movement across the heatsink fins (perhaps muffin fans) otherwise you'll burn yourself and possibly decrease the lifetime of the RF devices. The Power Amp was designed for intermittent duty cycle not continuos. You will not need the RF By-Pass Relays in a repeater configuration.
Dan
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George
- Posts: 265
- Joined: Wed Apr 16, 2003 11:14 am
- What radios do you own?: X9000, HT1550XLS, MTS2000, etc
Re: Motorola N1254A Power Amp for 2M repeater info
I used this power amp with a Micor base. It was running at 25 or 30 watts out. No more than that.
This is a 60 watt power amp and like what was described before, has an attenuator in front of it.
I lifted the high side of the attenuator resistors and essentually bypassed the relays by reconfiguring the transmit and receive sides and disconnecting the coill leads.
Set the power out to 30 watts and you are set.
Just make sure you align this amp with a test set or just tune for maximum power output and minimum input current. The 60 watt PA in 150 to 162 will work just fine in amateur service. I have put out several without modification and they have run fine. Those have been on continous duty heat sinks, but I know the Mocom convertacom version will be fine.
Wake me when I need to go home.
zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz NURSE! MORE MTD Drip!!!Zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz
George
This is a 60 watt power amp and like what was described before, has an attenuator in front of it.
I lifted the high side of the attenuator resistors and essentually bypassed the relays by reconfiguring the transmit and receive sides and disconnecting the coill leads.
Set the power out to 30 watts and you are set.
Just make sure you align this amp with a test set or just tune for maximum power output and minimum input current. The 60 watt PA in 150 to 162 will work just fine in amateur service. I have put out several without modification and they have run fine. Those have been on continous duty heat sinks, but I know the Mocom convertacom version will be fine.
Wake me when I need to go home.
zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz NURSE! MORE MTD Drip!!!Zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz
George
Re: Motorola N1254A Power Amp for 2M repeater info
Tnx for your input. I have a Mocom70 manual (1972) and a Micor manual (1975) thay don't use the same final board or transistors. That's not my issue here.
What I'm specifically looking for is the schematic on the Input attenuator & RF sense keying PC board, NLD7141A, so I can enable/disable the amplifier from the repeater controller. This input RF sense keying board would not normally be used in a base station or a mobile, so it's a little different animal. I know I can bypass this board & the relays, but it is VERY convenient to be able to turn on & off (bypass) the Amplifier via the remote controller to check for desense, range tests, Amplifier gain verify, etc. It's nice to be at home and be able to change the output power from 5 Watts to 50 Watts and verify the 10 dB change with my R2200 station monitor. I think you get the picture. I can do this now with the amplifier I'm now using but the N1254A seems to have a cleaner noise spectrum and a better power output control system. Thus, I would like to get a schematic of the RF sense keying board without having to reverse engineer it - Trying the easy way 1st - get a schematic.
I'd also like to see the specific schematic of the power controller section to see if I could utilize the temperature sensor to activate an external heat sink fan. I don't like to run a fan continously as they tend to fail after a few months. Default case is to key a 12 Volt heat sink fan only on
transmit.
BTW, I still have a 110W Micor T73RTN-3100 interfaced to the "infamous" GLB synthesizer. This radio has the stock Motorola 136-150 range parts and preamp. Puts "fire" up the coax in the mobile - unfortunately, it also keeps tearing up my alternator belts.
George
WA2VNV
What I'm specifically looking for is the schematic on the Input attenuator & RF sense keying PC board, NLD7141A, so I can enable/disable the amplifier from the repeater controller. This input RF sense keying board would not normally be used in a base station or a mobile, so it's a little different animal. I know I can bypass this board & the relays, but it is VERY convenient to be able to turn on & off (bypass) the Amplifier via the remote controller to check for desense, range tests, Amplifier gain verify, etc. It's nice to be at home and be able to change the output power from 5 Watts to 50 Watts and verify the 10 dB change with my R2200 station monitor. I think you get the picture. I can do this now with the amplifier I'm now using but the N1254A seems to have a cleaner noise spectrum and a better power output control system. Thus, I would like to get a schematic of the RF sense keying board without having to reverse engineer it - Trying the easy way 1st - get a schematic.
I'd also like to see the specific schematic of the power controller section to see if I could utilize the temperature sensor to activate an external heat sink fan. I don't like to run a fan continously as they tend to fail after a few months. Default case is to key a 12 Volt heat sink fan only on
transmit.
BTW, I still have a 110W Micor T73RTN-3100 interfaced to the "infamous" GLB synthesizer. This radio has the stock Motorola 136-150 range parts and preamp. Puts "fire" up the coax in the mobile - unfortunately, it also keeps tearing up my alternator belts.
George
WA2VNV