Ramsey Electronics FTR-146
Finished! ...In Only 20 Years!
This started as a posting in AntiqueRadios.com (the ARF)'for sale' forum. 'Johnnysan' posted this for $35. I mulled it over. Even if it didn't work, it'd be worth that much for the parts and the enclosure. So, I bought this in early July and it was shipped.
When I opened the box, it was like a time capsule. The original owner had almost completed the transceiver,
and had even put in the 146.520 Mhz Simplex frequency into the pin-diode array. The builder had extensive
notes throughout the assembly manual, even noting items that had been soldered backward and indicating
Whoever built it, poor fella, I suppose he didn't have a frequency counter to do the alignment, as he had stopped at that point. He finished assembly and never aligned it!
(Or, perhaps more likely he gave up once decent synthesized 2-meter mobile and hand-helds became cheap and popular around this time.)
Remarkably, his notes marked "Rec'd July 15, 1991" on the cover of the manual. I picked it up and started rechecking most of the assembly steps on July 17, 2011. I finished the alignment process on July 21, 2011 - just about 20 years later.
- This was just a swell kit. Even though it was Revision "F", apparently a pre-final version, and hardly marketed, instructions are very thorough.
- The released version of this was an entirely different circuit, and called FX-146.
- Transmit output, as best as I can measure, is just under 5 watts.
- Instruction manual was by Dan F. Onley, K4ZRA; references in later manuals were removed. K4ZRA is no longer a valid callsign.
- Certainly it was an expensive kit, as there are a lot of parts and the parts are good quality. Seperate +/- 600 Khz Crystal Oscillator circuits are used, which more than 2X the cost in parts and board complexity.
- I think for cost reasons, the later FX-146 kit (1995 and after?) has a much simpler circuit with fewer parts. Repeater Offset (+/- 600 Khz) is calculated into the PLL directly.
- Outside the Frequency Synthesis, all other aspects of the FX-146 appear to be the same as the FTR-146 - Speaker output (LM380), Packet DIN 5 Jack, Microphone Amplifier. Even the final Driver (2n3866 / MRF237) is the same.
- I've posted the "Revision 'F'" Schematic here, in case it's a help to anyone with one of these.
- Pinouts for the DIN 5 Connector are incorrect - an Addendum Sheet lays out the correct numbering.
Build Notes / Mods
It's unlikely another one of these will be found, but here are some mods and comments. Some of these mods were culled from Internet sources and refer to the FTR-146 / FX-146 and the FX-440.
- I replaced the RED Transmit LED (D25) with a Bi-Color, Red-Green LED. This is very easy to do. TX LED is driven by +12 TX line. This I just connected to the RED side of the Bi-Color LED. I provided an additional 1K Resistor jumpered from the +12 RCV line (After Q24) and fed this to the GREEN side of the Bi-Color LED. GREEN on RX / RED on TX. This provides a sort of 'power indicator', since RX is active if power is on.
- As suggested in the assembly instructions, I've brought out the EXT Audio jumper to the back with an SPDT switch. For APRS Use, it stays switched to 'Speaker'
- Even though Final Transistor MRF-237 is soldered to the board around it's rim, making the large circuit board ground it's heat-sink, I gave it and the 2N3866 Driver each a round, finned TO-39 Heat Sink for additional cooling.
- (TODO) C-101 (.01uf) possibly restricts/attenuates AFSK input audio and should be changed to 0.1uf.
- (TODO) Harsh Squelch - Break Land pattern from Q14 to Pin 1 of U3 (LM380). Bridge with 1K resistor. Parallel C88 (.01) with 2.2uf. Should smooth Squelch
- Problems with Crystal aging created a need to parallel Y2 (RX Oscillator) and Y3 (Simplex Oscillator) with additional capacitance in order to bring them in-line with the Spec'ed 44.1000 Mhz (Y2), and 47.6667 (Y3). I believe on the order of 8 pf to 12 pf was used for each.
- Crystals for +600 and -600 Crystals Y4 and Y6 were also out of tolerance, but since my plans only include Simplex anyway (and there is no Tone/Squelch Facility on-board), I didn't bother adjusting them.
- Fuse F1 was replaced with a proper Pig-tailed 1 Amp Slow-Blo Fuse.
DIN 5 Connector on the back of the FTR-146 pinouts are as follows:
FTR-146 Pinout (Revision "E") J3 Pin 1 - MIC (Audio IN) Pin 2 - Ground Pin 3 - Ext PTT Pin 4 - Speaker/DISC (Audio OUT) Pin 5 - +12V Layout (looking at J3) from Left to Right: Pins: 3, 5, 2, 4, 1 Shield is also Ground. For TinyTrak 3 / 4: FTR-146 DIN5 (J3) to TT3 DB9 (J1) DIN 5 - DB 9 1 - 1 Mic IN / TT3 Audio Out 2 - 6 Ground 3 - 3 PTT 4 - 5 Speaker/Discriminator / TT3 Audio IN 5 - 7 +12V
As of February, 2012, I'm planning to be use this tranceiver on 144.390 Mhz as an APRS Weather Station. APRS Fixed Location packets have been sent successfully with a TinyTrak 3 on the Packet Input, and using a Twin-Lead J-Pole as an antenna.