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I'm curious as to why the channel selector runs
1,2,3,4,5,6,A,B,C,D,E,F. Why numerals 1-6, and then letters A-F? Raymond- I had the HR-2A back in the 70s. It was one of the early solid-state Two Meter rigs. I don't think I have the exact information you need, but thought I would pass along some recollections. 1. The transmit crystals are in the 6 MHz range. The later HR-2B model had a multiplier chain with different multiplier ratios, using 8 MHz crystals in an attempt to increase drive. It seems that there is an instability that causes out-of-band spurs when drive isn't high enough. Unfortunately there is also an SWR protection circuit that reduces drive if SWR is high. Naturally the out-of-band spurs will have higher SWR when loaded by an antenna tuned to Two Meters, but not when loaded by a dummy load in the shop! (This isn't normally a problem with the HR-2, but is extremely serious with the Six Meter version, HR-6.) 2. There was a modification kit, maybe offered by another company, that added six additional crystal sockets and trimmer capacitors for the transmitter, to enable the full twelve channel transmit capability. The channel selector switch already has the terminals for the additional crystals. 3. One weak component is the channel selector switch. It develops bad contacts after much use. I recall using mine almost like a scanner, and wore out two sets of switches. The switch wafers can be replaced without replacing the other mechanical switch components, although disassembly is necessary. 4. The circuit boards are very similar or nearly identical to an early version of the Regency BTH-201 commercial VHF High-Band transceiver. I believe the commercial version may have used a higher-powered transistor. It used push-buttons rather than a rotary switch for versions with more than one frequency. (The HR-6 is similar to the commercial BTL-301.) 5. Receiver sensitivity is not very good by today's standards. Back then, there were at least a couple dual-gate mosfet preamplifier kits offered by other companies. They increased sensitivity from around 0.35 microvolts to around 0.2. Of course the radio becomes more susceptible to intermodulation interference when the preamp is used. 6. As far as I can tell, the company that was Regency was split, with the scanner portion going to Uniden and the commercial two-way radio portion becoming RELM, located in Melbourne, Florida. I doubt they can provide much information about the HR-2A, but it might still be possible to obtain service information about the commercial BTH (and BTL) series transceivers. 7. In recent years I have heard of several HR-2/2A/2B/2S/212 radios being used on packet. They apparently work OK in that application. The only problem I can think of, is knocking the audio level down far enough to keep from over-driving the microphone circuit. The HR-2/2A/2B/2S/212/6 used a high impedance ceramic microphone element. I spent a LOT of hours working on the HR-2A (and HR-6). If you have any specific questions, I might be able to recall something that would help. 73, Fred, K4DII |
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