| Author |
Message |
    
Rippedradio
| | Posted on Tuesday, July 15, 2003 - 6:48 am: | 
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hello everyone, i was wondering if anyone has had any luck with channeling an rec86345 pll?? i have one in a realistic 448 i have and need a channel mod??? also would an h expo expander kit work in this radio??? thanks for any info!! chris |
Viking
| | Posted on Tuesday, July 15, 2003 - 11:12 am: |
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I haven't done it but it looks like you just add a crystal switch. There's an Expander 160 kit that'll work. Not sure about the H expo. |
Rippedradio
| | Posted on Tuesday, July 15, 2003 - 4:55 pm: |
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ok need to build a crystal switch??? anyone??? |
2600
| | Posted on Thursday, July 17, 2003 - 5:27 pm: |
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Aww, man that is an ancient design on the inside. The PLL chip is an "unlocked" type, approved by the FCC before PLL chips were required to have extra frequencies "locked out" inside the chip.
It uses an old trick found in 23-channel SSB radios that saved them money on the "carrier" crystal (and crystal filter) that feeds from the SSB modulator and into the receiver. The PLL has TWO vco stages, one for AM and USB, the other for LSB only. Getting the VCO adjustment to 'lock in' on the extra frequencies is at least twice the trouble as on a radio with only one VCO stage. Back then, nearly every other factory just used a separate carrier crystal, one for USB and one for LSB. These guys did it the "tricky" way. Re-peaking it to be more "broadbanded" is also twice the effort, more or less.
The chip runs from 5 Volts, feeding into pin 2. A wire from pin 2, into a 1k resistor, then into a switch, and out of the switch to pin 11 will get you channels 28-59 on channel NUMBERS 1-27. The switch will not change anything on 28 to 40.
Getting any more channels than that involves molesting pins 9 AND 10 at the same time, along with pin 11. Gets involved.
The REC86345 is a primitive CMOS-technology chip that does NOT have any input protection on the channel input pins. Any AC leakage from the tip of an UNGROUNDED (two-wire AC cord) soldering iron tip into the chip will cripple or kill it. Unhooking EVERYTHING from the radio, including ground connections can prevent that. Static charges on your hand or tools that are WAY too small for your skin to feel can clobber it, too, while the pin is unhooked from the rest of the circuit during modification.
Either a VERY steady hand on the soldering iron, or a spare PLL chip might be wise before tearing too deeply into it.
Best I can tell, the reason there never was an EXPO 100 kit is this: The EXPO design requires that a SINGLE crystal in the radio control the PLL channel frequency for ALL modes, AM and USB/LSB. This one has a separate PLL crystal for AM and one for SSB. You would have to switch BOTH of them in pairs at a time, two crystals for each new "band". I don't think any of Lou Franklin's "Expander 160" crystal-switch kits will do that trick. The "EXPO" kits sure won't, the way they are designed.
At $20 or more apiece to have crystals custom-made these days, four of them (to get 40 above and 40 below) will cost you a lot more dollars per channel than some new radios that come with 5 or 6 bands. The switch wiring will be pretty involved, even if you're pretty adept with this stuff.
73 |
Kc0gxz
| | Posted on Friday, July 18, 2003 - 1:23 pm: |
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2600.
Man are you good.
And sometimes scary too.
But no one can ever say that you're not thorough.
You sure have my respect.
Jeff, kc0gxz. |
Rippedradio
| | Posted on Saturday, July 19, 2003 - 2:22 am: |
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2600 is the man but i didn't want to hear bad news about this chip!! oh well maybe i'll just do the one switch and a couple above 40! thanks 2600 73's chris |
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