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Expo 100 expander channel kits info needed

Discussion in 'General CB Services Discussion' started by dss56, Oct 10, 2018.

  1. dss56

    dss56 Member

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    I'm looking for the Expo channel expander kit crystal codes that are on the Xtals.
    I have an A Kit with 2 xtals 1 has a T and the other a J on xtals nothing else.

    Other kit is a Expo S+ and it has S X on xtal only single xtal on this board.

    I know what radios these are for but seems when made they coded the xtals and did not put the frequency of said xtal on them.

    Would anyone know the code to the xtals that was used for all the Expo 100 kits


     

  2. nomadradio

    nomadradio Analog Retentive

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    Never made a record of the letter codes.

    The A kit uses a crystal originally cut for 14.920 MHz to take the radio down 44 channels.

    NOT 45 channels like an export radio's band selector. These kits originated in the late 1970s before export radios with multiple bands became popular. The kit's lower band would put channel 1 onto the "40" position of the selector. Same deal for the upper channels, a 15.800 MHz crystal gave you channel 40 with the selector set to channel 1 on the upper band.


    When multi-band radios took over the market, they didn't order new crystals, they just added capacitors to the oscillator circuit. One in parallel with the lower crystal to pull it down one whole channel, and a capacitor in series with the upper-channel crystal to move it up one channel.

    Just one problem. This reduces the feedback through the crystal, and reduces the output level of the kit. We got in the habit of removing the disc cap in parallel with the lower crystal, and putting a 4.7 uH RF choke in series with the crystal to bring the frequency down one channel. The upper crystal doesn't seem to have this problem in the newer "plus/minus 45 channel" kits.

    To go down 45 channels in a radio like the Cobra 29, you want 14.910 MHz, and 15.810 for uppers.

    The lower-band crystal in a "C" kit is 11.1758 MHz, the upper is 11.4758 MHz. This kit fits radios that use a 11.325 MHz factory crystal.

    The other kit for radios that use a 11.125 MHz crystal like Uniden Washington use 11.2595 MHz for the upper band. Can't seem to find the lower-band frequency. Probably 10.9725 MHz. I think this is the "B" kit.

    And the "N" kit is just the "A" with a clarifier circuit and a green wire that connects to the radio's clarifier control.

    The A kit is for AM-only radios, the N is for SSB radios.

    73
     
  3. Dmans

    Dmans Well-Known Member

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    dss56,
    I would imagine that the crystal cases were not embossed with the frequency used for a reason. If you knew the crystal necessary, purchasing the kit wouldn't be necessary-and thats bad for business.
    When these kits came out, there were many "crystal cutters" in business and would make small quantities per request. And prices were cheap!
    Ah, the good ol' days!

    73's
    David
     
  4. dss56

    dss56 Member

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    Dmans

    Yes on the xtals price back when. I just got a price of $4600.00 for 250 xtals to be made about $30.00 a xtal. I know what freq. xtal should be in the Expo a and a+ and also the expo S- and S+ kits but some other kits would be nice to have that list to cross reference the Letters to xtals freq in the Expo 100 Kits
     
  5. nomadradio

    nomadradio Analog Retentive

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    Have you tried these folks?

    https://www.transko.com/crystal.html

    Says they'll still make HC-49 crystals.

    Gotta figure they would sell through a manufacturer's rep, with a sizeable minimum order.

    Haven't dug any deeper.

    73
     
  6. TheRealPorkchop

    TheRealPorkchop Certified Sith Pimp

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    Not to hi-jack the thread but I have a question relating to this...

    Nomad mentions Cobra, if you wanted a Cobra to cover 26.515 to 26.955 instead of the regular CB band, could you just change the 10.240 to another crystal? If so, which one?

    Sorry to hi-jack if that’s what this question is, and if so, please just send me a PM instead of replying here. Thanks.
     
  7. Dmans

    Dmans Well-Known Member

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    TheRealPorkchop,
    I believe that the 10.240 necessary for proper PLL operation by design of the PLL manufacturer. It is where the 455hz 2nd receive mixer signal is derived (if used) and is what the PLL uses as a devisor/multiplier for "N Code" steps. That 10.240 signal is also "injected" into the transmit mixer and "mixed" with the x 3 tripled frequency "created" by the PLL via channel switch position. Injection of a different frequency into the VCO/Mixer (upstream of the transmit mixer) is what is changed with a "channel kit". This "direct injection" would take the place of the onboard PLL x 3 tripler signal.

    Without the exact 10.240 crystal, the PLL goes on strike! At least I think so anyway. (n)

    73's
    David
     
  8. TheRealPorkchop

    TheRealPorkchop Certified Sith Pimp

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    I believe you’re right, no doubt you are now that I think about it. That’d be why you look for that 10.240 at pin 4 I believe. I was just thinking out to myself while reading this thread. One of those brain fart ideas to kill time.
     
    Dmans likes this.
  9. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Both of you are correct Its the "error correction" between the Xtal you use in the PLL loop (your replacement 10.240) and the tripler.

    The following deals with PLL's that use single reference Xtals - the all-in ones that many Expo kits used to synthesize - but only if you have a working "tripler / Exciter" the PLL can parse with...

    Firstly the radio needs the right PLL - if you ever see a trimmer cap on the 10.240 Xtal - and heard the radio thru a known good and tuned radio on SSB mode for the same channel - you'll hear the heterodyne as they BFO while you turn the trimmer in that radio as you TX and hear it thru the other one..

    Now, you can say to yourself - if this is possible - can I do more. Well, yes, but before you break out your Trident and try to harness lightning - remember there are limits - so put out the St. Elmos' Fire, Put Down that lightning rod of a Trident - and step back inside before Mother Nature decides to take you up on that offer - whether you're ready or not...

    There is also the issue of generating the proper IF image - if you say use a 10.240 Crystal filter and the radio is using a 10.690 Xtal - you have to remove the 10.240 RX crystal and sub in a RESONATOR.

    That's these little guys...
    CeramicFilter.jpg

    The above is a filter but not as "tight" as a Crystal one - and note the stamped frequency 10.75 - so it means it can be used in an IF strip of 10.7. IT also has a BANDWIDTH product - it peaks at 10.7 but it can let 10.4 ~10.3 thru - it's a lot quieter receiver but it can work...

    The 455kHz - you would have an UPPER image from the PLL's switching in the 2nd cap to lower or parse down the 2nd IF to 455kHz...

    There is also a PLL or two that is programmed to automatically shift 455kHz in one mode or the other - so you know...the 455kHz shift is generated inside the PLL so the above may not apply to you...

    If you tried to go outside too far, the error between the free-running tripler and it's method to send the PLL a reference frequency is too great - and the PLL simply goes into out of lock condition. There is a low-pass filter with values you'd have to change to make it so...

    But in a "exciter" running radio - the free running is different - you just have to use an Xtal that is close to what you already have - it just needs to make the IF part 44kHz shift. So your Xtal doesn't have to be all that much different - it's almost like you'd need a cruddy Xtal to make this work.

    Now, if you were to use - say a 10.695 or 10.7 - you can get away with it - but your frequencies would be way off the channel plan. I've had several radios come thru with people thinking "instant oddballs" using a 10.695 crystal - and yes you would have oddballs but only upper range and you'd have to have someone else with a similar setup to use this method.- at least to communicate - It's possible and its' been done - I've had to undo those "Monsters" and the users are not kind to their radios' - it's a butcher job.

    The Realistic one I had an S-2 for was for lowers, and it REPLACED the 10.240. And it was designed to be switchable - one Xtal (10.240 for standard 40) and the other Xtal for the lowers.

    Now one thing I did mention and I'll mention again is the "divisor" frequency that is your typical 10kHz spread between channels - it's different (no you're not changing IT - the frequencies it generates will be different (doh!) but also in spacing it thinks is correct - in LOWER frequencies the bandplan offsets changes to longer counts for the 10kHz fewer counts (in the same timing frame) means longer term for divide that shift is downward up to 2kHz lower as you approach Channel 1 (the lowest frequency) Its' slower. But - in higher/uppers the bandplan "shrinks" by as much 2kHz at the ends of the band it works in (channel 40 - or the highest frequency). In uppers it's speeded up. Simply due to the timing function the PLL looks at - its' not smart - but it looks at a deviation requirement - that being the other loop to obtain your first mixer Frequency (about 16~17MHz). So if you have a typical 17MHz oscillator "exciter" for say a Cobra 19 plus, your 10.240 Xtal for Lowers is just a hair under 10 MHz (about 9.7 to 9.8MHz) while the uppers is about 10.55 - why not the 44kHz? Because of the way the PLL divides down the loop frequency - your N count - and the Exciter frequency that is pre-set and doesn't change its' "window". You are still stuck with the 16~17MHz oscillator that the exciter is. Although - the results of the shift AFFECT the "window" because of the Xtal is slower (as in lowers) - so you don't want to go out of range - just enough deviation from 10.240 to obtain the channel 40 below Channel 1 and the Channel 1 below the 40 of that.

    I posted the above in reference to the Divider counter in the PLL - it uses the 10.240 timebase as the clock in which to reference the count itself in the F-Input pin from the VCO main oscillator - so as you go slower - the VCO tries to do the same - again all tied back to the 10.240 reference. It needs to know where to start and it's programmed to use that to do so.

    Now in a Galaxy - that's a whole other ballgame.

    (the above is a rough draft - subject to correction as I locate more of my notes...)
     
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  10. nomadradio

    nomadradio Analog Retentive

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    The 10.24 crystal ultimately controls the spacing between channels. A higher-frequency crystal puts them closer together than 10 kHz. A lower-frequency crystal will space them farther apart.

    The 'channel-proof' chips will now have a different spacing between channels if you change the frequency of the 10.24 crystal. Extra channels aren't so useful if they won't line up with the other radios' channel frequencies.

    And, as Andy points out above, your transmit and receive frequencies will no longer line up to each other. Changing the 10.24 crystal in your Cobra 21 or 25 will get you extra channels, but they won't be too useful if the radio transmits and receives each on a different frequency.

    The only real cure is a whole new PLL chip, or a plug-in module that takes the place of the factory PLL.

    Just one problem. That sort of solution costs as much or more than the radio. See http://funkservice.at/cb-radio.htm

    If all you had to do is change the 10.24 crystal to get a good result, those crystals would have flooded the market when radios using the TC9106 and 7122 first showed up decades ago. This was the incentive to design a PLL for legal CB radios this way. Doesn't make the radio totally channel proof, just too expensive to modify.

    73
     
    #10 nomadradio, Oct 12, 2018
    Last edited: Oct 12, 2018
  11. kopcicle

    kopcicle Well-Known Member

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  12. kopcicle

    kopcicle Well-Known Member

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    this


    ...past your bed time bonzo :)
     
  13. TheRealPorkchop

    TheRealPorkchop Certified Sith Pimp

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    So we’re back to the expo kit thing then, it seems. It was just a wandering thought in my mind to be able to just shift the radio down one band and leave it there. Oh well.

    Andy and Nomad, thank you. Kopcicle, maths hurts’s my head. Haha.
     
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