| Author |
Message |
    
Flybynight
| | Posted on Monday, July 07, 2003 - 1:58 am: | 
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Would like to know if and how a cobra 89xlr with the D858 PLL could be modified for upper's and lower's.Any info would be greatly appreciated. |
Kc0gxz
| | Posted on Tuesday, July 08, 2003 - 1:29 pm: |
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Flybynight
Yes, they can be modified but it is rarely done because, even though they have the 858 chip, they do not have the same frequency coverage as the sideband radio did with the same chip.
They would go up a few channels above 40 but it's 98% sideband up there anyways. So what's the point? Also, there will be many repeated channels. Too many to make it worth the bother.
The 858 chip in AM radios were very limited as far as frequencies go. But in the SSB radios, it was "The King" until the FCC put the kabosh on it. The 8719 chips in todays sideband CBs are a joke as compared to what the the old 858 chips could do. Like everything else, all good things come to an end after the government gets involved.
Jeff, kc0gxz. |
Flybynight
| | Posted on Tuesday, July 08, 2003 - 7:36 pm: |
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Thank's Kc0gxz.I was needing a few lower channel's mainly 26.905.That's pretty much the local channel out here.Thank's for the info! |
Kc0gxz
| | Posted on Wednesday, July 09, 2003 - 1:33 pm: |
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Flybynight
Well, wait a minute now. Let me check into this again. I believe it will go down at least that far. I'll get back to you either tonite or tomorrow about that.
Jeff, kc0gxz. |
Kc0gxz
| | Posted on Wednesday, July 09, 2003 - 4:26 pm: |
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Flybynight
I finally was able to fine the mod. I had to do a little digging in my archives for this one.
Here is the frequency modification you asked for. Good luck with it.
1- Find pin 19 on the PLL chip on the foil side of the circuit board. It will be a grounded pin in the near center of the row of pins.
2- Isolate this pin by making a cut in the foil so it is no longer grounded and install a small 1/4 watt 4.7K ohm mini resistor across this cut.
3- Mount a SPDT (center off) mini toggle switch in a convenient location on the front of the radio. (Lower front panel works for me)
4- Solder a wire from the center pole of the switch to pin 19.
5- Next, solder a wire from the top pole of the switch to board ground.
6- Last, solder a wire from the bottom pole of the switch to pin 21 which is a constant 5 volt source. Now you're done.
--------------------------------------------------
When the switch is in the center position, you will have the normal channels 1-40.
In the UP position, you will have some frequencies above channel 40.
In the DOWN position, it will only go 9 channels under channel one.
If everything was done right and there was no smoke or funny smell, you should be able to find the frequency you are looking for on channel 30 with the switch in the DOWN position.
You're going to need a frequency counter to figure out where you are on the radio. Or, I guess I could make you up a frequency chart if need be.
This modification is far easier to do than I described it. If any problems come up, you may Email me at .
73s
Jeff, kc0gxz. |
Flybynight
| | Posted on Thursday, July 10, 2003 - 11:05 am: |
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Thank's Jeff,done the trick!73's
Danny
KF4DXF |
Flybynight
| | Posted on Thursday, July 10, 2003 - 11:40 am: |
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Jeff,i spoke too soon.I counted the pins wrong on the chip.The only pins that go to ground on the 89xlr are pins 20,22,and 23.Pin 19 look's like it's going to the ribbon cable cable that goes to the channel selector.Pins 7,12,and 20 are tied together.
Sorry for the previous post.I know this radio can be converted.I did one years ago.Had the mod for it but my place burned down and i lost of my book's,note's,and test equimpment a while back.I guess the mind is the first to go cause i cant remember the mod for it. |
Kc0gxz
| | Posted on Thursday, July 10, 2003 - 5:04 pm: |
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Flybynight
Are you positive as to which one is number 19?
Jeff, kc0gxz. |
Kc0gxz
| | Posted on Thursday, July 10, 2003 - 6:28 pm: |
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Flybynight
I came across another way to do this PLL mod.If the first one doesn't work, then try this one.
This second one is almost identical to the first one I gave you but a different switch is used and TWO cuts are made on "PIN 20" instead of pin 19.
An x-acto knife works best for making foil cuts. After the cuts are made, do a continuity check from pin 20 to ground and make sure there is no connection to ground.
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1- Find pin 20 on the PLL chip on the foil side of the circuit board. It will be a grounded pin in the near center of the row of pins.
2- Isolate this pin by making a small cut on BOTH SIDES OF PIN 20 in the foil so it is no longer grounded.
3- Next, solder a small 1/4 watt 4.7K ohm mini resistor from pin 20 back to ground.
3- Mount a SPST mini toggle switch in a convenient location on the front of the radio.
4- Solder a wire from the center pole of the switch to pin 20.
5- Next, solder a wire from the top pole of the switch to board ground.
6- Last, solder a wire from the bottom pole of the switch to pin 21 which is a constant 5 volt source.
------------------------------------------------
Hopefully, this is what you can expect for low frequencies.
27= 26.875
28= 26.885
29= 26.895
30= 26.905
31= 26.915
32= 26.925
33= 26.935
34= 26.945
35= 26.955
Evidently there are two versions of this mod. Obviously it depends on what radio you are playing with.
I am very sorry for the mixup.
Jeff, kc0gxz. |
Flybynight
| | Posted on Monday, July 14, 2003 - 6:38 pm: |
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Jeff,
I done the mod as you specified.The result's were;
Ch1=27.765
Ch2=27.775
Ch3=27.785
Ch4=27.805
Ch5=27.815
Ch6-Ch9 would not lock in,all other channel's were normal.
Apparently this mod would only provide upper channel's.Back to the drawing board.Thank's again for the info Jeff!
Danny |
Kc0gxz
| | Posted on Wednesday, July 16, 2003 - 2:27 am: |
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Flybynight
Which mod version did you go with?
Pin 19 or pin 20 version?
Jeff, kc0gxz. |
Flybynight
| | Posted on Wednesday, July 16, 2003 - 10:00 am: |
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Jeff,i done the pin 20 mod. |
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