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Kenwood & EF Johnson Forum - For discussion of land mobile radio products manufactured by Kenwood or EF Johnson. For discussion of Kenwood Amateur Radio Equipment, please use the Amateur Radio Equipment forum.

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Old 08-23-2011, 11:54 AM
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Default TK 890 450-470 split

Anyone have any luck getting a TK 890 to go down to 442.000 and still able to use up to 468.000? My radio appears to un-lock around 446.000. I want to be able to cover some repeaters around 442 and the GMRS stuff at 467-468. I have seen several posts where people can get the radio to go down, but I assume the top end of the frequency range comes down at well?

Tim
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Old 08-24-2011, 10:27 PM
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Rated spec is 20 MHz for that radio but we all know they will lock above and below that but to what extent is kinda radio dependent. You're looking for about a 26 MHz spread and that seems reasonable.

The VCO can be adjusted fairly easy with a volt meter. You just program your highest and lowest frequencies, monitor the VCO steering line voltage, check high and low (both TX and RX) and see if the voltage stays within specs. There are tweekers for both TX and RX to achieve this. And yes, if you lower your VCO's range, you will lose the top freqs, the VCO can swing only so far.

Now for performance. The TX might do alright down at 442 (with a slight reduction of power), but check the RX down there and see if seems deaf. If so, the preselector will need to be aligned to your new freq spread and this will require some test equipment.

Last edited by ramal121; 08-24-2011 at 10:32 PM..
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Old 08-25-2011, 10:52 PM
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Which pot is for the vco adjustment on these. I am also trying to do the same.

Frank
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Old 08-26-2011, 8:38 AM
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Quote:
Originally Posted by n3obl View Post
Which pot is for the vco adjustment on these. I am also trying to do the same.

Frank
Inside that black circle is the CV point to test the voltage. Underneath the cover to the left is the pot to adjust the VCO. I used the very top(furthest towards the rear of the radio) top to make my adjustments. The CV point is used to check the voltage. This is all on the top side of the radio.

Tim K.
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Old 08-27-2011, 1:43 AM
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thanks for the pic. I assume the adjustments are under that piece of copper foil?

Frank
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Old 08-27-2011, 6:40 AM
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Yes. Remove the 6-7 screws holding the plate to the board and lift the plate off to access the adjustment pots.
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Old 05-27-2013, 11:30 PM
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Why not just peel the foil back, adjust, and put it back on?

By the way, I did an amateur band conversion on a TK-890 today and it worked fine. Details in my blog:

Wirelessness!: TK-890 Amateur Radio Mod
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