TK-880-1 won't TX/RX in ham band

[madlabs]

Hi All,

I am trying to program a TK-880-1 for the ham bands. I can program it but it won't key up the transmitter or receive, it just beeps when I try to key up. I can get the TK-880 to work but the -1 won't. I'm pretty sure I'm just missing something in the software.

Thanks!

Jonathan

 

[jaspence]

That sounds like you have entered an illegal frequency. Since the lower limit is 450 MHz, it may require a radio or CPS mod to work on lower frequencies. Many commercial radios will not work out of band, and some can not be modified.

 

[madlabs]

That would be most unfortunate. The TK-880 will but these TK-880-1 won't. I'll try to dig into what the exact difference is.

Thanks!

 

[jaspence]

That could be the difference in the 880 and the 880-1. This might have been necessary, as some radios will not transmit a clean signal outside of the normal range and would not get FCC certification.

 

[KK4JUG]

Try this:

mods.dk - Modifications for radioamateur

 

[jaspence]

Most of those mods are for amateur equipment and are to the radio, not the CPS. The commercial equipment that I have experience with was all done through CPS mods without opening the radio.

 

[KK4JUG]

Oh, well. I gave it a shot.

 

[madlabs]

TK-880, adjusting PLL

Hi All,

I'm working on using a TK-880 for a link radio in the ham band. I think RX isn't locking and from what I understand (very little!) I need to adjust the PLL. While I can't seem to find a procedure guide, from what I have been able to find is that I measure the voltage on TP1 when in test mode. With the test frequency set at the lowest I'll use the voltage reading should be 1.5V in both transmit and receive, adjust T109 and T106 until within .1V. Then go to the highest frequency to be used and make sure it is less than 8 volts. Is that correct?

Thanks!

Jonathan

 

[Project25_MASTR]

There is a good article somewhere about retuning the TK-880's to go down into the ham bands, haven't seen it in a few years though. It's basically an alignment as the VCO will only lock down to about 448 MHz on average and the receiver's filtering actually notches frequencies below 450 MHz.

 

[madlabs]

Finally found (I think) T106 and T109. They are on the underside of the PCB and it looks like there are holes to reach through and adjust. Any idea what type of diddle stick is required?

JOnathan

 

[madlabs]

Been looking and I can't seem to find the article. I guess I confused things with more than one thread. The issue here is that the -1 models won't key up, they just beep.

The plain TK880 is the one that works but won't lock. I'll keep that in the other thread.

Thanks!

 

[madlabs]

Pulled apart a dead TK-862G to get to the VCO. Seems to use the smallest flathead screwdriver in the world. I'll have to get an eyeglass screwdriver and grind it down.

Anybody ever done this adjustment?

Thanks!

 

[madlabs]

It seems the two threads were merged. Not sure why, they are two different radios and two different issues.

Anyway, adjusting the VCO worked, thanks for the help! While it still has poor sensitivity it works well enough for the intended purpose of a repeater link.

Since the threads have been merged, is there a way to reset/unlock a TK-880-1?