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Author Topic: TK-880 adjusting PLL for ham band  (Read 9224 times)
KK6RPX
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Posts: 115




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« on: July 20, 2017, 05:08:17 PM »

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

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N8EKT
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Posts: 593




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« Reply #1 on: July 21, 2017, 05:09:14 PM »

Repeater builder has the service manual for the tk-880
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KK6RPX
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Posts: 115




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« Reply #2 on: July 22, 2017, 06:54:26 AM »

I have the service manual but I am unsure of the procedure. Never done one so the above is my translation of the manual.

Thanks!
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K4JJL
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Posts: 835




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« Reply #3 on: July 24, 2017, 06:58:11 AM »

Found this on another site...

The VCO is easy. Put a voltmeter on TP-1. Select the highest frequency you have. Voltage should be 1.5V or greater. Go to the lowest frequency and TP-1 should be 8.0V or less. Adjust TX and RX VCOs separately so they fall within this range.

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KK6RPX
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« Reply #4 on: July 24, 2017, 07:36:28 AM »

Thanks. I found that as well. I have adjusted the thing as best I can and will take it to the site this week and see how it does.

Still looking for a real description of the procedure. It seems Kenwood doesn't like releasing information, keeps their techs busy I guess.
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K4JJL
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« Reply #5 on: July 24, 2017, 01:51:13 PM »

Remember that bending it out of its intended bandsplit is going to degrade performance.  The crystal filters are going to roll off a lot of your intended receive signals.  I went through that with 450-470 Motorola Spectras.  Couldn't get 20dB SINAD under -110 dBm.
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KK6RPX
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Posts: 115




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« Reply #6 on: July 24, 2017, 03:19:19 PM »

Yeah, I'm learning that. Luckily it was free. However, for this link project it may be fine anyway as long as it locks on the signal. I'll find out tomorrow.

Thanks!
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K4JJL
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« Reply #7 on: July 25, 2017, 07:59:51 AM »

Luckily it was free.

If you're dumping a ton of time into it, it's not really free.  I learned that with GE Mastr II receivers.  I had to replace a dozen caps in order to get it to even generate the IF mixing signals on top of fixing the reason it was "free".
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KK6RPX
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Posts: 115




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« Reply #8 on: July 25, 2017, 08:30:53 AM »

Well, as a new ham of only a couple of years it is also the price of tuition. So yeah, while the time spent is an issue because there are only 24 hours in a day, ehat I am learning is worth it. Doesn't mean I'm going to get more 880's for other projects though.
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KK6RPX
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« Reply #9 on: July 26, 2017, 07:02:49 AM »

Just an update: It is working fine for the repeater link. However, it's reception is weaker than one would like for general use. Luckily the two repeater sites have line of sight and good antennas so it is working and sounding great. But I wouldn't buy them for ham purposes.

Thanks!
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