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KL reference 12MHz to 10MHz

9 December, 2015 - Reading time: 4 minutes

The KL series uses a GFS-210W TCXO as a standard reference which operates at 12MHz. There is a "high-stability" option - a GPS-210X which locks with a frequency stability of +/-0.0002%. 

However we want to know if the radio will work with a 10MHz reference instead, such as a GPSDO for extra high stability. The process for calculating the correct Transmit and Receive Data is well documented in Section 6 of the manual. Most use the software UNIPROG to do this automatically for them.

With the help of Dion 7DB we set about this task. We used a KL70 for the example, as this is the radio we will be trying to lock most likely. As per section 6.3.5, the reference frequency needs to be changed to 625KHz as we are now using a 10MHz oscillator (10/16). We now calculate the Reference Division Rate to be 50 as the KL channel spacing when converting a KL70 to 6m needs to be 12.5KHz (625KHz/12.5KHz). Dion found some inconsistencies with channel data calculated with UNIPROG, and selecting 12.5KHz seems to fix these. UNIPROG also does not allow a 625KHz reference.

Section 6 of the manual states how to do all this manually, but we "cheated" and used an online calculator for the MC145146. The prescaler division is 64.

We are after the hex values. The values need to be reversed as explained in the A-D conversion list of section 6.3.4. Therefore our above answers in our example are: 80340230. This answer is for the exciter EPROM. The RX VCO frequency is plus 21.6MHz (1st IF - or if it was 52.700MHz, you would need to put into the calculator 74300KHz). We only use one channel in the KL for a repeater generally, so it makes it easy. The EPROM address is 80828F81818E8180. More information on channelling is in section 6.3.1.

UNIPROG was made to generate a standard RX/TX file, then this was modified manually. To confirm that the calculator was correct, Dion made a spreadsheet up to do the calculations, and I also confirmed what UNIPROG had calculated to what the MC145146 calculator said. They all came up with the same results so we were confident it was right.


The TBN (or RBN) file generated by UNIPROG is then opened edited with the correct values.

Burned the EPROM, chucked it into the KL.... I removed the 12MHz TCXO and injected the RF from a HP8924C test set to Pin 1 of IC106 (frequency divider). I had no idea on levels, so I started at 0dBm. Seemed like a good place to start.

Looks like it worked....

The PLL is locking at 96.6MHz as this was a receiver on 75MHz (75 + 21.6 = 96.6). I reduced the 10MHz level and it falls out of lock around -9dBm.  

Next test is to try to plug in the exciter and make sure that works... it should. What is all this in aid of? Having a play with a Synchronous/Voting network.

Thanks to Dion VK7DB again, otherwise I'd have no idea. 

KL Manuals: