EM 10.5-10.68GHz microwave modules - Mods to use on 10.368GHz

This started out as what appeared to be an ambitious project but it is so far straightforward. I was fortunate enough to be given the chance to modify a few sets of the FM Tx and Rx boxes for ham use. It transpires that just about every set of modules is the same but different! They are all broadly similar but subtle variations exist so if you have some of these modules and yours don't match exactly then this shouldn't deter you.

Here's what I have done so far:

1. Used a cheap logic analyser to check what was being loaded into the PLL chip by the micro. 
2. Inserted my own micro to control the 2.5GHz PLL
3. Achieved lock on several TX and RX units

PLL chip
The units I modified had the LM2326 PLL chip. It has a different data format than the LM2325 chip I saw on the units I have not yet modified.  In a few words the 2.5GHz PLL uses a 250KHz reference frequency. It is multiplied by 4 on both tx and rx units. On the tx units it is mixed with the IF, presently 69MHz but I am modifying this to use a 144MHz IF on tx. On Rx the multiplied signal is mixed with a 692MHz oscillator down to a 140MHz IF. At present I'm leaving this oscillator alone since the saw filter appears wide enough to be serviceable with a 2m IF.

Micro
Once I knew what the existing data stream was it was relatively simple to work out the data stream needed to load the PLL chip with data to put it on the desired frequency. See the chart below for an overview. I used an ATTINY13 and a few lines of assembly to do this.

Achieving lock.
This should be straightforward but sometimes the soldering proves difficult due to the heatsinking the board has. I moved the short until the PLL locked with around 4V-6V on the tuning voltage link.

I'll post some more pics soon but for now the following may prove useful.

Regards
Richard

An unmodified receiver showing what is required to modify for 10.368GHz use

Details of how the IF signal on Tx gets to the mixer diode for up-conversion to 10GHz

Data loaded into PLL chips to shift to 10.368GHz