OH2FFY

OH2FFY - CB Conversions

01/10/07


Click here to join CB2HAM
Click to join CB2HAM



This is a progressive web page , When you reach the end of the latest content you will see a 'page not found' error.

Come back later to see new additions to this section.




When I moved to Finland I brought along with me , a few high quality CB radios.
In Australia we have 2 types of cb , UHF , and 27mhz HF.
The HF ones that I brought have 12 watts output on sideband and are very well designed and made, with performance figures in the ballpark of some ham transceivers.

I used to do a lot of DXing on the CB band with many overseas contacts , and from Australia, that is a long way.

They are however generally classed as unmodifiable.
This was a deliberate action or agreement between the radio authorities and the radio manufacturers in an effort to prevent tampering and obtaining off frequency usage.

But I brought them here because I was sure that at least the components inside could be salvaged and used again in a ham band TRX.

After many months pondering over the schematics I have worked out a way of making them go down to at least 20 meters , perhaps even 40., but it is only practical to have it for one band., not switchable between bands.
This is more of a cabinet space limitation that an electronic one.

The PLL system would have to be removed and replaced with a stable VFO. (perhaps huff and puffed)
I am preparing to build a VFO now , and have drawn up the board , although it will be revised a few times yet depending upon the exact size of components.(that i don't as yet have on hand)

Additionally 3 IF style transformer cans need to be rewound for the receiver side and 4 for the transmit side.
Also the (8) bandpass and low pass filters on the output need to be rewound but they are very straight forward to do as they are air wound.

Apart from that ,its just a matter of alignment., and unlike other CB conversions to 10 meter this will preserve the full sensitivity and output power of the radio ,and not be limited in any way.


This radio (Uniden AX-144) has features like a real noise limiter (for mobile use) , real USB (not DSB) and a single conversion receiver (not direct conversion which are not single signal radios.)
Oh yeah , and a real squelch and signal meter (that might need to go if I put a digital frequency display in) and a generously powered audio amplifier.

The VFO build is coming probably within this week.
Next week should be disassembly and removal of the now unused sections of the radio.
The week after would be winding the coils.
Following that is reassembly.

Maybe , in about about a months time I will have a neat high performing QRP radio for 20 meters. (1 month! , yeah he's optimistic:-)

If I don't mess it up I will document the mods and put them up on this website , as there is no one else that has ever done it , ,, that I know of.

---------------------

The radio that I will be modifying is the Uniden AX-144.



The radio has the Uniden PC833 chassis which is common between many different radios.

PC833, PC965, PB015

Cobra 146GTL:
Midland 6001/7000 (late):
Midland 79-260:
Pearce-Simpson Super Cheetah:
President P300:
President AR-144:
President AX 144:
Realistic TRC451:
Sears 663.3810:
Uniden PC244:


This is a close up of the PLL chip, VCO , clarifier offset and USB AM and LSB offset circuitry.
Some parts of this will have to be removed, and some left.

This schematic part is from the AR-144 manual as my copy of the AX-144 one is quite fuzzy* -- They are almost identical.






*I have since located my original AX-144 schematic and this is shown in proceeding pages.