The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

Hi there

I've just returned home to Christchurch after many years in Australia

When I first moved to Aussie I's into cb for awhile then packed them away when I moved to another address within Aust. I have several Aussie am cb radions (27 Mhz?) , all about 20 years old but still in as new condition, one still even in the box !

While I've been away, the NZ govt changed things so now my old 11 channel Tait crystal controlled set is useless (yes the big thing with room for a bunch of c-cell batts inside)

I want to convert some of my Aussie sets to NZ frequencies

First I just want to convert a Uniden 40 ch am set model "Pro 520e"

If things go well then I'll also consider converting my fabulous Uniden AX 144 SSB set (liquid joy this set)

Firstly just the Pro 520e though, as this set owes me nothing, was a gift from a friend who salvaged it out of an old car It's a basic 40 ch am only set (NO sideband) but has a built in speaker and I've already rigged up a temporary mounting so it fits in the car easily

I've opened it up and it looks like it has just one crystal conveniently labelled as "Xtal 1" anyway

My understanding is that PLL type sets use just one crystal as a reference and then calculate all other frequencies off of that

As the NZ frequencies are just 0.635 Mhz less than Aussie frequencies, surely I can just swap out that one crystal to make it NZ ready by installing an xtal with a figure lower by 0.635 Mhz ??

I asked at one of the few Chch places that could seemingly do such a task and they were talking of about $160 to do that, too close to the purchase price of a brand new set at $189 if y'ask me....... and as I already have plenty of Aussie cbs.....

It is my understanding that when "NZ" cbs are sold here new, they are just Aussie sets which have been modded prior to sale, and that that modification costs almost nothing to do with regards to either parts or labour

Can someone please tell me how to modify my Uniden Pro 520e myself please ?

The electronics technicians types where I work can do some stuff for me like fine soldering jobs if need be, but none of them are into cb radio (one's an ex tv repairman and also another post office telphone background)

Supposedly Jaycar can supply crystals upon request or order them in. But I also need to know basic stuff, like how do I remove xtals ? I didn't want to break it, is it just a push in/pull out fitment ? I screwed my Uniden 520e back together and though I'd ask for advice even before trying even just to unplug the existing crystal

I will check back on this forum regularly but so long as forum rules allow, you may also email me directly to ensure I get your reply. catejemma AT hotmail DOT com

thanks and cheerio from forum newbie

Catherine
Christchurch

First I just want to convert a Uniden 40 ch am set model "Pro 520e"
...
also consider converting my fabulous Uniden AX 144

The first one would not be economic to convert (would be in the order of $300 Aus plus). Cheaper to buy a secondhand or even a new radio, and I'd say it would be a lot more legal.

The AX144 just needs a new crystal oscillator and realignment, and would cost about a third of what it would cost to do the Pro520e.

that modification costs almost nothing to do with regards to either parts or labour

It is a LOT cheaper (on a per-set cost basis) to do them new and in bulk (like lots of 1000).

Can someone please tell me how to modify my Uniden Pro 520e myself please ?

Sure: Rip out the PLL and make a new one on a PCB, then install it into the radio and realign the thing.

Requires RF and PCB design experience, ability to source some very specialised components, PCB fabrication experience, and most likely knowledge of a suitable firmware hardware+software system, such as Microchip PIC or Atmel's AVR, to name a couple.

One thing that is NOT changed in the radio is the crystal

Hope this helps,
Sue

Thanks Sue

I *thought* it'd be an easy-peasy modification. Oh well.

Yeah nar, sounds like I'll trawl Trademe and buy a 2nd hand NZ cb or two !

I'll keep all my lovely old Aussie ones back in their boxes, maybe I'll move back there one day ! Certainly in country/outback WA you can still buy a livable house on freehold land for a price (Au $ 30,000) that in country Canterbury NZ, wouldn't even be a deposit on a scummy house !

Thanks for your VERY prompt and knowledgable reply

Catherine
Christchurch NZ

I have converted AX144 for NZ channels before, it is a bit involved, but can be done by modifying the current circuitry's design and adding a few parts, realistically it can be tricky to get working properly sometimes, which can take a lot of time to convince it to work properly on all modes, as one of the oscillators needs to be stretched beyond its designed frequency.

At a guess (dependent upon how much time is required to get it to work) you would be looking at around NZ$100 to convert it.

It is not something you could do yourself, as Sue stated, you need specialist equipment and experience in order to even attempt it.

Just looked back thru the records and we did an AX144 about 18 month ago - converted to NZ40 only.
It involved one crystal and I had to add a second varactor to the circuit to get a decent range out of the clarifier - other than that, it looked straightforward enough.

The AX144 is a decent enough set and well worth converting.

Cheers

What I have done is move the 10.24MHz xtal to the PLL, break the tripled 5.12MHz output, add a crystal for NZ and then modify the oscillator to allow it to work 4MHz higher for the new crystal. the tricky bit is that sometimes this can load the oscillator when on SSB and the clarifier is turned fully one way, so capacitor values also have to be changed in the oscillator circuit to prevent excessive loading of it.

From memory, I just removed / disconnected the tripler components and fed it 14.725 from an crystal oscillator made up on a tiny PCB.
Quick and dirty, oscillator just made it to the USB and LSB offsets, and had to wire a varactor from the clarifier to get a decent range out of it.

That was my last crystal from a bunch I had made for this purpose back in the 90's.

If I got another one, I'd use a digiswitch chip (programmable PLL, 1024 channels, 3 offsets, 10 to 60 Mhz in 500hz steps):



and get rid of those troublesome offset cans that bought us grief all those years ago

Memories...

hi kiwiaussie, if you convert the ax144 and still want to keep 27mhz in it youll need a 14.730mhz crystal .also if you want to go from 41 to 80 youll need a 15.810 xtal ok. both xtals mounted on a board pretty easy to do the mods ,thx hamguy2 nsw australia

hi there kiwi aussie, i have plenty of rigs here atm cobra 138xlr 40 channels 4 to 5 of them all from the usa , president adams 5 of them all 40 channels from the usa ,4 148gtl cobras from the usa all stock standard also i have a cobra 200gtl i modded as well for 26 and 27mhz it does 100watts ssb etc .also i have various ham radio ts 50 kenwood ft950 yaesu brandknew in the box, a yaesu ft990 base radio modded ,also i have a kenwood ts850sat gettihng fixed with a low receive,thx hamguy2 nsw australia

youll need a 14.730mhz crystal

You'll also need to make up a an oscillator circuit and do some switching. Then you'll notice the clarifier doesn't work correctly (because the tripler you disconnected is part of the original clarifier circuit).
You'll lose 75% of the clarifier range, if you can get it to centre at all, especially on USB.

plenty of rigs here cobra 138xlr president adams 148gtl cobras cobra 200gtl

What does that have to do with converting an AX144 to NZ channels?