fidelity CB2001FM mods

[Yank tank]

Hi guys n galls. I have my late daughters UK CB set and would like to mod it to operate in the 10m ham bands. It's a Fidelity CB 2001 FM rig.
I understand the processor is special but surely by now someone would have 'cracked it' and can use a replacement. Anyone please. It would mean a lot to me. Cost not a problem. Just want to do it.

[Sholy]

thank you good post

[zodiac]

I can't remember what board is in that radio but if it's the 134 board with the LC7137 UK PLL in it, don't bother.
The only thing you can do is add the LC7132 FCC Mid band PLL to give you 26.965 to 27.405 but it's not that simple.
Both PLL's are ROM chips and cannot be altered.

[Yank tank]

Hi Zodiac,
one chip is LC7137 and the other is LC1230. Does this help?

I'm not an electronics expert but, surely they can be replaced with another ROM that will give different frquencies?

[zodiac]

The board number is at the back of the board on the Cybernet 134 radios that use the LC7137 PLL but other radios also use the same PLL.

[Yank tank]

The only writing on the back is "PCMA002F"
would a picture help?

[Yank tank]

Hi Zodiac and any other techs watching,
a mate of mine from years ago in the UK as a radio engineer, says that "They don't use ROMs but PLL synthesiser ICs. Not usually pin for pin compatible, but I guess it is possible to put multiband PLLs in place of the fixed PLLs..."
any comments anyone? pretty please

[lbcomms]

other techs watching

What about engineers?

They don't use ROMs but PLL synthesiser ICs.

They use a mask programmed ROM with a PLL in the same package.

A ROM is a memory device - it has address lines (INPUT) and data lines (OUTPUT).

The address lines connect to the channel switch, TX/RX offsets, and other things like channel9/19 recall switches.
The Data lines connect to the internal PLL.

This limits the PLL to whatever is programmed into the ROM. Done for 2 reasons...
- it's needed to get type approval so the radio can be sold (user cannot easily add channels)
- saves on cost - for example, building in the TX offset means one less crystal required

I guess it is possible to put multiband PLLs in place of the fixed PLLs

Absolutely. We make them here: USB (that's Universal Serial Bus, not Upper Sideband!) programmable PLLs with 400 channels and 3 offsets for TX/RX/SSB.
Covers a local oscillator range of 4.1 to 60 Mhz in 1Hz steps:

Not usually pin for pin compatible

Correct again. It requires expert programming and installation.

any comments anyone? pretty please

For throwing a few extra channels in a CB, it's not worth the cost or expense.
The chips cost over $150 to buy and about the same again for programming and installation, if you can find anyone willing to take the risk of programming illegal frequencies into it. For the same $300, you can get a 10 metre multimode AM/FM/SSB "CB" covering 25 to 30 Mhz...

Hope this helps,
Sue

[Yank tank]

Hey! thanks Sue, thats excelent information. The rig has sentimental value to me as it was my late daughters set and cost is somewhat immaterial.
Basically then it is possible to convert this CB to operate in the 10m ham band as an FM rig but at a cost of some $300. Is that US dollars? and who do I talk to?

[lbcomms]

it is possible to convert this CB to operate in the 10m ham band as an FM rig

Yes, it can be done. The screen capture I showed earlier was where we used one to do a 10 meter conversion - look closely at it...

but at a cost of some $300

That's a rough "guesstimate". You are looking at a 30 year old radio - component aging and screwdriver jockeys take their toll.
The "guesstimate" assumes the thing is in good working order.

Is that US dollars?

Aussie dollars, we are located near Sydney, Australia. Where is Gisborne? In the UK?

and who do I talk to?

There are people around that can do it, I've supplied about a dozen regulars worldwide with these.
They are NOT for inexperienced or wannabe tech types though.
You'll need to know RF fairly well and have the right tools for the job (Minimum: Spectrum analyser, CRO, Counter accurate to 1ppm or better, and an SMT rework station).

Alternatly, you could send it here to us in Oz, but itwould be a "spare time" job as we are in the middle of a fairly major project... I'd also need to know your amateur licence details. Unfortunatly, doing most of our work for government departments (police and/or ASIO clearance essential), I have to keep clean these days.

Personally, I'd keep it as it is (as it was owned by the loved one) and spend your money on a modern multmode set.

Cheers

[Yank tank]

hi there,
OK Gisborne is in NZ and I'm a licenced ham. The rig has never been abused/modified but I noticed sometime after I bought it that there were some board mods with components on the reverse side. The cover was taken off by a professional radio engineer (also a ham) to check the output (no not to screw it up) and see if the mic gain could be increased. Both myself and my daughter spoke quietly.

I know I could buy a 'multi mode' CB rig for the money. In fact I sold my Cobra 148 dx, officially modified to 10m in the UK, only a year ago. Strangley the ham that bought it was going to "de-modify' back to a CB as he said it would be worth 4 times as much as a CB in NZ.

If I leave it as it is, I can't use it at all as the frequencies are not allowed in NZ.

Can you send me contact details and I'll give it some thought or is that against the rules of this site.

Regards Mike

[zodiac]

If you need the schematic for that radio you'll find it on CBTricks.com
under radio information, then "A" for Amstrad 900/901.

[lbcomms]

OK Gisborne is in NZ

Found it in Wiki. Nice view from the hill overlooing the river / harbour...

and I'm a licenced ham

That'll clear any legality type issues.

The rig has never been abused/modified

Again, that's a good sign. CB experts (the "swing kit" crowd) are your radios worst enemy

but I noticed sometime after I bought it that there were some board mods with components on the reverse side.

That's quite normal. For changes such as customising a chassis for a particular country or reseller, it's cheaper than redesigning a PCB and junking thousands of existing ones.

I'm not overly familiar with 10 metre FM operation. Could you provide a list of say 80 channels (40 simplex and 40 duplex) that would need to be programmed into it?

As I said before, we are in the middle of a fairly major project (changing an analog network over to as trunked digital system involving 8 base stations and 60 mobiles).
If you can wait a few months I might be able to look at it, otherwise I can let you now others who can do it sooner (you'll still need to provide a ZL call and send the radio to Brisbane or Perth here in Oz). Send a PM if interested.

Cheers

[Yank tank]

Tnx for the replies and information. You guys (and galls) have been a great help on this one.

will send PM and go from there.
Again tnx.
I wonder how many others will be interested in conversions of UK CB's?

[Yank tank]

Wow, I'm well pleased with the results of my UK CB mods to ham band 10fm. Great job guys tnx. Price reasonable too even with the exchange rate.