Converting my AR144 to cover 555

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Clint
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Converting my AR144 to cover 555

Post by Clint »

I have a lovely President AR144 in the shack but as it covers lows only it’s pretty useless, so I have been looking for a way to cheaply convert this to cover the Hi band so it can get on 27.555.

One way to do this is to mess about with installing a upd2816 PLL and using the chip in TX mode but this still puts you on an odd band and also puts you off frequency so you need to get it back by pulling the clarifier.

After asking around and getting some advice off a couple of peeps on here it seemed the best method was to add in a new oscillator board with a 15.810 crystal and 3 variable inductors to create the new SSB offsets. This seemed like more work than I wanted to do and I kept thinking that there is already a 10.240 oscillator in the radio that has the offsets (as a side note this design is a bit of a bodge as it does put the offsets 100Hz off due to the output getting halved then tripled)

I had a small external oscillator board I had removed from my Stalker that had been added at some point, I won’t use this back in the stalker as I will expand the PLL rather than adding new oscillators, this had the required 15.810 MHz crystal on it too. So I thought this might come in handy.

My Plan that came to me last night was to install a 10.240 crystal out of a scrap radio into the small external board that currently had the 15.810 crystal in it. (I wanted to keep the original 10.2417 crystal) then feed the PLL with this signal instead of the on board one with the 3 offsets. I would then replace the original 10.2417Mhz crystal with the 15.810 and modify the colpitts oscillator to suit and reroute the output back into the mixer.
Anyway today I put my plan into action and it works a treat, so I thought I would show everyone how I did it.

My Lovely AR144 :)
Image

Heres the osciallator board I had spare:

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The virgin PLL area:
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Remove C72 and replace it with C87 (C87 stays out) you can see the new 10.240 injection point here:
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The fitted 10.240 Oscillator:
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Another view:
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Remove JP41 this was where the 1/2 reference 5.12Mhz was fed to the mixer:
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Replace R113 with 560R
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Replace C91(180pF) and C92(390pF) with 56pF and 270pF respectivly:
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And there you go all converted:
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Then you just need to realign the radio checking the offsets are correct mine at Ch20:
Image
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Anyway I hope this might help someone, I am going to finish off the radio with a dual clarifier :)
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Re: Converting my AR144 to cover 555

Post by M0MTH »

nice, thanks for posting 8-)
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Re: Converting my AR144 to cover 555

Post by radio pete »

why not install a MC145106 & pep it up a bit easy a pie :geek:
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Re: Converting my AR144 to cover 555

Post by adonis »

Hi Clint,

Very nice job!!
How did you get your pcb and components so clean? Last time I opened a rig up it was full of dust and all sorts!!
I am fairly new to the forum but is there somewhere else on the site where this sort of stuff can also be found as it would provide a really useful repository of knowledge /practical know-how?
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Re: Converting my AR144 to cover 555

Post by Ashtec »

What a dam good mod there clint.......................................

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Re: Converting my AR144 to cover 555

Post by 163TM847 »

Alot easier than the previous 2 methods i got too admit, And if you dont have the board from an old korean type 80ch AM [as shown in pic] then to build a small colpitts for the 10.240 only requires a handfull of bits on a peice of vero no bigger than a 50p peice, No track cuts either.

Gonna try this method in the 146 [same board as the 144].

How about now knocking up a Crystal switch board with both 15.810 & 15.360 for Mid & High bands.
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Re: Converting my AR144 to cover 555

Post by Clint »

Cheers guys

Pete, because its much more dificult and requires cash for components and a pcb etched really, what I have done is for a cost of 50p made an old radio useful again.

Nick, I think you may have hit your pm quota as I sent you 2 pms :)
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Re: Converting my AR144 to cover 555

Post by pioneer »

Ive a few AR144s and a Cobra 146 GTL, all have been moded using the PLL change, ive also moded the clarifiers for tx-rx with a shift of about plus minus 6 khz, there really stable, no signs of warble.

heres a link to my video showning a superstar counter connected to it, showing the freqencies.


http://www.youtube.com/watch?v=vEyinkeYdp0


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Re: Converting my AR144 to cover 555

Post by RD250 »

Wow, I keep seeinig these radios on this site :)

I modded one of these to 80 channels way back when I was a student on the early 1980s. I did it by adding the extra XTAL plus the three inductors on a little daughter PCB. I wish I was still that young today :(

I made the PCB using a classic blue marker pen and etched the board in the kitchen sink.

I kept the original PCB design artwork in a metal tin with all my old CB crystals and it's been there ever since.
It's looking a bit old and crinkly but you can see the approx layout of the XTAL and other parts.

See the image below

http://www.4shared.com/photo/2CFdbXDj/Dsc01994A.html

I've never ever seen one of these radios in the 26+ years since I modded that early one. But they seem quite popular on here.
I thought it was a really nice looking radio and had really clean SSB Tx audio.
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Re: Converting my AR144 to cover 555

Post by MM1EWA »

radio petes suggestion of a MC145106 PLL got me wondering, I've had a look at the data sheets of this PLL and the uPD858 PLL what would be the main obstacle to fitting one of these?
the pinouts are offcourse different, but a daughterboard and crossover leads to the old socket could get round that.

So thats the physical problems sorted, what other issues would likely present themselves?
connecting up the channel switch would likely be drama, in the case of the MC145106 PLL maybe using the Digimax lite PLL control board would solve a number of issues?

Just throwing it out there as radio petes suggestion has got it on my mind.

Regards

Michael - MM1EWA
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Re: Converting my AR144 to cover 555

Post by Ashtec »

Look in the CB radio eprom date book this will answer a lot of your questions regarding these radio's the MC145106 PLL can be used as well as an eprom..................

Ive not really looked in to these rig's my self but i did read some info about moding the Pll ic that these radio's use.

You can download the Eprom data book off the net here for free..............

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Re: Converting my AR144 to cover 555

Post by 163TM847 »

Not sure what the UPD858 has to do with the AR144 maybe you just added your question to the thread rather than starting a new one :?: , Also if radio pete says its easy as pie to install the MC145106 instead of the UPD2824 i wish he would have given just a little more info than just saying its easy..
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Re: Converting my AR144 to cover 555

Post by RD250 »

I'm a bit rusty on these radios as I only ever saw one of them (and that was in about 1984 :lol: )

But you can see from the pics that it uses a uPD2824 PLL chip. This will use an active (inverting) loop filter so if you swap to a 145106 then you would have to bin the RC network associated with the old active loop filter and design a new passive loop filter circuit.

You shouldn't really try and copy a loop filter from another radio with a 145106 unless it has similar design characteristics.

eg the PLL in a 148 will have a different phase detector gain because it runs the PLL chip at 8.3V and also I would guess the VCO gain will be different too. Also, because the AR144 doesn't do FM (IIRC) this allows the designer to choose a loop filter that doesn't have to support FM modulation so that's another reason to design an optimised loop filter rather than copy one.

BTW I'm assuming the uPD 2824 uses a type 2 (edge triggered) phase/frequency detector but I'd be amazed if it doesn't.

I suppose you could try copying a loop filter and tinker from there but it's probably wiser to design one, plus it's more fun that way ... (I'll get my coat...)
Last edited by RD250 on 12 May 2011, 15:24, edited 3 times in total.
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Re: Converting my AR144 to cover 555

Post by Ashtec »

I was on about the UPD2824 there Nick sorry there was a bit in the Eprom data book about moding these UPD2824 pll ic's which you used the MC145106 and an Eprom but i can not remember if the radio had to still use the UPD2824 pll ic and not for geting this was for Usa 10 meter band so you would still have to work out the addressing for the 11 meter's.

But then im not the one to ask about Eprom's as im still on the steping stone's of learning about it all I can copy them :lol: :lol: :lol: so im geting there one day i will get it all im me head :lol: :lol: :lol: :lol: :lol: ..........

I do know that CB city did a conversion for these radio's some years ago and a conversion for the 858 pll's but there's not much in the way of info on them........................


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Re: Converting my AR144 to cover 555

Post by RD250 »

OK I'm confused here... I don't have much time to ponder over this but something isn't right about the instructions above.

As I said in my prev post the uPD2824 uses an inverting amplifier in the PLL loop filter.
The MC145106 used in similar VCO + 15.xxxMHz downmix downcircuits (like the 148) doesn't use an active (inverting) filter but uses a simple non inverting passive filter.

So this means (to me at least) that these two chips have an opposite phase detector gain at the PD out pin.

So I can't quite get my head around why they say you should simply add the missing active inverting amplifier for the existing loop filter.
The loop will try and steer the VCO backwards? So it couldn't ever lock unless the VCO could tune BELOW 15.36MHz to the low side mix (which nobody wants)

Has anyone ever tried this mod? I guess I'm missing something here... IMO you should use a non inverting passive loop filter with the 145106 with this PLL topology. Presumably people have actually tested this mod at some point so I must be missing something.
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