RF Heads CMOS PLL

sinus trouble · Post by **sinus trouble** » Wed Feb 09, 2022 12:42 am

I came across this interesting but mysterious PCB (Print)

There is little information disclosed on this! Whilst i am familiar with CMOS PLLs there are some questions remaining?

For those who are not familiar? I will give my brief explanation!

There are 4 main components! The local or 'Reference' oscillator, VCO or 'Main TX' and a divider to lower the working frequency! These are both then fed to a Comparator which reacts to the difference in phase!

Ofcourse i did not include the Loop Filter!

The description of this circuit states that it covers a range of 5 - 500Mhz? That seems a bit too broad to me?

Are there changes required in either the 'Ref' Oscillator or the divider to achieve this range?

Pic below!

CMOS PLL.PNG

yellowbeard · Post by **yellowbeard** » Wed Feb 09, 2022 2:03 am

There is no VCO on that board, it's original manufacturer was these guys:
https://spi-electronics.com/
they are defunct now but googling "SPI PLL" does produce good results. Here is the circuit, overlay and a picture of it assembled:
https://www.piratenpraten.nl/schemas/3- ... SPI%20PLL/
Good luck getting that SAB6456 prescaler chip for cheap, I seen them at €22 Euro recently.

yellowbeard · Post by **yellowbeard** » Wed Feb 09, 2022 2:44 am

I forgot about this;
https://www.hf-electronics.nl/SPI-PLL-KIT-5-500MHz

RF-Head · Post by **RF-Head** » Wed Feb 09, 2022 8:39 am

It was me that made it thats correct and SPI made the PCB design for me in 1998

We were selling lots of kits back in the time

Bton-FM · Post by **Bton-FM** » Wed Feb 09, 2022 10:40 am

5 SAB6456 prescalers for 50p.
https://a.aliexpress.com/_mPGV6De

sinus trouble · Post by **sinus trouble** » Wed Feb 09, 2022 10:57 pm

yellowbeard wrote: ↑Wed Feb 09, 2022 2:03 am There is no VCO on that board, it's original manufacturer was these guys:
https://spi-electronics.com/
they are defunct now but googling "SPI PLL" does produce good results. Here is the circuit, overlay and a picture of it assembled:
https://www.piratenpraten.nl/schemas/3- ... SPI%20PLL/
Good luck getting that SAB6456 prescaler chip for cheap, I seen them at €22 Euro recently.

Nice one YB! You are an absolute Ledge!

I think the CD4046 has an onboard VCO? But you are right, It is totally useless for VHF! The VCO would be the actual transmitter that you are aiming to stabilise!

Gonna have a look through the links you posted!

sinus trouble · Post by **sinus trouble** » Wed Feb 09, 2022 10:59 pm

Bton-FM wrote: ↑Wed Feb 09, 2022 10:40 am 5 SAB6456 prescalers for 50p.
https://a.aliexpress.com/_mPGV6De

Excellent find Bton-FM

sinus trouble · Post by **sinus trouble** » Wed Feb 09, 2022 11:09 pm

RF-Head wrote: ↑Wed Feb 09, 2022 8:39 am It was me that made it thats correct and SPI made the PCB design for me in 1998
We were selling lots of kits back in the time

Nice work RF-Head

I will most likely order a couple of those kits from you in the near future! (If you still stock them)

I know they are old but i like the 'Vintage' stuff!

sinus trouble · Post by **sinus trouble** » Wed Feb 09, 2022 11:22 pm

WoW!! I just been checking out the specs on the SAB6456!

Seems to have a divide ratio of 64 or 256 selectable! @ 70 - 1000Mhz which is hugely broad!

However the SPI PLL is labelled as 5 -500Mhz is the SAB6456 actually capable of operating correctly @ such low frequencies?

Albert H · Post by **Albert H** » Thu Feb 10, 2022 4:16 am

The SAB6456 is a wonderful chip - I still have a bag of them here! It's pretty sensitive - you can feed the chip from a "sniff" loop in the vicinity of a VCO coil, or (as I used to usually do) from an extra winding on a buffer toroidal coil.

If you want the SPI PLL to go lower, you either switch the '6456 to ÷64, or bypass it altogether and go straight in to the 74HCT4059 (which has a useful frequency response on its own!).

My PLL uses a 6456 as the prescaler, then a diode-programmed 74HC4040 as the "pre-settable" divider, a diode-programmed 74HC4060 as the reference oscillator and reference divider (allowing the use of the really cheap 4MHz rock), and a 4046 (or 7046 if I needed a really solid lock detect output) for the phase comparator. The loop filter was done with an LM324.

There was a second version that I did that used a 74HC74 and a 74HC00 for the phase comparator - this gave even better results, and provided a really solid locked (and unlocked) output.

The beauty of the basic CMOS PLLs is that they're so versatile: with only minor modification, you can make them work on virtually any frequency! They're also cheaper than a PIC and a dedicated PLL IC. I had a whole pile of PLL PCBs etched, and they were used on every conceivable frequency, from short wave, through Band I without the prescaler, then Band II, III, IV and V with the prescaler in front. One other useful thing was that I could easily add PLL frequency control to almost any VFO rig that came to me.

For medium wave and long wave, I used the ordinary CMOS 4046 including its oscillator, a 40103 as the switchable divider, and a 4060 for the reference and reference divider. I'd use either a 4608kHz rock for Europe or a 5120kHz rock for the Americas to give either 9kHz or 10kHz steps up each band. Depending on the type of rig, I'd sometimes generate the carrier at twice the required frequency, then use a 4013 bistable to get an absolutely 1 : 1 square wave drive.

The more sophisticated medium wave rig type that I did used a CMOS synthesiser generating a 64-step pseudo sine wave (which was then filtered to smooth it), into a pair of fast comparators, driving a pair of Class D amplifiers. The modulation was applied to the other inputs of the comparators to give PWM/PDM outputs. The outputs of the Class D amplifiers were combined in a tuned bridge configuration, thereby generating AM as the two signals added to and subtracted from each other. With a few dBs of envelope feedback, the modulation quality was better than anything else on the band! The rigs were also well over 90% efficient, making the very best use of the available DC supply! I built these up to 800 Watts carrier (3.2kW peak), and a few of them are still in use around the world. The power limitation (at the time) was determined largely by the FETs that were cheaply available for the output stages. The ones I used cost around £1 each, and the bigger rigs had 48 of them on board! Modern cheap switching FETs would make rigs at 10s of kilowatts quite cheap to build!

Bton-FM · Post by **Bton-FM** » Thu Feb 10, 2022 10:33 am

Albert H wrote: ↑Thu Feb 10, 2022 4:16 am They're also cheaper than a PIC and a dedicated PLL IC.

It’s not cheaper - you looking at around 30p per IC and you need 4 of them. It’s cheaper to use the TSA5511, an 8 pin Microcontroller and a 3.2MHz crystal. I reckon I can do it for 70p. Plus it doesn’t take up a square foot on your PCB!

It might have been cheaper in the 80s to do it with discrete logic but it’s not now.

I’m not trying to discourage anyone from trying it! I want to have a go with it one day when I get the chance since it’s good to learn from old methods (heck, the TSA5511 is a pretty old way of doing thing as well!). However, when it comes to leaving equipment up blocks it’s cheaper to just use an all in one PLL.

zulu53 · Post by **zulu53** » Thu Feb 10, 2022 4:10 pm

Hi Bton-FM

I would like to know where can I get the suggested components for a cheap TSA5511 PLL circuit?

Albert H · Post by **Albert H** » Thu Feb 10, 2022 7:00 pm

The TSA5511 is OK, but the lock detect is dreadful, and the lock-up time is really slow unless you add "dual speed" loops..... adding to the complexity of the PLL circuit.

My PLL sub-board was only ~8cm square, so it fitted easily next to / above / blow most exciter boards.....

sinus trouble · Post by **sinus trouble** » Thu Feb 10, 2022 11:26 pm

Albert H wrote: ↑Thu Feb 10, 2022 7:00 pm The TSA5511 is OK, but the lock detect is dreadful, and the lock-up time is really slow unless you add "dual speed" loops..... adding to the complexity of the PLL circuit.

Now that you mention the Lock Detect Albert!

Looking at the SPI schematic, It has a novel way of deriving the Lock State? Im not 100% sure of of its operation but it seems to utilise the 'Demodulation' pin of the CD4046?

Which would make sense in theory as a change in phase would show an output?

I have all of these parts in stock apart from the SAB6456!

Im intrigued to knock one of these up on a breadboard to see how it performs? (Not for VHF obviously)

sinus trouble · Post by **sinus trouble** » Thu Feb 10, 2022 11:52 pm

Also, Albert you mentioned the 7046 which is news to me?

I will have to look into that!

Krakatoa · Post by **Krakatoa** » Fri Feb 11, 2022 2:05 pm

Maybe he meant the 74HCT9046 which is an improved version of the 4046

Bton-FM · Post by **Bton-FM** » Fri Feb 11, 2022 6:34 pm

zulu53 wrote: ↑Thu Feb 10, 2022 4:10 pm Hi Bton-FM

I would like to know where can I get the suggested components for a cheap TSA5511 PLL circuit?

Aliexpress:

TSA5511ali.PNG

The place is teeming with them! I'm not quite sure how the Chinese ended up with so many? Not that I am complaining!

As for the Microcontroller, I use the Attiny2xx/Attiny4xx series which are about 30p each. That said, they are sold out everywhere right now. Every time they come back in stock anywhere, they get bought up really quickly. The code is really simple.

Shedbuilt · Post by **Shedbuilt** » Sun Feb 13, 2022 9:07 am

Krakatoa wrote: ↑Fri Feb 11, 2022 2:05 pm Maybe he meant the 74HCT9046 which is an improved version of the 4046

Most likely this one I think: https://www.ti.com/lit/ds/symlink/cd74h ... e.com%252F

Albert H · Post by **Albert H** » Sun Feb 13, 2022 9:44 am

https://datasheetspdf.com/datasheet/74HC7046A.html

You'll see that it has several enhancements over the 4046. When available, they were getting a bit expensive, but they really worked exceptionally well!

sinus trouble · Post by **sinus trouble** » Tue Mar 15, 2022 11:58 pm

I have been reading through the 4059 datasheet and it is not what i assumed it was?

The 4059 is NOT a programmable divider, But is actually a frequency counter! This means that it gives a out a pulse signal once it has counted the relevant cycles!

Im guessing that at a high enough frequency? The cycles would be more uniform to compare with the VCO frequency?

Im not entirely sure how the SPI works? But a similar circuit used on the NRG PLL PRO 3 seems to utilise another IC to correct these pulse signals?

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