Sinus 1watt PLL

[Zozo]

Only a minor problem by the sounds of things. I'm sure your just need to tweak a few component valve's and your be getting a bit more from the 2n4427. Just out of curiosity. what flavor of 4427 are you using? I have a cheap no brand from china I'm testing now, Well it's been on all day to be honest and gives just over 800mW across the band @13.8v.

20210322_233201.jpg

[sinus trouble]

Yeh my scope is indicating the amplitude per side of the oscillator is lower than i expected?

Also 8V DC is quite low for this type of oscillator.

Back to your exciter, Looking good Zozo!

800mW is good going for a 'No Name' 4427! With so many different types floating around the results are likely to be variable.

Im currently using a 4427 with the ST logo printed, That does not guarantee its genuine tho!

[Zozo]

Thanks Sinus.

Ok ST usually are good for 1W if I recall, I have a few different ones to test out over the next dew days. I just though I'd see what this cheap one could do. It's running a bit warm though.

Back to your exciter, I don't think you need to do to much to get somewhere close to 1W. Hopefully it's just as you say with it being a little under driven by the oscillator. Also be nice if you don't have to get another PCB made up and just replace the 78L08 with maybe a 78L10?

I was reading something you mentioned in an earlier post about the use of the transformer from the oscillator to the final. Might be something worth experimenting with? May need to introduce that as being part of a buffer stage in the middle with another transistor?

[Bton-FM]

@zozo
Incidentally, I’ve tried the Chinese 2N4427s recently (which is the same the Chinese ‘3866, ‘3555 ,’5109 ect) and they are really hit and miss, I have found.

The first one I had was doing about 1.2 Watts near the top end of the band but then most of subsequent ones have only given around 100mW or nothing! I’m not too sure why this is ; perhaps poor quality control and the batch are factors in their performance.

These Chinese transistors are marked with a Motorola logo and then ‘2N4427’ and a serial number in the format ‘KO***’. I’ve found the most common serial numbers at the moment are ‘KO235’ and ‘KO215’.

If anyone can shed some light on what these transistors really are I would be interested.

[sinus trouble]

Yeh i doubt i would need to re design the PCB, I think its more minor adjustments to component values to centre it on the band.

The idea of of a transformer is something i may look into?

The 4427 is more of a difficult question? As we all know gain can vary even in genuine components. i also have a original Stephen Moss VFO here and that does nearly 1.2W @ 13.8V (Motorola)

Capture.PNG

When you look at the datasheet, you need a decent amount of drive to start with to achieve gain.

[teckniqs]

If getting 800mW at 13.8v you should probably get around 1000mW @15v.

[Zozo]

If getting 800mW at 13.8v you should probably get around 1000mW @15v.

Yes it's very possible your correct with that Tech. I'll give it a go before I pull it out to see what a Philips branded 2n4427 can do.

[Zozo]

@zozo
Incidentally, I’ve tried the Chinese 2N4427s recently (which is the same the Chinese ‘3866, ‘3555 ,’5109 ect) and they are really hit and miss, I have found.

The first one I had was doing about 1.2 Watts near the top end of the band but then most of subsequent ones have only given around 100mW or nothing! I’m not too sure why this is ; perhaps poor quality control and the batch are factors in their performance.

These Chinese transistors are marked with a Motorola logo and then ‘2N4427’ and a serial number in the format ‘KO***’. I’ve found the most common serial numbers at the moment are ‘KO235’ and ‘KO215’.

If anyone can shed some light on what these transistors really are I would be interested.

I can't remember what the serial on the top said. The one I have installed at the moment has such a high polished finish the print came off with my finger.

[teckniqs]

Some of those cheap Chinese Motorola 2N4427 clones are so bad you can just wet your finger and remove the stamp/print.

[reverend]

I’ve tried the Chinese 2N4427s recently (which is the same the Chinese ‘3866, ‘3555 ,’5109 ect) and they are really hit and miss, I have found.

The first one I had was doing about 1.2 Watts near the top end of the band but then most of subsequent ones have only given around 100mW or nothing! I’m not too sure why this is ; perhaps poor quality control and the batch are factors in their performance.

These Chinese transistors are marked with a Motorola logo and then ‘2N4427’ and a serial number in the format ‘KO***’. I’ve found the most common serial numbers at the moment are ‘KO235’ and ‘KO215’.

I've tried the Chinese trannies and have generally ended up with roughly 800mW out at 13.8V but even with a 15V supply, the output doesn't quite squeeze to a full blown Watt. They are definitely different from 'standard' 4427s as the matching to the base is very different. With my 'Rev3.02' PCB, if you use the Chinese ones no changes are needed and you'll get ~800mW at 13.8V. If you use a normal 4427, you need to put an ~33pf capacitor between base and emitter of the transistor to correct the match, the output is then closer to 1W.

Has anyone tried the MRF4427? They look like useful devices, but how do you get rid of the heat of the small SMD component? I know there are SMD heatsinks, so I guess you would need to use one of these, unless there's a way to conduct the heat away through the PCB.

As far as I can tell, the only devices in this power range that aren't now obsolete are all SMD devices with the associated heat removal problems.

Rev

[Bton-FM]

I’ve tried the Chinese 2N4427s recently (which is the same the Chinese ‘3866, ‘3555 ,’5109 ect) and they are really hit and miss, I have found.

The first one I had was doing about 1.2 Watts near the top end of the band but then most of subsequent ones have only given around 100mW or nothing! I’m not too sure why this is ; perhaps poor quality control and the batch are factors in their performance.

These Chinese transistors are marked with a Motorola logo and then ‘2N4427’ and a serial number in the format ‘KO***’. I’ve found the most common serial numbers at the moment are ‘KO235’ and ‘KO215’.

I've tried the Chinese trannies and have generally ended up with roughly 800mW out at 13.8V but even with a 15V supply, the output doesn't quite squeeze to a full blown Watt. They are definitely different from 'standard' 4427s as the matching to the base is very different. With my 'Rev3.02' PCB, if you use the Chinese ones no changes are needed and you'll get ~800mW at 13.8V. If you use a normal 4427, you need to put an ~33pf capacitor between base and emitter of the transistor to correct the match, the output is then closer to 1W.

Has anyone tried the MRF4427? They look like useful devices, but how do you get rid of the heat of the small SMD component? I know there are SMD heatsinks, so I guess you would need to use one of these, unless there's a way to conduct the heat away through the PCB.

As far as I can tell, the only devices in this power range that aren't now obsolete are all SMD devices with the associated heat removal problems.

Rev

I had a similar experience with the input match of the Chinese 2N4427. It’s very different to the Phillips parts.

The MRF4427 (and all the other SM transistors you might use in the final for that matter) can be clamped to case on the track side of the board. The only attraction of using a newer surface mount device for the 1 watt to me is if they are cheaper than the 2N4427. The cheapest I can find the MRF4427 is a little under £2.00 so it doesn’t really justify it IMO.

I have experimented with the BFG135, but they can really easily ‘take off’ at low frequencies because of their high transition frequency! Also, I found that it was difficult to squeeze a watt out of them without them releasing the magic smoke...

There’s a quite few other BFG devices that could work or the RD01 from Mitsubishi. The only thing that puts me off the RD01 is the supply voltage.

[reverend]

I have experimented with the BFG135, but they can really easily ‘take off’ at low frequencies because of their high transition frequency! Also, I found that it was difficult to squeeze a watt out of them without them releasing the magic smoke...

I've had exactly the same experience with them. Their magic smoking jackets aren't made of the right kind of velvet.

Rev

[sinus trouble]

Another quick update!

I have increased the diameter of the oscillator coils (L1 -L6) from 5mm to 5.5mm which has increased the output power by 100mW or so?

This also corrected an offset on the oscillator trimmer (U15) which is now bang on centre @ 98Mhz

Replacing the oscillator regulator from a 78L08 to a 78L10 (U5) increased gain further? But still not reaching 1 Watt!

I will update the schematic soon.

[Zozo]

Sounds like your getting there slowly Sinus. Just out of curiosity what's the inductance of L19?

Have you tried to swap out the 2N4427 with something else to see if it's that which maybe on the weak side?

[Zozo]

I ended up checking quickly. I think your schematic calls for 12 Turns @ 4mm close winding?

I see it's around 600nH. I'm using a 1.5uH as my DC choke. But apparently it should be less than that really.

20210326_125401 (1).jpg

[sinus trouble]

Sounds like your getting there slowly Sinus. Just out of curiosity what's the inductance of L19?

Have you tried to swap out the 2N4427 with something else to see if it's that which maybe on the weak side?

Cheers Zozo!

Yes the 4427 is one of those unknowns that i cant really answer? I could maybe perform a rough gain test on those that i have in my stock? But still would not prove how they perform?

This one needs a bit of thinking? I do have some gold bottom types which normally give good results?

[sinus trouble]

I ended up checking quickly. I think your schematic calls for 12 Turns @ 4mm close winding?

I see it's around 600nH. I'm using a 1.5uH as my DC choke. But apparently it should be less than that really.

Now that you mention it, I did try stretching the coil to see if there was any improvement? But no significant difference occured?

I might try teasing it with a small ferrite for any response? Deffo worth a go!

Cheers Zozo!

[Zozo]

I've had another thought. I'm not sure the size of the tracks on your PCB in regards to the output stage. I've increased the size of the tracks on my project, "not by much though".

I'm not sure in my case I really needed to, but I know @ VHF frequencies the loses can be greater due to the "Skin Effect". So I thought a little wider tracks in that area might help possibly?

Just some food for thought

[sinus trouble]

I've had another thought. I'm not sure the size of the tracks on your PCB in regards to the output stage. I've increased the size of the tracks on my project, "not by much though".

I'm not sure in my case I really needed to, but I know @ VHF frequencies the loses can be greater due to the "Skin Effect". So I thought a little wider tracks in that area might help possibly?

Just some food for thought

You are spot on!

All tracks on my PCB are 1.5mm apart from some? The PIC has some tracks which are 1.0mm

The tracks to and from the 4427 collector are 2.0mm which seem to be the most current hungry areas? Maybe not a wise decision from an RF design point of view?? I dunno?

[Zozo]

The original track size for my project was 0.80mm and I was getting just over 800mW with the cheap no brand Chinese 2n4427. I've now increased it to 1mm which isn't much. But I think my track lengths in that area of the PCB aren't particularly long before it's fed into the next stage or element.

If yours are 2mm, then I think that should be fine?