You really do want to add a PLL to that!

Whilst it looks promising? It did not perform as expected?

It was seriously lacking power! With a few small adjustments, I managed to get just over 3 Watt!

But the power over the full tuning band was more stable which is good! Also current consumption was within acceptable standards!

I am not sure what the issue is as yet? So i wont release the Gerber files until i have a better idea of whats going on?

Either way, 3 Watt is a massive improvement!

Albert H wrote: ↑Tue Nov 01, 2022 11:15 pm You really do want to add a PLL to that!

Haha! Yeh that is defo something i am considering!

I need to first get this PA working as best i can? I am not expecting much from the 1947 as it has pretty poor efficiency (50% at best) Also its Collector/Emitter voltage is very low!

However, the second harmonic so far has been greatly reduced which is always a good thing!

Some more testing needs to be carried out for now!

The 1947 is a peculiar device. I found that some of them had huge gain, and others were much more modest. These days I design with FETs - the 12V Mitsubishi FETs have consistently high gain, and quite spectacular efficiency figures. The RD06 variant would be ideal for your Band I, and could give as much as 10 Watts (if you thrash it!). I'd aim for 5 Watts, and have everything run cold!

perfect

radium98 wrote: ↑Thu Nov 03, 2022 3:46 pmperfect

Thank you Radium!

Albert H wrote: ↑Wed Nov 02, 2022 3:31 am The 1947 is a peculiar device. I found that some of them had huge gain, and others were much more modest. These days I design with FETs - the 12V Mitsubishi FETs have consistently high gain, and quite spectacular efficiency figures. The RD06 variant would be ideal for your Band I, and could give as much as 10 Watts (if you thrash it!). I'd aim for 5 Watts, and have everything run cold!

Yeh in hindsight, the 1947 is not the perfect solution!

I have now managed to get 4 watt from the B1 PA PCB but i am still not quite satisfied!

The current consumption is a bit higher than i would like? (Approx 700mA @ 13.5V)

I think i have tracked down the problem? The input match from the VFO to the 1947 seems to be a bit off, restricting drive!

The 1947 output Pi match seems pretty good! And the LPF seems to be operating as intended!

Good news way to perfect .love the tracking way for troubleshooting and diagnose .happy ending .what is to be best for the tx antenna .Slim Jim? For tx

sinus trouble wrote: ↑Fri Nov 04, 2022 12:24 am I think i have tracked down the problem? The input match from the VFO to the 1947 seems to be a bit off, restricting drive!

I've found that getting the input match right can affect both output power and efficiency. In some cases the difference can be 10% in each direction (i.e. 10% more output for 10% less current draw). Usually a few tens of pF between the base and emitter of the transistor can help no end. For a 1947 this may need to be 100pF or more.

radium98 wrote: ↑Fri Nov 04, 2022 6:12 am What is to be best for the tx antenna .Slim Jim? For tx

A Band I Slim Jim is a very big aerial! Usually I use a ⅜-wave vertical with groundplanes. This has an omni-directional radiation pattern, so doesn't give any clue where it's transmitting to!

reverend wrote: ↑Fri Nov 04, 2022 9:27 am

sinus trouble wrote: ↑Fri Nov 04, 2022 12:24 am I think i have tracked down the problem? The input match from the VFO to the 1947 seems to be a bit off, restricting drive!

I've found that getting the input match right can affect both output power and efficiency. In some cases the difference can be 10% in each direction (i.e. 10% more output for 10% less current draw). Usually a few tens of pF between the base and emitter of the transistor can help no end. For a 1947 this may need to be 100pF or more.

REV!! YOU ARE AN ABSOLUTE LEDGE!!!!

I took your advice and added 100pF in parallel with the VFO output! (Shown below)
The output power shot up to 5 Watts!!

The current consumption had risen a bit as to be expected, But was still within tolerances!

There is still some final touches in need to finalise, But i cannot thank you enough for your help!

Much appreciated!

Also to add!

Output power remained pretty stable @ around 5 Watt across 53 - 59Mhz

Previously the power would slump about a Watt as the frequency was increased from 53Mhz!

Albert H wrote: ↑Fri Nov 04, 2022 8:44 pm

radium98 wrote: ↑Fri Nov 04, 2022 6:12 am What is to be best for the tx antenna .Slim Jim? For tx

A Band I Slim Jim is a very big aerial! Usually I use a ⅜-wave vertical with groundplanes. This has an omni-directional radiation pattern, so doesn't give any clue where it's transmitting to!

Whoa! Easy Radium!

A Slim Jim is far too good for Band 1! I was thinking more of a cheap horizontal polarised dipole!

I see that you have 68Ω base to ground. You could try increasing that a bit - perhaps to as high as 470Ω. 68Ω might be damping down the drive a bit too much.

Also, your additional 100pF should be on the PA board - as close to the base and emitter pins as possible.

Thank you guys..I kept an eye here

Albert H wrote: ↑Sat Nov 05, 2022 1:02 am I see that you have 68Ω base to ground. You could try increasing that a bit - perhaps to as high as 470Ω. 68Ω might be damping down the drive a bit too much.

Also, your additional 100pF should be on the PA board - as close to the base and emitter pins as possible.

Cheers Albert!

Interestingly, whilst Revs suggestion does work? Once soldered into place it did not perform as expected?

I have actually found some more options that perform just as well!

This whole problem was caused by me when i tested the prototype! I used coax lengths for connections to and from each PCB! This inevitably added extra inductance and capacitance to the circuit! once directly wired, these values were obviously missing!

This mismatch is very tiny but makes a big difference to the transfer of drive!

Anyways heres some alternatives i have found that work pretty well!
As can be seen, i have coupled the two PCBs with a capacitor (The value yet to be determined) which gave excellent results!

Also a "Hairpin" inductor also gives excellent results too!

Adjustment of the drive collector coil also gives a smoother power output across the band!

Infact!

Maybe C17, C18 and C19 could be redundant and replaced by a single capacitor?

As Stephen used in his PLL PRO!

Right!

I have done more testing and some promising results indicate that i am on the right track!

You may have noticed that i have fitted trimmer caps to parts of the circuit! This is for testing only!

I am now getting a stable 3.5 - 4 Watt stable output across the band!

The current consumption is 700mA but 90 - 100mA of that is the driver VFO consumption!

After trimming the capacitors for Max forward power, It turns out that the values are VERY VERY close to my original schematic predictions!

Image below!

Also!

For a device that is dissipating over 8 Watts? Heat extraction is a big deal!

I made a few changes to the enclosure to accommodate this issue, Based on a simple convection system, It works pretty well!

Images below!