• SINUS B1 PROJECT

Posted: **Tue Sep 20, 2022 11:19 pm**

So, I have built and briefly tested a prototype!

With very little adjustment, The results are looking very promising!

The prototype is producing 3 Watt @ 60Mhz and gradually rises to 4 Watt @ 50Mhz! Tests were performed @ 13.8V and was consuming around 520 mA!

SWR was excellent and consistent through tuning!

Image of the prototype below!

Posted: **Tue Sep 20, 2022 11:20 pm**

B1 Amplifier.png

Posted: **Tue Sep 20, 2022 11:32 pm**

As can be seen, A rather butchered old PRO III PCB!

The Low Pass Filter has been adapted for Band 1 and i now have a rough starting point for the missing component values previously shown in the first layout!

I have updated the layout below!

Posted: **Tue Sep 20, 2022 11:33 pm**

Schematic_B1 Amplifier_2022-09-20.png

Posted: **Tue Sep 20, 2022 11:45 pm**

The matching circuit (L2, C4, C5) will produce better gain and efficiency with an increase in values!

But pretty close for anyone who wishes to experiment?

The output is far cleaner than i expected! And harmonics are greatly reduced!

Posted: **Wed Sep 21, 2022 12:30 am**

I will be creating an "Add On" PCB soon? Or even a complete "All In One" maybe later?

But for now? The Amplifier is so simple! It could easily be knocked up onto a plain piece of copper clad board!

Posted: **Thu Sep 22, 2022 5:18 pm**

i will wait to see the beautiful piece of art , then add an extra directionel coupler and litle swr prot

Posted: **Fri Sep 23, 2022 12:17 am**

Albert H wrote: ↑Tue Sep 20, 2022 11:13 pm One word of advice - the 2SC1947 has incredible amounts of gain at 50 MHz. When I tried them on Band 1, I found that it was necessary to either include a small value emitter resistor, or use negative feedback from collector back to the base with a resistor, inductor and capacitor in series. This kind of negative feedback will reduce the gain, and will open out the bandwidth, whilst improving stability.

I used a 2SC1971 as a 5W final on Band 1, and found that it also had a huge amount of gain, necessitating negative feedback. I found that I could get over 5 Watts out with just 300mW of drive

YES!!! Albert you are absolutely spot on here!!

For such a small device, The gain is shocking!! With further adjustments, gain has increased and current consumption has dropped!

I dont want to go too far as it may burst into a mess of harmonics!

But yeh! I think the Input match could do with a bit of tweaking? But so far so good!

Posted: **Fri Sep 23, 2022 12:32 am**

radium98 wrote: ↑Thu Sep 22, 2022 5:18 pm i will wait to see the beautiful piece of art , then add an extra directionel coupler and litle swr prot

Thank you Radium!

I know the "Butchered" PLL PRO looks a bit strange? A proper PCB will follow!

I was thinking of adding an adjustable power output control? A 3 to 4 watt increase is not exactly worthy of the circuit complexity!

Posted: **Fri Sep 23, 2022 12:51 am**

Don't mess with "variable power" - it's never a good idea. Stephen Moss spent a whole fortnight getting the 1W / 4W amplifier right for the PLL Pro III ! He was lucky - he discovered that he could get pretty accurate "conjugate" matches at the two power outputs....

Posted: **Fri Sep 23, 2022 6:29 am**

Sorry but why is it a mess .if the collector voltage varies then a harmonic produced but why ?

Posted: **Fri Sep 23, 2022 11:07 pm**

radium98 wrote: ↑Fri Sep 23, 2022 6:29 am Sorry but why is it a mess .if the collector voltage varies then a harmonic produced but why ?

Radium

I believe Albert is referring to the relation between Collector voltage and current which determines the output impedance of the transistor!

Changes in any of those parameters could cause a "Mismatch" In turn allowing possible unwanted signals to emerge!

Posted: **Fri Sep 23, 2022 11:30 pm**

Just to add!

We seem to overlook the fact that in all transistor circuits, The "Gain" actually comes from the DC Supply!

The transistor is merely a "Switch" and has NO GAIN at all!

Unless the DC supply and switching parameters are correct? It wont work!

Posted: **Fri Sep 23, 2022 11:35 pm**

Anyways! Here is the latest update!

Schematic_B1 Amplifier_2022-09-23.png

Posted: **Fri Sep 23, 2022 11:43 pm**

After more tests!

C4 and L2 have been modified which has decreased current consumption and temperature whilst maintaining output power!

Posted: **Fri Sep 23, 2022 11:51 pm**

Also!

L1 2.2K resistor is 1 watt carbon type!

Posted: **Sat Sep 24, 2022 1:51 am**

How much power are you getting? I had a '1947 doing a shade over 8 Watts (before I throttled it back) on Band 1.

I generally prefer the '1971 for that kind of output stage - they're easier to heatsink, and have plenty of gain at Band 1. I've run them at up to 10 Watts without distress, but usually aimed for 5 Watts for the somewhat inefficient horizontal dipoles that most people used to link "up the road" to their block!

Posted: **Sat Sep 24, 2022 11:46 pm**

Albert H wrote: ↑Sat Sep 24, 2022 1:51 am How much power are you getting? I had a '1947 doing a shade over 8 Watts (before I throttled it back) on Band 1.

I generally prefer the '1971 for that kind of output stage - they're easier to heatsink, and have plenty of gain at Band 1. I've run them at up to 10 Watts without distress, but usually aimed for 5 Watts for the somewhat inefficient horizontal dipoles that most people used to link "up the road" to their block!

Some VERY interesting points and questions Albert!

@ 13.8V I am getting a good 4 Watt! But i have made a discovery that i will come back to shortly!

Heatsinking IS a massive problem that i have been pondering on for some time! I could go for some abstract oversized heatsink that sits on top like a huge bunion!

As the "Link Box" chassis is a mass of metallic heat extraction? i was thinking of adding the option to the design of the PCB to mount the 1947 on the underside?

With some careful engineering, The 1947 could be pressed into the chassis?

Posted: **Sun Sep 25, 2022 12:04 am**

So back to power output which Albert mentioned!

I did suspect that the input from the B1 VFO would need tweaking? But the outcome was not what i expected!

I tried adjusting the output capacitance of the VFO to match the 1947 but it made little difference?

However, L8 on the VFO when adjusted caused the output power to rocket up to 6 Watts!!!!

Gently spreading the coils of L8 not only increased gain! But also flattened the gain across the complete tuning range!

Schematic Sinus B1TX.png

Posted: **Sun Sep 25, 2022 12:12 am**

B1 Test.png

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