yellowbeard wrote: ↑Wed Dec 07, 2022 4:11 pm Le sigh.
https://www.pira.cz/entx4.htm
No swanky variable inductors in the original. You kids play nice now!

Oh Rigmo!

You are a funny guy!! This thread made my day!!

This is impossible to build with variable inductors without the inductor values.

I suspect Rigmo did not design this new version?

The original dimensions are 3.5 turns with a diameter of 7mm?

Assuming a footprint of around 10mm? (Roughly) would indicate around 45nH?

sinus trouble wrote: ↑Thu Dec 08, 2022 12:58 am I suspect Rigmo did not design this new version?

The original dimensions are 3.5 turns with a diameter of 7mm?

Assuming a footprint of around 10mm? (Roughly) would indicate around 45nH?

PIRA 5w PLL part list:
L1 - 3.5 turns on 7 mm diameter ( 120nH no space, max wide coil 80nH) midle is 100uH @100mhz

Is the Q of these variable inductors better than an ordinary handmade inductor?

Found a datasheet of KLS18-MD 0505 that are sold very cheap on aliexpress
https://www.rcscomponents.kiev.ua/datas ... asheet.pdf

there was also a nice modification to the piracz 5watt circuit to provide variable power and RF shutdown when the PLL is unlocked.you could incororate it to your new layout.

https://pira.cz/forum/index.php?topic=111.0

fmmpastouni wrote: ↑Thu Dec 08, 2022 8:27 pm there was also a nice modification to the piracz 5watt circuit to provide variable power and RF shutdown when the PLL is unlocked.you could incororate it to your new layout.

https://pira.cz/forum/index.php?topic=111.0

photos not a viable

rigmo wrote: ↑Thu Dec 08, 2022 11:48 am

sinus trouble wrote: ↑Thu Dec 08, 2022 12:58 am I suspect Rigmo did not design this new version?

The original dimensions are 3.5 turns with a diameter of 7mm?

Assuming a footprint of around 10mm? (Roughly) would indicate around 45nH?

PIRA 5w PLL part list:
L1 - 3.5 turns on 7 mm diameter ( 120nH no space, max wide coil 80nH) midle is 100uH @100mhz

Ah! So judging by the images, 4.5 turns would be a better starting point!

Either way, it is not a big problem! Worst case, you would not cover the full band!

Easily fixed by adjusting the coil in relation to the tuning voltage! A proceedure that is usually performed on most new builds anyway!

rigmo how do you want him to contact you if the post is outdated since May 10, 2012

mine

radium98 wrote: ↑Fri Dec 09, 2022 5:29 pm rigmo how do you want him to contact you if the post is outdated since May 10, 2012

user Barell Last Active: November 03, 2020, 12:17:12 am ( ho know is still alive ! )

Previous home made

Hello.I tried to make the mods for variable rf power and rf power shutdown when unlocked.Parts that need to be added are in blue rectangles.Hope it works and its not an overkill of parts

I also think that PIC16F627 asks the TSA5511 if it's in lock state and after it locks it stops asking on a regular basis whether it is locked or unlocked .the state on pin 1 of PIC16F627 will remains unchanged (5V) even if PLL is considered unlocked(for example if keep touching the coil to manually cause an unlock state). But when you change frequency the lock state changes to unlock until it locks and then after the lock it doesnt change.

I also attach the asm file if someone knows programming.

Page of the transmitter : https://www.pira.cz/entx4.htm

pcb pira 5W

fmmpastouni wrote: ↑Mon Dec 19, 2022 10:14 am Hello.I tried to make the mods for variable rf power and rf power shutdown when unlocked.Parts that need to be added are in blue rectangles.Hope it works and its not an overkill of parts

Sadly, your variable power modification won't work, because the final stage isn't linear - varying the drive power might make a very small change to the power output, but when the drive drops below the point at which the final will conduct, you'll just get no output at all! It's usually best to run the Class C final with just the right amount of drive so that it doesn't get saturated (which gives rise to harmonics).

Some "engineers" don't understand the problem, and try to make their exciters "no tune" by overdriving their final stage to get a "flat" output across the band (look at the A****f effort for an example of this). This practice invariably makes for a really nasty, dirty output spectrum - especially if the output filter is inadequate or poorly laid out (A****f again!).

Variable power out isn't trivial to achieve, and most design engineers don't bother to try to do this. You have to bear in mind that if you change the supply voltage, you'll also change the output match impedance, so the values needed in the final match to convert the lower output impedance of the transistor to the 50Ω or 75Ω that you want to feed into your coax. This is true both in exciter stages and in PAs.

Stephen Moss was lucky with the PLL Pro III (after a hell of a lot of experimentation) - he was able to get the final transistor to deliver ~4 Watts with its emitter grounded, and 1 Watt with the emitter sitting on top of a couple of power resistors. He managed to achieve a "conjugate" match in the lower power setting. If you try different emitter resistors (in an effort to get 2 Watts, perhaps), you'll find that you have a mismatch at the collector.... There are only the two power settings that work! In reality, the output match is even cleverer than it looks - the PLL Pro III gives 4 Watts at 88 MHz, and about 4.3 Watts at 108 MHz - this "sloping" output power was done to account for the gain droop with increasing frequency of the transistors he used in his PA modules. The 40 Watt BLW60C PA would give exactly 40 Watts out at any Band II frequency when driven by the PLL Pro III board.

There is little point in trying to make a variable power transmitter. For example: DB Elettronica make one which gives 300 Watts out at full power. They specify the harmonic and spurious content at 300 Watts out, but don't give any figures for when the power is turned down!

If you want your rig to deliver 10 Watts, design for 10 Watts, not 1 - 10 Watts! If you want 1 Watt, just design for 1 Watt. Incidentally, with a 12.65 Volt supply (allowing for 0.65V transistor loss) and 1 Watt, you'll get a natural match of 72Ω - ideal for feeding into "75Ω" coax (it's not - it's usually closer to 72Ω). Most of my Band IV link rigs would do 1 Watt, and would naturally match into TV coax and a TV Yagi. This makes for efficient, cheap link gear!

Thanks Albert .Merry Chritmas .

Thanks for the valuable feedback mr Albert H.What if using gate voltage of RD01,RD06,RD15...type mosfets to control output power.Are the same drawbacks as above aplied here?By the way do you have a schematic to post based on jfet or dual gate as oscillator,then buffer ,RD01 as driver and RD06 or RD15 as final??

This modification that says in the scheme is to prevent gain at low frequencies, do you think it is correct? Or would it be like the second scheme? Thanks.

Neither of those will drop gain at low frequencies.

The first one is adding negative feedback which will drop gain at high frequencies (not low) but in turn will make the gain and matching more even across the band and might reduce harmonics a little bit.

The second circuit will do nothing. In theory it would also drop gain at high frequencies but in practice the impedance at that part of the circuit will be too low for a 330r resistor to make much difference.