pirateaddict wrote: ↑Tue Sep 10, 2024 2:47 pm Or8 Brian... I'm pretty sure NRG.nz were selling kits a while ago but don't do kits anymore afaik!

tvtv wrote: ↑Fri Sep 13, 2024 1:43 am For some reason this doesn’t show when I search for the word title, also sellers other items comes up empty. Only viewed by clicking the above link

Albert H wrote: ↑Fri Sep 13, 2024 10:27 pm YASIUK GCE Is a Greek copyist. The board you see above is closely based on the update that NRG NZ did. I suggested many of the improvements that are included on that version to NRG NZ.

I built my own variant of the board with a two-IC PLL (which was approved by Stephen and was going to become the Pro IV), and changed the output stage so that it would give ~20 Watts (using a FET).

I also modified the VCO so that the trimmer became unnecessary - it would tune from 85.5 - 110 MHz without any tweaking! I gave the Varicap supply 33V derived from a voltage multiplier that was driven from a spare output of the PIC that was used for the PLL - it used a diode / capacitor ladder and a low noise zener to give a clean and stable 33V. This increased the tuning range, but allowed the modulation sensitivity to remain sensible - it needed ~2V p-p for 75 kHz deviation, ensuring that it wouldn't suffer from the hum issues experienced by other circuits.

The layout was redesigned somewhat to allow the VCO to have a tinplate can around it (for lowest noise), and the output filter was screened from the rest of the board. There was a large metal H-section flange that provided the heatsinking for the output device and the voltage regulators, and provided mounting points. I etched several boards by hand, and made three prototypes (and found one mistake in the first two boards that I corrected subsequently!). The prototypes worked well, and produced in excess to 20 Watts at any frequency that they could be tuned to.

I was considering adding deviation limiting to the board - to make it impossible to over-modulate - but this would have required an enlarged board and lots of extra circuitry. The boards ended up being just 11cm X 8cm, and would fit neatly inside a standard Eddystone diecast box. We also considered adding a "control" PCB, containing the BCD rotary switches for frequency setting and the status LEDs, but thought that it was just adding unneccessary complexity.

The spectral purity was very good, and with the reduced number of components on the board, a competent constructor would have been able to complete one and test it in a couple of hours. It would also have worked out (marginally) cheaper than the PLL Pro III 4 Watt board!

I experimented with variable output power, but abandoned the idea, as it proved impossible to maintain the great purity at reduced power. If I want reduced power, I either use a different circuit, or add a resistive "pad" to attenuate the signal.

Now I've got more time, I might return to the circuit and see if I can come up with a finalised version....!

Albert H wrote: ↑Fri Sep 13, 2024 10:27 pm Now I've got more time, I might return to the circuit and see if I can come up with a finalised version....!

BriansBrain wrote: ↑Sat Sep 14, 2024 12:45 pm

Albert H wrote: ↑Fri Sep 13, 2024 10:27 pm Now I've got more time, I might return to the circuit and see if I can come up with a finalised version....!

That would be great

Albert H wrote: ↑Fri Sep 13, 2024 10:27 pm YASIUK GCE Is a Greek copyist.

Albert H wrote: ↑Sun Sep 15, 2024 12:50 am I'll give you all some simple circuits shortly, but it'll be up to you to get hold of the parts!

teckniqs wrote: ↑Wed Sep 18, 2024 1:55 am ....These original Veronica/NRG things have been around for the best part of 30 years, it's good to see people still using them. I think the PCB looks quite cheaply made on this one though.

yellowbeard wrote: ↑Mon Sep 23, 2024 2:57 am ... since then the price of weed and beer has tripled - the weed is much stronger though...