Anyone? Exiter TX's tested 1w to 7w models Sinus /rev / driver board / pira / nrg pll pro III / zozo

[LeeCavanagh]

Funny story
, I tested NRG (which isn’t the issue ) with a 500w pa and one led light popped and the other stayed on for a few seconds after I turned the light off, but when the pa isn’t on it turns off right away . I know right …

Has anyone seen this before ?
I suspect it was because the antenna was mounted on the other side of the outside wall and not very high, and the installer went and put the mounting pole right behind the main dipole on the yagi ! Would that be the cause ? I say that because the cables were good and the amp had a separate filter on the output, and the antenna was a tuned antenna more than capable of 1.5kw

[Albert H]

That sounds like RF getting to where it shouldn't!

[jvok]

Do you have a proper balun on the antenna? If not you might be getting rf going back up the coax shield

[LeeCavanagh]

That sounds like RF getting to where it shouldn't!

Indeed Albert.

Leads all kept short, proper case but kid was off. Could it be the vertical antenna and because the poke is between the dipole and back reflector (i didn’t do it that way), I know you are not meant to do that but would it be so bad to cause the led light bulb on my ceiling! to blow or stay on when switch is off..

May ask to swap to horizontal but I’m not going up no ladder. It was getting out. only worked for 2hrs tho. Swr looked fine and power was showing as 400w (rather than 500+ but I’m sure that’s because it was only tested with the antenna and no dummy load).
Need longer pole I’d say and height , not easy to install an antenna this heavy I was told (not got one guy anyway).

[LeeCavanagh]

Do you have a proper balun on the antenna? If not you might be getting rf going back up the coax shield

No. But it’s tuned by the factory in Italy. It’s a pro 5 element yagi v heavy and a lot to ship , overkill I’d say but should work tho , if it was the connector id doubt it would have got as far as it did (but what do I know - that’s right , not much ha), we are all learning but at different rates. I chose coding rather than electronics as my preference

[LeeCavanagh]

When I said led popped , I meant light bulb on ceiling, not pcb . And other stayed on turning amp off meant it went of straight away, on it would be a slow fade out , no wonder birds used to die from being too close to some antennas

[LeeCavanagh]

I sent this thread a little off topic, my bad.

[Shedbuilt]

I’d say the wiring to your lights is acting as a receive antenna, and providing a strong signal to the LED lights. This may be made worse, by radiation from the coax, in which case a balun may improve things, but it may well just be the proximity of the wires in the ceiling and wall, to the antenna itself.

[LeeCavanagh]

Yeah, right next to each other essentially

How does the NRG pro IV compare to the NRG pro III. ? Anyone ? Albert will know for sure

[Albert H]

The Pro IV takes the design a stage further. Gareth in NZ worked very hard on this further version, and the results he got were very good.

[LeeCavanagh]

The Pro IV takes the design a stage further. Gareth in NZ worked very hard on this further version, and the results he got were very good.

Nice, Did I read that work has started on using a 1971 , is that also with the same frequency selectors?

[Albert H]

Steve and I worked on our version of a Pro IV (using a 2SC1971), but it was never completed because he died. The Pro IV that is (or was) available came from NRG in New Zealand at https://nrgkits.co.nz/....

I had got rid of the trimmer in the oscillator (by using a spare output from the 4060 (IC1) in the PLL to drive a diode pump-based inverter to give a Varicap bias supply of 33V), and we'd replaced the DIP Switches with four BCD-coded rotary switches. The switches showed the frequency that the PLL was set to, and with the bigger varicap swing, tuning the rig just involved setting the frequency on the switches!

We'd also designed a big metal flange, which provided the heatsink for the '1971 and for the two Voltage Regulators, and was earthed. It also provided a screen between the output lowpass filter and the rest of the circuit. It was a little wider than the PCB, and allowed mounting screws to be fitted through it to the case.

We had also added separate modulation varicaps, and a resistive bias network that kept the deviation the same all the way up the band. The VCO was configured so that 1.55V p-p would give 75kHz deviation - allowing the use of a precise clipper and filter to prevent overdeviation. We had plans to include this overdeviation protection on the board too.

We also had plans to add several other monitoring options - supply Voltage, temperature and so on - but never got to complete it. I had re-routed the LED drive on the PCB so that we would have had a row of bi-colour (red / green) LEDs along the front edge of the board - green would indicate "locked" and "OK", and red would be "Out Of Lock" or "Fault".

The next version (Pro V) was to include a single chip PLL, with a PIC controlling it, and a somewhat smaller PCB. I have the early sketches for this design here somewhere.....

[LeeCavanagh]

Albert, I mean you mentioned realising a version with Rigmo recently that featured the 1971, I get confused easily

That sounds really good, it would be good to re-invigorate that with either of the NRG companies, the designs that exist will be in the history books for ever… or if allowed , licensing someone new, there is still a market out there ? No? Or do most people go for something slim they can fit into a pipe (or whatever they are stuffing their bits into these days).

[Albert H]

A friend of mine is working on an update to the Pro III, adding a bandpass filter to the output of the oscillator (to prevent ½f breakthrough) and a second pair of varicaps for the modulation. He's making a few other refinements to the RF side of the board, and is using a 2-chip PLL solution to allow the PCB to be shrunk. I don't know if this variant is going to be made widely available - I'll let you know when I know!

[LeeCavanagh]

Awesome,
Oh, i remember our older tx from back when Stephen was having the trouble over the PH content of a rather unpalatable time. I wasnt sure who that came from but id been told it wasnt one of SM, maybe it was a beta from you two?

[LeeCavanagh]

Who else was doing bcd back then?

[Albert H]

All my early synthesisers used BCD programming to simplify the controls. Even the most hardened transmitter engineers used to balk at a row of tiny binary switches!

I used BCD-coded rotary switches as soon as I discovered the way to do variable division ratios with TTL chips! My first synthesisers were for medium and shortwave, but as soon as fast prescalers became available (Plessey and Texas Instruments were the two manufacturers in those days in the '70s) I developed my first VHF PLL circuit:

My first VHF PLL used an Exclusive-OR gate as the phase comparator, which ran at 1/100th of the carrier frequency. The reference was variable from 875 kHz to 1.080 MHz in 100 kHz steps! The reference frequency was derived from a 10 MHz crystal (in TTL logic - lots of it!), and the 5V logic took almost as much current as the rest of the rig! It might have been a bit of an ugly hack, but it worked well, and was easy to programme! The Plessey SP8629 divider chip sampled the output frequency and fed it (divided by 100) into the logic.

Soon, fast CMOS (74HC4xxx series) became available, along with a purpose designed phase comparator IC (4046), and simple CMOS synthesisers drew much less current than their TTL counterparts. When the 4059 arrived - four decades of BCD-programmed division - even better synthesisers became possible - at fairly low cost.

For entirely pirate purposes, I developed the 4-chip synthesiser - 4 MHz crystal (really cheap!), 4060 reference oscillator and divider, 74HC4024 to divide the VCO ½f signal by 8, a diode-programmed 74HC4040 as the main presettable divider,and a 4046 as the phase comparator. Early rigs used a passive loop filter, but later I found that I could get better results by using a fifth chip - a quad op-amp - to provide the loop filter and the modulation audio buffer. The whole synthesised exciter used to cost ~£9 in parts, and gave 4W of very stable Band II.

[LeeCavanagh]

I like your posts , always a good read

How much is £9 in todays money ? Do you mean when buying in bulk to reduce costs ? I can’t find many things on parts lists that make it worthwhile for me, that said I did recently blow 6 transistors that cost £45 each ! So I’m talking out my .£) I’m going to try and make some more of these smaller projects if it’s still doable and not obsolete

No did respect , but we must soak up everything we can whilst we can, especially the youngsters on here (which I’m not), we/you are not going to be able to hold our hands for ever, but the kit, advice and all the good stuff you do every day will inspire new generations (your generosity is respected and comes from a good place). Thank you

[radium98]

Nice words

[Albert H]

Thanks Lee.