TheRadioBoard

OK, after PM and mails I will try to post schematic and some scope images of waveform and such of the oscillator I made.
If we are lucky I can perhaps even record some sound.

just one thing, if you are going to use this to measure Q you must make as high Q coil as you can get for it as bandwith will otherwise be quite wide (even wider if you use modulation while measuring).

ok, here is the schematic. i will post some scope image of the received signal on my scope and such when I have managed to get some clear images, after trying 20 times or so it looks like I have to recruit Monica to help, am no digital camera whiz...

meanwhile here is the schematic, hope it is clear enough.
you may have to play with the 2k2 value some but it should work.

first we have my poormans breadboard with the parts,

it is just some IC sockets with the leg "rows" soldered together with a wire, that makes six rows (each side of the socket is one row of interconnected sockets)
and the "battery terminal", the 8 pin socket, one side is + other - wire from a 9V batteryholder.

here you have how the wave looks without modulation (transformer is not in circuit yet).

the distortion me not bothering to calibrate for the probe and center the beam than any actual distortion, scope was just started and i snapped the pictures.

here is an image of "modulation" this is me feeding output from a radio to the transformer, I did this simply with two wires from 3.5mm plug to to 12V winding of transformer, not HIFI but enough to hear clearly if things work.

the image above is at something like 1 or 2 milisecond/div to show the audio (do not remember what I used).

You do nice work OErjan!

73, Dan

thankyou
oh, just one thing, the kleijer amp was swamped with coils closer than 15" (400mm), it simply started clipping the signal, this means over2V p-p 15" away and using a 9V battery. plenty strong signal.

OK, did some more serious testing with this set-up to measure Q, biggest trouble was setting frequency well enough on high Q coils, uhm, actually only trouble, took me something like 25 min or slightly more just to get Q at ONE frequency of a 1000@1700kHz coil with this, must put better shielding and vernier, the built in 3:1 is waaay to low, 36:1 is more like what is needed or even 100:1.

another problem was that If I had my hand within 6" I changed frequency enough to move past + or - 3db points so carefully twiddle dial remove hand and repeat untill i got top voltage then noted the freq and repeated for upper and lower frequencies.
Good news is that it worked within 7% of what i usually get on this tank, I had to remove modulation by bypassing transformer with a jumper to get stability needed...

Oh I used a scope and counter AFTER the Kleijer amp by the way, with some tweaking i suspect a counter and voltmeter would be enough.

OK, now a revised version is about to be posted here (tomorrow I hope),
revision is a somewhat simpler coil (only one tap) giving a better sinewave, second change is recomendation to use lower voltage, actually 1-3V is advisable, more and you will swamp measurements with excess power.

OK, here it is, not much changed, one turn more on the coil and only one tap in middle, lower voltage.

actually I just moved variable capacitor and shortened coil on schematic above with gimp then edited text in image some.

depending on what transistor you use you could use higher voltages but be aware that this is a "strong" transmitter even with just a 9V battery.
I should guess you are getting around 100-200mW depending on exact transistor and tank Q.

Hi OErjan,
How much has the frequency drift improved with the new model 'quicky'?

it drifts about as much, slightly less distorted sinewave though.
I think much of the drift is due to temperature and battery wear, and ofcourse these two interact.
drift is still very good considering how simple the circuit is.
certainly low enough to check if a set is working or not.

I got a mail asking what gimp is.
Gimp is a free image maniulation program.
works about as well as photoshop and paintshop pro for most simpler things, some more advanced filters... are not up to photoshop standard though.
here is a pair of links
http://www.gimp.org/
http://gimp-win.sourceforge.net/

to simplify things I have a "template" with symbols that I copy paste and then just draw lines joining them