Magnetic Resonance Devices based on Don Smith Concepts

[stprue]

hi MasterPlaster,


http://www.electrotherapymuseum.com/Library/Library2008Tesla.htm

search page:Armagnat

I like this thought( in regards to the pic you posted), to me I see SM as well as a version of the tesla hairpin circuit.

[Yucca]

Finished my secondary coil build now....

Superb work! I glanced the pic before I read your text, I thought it was a pic of one of Dons devices I hadn't seen yet lol.

This is a good coil inductance calculator, you could use for ballpark figure:
http://hamwaves.com/antennas/inductance.html

edit:
What did you use for your six support ribs? looks like square wooden dowel, maybe hard balsa?

silver plated wire too, very nice. Looking like a serious replication of the tabletop device.

[gyulasun]

...
I am not sure how accurate my GDO is and don't have a freq meter to confirm this, but when i did a dip on a small coil i connected my scope to one side of the dip meter coil and got a totally different freq on my scope than the GDO was reading, but this may have been because the scope loaded the coil i suspect, and i realize now i shouldnt have monitored the GDO this way, as i am new to using the GDO i need to get a bit more familar with it. 

Hi Peter,

You realized it correctly, connecting a scope (or its probe) onto one side of a GDO coil may pull the measuring frequency (normally downwards) with respect to the dial. However if you place the scope probe near to the GDO coil, say at least 3-4cm from it, (the ground clip can either be floating or connected to the metal body of the GDO if any or to the GDO's battery pole), then you should see on the scope the picked-up sinusoidal oscillator signal of the GDO in the most sensitive scope input range, the benefit is that such a loose coupling will alter the dial of the GDO but a very little. This way you can even check the dial's accuracy to +/-5% or so if your scope time base accuracy is around that. If you happen to have any digital scale radio receiver for AM up to 26MHz or so or an FM receiver (89-107MHz), then you may use them also for checking at certain frequencies. (if your GDO happens to have switchable AM modulation feature, then use it for finding the GDO signal by a digitally scaled AM receiver, but even without  any modulation, you will surely 'hear' it in the speaker whenever your sweep through slowly)

...
I am also worried that there are signs of it having been opened up in the past for what ever reason.

Another thing i notice when using the GDO is that the meter does move lower by itself when i move the tuning dial from min freq to max freq when sweeping, so it appears i need to keep adjusting the meter to read 0.8 as per the instruction manual, i am not sure if this is normal.
...

Well, most of the GDOs on market behave like you describe.  This is because the wideband oscillator included in the GDO has a changing oscillating amplitude. This change is manifested in the meter movement. However, the 0.8 reading requirement is not so strick you always have to observe,  you can surely use it around 0.4 or 0.6 for the quick sweeps, so you do not have to stop sweeping in the middle of a frequency range and adjust the level again to bring the meter down,  you can do level adjusting to near 0.8 later when you have found a dip.

Here are two links you may find useful on how to use a GDO (I assume the GDO manual also have some hints):
http://www.qsl.net/iz7ath/web/02_brew/15_lab/02_dipper/english/pag02_eng.htm
http://www.qsl.net/m3msm/gdo/gdo.htm

(Re on your notice of the GDO box have been opened up in the past,  well if you find big inaccuracies in the dial reading wrt the actual oscillating frequency, especially in the higher tens MHz ranges, then you may look for replacements of components inside the box, otherwise it has no significance.
Digital radio receivers can be accurate to 10kHz or so on AM and to 150-200kHz on FM.)

rgds, Gyula

[Yucca]

I did some work with sig-gen and oscope on my setup last night:

pri:
7 turn with 2000pF

sec:
24 turn into FWBR into 2000pF

I measured the primary LC at about 1.6MHz with the gap closed and 7.5MHz with the gap open. But I know when it transmits it is closer to 2MHz (I sniff it with a probe 1m away when running). So when I hang any wires on this thing it increases C and lowers res.f.

I then checked for natural resonance of the secondary in situ using an unconnected sniffer scope probe. I excited the base of the secondary using a single wire off my sig-gen. I then swept looking for first resonance.

With FWBR connected:
fr = 16MHz

With FWBR disconnected:
fr = 16MHz

So maybe I need to get my primary singing at 16MHz, I will need a much smaller cap than 2000pF to get that even with only 2 turns. I'm seriously thinking of getting a vacuum variable cap although I suppose provided the input gap is narrow enough I could get away with a normal metal plate in air variable cap (much cheaper)

[Peterae]

Hi Yucca

Thanks for the comments.
I used grommet strip, see my post and picture on page 12 of this thread.
the grommet strip is quiet flimsey.
First i found a 3 inch tube, and it so happened i had been given a bottle of Glenfiddick Whiskey which came in a 3 inch carboard tube, so i first drank the whiskey over a 7 day period HICK Still got hangover LOL

I then tapped the grommed strips around the circumference, used a bakebean can from asda LOL to wind the coil first, i then transferred the 20 turn coil onto the Tube and into the grooves of the grommet strip.
I then applied 5 min epoxy glue into the grommet channels and let it harden.

I trimmed the ends of the coil noting how much length i took off to work out the final wire length.

The wire i used is tinned, i used this incase the enameled stops coupling to the atmosphere.

gyulasun
Thanks for this information it answers all my questions about how to use the GDO just need to get some hands on now
The radio idea is great and will enable me to check the higher freq acuracy.

Yucca great stuff with the hands on looks like i may need a better Sig Gen as mine only goes to 12mhz 

Very interesting the bridge doesn't alter the res freq.