Dr Ronald Stiffler SEC technology

[itsu]

Here the differential measurement across the 2th AV-plug (middle coil) using the oscillator, see screenshot 1
I have offset the both blue and purple traces for better viewing.
The math function (purple - blue) shows a negative result, even when i swap the probes.

The probes have some influence (negative) on the brightness of the leds.

The analoge voltmeter in the supply line goes all the way to max (250mA) so is again influenced by the RF field.




Doing the 1 Ohm csr measurement again using the oscillator posses some problems as the signals are far from
stable (csr in front of the trimmer cap).
Again the result is always negative which way i put the probes and the difference is about the same with
or without the 3th coil/leds strip combo inserted into the 2th coil (between -400 and -650mV).

So i do not really trust this measurement.

Screenshot 2 is with 3th coil/ledstrip inserted,
Screenshot 3 is with 3th coil/ledstrip removed.

Swapping the csr and trimmer cap (trimmer cap in front of the csr) complicates things further as the
oscillator stops when removing the 3th coil/ledstrip (needing new tuning).

Itsu

[gyulasun]

Okay Itsu, many thanks and I will try to digest your findings today but may be able to answer tomorrow evening only, due to some travel daytime, I will see.
Gyula

[itsu]

Hi Itsu,

My bad, somehow I missed your post #555 and commented only your post #561 when you were measuring the output to the LED board in the 3 coil setup. So you already gave the answers to my most questions. 

You wrote: Well, okay but I was pondering why the shorted DC component as a result of rectification may or may not cause loss in the setup? Because the AV plug diodes rectify the RF as they should and if you place a puffer cap across the diodes output, then DC voltage remains and the RF is killed as usual.  Now there is the coil across the diodes output and the DC is surely killed (at least voltage wise) and the RF voltage remains. This is why I mentioned this. 

In the Doc's video his scope showed only a little change in the RF amplitude the probes measured (I do not mean the Math channel) when he removed the 3rd (output) coil + LED board combo,  while in your setup the RF amplitude changes about 5V (from 17Vpp to 12Vpp) when you remove the 3rd coil.  I think this may come from the small differences between your coils especially due to the small difference between the middle and the 3rd  (output) coil.
So probably the 5 Vpp change could be reduced if you replace the input and the output coils with each other: this way, after the change, the two most identical coils would be at the critical places as I think.  Of course we do not know yet whether such 5 Vpp or whatever change at the input of the 3 coil setup may prove to be unwanted or not, I mention this because in the Doc's setup such amplitude change is not seen.

Gyula

Gyula,

i have swapped the output coil (27uH) with the input coil (26.7uH) and left the middle coil (26.7uH).

Using my FG i measure again across the 1 Ohm csr, but still the voltage pp differs about 5V (17V v 12V)
leaving a steady 40mV difference with or without the 3th coil/leds.


The problem i notice now however is that the Vpp on the csr input (from the FG) is lower then on the
csr output, see screenshot.

Blue is on input csr (next to the red lead FG), purple is on output csr.
Math function is blue - purple giving a negative value.

I believe that was also the case (more Vpp on output) on the post #555 screenshot but am not sure.

Need to do some more tests tomorrow.


Itsu

[itsu]

Okay Itsu, many thanks and I will try to digest your findings today but may be able to answer tomorrow evening only, due to some travel daytime, I will see.
Gyula

No problem, take your time,  doing the same overhere.
Itsu

[gyulasun]

Hi Slider,

Let me suggest this: first adjust a some kHz or some 10 kHz output frequency for the AD9850 board and check its waveform, it should not be wonky. Your scope nicely shows the 1 kHz built-in test signal, though I am surprised it has 30 Vpp amplitude ? (It can be correct of course I do not know your scope and I got used to 5 Vpp built-in test signals.)
If the lower frequencies are nice-looking, taken directly across the output from the AD9850 board, then drive the boost circuit with such low frequency signal and see then its output how it operates at low frequencies too. Of course you need to reduce the output from the generator to as low as some 10 mVpp maximum, not to overdrive the booster.
If that also seems ok, then increase the output frequency and sweep or simply step through up to the hundred kHz and then to the some MHz range.

I just watched your video entitled "AD9850 signal generator - arrived, built, tested" where you went up to 29.999 MHz.
Would like to ask whether the output impedance for the AD9850 board is specified as ?  Is it a low impedance like 50 Ohm or some hundred Ohm?  I ask this because as you surely know, normally such generators should be terminated by a non inductive resistance that equals to their own output impedance, this way the change you see as a gradual amplitude decrease across the output becomes less than in the unterminated case. OF course I know that for the Doc's tests the generator is used as unterminated but if a booster is used then a decent termination across the generator output is helpful for a nicer output waveform.
Be careful with such termination directly across the generator output because if there is a DC level at the output too, then it should not be terminated by a low value resistor directly but only via a series coupling capacitor. 

"then dump the boost circuit into a bath of kerosene and ignite it "   I think you can wait with this... 

Gyula
Edit: if the waveforms remain 'wonky' via the booster only (but good from the gen output), then try to use a 9 or 12 V battery as the power supply for the booster to make it totally ground independent and see the waveforms then.