Thank you for your video. I've been looking for a circuit like this for some time. I'm going to have a go at building one, once the JFET transistors arrive.
Nice circuit. However, I think you have power supply coupling. So, you can either use RF bead or C-R-C network for your power supply for drain of JFET and another for Collector of NPN transistor, so you do not have power supply coupling. Basically on side of Cs are connected to ground and another to the each side of resistor like a PI network. Also, you should use several Cs in parallel to get ride of self resonance frequency of Capacitor. That is you should use 47nF II 4.7nFll 470pF ll 47pFll 4.7pf ll 0.47uf. In general, I am not a fan of this type of probing anyhow, I would use E or M field probing for sensitive nodes.
I think this is an awesome little project and worth while addition to a spectrum analyser. How practical would it be to add some higher voltage DC blocking and perhaps some additional attenuation I’m thinking valve radios Thanks for sharing
Good point. The simulation indicates the passband is at minus 13.4 dB and the 3dB response is 5.5 kHz to 52.3 MHz when driving into a 50 ohm impedance.
Could you connect sync out from the sig gen to external sync in on the scope to get reliable triggering, that should show the waveform clearly so any distortion et cetra would be visible; avoiding all the noise mush?
Yes, I should have mentioned that I use a 10X probe which divides the input signal by 10 and multiplies the input impedance by 10 giving a 10 Meg Ohm load to the circuit under test. Most scope probes over 100 MHz are 10X and that is what I use with this circuit. Thanks for the comment and question.
I like what you are doing and thanks for sharing. However, I would not trust it for everything. Your probe capacitance is going to be high and will load various circuits.
Thank you for your video. I've been looking for a circuit like this for some time. I'm going to have a go at building one, once the JFET transistors arrive.
Very enjoyable project!
Nice circuit.
However, I think you have power supply coupling. So, you can either use RF bead or C-R-C network for your power supply for drain of JFET and another for Collector of NPN transistor, so you do not have power supply coupling. Basically on side of Cs are connected to ground and another to the each side of resistor like a PI network.
Also, you should use several Cs in parallel to get ride of self resonance frequency of Capacitor. That is you should use 47nF II 4.7nFll 470pF ll 47pFll 4.7pf ll 0.47uf.
In general, I am not a fan of this type of probing anyhow, I would use E or M field probing for sensitive nodes.
Superb !!
Very nice!
I think this is an awesome little project and worth while addition to a spectrum analyser. How practical would it be to add some higher voltage DC blocking and perhaps some additional attenuation I’m thinking valve radios Thanks for sharing
It would have been nice to show the Bode plot. A quick LTspice simulation shows that the base stopper cuts it by half to about 50MHz. -12dB at 100MHz.
Good point. The simulation indicates the passband is at minus 13.4 dB and the 3dB response is 5.5 kHz to 52.3 MHz when driving into a 50 ohm impedance.
Could you connect sync out from the sig gen to external sync in on the scope to get reliable triggering, that should show the waveform clearly so any distortion et cetra would be visible; avoiding all the noise mush?
Would a 10 meg input be more appropriate for less circuit loading?
Yes, I should have mentioned that I use a 10X probe which divides the input signal by 10 and multiplies the input impedance by 10 giving a 10 Meg Ohm load to the circuit under test. Most scope probes over 100 MHz are 10X and that is what I use with this circuit. Thanks for the comment and question.
I like what you are doing and thanks for sharing. However, I would not trust it for everything. Your probe capacitance is going to be high and will load various circuits.