Nuclear Magnetic Resonance (NMR)

[conradelektro]

What large value should the capacitor have to match the 50 Ohm source of the RF amplifier shown in my post above? (100KHz-60MHz RF Power Amplifier 5W Liner Amplifier RF Broadband HF Amp)

I did a simple calculation for Q=1 of the circuit:

U * I = 5 Watt  ,  U = I * 50 Ohm

From this follows:  I = 0,31 and V = 15,8

Greetings, Conrad

[Smudge]

What large value should the capacitor have to match the 50 Ohm source of the RF amplifier shown in my post above? (100KHz-60MHz RF Power Amplifier 5W Liner Amplifier RF Broadband HF Amp)

I did a simple calculation for Q=1 of the circuit:

U * I = 5 Watt  ,  U = I * 50 Ohm

From this follows:  I = 0,31 and V = 15,8

Greetings, Conrad

Well it all depends on your inductance value for the pair of pancake coils.  The variable capacitor (shown as 100pF max) will tune to the desired frequency and the fixed capacitor has to be much greater than whatever that tuned value comes to.  And the frequency to tune to will depend on the magnitude of the applied field from the magnets.  A good guide to get high Q is for the fixed capacitor to be be at least 10 times the variable one, possibly even 100 times.  I will try to do a spreadsheet where you can input your inductance value, the resistance of the coils (taking into account skin effect), the tuned capacitor value, the fixed capacitor value, the generator voltage and the generator source impedance.  Hopefully it will give you a chart of the voltage across the pancake coils against frequency showing it peaking in the typical resonant manner.

Smudge

[conradelektro]

Well it all depends on your inductance value for the pair of pancake coils.  The variable capacitor (shown as 100pF max) will tune to the desired frequency and the fixed capacitor has to be much greater than whatever that tuned value comes to.  And the frequency to tune to will depend on the magnitude of the applied field from the magnets.  A good guide to get high Q is for the fixed capacitor to be be at least 10 times the variable one, possibly even 100 times.  I will try to do a spreadsheet where you can input your inductance value, the resistance of the coils (taking into account skin effect), the tuned capacitor value, the fixed capacitor value, the generator voltage and the generator source impedance.  Hopefully it will give you a chart of the voltage across the pancake coils against frequency showing it peaking in the typical resonant manner.

Smudge

Thank you for your help.

I will try to print the circular water tube with my 3D-Printer within the next days. It will be interesting whether this will be possible.

And then I will order the following RF amplifier from China. The resistance of the output is not clear, but I hope to be able to figure it out. The EUR 22,04 will not hurt me, even if all is in vain. May be I can set up a revolutionary radio station if all fails.

https://www.ebay.at/itm/1-1000MHz-2-5W-HF-VHF-UHF-FM-Transmitter-RF-Power-Amplifier-AMP-For-Ham-Radio/192772405806

Broadband RF small power amplifier, suitable for all types of radio transmission, such as: short-wave FM wireless remote control, FM radio station transmission, amateur radio 135-175MHz, 380-470 MHz walkie-talkie and other launches. The low-frequency input 2mW can output 2.5W maximum power, and the maximum output can be 2W at 500MHz. The maximum output can be 1.5W at 800MHz. The maximum output can be 1.0W at 1000MHz. The amplifier housing has a heat dissipation function and can work stably for a long time.

Technical parameters:

     1) Operating frequency: 1-1000 MHz
     2) Output power: input power: 2mW (3dBm)
                           2.5W (34 dBm) low frequency end (100 MHz)
                           2.0W (33 dBm) IF terminal (500 MHz)
                           1.5W (31 dBm) high frequency end (800 MHz)
                           1.0W (30 dBm) high frequency end (1000 MHz)
    3) Working voltage: 15V (DC)
    4) Operating current: 430 mA (determined by output power)
    5) RF connector: standard SMA female
    6) Dimensions: 82*71*25 mm (length * width * height)
    7) Product weight: 90 g (the housing has heat dissipation function)

Getting the RF amplifier will take up top a month, so, do not hold your breath.

Greetings, Conrad

[Thaelin]

Conrad:
   Fairly standard amp, most likely 50ohm impd. Typical for most.


thay

[conradelektro]

Conrad:
   Fairly standard amp, most likely 50ohm impd. Typical for most.
thay

Thank you for the reply.

What do you think about it's input impedance? I want to drive it with my 50 Ohm function generator (sine wave at about 4 MHz).

https://www.peaktech.de/produktdetails/kategorie/dds-multifunktionsgeneratoren/produkt/peaktech-4060.871.html

Greetings, Conrad