Information about RF current meter
Somone can help me to find informations about RF current meter ?
... links, schematics ...
In fact , i would like to measure the power on a variable Load...
The only solution to have a constant power on the load is to measure the Current and the voltage across the load...
I think i can measure the current with a current transformer and the voltage with a resistor bridge + HF peak detector..
The load can fluctuate between 30 ohms and 100 ohms and the maximum output power is 30W ! The signal frequency is between 1Mhz and 5Mhz!
Give me your opinons please ...
Best Regards
You are using the classical method which is also low cost. The alternative to measuring the current is to have a thermistor type meter which are still made for use in AM MW band broadcast transmitters in the US.
Some practical ideas:
http://www.w8ji.com/building_a_current_meter.htm
http://www.computerpro.com/~lyle/currprob/currprob.htm
http://www.ifwtech.co.uk/g3sek/clip-on/clip-on.htm
regards
Why not use a bidirectional wattmeter?
The advantage is that you may "cut" the feeding line everywhere you want, and it take in account every eventual variation of the delivered power.
The power measurement thry directional coupler is RF aproach and voltage/current meashurement is DC approach. Going by RF , type "amateur power meter" in Google's window.
Ok, I think the best solution is to have a bidirectionnal coupler but it doesn't exist for Low frequency ( 1Mhz) and for 30 W input power !
Perhaps somenone know a manufacturer who has this kind of coupler ?
How can i do to design this kind of bidirectionnal coupler ?
Best Regards
I've read the links proposed by vfone, the answer by divan and bobytronic.
The idea to pick the RF current by an inductive coupler is better than E probe, because solve the problem of false contact.
But it's still a RF coupling and need a detector
In all cases the measurement still a DC substitution, also using a bidirectional wattmeter.
Agilent build a directional coupler in the range 100Khz-100MHz. It's unable to carry 30W CW but for short periods it's possible