Help, need simple probe for 14 GHz EMF Measurements
Help, need simple probe for 14 GHz EMF Measurements
(OP)
Does anyone have some specs I can use to build a simple probe with known gain and bandwidth characteristics for 14.0 GHz? I need one to investigate the level of EMF from a 14 GHz transmitter to assure the amount of radiated microwave energy is below 10 mw per cm.
I am looking for a simple 1/4 wave monopole design using a SMA connector and ground plane if anyone has that info or can direct me to it, I've googled for two days without success.
Chris KL7FB
I am looking for a simple 1/4 wave monopole design using a SMA connector and ground plane if anyone has that info or can direct me to it, I've googled for two days without success.
Chris KL7FB





RE: Help, need simple probe for 14 GHz EMF Measurements
1) cut a cable, tune for VSWR, call it 0 dBi gain.
Just strip a semirigid cable outer conductor back and expose about 1/2 inch, then cut the center conductor shorter while looking at VSWR, when you get around 1/4 inch length of the center conductor you'll get a good VSWR point.
You could make a dipole too if needed, but a monopole is easier.
2) find or buy a Pentel Pencil 0.5 mm with metallic head (part where the lead comes out), unscrew the metal cap of the pencil and stick it in an sma-f connector (fits nicely)and use that as a probe, it's good from 3-40 ghz typically. You might want to cut the height of the pentel part down to make it shorter.
kch
RE: Help, need simple probe for 14 GHz EMF Measurements
I found this link for a COUPLED SECTORIAL LOOP ANTENNA UWB antenna/probe http:/
RE: Help, need simple probe for 14 GHz EMF Measurements
Knowing the "spaceloss", if you measure exactly that value, your probes are zero dBi. If you measure 2 dB less than that value, your probes are +1 dBi each, etc.
It's a legal way to determine antenna gains that's used industry wide in the antenna world. It'll help convince people if you do the calibration, then do the measurement at 1.5", 2", 2.5" and 3" and use the space loss equation to calculate all the results and see how close they are to each other.
The orientation of the cables of both probes can change results a bit (+/- ?1,2 dB). If you get the probes too close to each other, they'll hurt the accuracy. You may be able to be 3/4 inch apart and still have good results.
If you are really in need of accuracy, make 3 probes. It's called a "3 antenna test method", you can determine the exact value of each probe that way. 3 coupling measurements 1-2,1-3,2-3 and 3 variables gain1,gain2,gain3, hence 3 equations, 3 unknowns is solvable for the individual gain of each probe. It'll look more impressive to the management. Either way will work though.
kch
RE: Help, need simple probe for 14 GHz EMF Measurements
You have been great help!
Chris
RE: Help, need simple probe for 14 GHz EMF Measurements
1.5 Inches = 2.3674242E-5 Miles
Entering .000023674 in the online path loss calcuator at your link to http://www.comsearch.com/broadband/tools_fsl.jsp the answer was 27 dB of path loss at 14 GHz.
Very nice!
RE: Help, need simple probe for 14 GHz EMF Measurements
RE: Help, need simple probe for 14 GHz EMF Measurements
Either make sure the pentel unit is metal, or buy some metal spray paint to metalize it better. You can buy small quantities from Chomerics, etc. that aren't too costly.
Many companies have gone to plastic tips, though some still use metal.
Any wedge shape will work. You could probably find alternative items, like any pin that fits in an sma and wrap metal tape around it to flare it out to increase it's bandwidth, making it more useful.
Or trim a semi-rigid cable and solder a copper tape triangle on it, that'd work too. Make it an inch long, look at VSWR and trim it if needed.
kch