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Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
coillah wrote ...
You said a few inches of coax, can I do up to .5m? .8m?
I may need to see your setup, but at 0.5m youll need to buy your SMA coax from mouser or whoever, or maybe radioshack rg59, bnc - bnc cable, with the ends cut off and solderd. 0.5m is probably ok, but remember your addding 2.77pF per inch of radioshack BNC-coax. if your capacitence cant be charged then youll lose the ability to transmit, in the mW power range, such loading must be considered.
Maybe if this doesnt work youll have to move the transmitter to the antenna location, and the try serial data across the large distance.
Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
Patrick wrote ...
coillah wrote ...
You said a few inches of coax, can I do up to .5m? .8m?
I may need to see your setup, but at 0.5m youll need to buy your SMA coax from mouser or whoever, or maybe radioshack rg59, bnc - bnc cable, with the ends cut off and solderd. 0.5m is probably ok, but remember your addding 2.77pF per inch of radioshack BNC-coax. if your capacitence cant be charged then youll lose the ability to transmit, in the mW power range, such loading must be considered.
As long as the coax is 50ohm impedance then the actual capacitance of the cable doesn't matter, since it's balanced out by the right amount of inductance so the impedance is 50ohm. But your signal loss will increase with distance, any cable you buy should be specify loss in dB/meter or dB/foot at various cardinal frequencies.
Since 400MHz is pretty low frequency even with relatively cheap cable you can probably get only 1dB of loss in a 1meter cable which will reduce your range a bit but it will still work fine.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Yes I should have said that differently Mattski. I realise the deal with coax being L and C compensated, but there is some loading (or at least ive seen some by some means or another) of weak signals, at the mW power he must be carefull the Sparkfun and other "FCC Part 15"compliant devices can get finnicky if you lengthen stuff carelessly. He must be careful and wise about the route, path, terminations and the rest of it.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
coillah wrote ...
Cool to see someone from CSUC on here. When did you graduate?
Havent. Still an Undergrad, (EE), working with Professor Dale Word, I am trying to get authorized to start a CSU Chico Flight Team for entry in the 2012 International Aerial Robotics Competition. (IARC) Though Dr. Ghandakly and the Dean havent signed off yet.
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RF PCB: Hooking up an SMA/BNC
Still an Undergrad, (EE), working with Professor Dale Word, I am trying to get authorized to start a CSU Chico Flight Team for entry in the 2012 International Aerial Robotics Competition. (IARC) Though Dr. Ghandakly and the Dean havent signed off yet.