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Will Foam reduce my biquads signal?

#1
I have a Cp Biquad that I have built for my 910Mhz system. I have tested it, and I am pleased with its ability. I want to build a foam box around it just to help prevent damaging the elements while transporting is. I am sure it wouldn't effect its range, but before I go and make it I figured I should ask some one with more knowledge first.
 

colorex

Rotor Riot!
Mentor
#2
Shouldn't reduce it much. Metal and carbon fiber will affect radio waves drastically, but RF goes through foam easily. Think about how the aircraft receiver gets the signal despite being inside the foam airplane.
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#3
Don't want to geek out twice in one night, but . . .

The RF at 900Mhz will see right through the foam like glass, *but* very near the antenna it will change the "dialectic constant" a bit -- meaning it will *slightly* de-tune the antenna. Remove the foam, it all goes back to normal. Having a sturdy cover is a great idea, and transmitting though a foam cover is *probably* ok, but I'd remove the foam when it's in use.
 
#4
Hmm, may have to place a cover over it and test the range again. I have seen people place a thin plastic cover on them and still use them, although it would probably not be very noticeable, I could defiantly see how it could cause a reduction in signal. The great part about it, I am not really going for a super long range system. So even a slight reduction in range shouldn't make much of a difference in how I would like to fly. I am using a clover leaf, cp biquad combo. Next I hope to try a skew planner. Just need to build it. I want to hit 1 mile, just once to know I can. Then most of my flights will stay within that range. Not sure a biquad is what I needed to build, but I enjoy experimenting, and building these antennas. It is very rewarding when they are finished, and performing the way they were intended to.
 

Craftydan

Hostage Taker of Quads
Moderator
Mentor
#5
Range isn't what I'd worry about.

the de-tuning will affect range a bit, but mostly because the extra energy that isn't going out is being pushed back into your Tx. High enough mis-match and you burn out your Tx. I'm not saying you're anywhere near this, but things become really wonky in near-field.

Positive side is any effect would be foam-is-not-air change in the local dialectric constant, but foam *is* mostly air. I have better confidence with your foam cover than transmitting through a hard plastic case.