Generic Cloverleaf antenna element length for 5.8Ghz FPV

[mikez104]

Hi all. This is my first post here. I figured I'd try out these forums and see how the community is here.

I built a TriCopter using mostly David W's design and it is awesome. Have a multiWii pro3 black board on it and it works great. So the next logical step is FPV right? So I have my gear but want to build a cloverleaf antenna for my transmitter.

I see that the measurements using the calculator are down to the hundredths of mm? Really? I can cut it close and then solder it a little high on the center conductor of the coax and be way off according to these numbers.

My question is is there an antenna length that I can use when I build a cloverleaf antenna so I can use more than one frequency. Obviously it will work best for the frequency that I cut it to but being new to FPV I may need to jump around to the other channels.

From the chart I found I see that from the lowest freq ch4 @ 5.645Ghz to the highest freq @ 5.945 Ghz the measurement for each element would be from 57.44mm to 51.64mm. Can I split the difference and go 54mm? I looked at readymaderc site and he sells ibcrazy antennas but they are not for a specific channel or at least I did not see that in the description.

So is there a happy medium that I can use for my dimensions?

Thanks!
Mike

 

[Cyberdactyl]

That is correct. You build the antenna to the frequency you believe you will use most of the time. Once you drift off the length, you compromise the reception.

 

[mikez104]

I guess my main concern is SWR on my TX as I have no SWR meter and prefer not to cook my nice new video TX. I assume that if I pick any freq on the 5.8Ghz band and cut my antenna for it I can use any of the other channels safely but with slightly degraded performance.

 

[Cyberdactyl]

I'm certainly no expert, but I would think as long as you have "something" connected to the transmission socket you will be ok. That's all within reason, meaning as long as you aren't pumping out multiple watts and not heat sinking. For goodness sakes, most Vtx's come with a pretty much useless monopole.

When I got my fatshark 250mw I put the Spironet omni on and the clear shrink wrapping the vtx immediately melted at the spot at the yellow arrow. Don't know if I received a bum transmitter or what, but I wrapped some 1mm aluminum plate around it with some heat sink adhesive and it's been working fine since.