Hi I have been repairing and researching both shielded and no shielded antenna for quad/park flyer and full range use and was wondering if any one knew why the 4mm difference in shipped vs. suggested legths?

Doing the math (300/2.4)/4 for a 2.4Ghz 1/4 wave comes out to 31.25 mm but there are some discussions that manufactures are shipping 27mm antenna's. Not doubting nor am I an electrical engineer just curious to understand this better when doing repairs.

Secondary question is does the above formula hold true for non shielded short range non diversity satellite antenna's also?

Thanks in advance or sorry if this is the umpteenth million time this has been asked 

~Kirk

Somebody somewhere said that the manufacturer knows better. All I know is that my a8s comes with a 27mm quarter wave antenna and it happens to have small glitches even as close as 100m with small obstructions and serious failsafe scenarios hitting in about 70m with obstructions like cars and me

If I use a 31mm dipole (so really a half-wave?), I fly over 250m with no issues at all with some trees on the way.

Example of what I flew lately, the antenna was pointing straight in my direction so it is a bad case scenario... but it was 100% reliable:



After this I turned back, so the antenna was obstructed totally by the quad... still, everything was fine.

My receiver antennas are 31.25mm, but I have low RSSI after only  few hundred feet, but I am flying through dense trees and underbrush and on the other side of a house with a lot of steel in the walls.  Oh well...it is what it is.

(24-Aug-2017, 08:46 PM)KonradS Wrote: Somebody somewhere said that the manufacturer knows better.

That was me. I'm still not sure one way or the other.

I did get a set of FrSky replacement antennas and cut them to various lengths. The idea was to evaluate each length on my spectrum analyser.

The problem is that these single wire antennas are not really antennas at all! A wire antenna needs to be a dipole and these are 'monopoles' with no corresponding ground plane or matching wire to make it a dipole. Because of this, the results I got were useless.

If I can figure out how they are  supposed to work even when connected to the receiver and duplicate that when they are attached to my spectrum analyser, I'll try testing them again.

rotorriot did a test with the moddified XSR antenna and found it to have similar range to the X4R-SB (longer range than before it was modified)

That's not "a test".

It's entirely subjective and tells you nothing at all. It also contains dumb statements like "the longer the antenna, the higher the gain" which shows that Steele clearly has no idea what he's talking about.

Bad advice.

(25-Aug-2017, 01:09 PM)Oscar Wrote: rotorriot did a test with the moddified XSR antenna and found it to have similar range to the X4R-SB (longer range than before it was modified)
_https://www.youtube.com/watch?v=UMSYa5fxq8Q

Hi Oscar,

I've seen that and it's giving me the impression that it could be mfg's tune of there RX. I need to re-watch it to see thier control model and see how it applies to my question.

I have also seen your repair video (it was you correct?) on the 31mm repair. my initial question after seeing your repair video was do stub antennae like on a lemon short range (park flier) rx follow the same rules 31mm as the shielded antennae?

BTW... thanks for the wealth of information you share with the community : love this stuff !! 

~Kirk

(24-Aug-2017, 08:46 PM)KonradS Wrote: Somebody somewhere said that the manufacturer knows better. All I know is that my a8s comes with a 27mm quarter wave antenna and it happens to have small glitches even as close as 100m with small obstructions and serious failsafe scenarios hitting in about 70m with obstructions like cars and me

If I use a 31mm dipole (so really a half-wave?), I fly over 250m with no issues at all with some trees on the way.

Example of what I flew lately, the antenna was pointing straight in my direction so it is a bad case scenario... but it was 100% reliable:



After this I turned back, so the antenna was obstructed totally by the quad... still, everything was fine.

Interesting information thanks for sharing ! ...I grues I'm going do the rabbit hole and will proceed with some testing of my own. could also be manufacturer specific tuningfor signal strength and range, I guess ass you found out, your a8s's perform better for you with 31mm legths

~Kirk

(25-Aug-2017, 08:17 PM)kirkmunn Wrote: Interesting information thanks for sharing ! ...I grues I'm going do the rabbit hole and will proceed with some testing of my own. could also be manufacturer specific tuningfor signal strength and range, I guess ass you found out, your a8s's perform better for you with 31mm legths

~Kirk

Exactly - I would expect that they are tuned to work great with this receiver. But that is the best part of this hobby - you can use whatever works the best for you! Don't be afraid to experiment

But keep in mind that I used a dipole here, not just a "retuned" stock antenna. The ones that I used are something like these (not affiliate): https://www.banggood.com/10X-3DBI-Brass-...93273.html

(25-Aug-2017, 08:27 PM)KonradS Wrote: Exactly - I would expect that they are tuned to work great with this receiver. But that is the best part of this hobby - you can use whatever works the best for you! Don't be afraid to experiment

But keep in mind that I used a dipole here, not just a "retuned" stock antenna. The ones that I used are something like these (not affiliate): https://www.banggood.com/10X-3DBI-Brass-...93273.html

Gotcha... I

t's a complete life cycle !! build, fly, crash, assess and repeat. Got to love it