Not content with the performance of the TBS MicroRX half wave dipole that looks to be measure and tuned for 915mhz i decided to have a go at a “Turnstile” antenna originally used for Long Range work on 433mhz band.
I simply divided the original measurements /2 as 868 is a 2nd harmonic of 433mhz or near as damnit
Warning the build is fiddly due to the u.fl pigtails, requires delicate soldering and also testing with a multimeter afterwards to ensure there is no electrical short between the elements.
So after transposing the dimensions i followed IBcrazy’s original video which can be found here https://www.youtube.com/watch?v=sCypz0ZeDdo
Picture heavy from here on in with explanations.
TLDR – Scroll to bottom of post for results and thoughts.
So here i’m measuring out each side or element.
Remove some insulation and twist then flux and tin once bent to an angle, i only had 20AWG servo wire to hand so that will have to do for my first attempt, don’t know whether single strand wire would be better in this design.??
Strip a length of your u.fl pigtail in readiness.
Final design i had to glue onto a piece of cardboard to make the form / angles, ill come up with a better idea for next time.
The test bed is a TBS MicroRX and to benchmark i have a TBS supplied half wave dipole.
With the transmitter a few feet away i took some signal readings as below, this is with the TX on 10mW.
Now i went to the other side of the house and took another signal reading
Next i turned off the MicroRX and replaced the dipole for the turnstile antenna and powered back on again.
Went back to my transmitter in the other side of the house and noted the figures.
Quick picture of the antenna installed.
Results – Well they’re kind of inconclusive just now as i need to test it in the air and with my ET Vector as well.
Its worth noting my TX was set to 10mW erp and the MicroRX has an erp of 30mW which would explain my downlink results being better than my uplink.
Thoughts – due to the difficulty accurately measuring the lengths and not having a suitable antenna RF analyser then getting consistent repeatable results is going to be difficult.
Ill test the antenna next time i go flying and see how it fairs.