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2.4G Transmitter aerials

Started by dogshome, August 22, 2013, 21:10:46 pm

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The thread on Rx aerials prompted this. I've replaced those before and understand co-ax, velocity factor, 1/4 wave etc.

I've seen that some of the latest sets have diverse aerials. I've also constructed and played about with various wireless bowties, corner reflectors and high gain aerials at home. So, I know a little.

My Hotship lost contact for about 2 seconds a couple weeks ago (failsafe). I quickly saw what was happening, which way my aerial was pointing (straight at it), moved a few degrees, regained control and then carried on flying. Tweaked my aerial to a better position and cursed myself for being so stupid with where it was pointed in the first place.

The Orange Tx converter I just bought for my old PCM9 has the aerial pointing straight up and likely straight at the model most of the time (if i have the tx typically resting on the paunch  ::)   ).

Has anyone tried other aerials apart from the normal single element rubber duck i.e. without it's inherent directional limitations?

Is there a design for two diverse aerials on a single tx that will work with any sort of reasonable SWR?

肉(ròu)包(bāo)子(zi)打(dǎ)狗(gǒu) (meat+bun(2nd and 3rd)+hit+dog)
Literally: To hit a dog with a meat-bun


The transmitters with two diverse aerials typically have an RF switch (ES02 or Skyworks S79 etc) to select one or the other, and the software is such that packets are sent on one, the RF switch flipped, then the same packets are repeated on the other aerial which usually has opposed polarisation.  Its a combined effort of hardware and software which you cant easily replicate on a simplex setup - you only have one RF source in a 'normal' 2.4 tx.   Even if you carefully match two aerials into one feed (you cant simply parallel aerials) it effectively acts as one - the overall radiation pattern still has to obey the 'rob peter to pay paul' gain theory - with gain you will also have nulls, more gain in one direction, less in another.  We cant even agree what pattern is best - some say omni is best, some say gain to the front of the tx is best.  Maybe circular polarisation in a conical pattern would be ideal.  But really, at 100mW and over the short distances we use, this should all be acedemic!   :af