Because you asked and for educational purposes only,
Most RC flyers don't understand antenna theory because we usually don't work on our TXs. Most big brand systems won't even sell parts unless its a simple PNP part or antenna replacement. One reason is if the output power stage is in anyway modified from the original circuit it can possibly cause unwanted emissions of spurious signals that can interfere with other systems and also void the original type acceptance that countries "FCC" have for the equipment. Just adding a connector in the antenna line has voided that certification. The coax used and each added connection can cause a reduction in the TX or RX ability of the system. Remember most 2.4G systems TX and RX at the same time. Each added antenna connection can add a 3db loss of efficiency. 3db can be 1/2 power out.
Many times due to the nature of the coaxes velocity factor in relation to the antenna used, the actual antenna itself is modified in length, or the coax length is modified to cheat the physics to get maximum antenna performance.
A different brand or type of coax and connector added to the same antenna may actually produce performance!
This was never an issue in the past since the TX came with a long whip and the RX if not messed with had a long wire antenna tuned for the frequency.
Now with so may 2.4G spare antenna parts out there everyone's messing with their antenna systems. Most violating the certifications. Usually the risk is less range however!
To quote from posted antenna theory, not my words,
"An antenna will still transmit even if the length is not ideal for resonance. However, less of the power input to the transmitter will actually show up as useful output signal. In other words, the efficiency of the system will be significantly lower."
So mod all you want but do a serious range check before and after your mods to at least your normal line of sight flying.
SM
As an added note of info,
You'll read about how the silly RX manufactures sell their RX with an antenna length shorter or longer than the math says it should be?
Then it's recommended to alter the length?
Depending on the snap connector at the RX end if used, not soldered, and the velocity factor of the coax used, the length is usually set at the factory using high end test equipment. The antenna is then cut for the center of the band since most systems hop, to ensure a consistent power out or reception. It's also done to insure minimum transmission of spurious harmonics to be certified. Sometimes a retuning can generate more power out in the tx case, but it can also cause more in band emissions that can cause trouble for other flyers close by or they to you.
Using a "booster" will certainly cause trouble for others close!
It's all good if you're aware of it all.
BTW, all this is covered elsewhere and required knowledge when you're a licensed rf repair person and have to sign off your work like Futaba, Spektrum, and the other repair stations must do. I'm just pointing it out for safety's sake. That 100+ mph plane going by my head hopefully is safe!
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