After having initial trouble getting two modules communicate, I ran across a post that said that antennas interfered with short-distance communication. So, I removed the antennas and it worked perfectly. Then, in the field, when I walk away from a receiver, about 50 feet away I need to gently start screwing antenna on to keep the communications going but have never been able to fully secure antenna on and get communication (tried maximum distance of around 200 feet).
i would also need a second person standing at the receiver and screwing the antenna on tighter and tighter as I am walking away with the transmitter - obviously makes no sense.
Anybody experienced anything similar and do you have any suggestions?
Also:
I have been reading a lot about "authentic" vs. "knock-off" modules and opinions vary whether the two are different. Would like to try "authentic" module but have trouble locating one (Adafruit or Arduino store don't have one). Any suggestions?
RF transmitters do not transfer energy like an you would expect. In a DC circuit you connect 5V to something the receiving circuit gets 5V. You want the internal resistance of the DC source to be as low as possible to not loose any voltage.
In RF circuits its totally different. RF circuits inherently have an significant output impedance. Consider Cable TV has an output impedance of 75 ohms. Even the cable is "tuned" for this impedance. Such a circuits expects a "load" of 75 ohms. If the "load impedance" is open all the energy that would have gone to the load is reflected back to the transmitter. In such a condition the transmitter is overloaded and will eventually burn out.
I'm not familiar with the NRF24L01+, however I doubt you are the first person to run into your situation. You might want to look in one of the forums that specialized in the NRF24L01+
Yes, that makes sense and that goes to my second questions then: i have seen number of posts about knock-off modules but not sure what is "authentic" module. Major electronics (sparkfun, adafruit, arduino shop) don't carry it...
I will try to find the posts that talk about it and find out if anybody can point in the right direction but the defective antenna idea makes sense. thanks.
Sorry, confused: first the advise was not to use without antenna and then to use without it...
The whole idea of buying one with an antenna was to be able to use it and benefit from a longer range...
I use them, but not familiar with the precise design.
However given the number of dubious clones out there, who can be sure whats been designed or built but I would be very surprised if they had circuits which protected themselves totally against antenna cock ups.
I built up 10 PCBs with LoRa modules recently and was testing that they could TX OK. Alas on one module I forgot to clip the wire antenna in place, sadly that LoRa module does not work properly anymore.
Thanks again. someone else recommended LoRa. Perhaps I will give it a try. Also exploring OpenTx option - wouldn't mind to pay $100-$200 for a ready to go solution - this is a big project for a school fundraiser and need to get it working at any cost quickly. Most of the stuff is functional except of a remote to operate it.
RF circuits still obey Ohm's law etc. If the output stage "sees" an open circuit it cannot actually drive any power. The "trick" is that a quarter wave (or odd multiples thereof) transmission line "converts" an open circuit at the end, to a short circuit which can overload the output stage.
And if the transmitter is only generating a few milliwatts in the first place, then it is rather unlikely to burn out.
And its more complex that that, however for a beginner I found its best not to get into the "technically correct" descriptions. So often I take liberties in my explanations to make it easier for the new user to understand. I'm sure you or I could describe it in such terms that it would be useless for the OP.
True, but some are much much better than others.
Not uncommon to see "rejected" units brought back into the market and sold for "low prices".
I already provided a link to a site where they use proven good units from "good suppliers".
I was under the impression the NRF24L01+ radio IC is from Nordic. If this is the case and there are no IC clones (unknown to me) then the only things the China assembly plant can do is screw up the assembly.
Personally I've had great luck with clones. I purchase them all from ebay and none from AilExpress.
