Author Topic: limited range - what am I doing wrong?  (Read 1032 times)

Bugeye60

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limited range - what am I doing wrong?
« on: February 20, 2017, 10:00:55 PM »
Hi,

I'm using RFM69HCW 915 MHz Moteino Mega-USBs, ATC is not enabled.  One Mega has a standard quarter-wave wire antenna and the other has one of Captcha's dipoles attached via an 8.25 inch coaxial cable.  One Mega is powered with two AA batteries through VIN and the other is powered by USB (laptop).  With this setup I get an RSSI of  -69 at only 120 feet, line of sight and clear of obstacles.  I need the range to be much greater, 1000 feet.

(I previously used a quarter-wave antenna on each Mega, but thought I'd try adding a dipole to one.  RSSI improved some, but not as much as I need.)

The following lines are included in the sketch (among others of course):

Code: [Select]
#define FREQUENCY  RF69_915MHZ
#define IS_RFM69HW
#define SERIAL_BAUD  115200

void setup()  {
  Serial.begin(SERIAL_BAUD);
  delay(10);
  radio.initialize(FREQUENCY,NODEID,NETWORKID);
#ifdef IS_RFM69HW
  radio.setHighPower();
#endif
}

I haven't changed any default radio settings because I don't know how and wouldn't really know what to change.

Is there anything wrong with the definitions listed above? 

I'm looking for some advice to get the desired 1000 feet range.  Thanks!



LukaQ

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Re: limited range - what am I doing wrong?
« Reply #1 on: February 21, 2017, 12:48:46 AM »
I don't see anything wrong with the code, so I will ask you this:
I haven't done any range test myself, but I get 147ft range through several (at angle) reinforced concrete walls and some trees and so on.

How long are your antennas?
-69 is still pretty high, you can go a lot lower. Does your connection drop or what?

LukaQ

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Re: limited range - what am I doing wrong?
« Reply #2 on: February 21, 2017, 06:03:27 AM »
also you can use when you have low RSSI value (edge of range)

Code: [Select]
radio.writeReg(0x58, 0x2D);

Felix

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Re: limited range - what am I doing wrong?
« Reply #3 on: February 21, 2017, 08:35:25 AM »
Can you please try 3xAAA instead of just 2x?
The VIN is expected to be above ~3.55v for the regulator to be completely happy.

Bugeye60

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Re: limited range - what am I doing wrong?
« Reply #4 on: February 21, 2017, 10:23:30 AM »
Thanks, Felix and LukaQ for the quick replies!

I'll try 3 AAs and let you know how it goes.  I need to find and purchase a holder for three first.

As for antennas, the wire antenna is 3 inches from tip to base of the Mega (another is about 1/16 inch shorter).  The pcb dipole I'm using is one of Captcha's designs for the 915 MHz radio.  It has legs of 2.35 inch each.

Bugeye60

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Re: limited range - what am I doing wrong?
« Reply #5 on: March 04, 2017, 05:34:41 PM »
Update:

I swapped out the 2 AA batteries from the prior test and replaced them with for 4 AA batteries in both Moteino Megas, keeping everything else the same.  I obtained about the same RSSIs from the same test as before (same location and same distance of 120 feet).  It was nice outside so I decided to find an open field and test at longer distances.  The radios successfully communicated at a distance of 400 feet before I ran out of time and had to stop.

Felix

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Re: limited range - what am I doing wrong?
« Reply #6 on: March 04, 2017, 08:01:37 PM »
Great! Problem solved?

Bugeye60

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Re: limited range - what am I doing wrong?
« Reply #7 on: March 05, 2017, 08:05:05 AM »
Hi Felix, the answer is yes, close enough!  I was originally shooting for 1000 feet but I simply ran out of time yesterday.  However, I've recently re-thought my overall project and came up with a much better idea that provides collection of more useful data over a very short range using the same Moteinos.  I still may continue to tweak the antennas and see if I can hit the original 1000 ft target, just for fun.   :)

Felix

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Re: limited range - what am I doing wrong?
« Reply #8 on: March 05, 2017, 09:51:23 PM »
Cool, depending what antennas you use now (the default monopoles?) you might want to check out the dipole thread for a better antenna solution.