Increasing Receiver Range

[adam1010]

Hi everyone,

I'm currently using a $20 NooElec NESDR Mini 2 receiver to pick up signals on 345Mhz (Honeywell Window/Door Sensors) in the U.S. --  The receiver is placed high on a shelf in the center of my house but there is one sensor/transmitter that is out of range.

I've tried increasing the gain to its max (./rtl_433 -f 345000000 -R 69 -F json -g 49.6 -l 0) and I have the antenna fully extended.

1) Is there anything else I can do to improve the receiver range (aside from moving it closer to the transmitter)?

2) Would a more expensive receiver increase the range? Such as an Airspy ($200), SDRPlay ($150) or HackRF ($300)

Thanks a lot!

[Helge Weissig]

This is most likely due to the antenna being more or less optimized for the entire range of frequencies these dongles are capable of receiving. I just replaced my dongle's antenna with a primitive coil-loaded one (http://www.instructables.com/id/433-MHz-Coil-loaded-antenna/) and have seen a marked improvement in reliability of my signals. 

cheers,

h. 

--
You received this message because you are subscribed to the Google Groups "rtl_433" group.
To unsubscribe from this group and stop receiving emails from it, send an email to rtl_433+u...@googlegroups.com.
To post to this group, send email to rtl...@googlegroups.com.
Visit this group at https://groups.google.com/group/rtl_433.
To view this discussion on the web, visit https://groups.google.com/d/msgid/rtl_433/a459d160-9faa-4a28-8460-471e8dd29925%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[Kevin Reid]

On Tue, Dec 20, 2016 at 8:35 PM, adam1010 <adamma...@gmail.com> wrote:

I'm currently using a $20 NooElec NESDR Mini 2 receiver to pick up signals on 345Mhz (Honeywell Window/Door Sensors) in the U.S. --  The receiver is placed high on a shelf in the center of my house but there is one sensor/transmitter that is out of range.

I've tried increasing the gain to its max (./rtl_433 -f 345000000 -R 69 -F json -g 49.6 -l 0) and I have the antenna fully extended.

Excess gain may make things worse. You want to optimize for SNR, not absolute signal strength.

 

1) Is there anything else I can do to improve the receiver range (aside from moving it closer to the transmitter)?

Don't “fully extend” the antenna. You want it to be (slightly shorter than) a quarter-wavelength at 345 MHz.

http://www.wolframalpha.com/input/?i=(c+%2F+345+MHz)+%2F+4       → 8.5 inches or 22 cm

This will improve the reception of signals at 345 MHz and worsen everything else, which is exactly what you want — preselection of the signal.

 

Also putting some kind of metal sheet underneath the magnet base of the antenna (assuming you have the same type of rtlsdr-bundled antenna I'm thinking of) may help. Cookie sheet, top of refrigerator, jar lid, whatever's handy.

2) Would a more expensive receiver increase the range? Such as an Airspy ($200), SDRPlay ($150) or HackRF ($300)

Better receivers may have a better noise floor which means they can produce usable results from weaker signals. This does not help you if the limiting factor is ambient noise rather than receiver internal noise. You can find this out by using looking at a spectrum display and unplugging the antenna: if the noise at the bottom goes down, you have ambient noise; if it stays unchanged, your receiver is the limiting factor.

Better receivers may also have better analog filters, which are better at rejecting frequencies you haven't tuned to. (If you've ever tuned around with a RTL-SDR and seen a strong signal "wrap around" and appear on the opposite end of the spectrum as you tune away from it, that's what's going on.) This is the same benefit as having a more selective antenna.

The HackRF One has significantly better filters but only a tiny bit better noise floor, in my experience; its primary benefit is transmit capability. Can't comment on the others.

--

You received this message because you are subscribed to the Google Groups "rtl_433" group.

To unsubscribe from this group and stop receiving emails from it, send an email to rtl_433+unsubscribe@googlegroups.com.

[adam1010]

Thank you all very much for the guidance!

1) I have purchased an antenna specifically for my target frequency

2) I have added a USB extension cord (with 2 ferrites) to the tuner to separate it from the RaspberryPi

3) I added the -p NN argument with my cumulative PPM (from rtl_test -a)

I guess the last step is to optimize the GAIN setting, correct?  I've tried using rtl_tcp + GQRX to visualize the signal, but I'm unsure which signal is "better" when comparing the waterfall graphs recorded from two different gain settings. Is there a tutorial you could point me to that explains how to optimize the gain level?

To unsubscribe from this group and stop receiving emails from it, send an email to rtl_433+u...@googlegroups.com.