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I am trying to increase the working range of cheap arduino 433 mhz RF link modules like these https://www.sparkfun.com/products/10534.

The page says they have range of 500 feet in perfect conditions however in my case it's more like several feet.

So I know I can extend the range by simply applying more powerful power supply, but I thought if I can take the Tx output and feed it into some sort of high frequency amplifier.

I can't buy any here so I'll have to make my own. I am interested if it is even worth trying or will it be so complicated I am better of doing something else?

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    \$\begingroup\$ What are you using for an antenna? What are you using for a receiver? Modifying or amplifying the module itself would probably violate regulations covering ISM band devices. \$\endgroup\$ – Dave Tweed Aug 12 '17 at 13:52
  • \$\begingroup\$ Antenna is a 17cm long piece of magnet wire. The receiver is the second part of such a module pair like this: sparkfun.com/products/10532 . In regards to the regulations I don't live in the US we don't have such a law here. \$\endgroup\$ – Anthropomorphous Dodecahedron Aug 12 '17 at 13:58
  • \$\begingroup\$ @AnthropomorphousDodecahedron re: no law: Are you in Antarctica? Seriously, ISM regulations are not that different around the world. There's certainly different power limits in different countries, but "no such law" is almost certainly not true. \$\endgroup\$ – Marcus Müller Aug 12 '17 at 14:02
  • \$\begingroup\$ I am using VirtualWire library. In regards to law there are no practical laws on radio frequencies in the mountains of Caucasus, since there is no one to enforce them, they just don't care enough. Well if you interfere with the military or something that's another thing but we're getting off track. The question is not that I just want to increase the range somehow. The question is if it is viable to try to use an external home made amp. Let's consider this a theoretical technical question rather than a complex practical one. \$\endgroup\$ – Anthropomorphous Dodecahedron Aug 12 '17 at 14:10
  • \$\begingroup\$ and what do you think would be "interfering with the military" be if not putting out too much power with an ISM band amplifier that might or might not have unwanted harmonics anywhere in spectrum? Anyway, as I said in my comment to Olin's answer: nope, not feasible for you, unless you buy very expensive equipment to test and improve your amplifier, and even then might the higher power of the TX amplifier actually damage the RX part. So, no. \$\endgroup\$ – Marcus Müller Aug 12 '17 at 14:15
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I used to sell modules that look like they came from the same reference design, and found they were normally good for about 100 meters but out of thousands sold here are the most common problems with range:

  • The SparkFun pages say lists them as being a 5V module but the datasheet says the operating voltage is up to 12V, you should definitely use that.

  • Those simple ASK transmitter / receiver pairs need to have a balanced signal to work well like Manchester or NRZ encoding, but the VirtualWire library you've mentioned in a comment should take care of that.

  • The bitrates they mention are probably somewhat optimistic, try lowering it so something like 1200bps and experiment with going even lower.

  • They also need a preamble for the receiver to lock on, but once again the VirtualWire library should take care of that.

  • Also take a took at sending the data multiple times and additional error detection - that may help if the packets are mostly received but you get the odd inteference from being on an ISM frequency.

On the receiver side you can also look at using a larger antenna that won't have any regulatory implications. As Olin mentioned a proper ground plane for the antenna is worth looking at if practical.

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  • \$\begingroup\$ Thanks, I'll lower the bitrate and see how it goes. The additional error correction and antenna are also good ideas. \$\endgroup\$ – Anthropomorphous Dodecahedron Aug 12 '17 at 14:34
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Using a more "powerful" power supply is a bad idea. It will probably just fry something.

If you are getting very low range, then the first thing to look at are both the transmitting and receiving antennas, and their ground planes if appropriate.

Otherwise, adding out of spec antennas or a RF power amplifier will violate whatever license this product has, and may cause emissions past the legal limit. Not a good idea.

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  • \$\begingroup\$ Also, just adding "any" amplifier will most probably not make an RF system work better. That amplifier needs to be matched, working well on the frequencies and bandwidths you're going to use, be linear enough where the system needs it, needs to have a sensibly limited noise figure… \$\endgroup\$ – Marcus Müller Aug 12 '17 at 14:05
  • \$\begingroup\$ What linearity are we talking about? The modulation is just common ASK, do we still care about linearity in this case? Genuinely asking. And of course I am not talking about any amp, let's say I do match the characteristics. Will it be worthwhile? \$\endgroup\$ – Anthropomorphous Dodecahedron Aug 12 '17 at 14:13
  • \$\begingroup\$ ASK needs pretty good linearity, since it's explicitly... amplitude shifting! No, it won't be worthwhile, pretty certainly. Get a better antenna, or better transceiver modules. \$\endgroup\$ – Marcus Müller Aug 12 '17 at 14:16
  • \$\begingroup\$ If you do OOK On Off Keying, does the linearity matter? \$\endgroup\$ – analogsystemsrf Aug 12 '17 at 17:42

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