Posted on 05/19/2023 11:20:55 AM PDT by mikelets456
I can get 10 miles or more out of the RFM69HCW. I think it's top speed is 300kbs, but for what i'm doing I don't need high speed. I do need the distance though.
I need 10 mi range, low baud rate would be fine. What sort of antenna do you use?
I am intending to use a large building in the center of town with a 50' tower on top of it to give me a fairly good line of sight to all my distributed units.
For that location, I have a commercial stacked co-linear array with a gain of about 13db if I remember correctly. I also intend to put the RF module right at the base of the antenna instead of using heliax. Too much losses at those frequencies. I'm going to talk to it through cat 5.
For my distributed units, i'm building the RF module right into the Yagis. At 900 mhz, coax has a lot of loss. Putting the transceiver right at the antenna allows the best output power and receive signal, and the data can just come down the cat 5.
If you are trying to do it through coax, you need to look at your losses. You will probably lose most of the signal both ways if you have any significant length of coax/heliax.
Line of sight is pretty much necessary to get a distance of 10 miles at that band.
Understood. Thank you for your advice. It did occur to me to put the radio at the antenna, I just didn’t do it. Now I’ll give that a try.
If you don’t mind me asking, how far apart were you originally intending to have the antenna from the radio?
The previous project used the NRF24L01+ with Yagi antennas. That gave them about a 1-1/2 mile reach.
The previous project used the NRF24L01+ with Yagi antennas. That gave them about a 1-1/2 mile reach.
Interesting, but I meant how long were your coaxes going to be?
3 km is pretty easy. That's less than 2 miles. So long as you have line of sight, it won't be a problem.
Let me back up a bit. I looked at the specs for the NRF24L01, and it's only 1 miliwatt output power. The RFM69HCW i'm using is 100 miliwatts. I know 100 miliwatts will easily make several miles, but I don't know about 1 miliwatt unless you use some really high gain antennas.
More power is always better. You can't do anything on the receive side other than using a good antenna, but more power on the transmit side will make up for other issues.
I’m in Pharma in IT and we are going gangbusters.
The Dubai project will use little bat antennas with about 2 meters of coax. They are supposed to last 5-10 years on a C sized lithium primary.
Next radio project I get strong-armed into will definitely make use of something like a RFM69HCW. I'm not fond of radio projects.
I had a nice setup going with DIGI HP900 S3B radios; but, the customer canceled the project:
A meter is not bad. I was looking at some cable specs for what I assume you are using and they range from about 11 db/100' to 17 db/100'. Not all that much of a loss at 1 meter.
The client has an installation with a 50ft coax; and, much to my surprise it actually works.
With around a 6db loss both ways through the cable, but if it's not too far apart, I can see it working.
Next radio project I get strong-armed into will definitely make use of something like a RFM69HCW. I'm not fond of radio projects.
They also make a LoRa version.
https://www.hoperf.com/modules/lora/RFM95.html
I had a nice setup going with DIGI HP900 S3B radios; but, the customer canceled the project:
That looks like a better device for long range communications.
From the specs. "Transmit power output 24 dBm (250 mW) (software selectable) "
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