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Author Topic: RFM69HC Range Problem  (Read 3840 times)

mrmin24

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RFM69HC Range Problem
« on: August 04, 2015, 05:23:24 PM »
Hi,

I am unable to get proper reception between two RFM69HC modules. The best RSSI I can manage is -65 with two modules sitting right next to each other. Max range 5 meters.

Each module has a quarter wavelength wire antenna and is powered via a 3.3V breadboard power supply - different power sources give same results. I even tried half wavelength antenna but this made things worse.

I am using the standard RFM69 library config  - 915MHz

Is there something obvious I am missing?

Thanks.
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TomWS

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Re: RFM69HC Range Problem
« Reply #1 on: August 04, 2015, 08:26:57 PM »
Quote from: mrmin24 on August 04, 2015, 05:23:24 PM
Hi,

I am unable to get proper reception between two RFM69HC modules. The best RSSI I can manage is -65 with two modules sitting right next to each other. Max range 5 meters.

Each module has a quarter wavelength wire antenna and is powered via a 3.3V breadboard power supply - different power sources give same results. I even tried half wavelength antenna but this made things worse.

I am using the standard RFM69 library config  - 915MHz

Is there something obvious I am missing?

Thanks.
In your code, did you define isRFM69HW?  I know you're using the HC, but to use this device you need to define this constant.

Tom
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Felix

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Re: RFM69HC Range Problem
« Reply #2 on: August 04, 2015, 09:48:16 PM »
mrmin24,
What hardware are you using (that you connect the RFM69HCW to)?
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mrmin24

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Re: RFM69HC Range Problem
« Reply #3 on: August 05, 2015, 02:58:49 AM »
Thanks TomWS, will give it a try (I think I might have previously, but will try again).

Felix - The gateway is running on an UNO and is connected via level converter. The Node is running on a 5V pro-mini also via level converter.

Thanks thus far
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mrmin24

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Re: RFM69HC Range Problem
« Reply #4 on: August 05, 2015, 03:24:00 PM »
OK!! TomWS your suggestion made a big difference. RSSI is now -35 when radios are close to each other and -67 at about 20m through a couple of walls.

I was still expecting better than that, but I have no baseline to compare. Can you maybe comment on what I should expect?

Thanks
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TomWS

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Re: RFM69HC Range Problem
« Reply #5 on: August 05, 2015, 04:32:17 PM »
Quote from: mrmin24 on August 05, 2015, 03:24:00 PM
OK!! TomWS your suggestion made a big difference. RSSI is now -35 when radios are close to each other and -67 at about 20m through a couple of walls.

I was still expecting better than that, but I have no baseline to compare. Can you maybe comment on what I should expect?

Thanks
These numbers look ok although 'close' together I would expect RSSI values in the -20s, but, bear in mind, the RFM69 has a very wide range AGC circuit so even -67 is going to give you good signal quality.  I'm assuming that you've trimmed the antenna wires to the proper length... 

What is your transmit power level set to?

Tom
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mrmin24

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Re: RFM69HC Range Problem
« Reply #6 on: August 05, 2015, 05:00:07 PM »
Yes, I see that on the node the RSSI when radios are close together is about -10, but the gateway still -35. I did however test up to about 50m and still had RSSI -70 on gateway through multiple walls, so I am happy for now. I will play around with the power settings as I go along. At the moment they are default.

Antennas are 78mm for 915MHz, so... I think this is right

Thanks again for the replies Tom.
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