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Messages posted by: rivers
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I found something odd about the details of the PaConfig settings for the RFM95W device at address 0x09. Referring page 103 of the data sheet there appears to be a conflict between the MaxPower setting (bits6-4) and the OutPower (bits3-0).

I want to use the PA_Boost pin in order to get to +17dBm. Fine, I set bit 7 to 1, and bits 3-0 to 0xF. This gives +17dBm for Pout.

However, the MaxPower setting uses bits 6-4. For three bits the largest possible value is 07. Using the given formula of Pmax = 10.8+0.6*7 results in a MaxPower of only +15 dBm.

Am I missing something or is there a typo in the formula?. It would work if the multiplier 0.6 were increased to a value of about 1.3. Then Max Power would +20dBm .
An internet search yielded the following information about dual band circuit design for the SX127x radios:

Update #2
Upon further review of the RFM95W data sheet it appears to be normal for this radio to have a default rf frequency of 434 Mhz.

The module has two frequency bands; a lower band below 525 Mhz and a high frequency band above 860 Mhz. The default value is the low band. The default freq. is 434 Mhz. To get to the high band and to tune to 915 Mhz requires re-configuration via SPI and that's what I have done (see post#1). So I think all is OK with my radio link..

It is odd that the radio can operate over such a wide freq range without a change in the values of the rf filter components. Does the switch over in bands also involve electronic switching of filter components?

Hi again,
Update on the issue regarding my RFM95W-915 Mhz modules:

I now know for sure that the radios shipped to me are not 915 Mhz devices. I was able to read the default frequency settings on the parts I received. I did this by reading registers 06, 07, and 08 through SPI and then writing the values in those registers to my microprocessor's eeprom. I then read the eeprom using a my pic programmer. The results are as follows:

06 MSB = 6C hex
07 MIB = 80 hex
08 LSB = 00 hex

Collecting the results together gives a sum value is 7,110,656 decimal

Multiply this number by the freq resolution of 61.035 gives a final result of 434 Mhz

Needless to say this is a very upsetting finding. The parts are way off from the intended frequency. Also, they are soldered to my boards making replacement difficult if not impossible.

Is there anyone at Anarduino who can explain this situation? My emails go unanswered.

Dick Ivers

Hi Steve,
Thanks for your comments. You're correct that the radios had markings on the bottom. I looked at them briefly before installation but can't recall the i.d. However, if something was amiss I probably would have noticed???

Here is what led to my question: I have a second radio system which is identical to the one in question, but uses Hope LoRa 915 Mhz transceivers that I got from D6 Labs. These radios are most definitely 915 Mhz. It is the only freq. sold by D6 Labs and is the default configuration.

When I built a receiver using the Anarduino module it would not pick up a signal from the D6 transmitter. I had assumed that the Anarduino radio was 915 Mhz by default. When I reconfigured the Anarduino receiver to 915 it did work correctly and picked up the transmitter signal.

This led me to question what kind of part I got from Anarduino. Is there anyone at the company who could check and confirm what kind of radios were shipped to me?

Dick Ivers
I have two RFM95W-915Mhz LoRa transceivers I purchased a while back. They are now assembled in a long range, one way rf actuator of my own design. When I first got the devices they were not configured for 915 Mhz, it was some other frequency, not sure what. My micro software drives the rf to 915 mhz on start up, so all is OK.

Is it normal for these parts to be shipped at something other than 915 Mhz?
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