# SX1262+LoraMac-Node, wrong frequency?

**URL:** <https://www.thethingsnetwork.org/forum/t/sx1262-loramac-node-wrong-frequency/69737>\
**Category:** Generic Node\
**Created:** [November 12, 2024, 5:55am UTC](https://www.thethingsnetwork.org/forum/t/sx1262-loramac-node-wrong-frequency/69737 "2024-11-12T05:55:58Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![bruno\_aa](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/bruno_aa/32/35697_2.png) [@bruno\_aa](https://www.thethingsnetwork.org/forum/u/bruno_aa)\
**Post date:** [November 12, 2024, 5:55am UTC](https://www.thethingsnetwork.org/forum/t/sx1262-loramac-node-wrong-frequency/69737/1 "2024-11-12T05:55:59Z")

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Hi,

I’m using a relatively old version of Loramac-node (4.4.7) with this board review that I’ve made with SX1262, it was working fine with the older revision using the SX1272, but I cannot get a single packet to TTN with this new board. Device is set as ABP for now.

During debug, I saw this packet was sent on channel 918.2MHz (by looking at SX126xSetRfFrequency() just before the TX), and I wonder if the frequency is ok, shouldn’t the 918.2 be the center frequency? The SX1272 that is working is indeed a bit more centered, but not completely.  
 ![image](https://www.thethingsnetwork.org/forum/uploads/default/original/3X/f/c/fc2f2fd8025898c25d539a433951f6f494800ff5.jpeg)

I’ve setup a gateway to TTN using AU915, and this node is ~15m from it. The SDR capture was done close to the device antenna.

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<div class="post-metadata">

**Author:** ![jreiss](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/jreiss/32/46529_2.png) [@jreiss](https://www.thethingsnetwork.org/forum/u/jreiss)\
**Post date:** [November 22, 2024, 2:43pm UTC](https://www.thethingsnetwork.org/forum/t/sx1262-loramac-node-wrong-frequency/69737/2 "2024-11-22T14:43:55Z")

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Yes, 918.2 MHz is the center frequency for the channel. LoRa can receive with a maximum frequency error of 25% of the bandwidth. Your signal looks to be ~62.5KHz offset, 918.13 MHz?

> **[LoRa® Receiver – Automatic Frequency Control](https://stuartsprojects.github.io/2020/06/11/LoRa-receiver-automatic-frequency-control.html)**
>
> The maximum permitted frequency error between transmitter and receiver, for reception of a LoRa® packet, is 25% of the bandwidth in use. So at 125000hz bandwidth the maximum frequency error is 31500hz, if the bandwidth is 7800hz the maximum frequency...

You could try to offset the input frequency in software to nudge the transmission over until you can review the hardware.

You may want to check the 32MHz input clock to the SX1262.

Do you have a ground plane isolating the crystal from the sx1262 as shown in the reference design?

> **[SX1262](https://www.semtech.com/products/wireless-rf/lora-connect/sx1262)**
>
> The SX1262 LoRa Connect transceiver supports LoRa modulation for LPWAN use cases and (G)FSK modulation for legacy use cases.

PCB design guidelines also discuss isolating the SX1262 to protect from the temperature of the transmitter.  
[https://semtech.my.salesforce.com/sfc/p/E0000000JelG/a/3n000000qSpp/1S54A2bMsfzpJymOwrgiS\_j0dcDtgUQOoegEnEYwbJ0](https://semtech.my.salesforce.com/sfc/p/E0000000JelG/a/3n000000qSpp/1S54A2bMsfzpJymOwrgiS_j0dcDtgUQOoegEnEYwbJ0)

There are also trimming capacitors on the SX1262 which can be adjusted.  
[https://semtech.my.salesforce.com/sfc/p/E0000000JelG/a/3n000000qSqx/zA116VywGQq.p2z7FLfB.aPA\_pli.7v7ONxACKqt1Kw](https://semtech.my.salesforce.com/sfc/p/E0000000JelG/a/3n000000qSqx/zA116VywGQq.p2z7FLfB.aPA_pli.7v7ONxACKqt1Kw)

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<div class="post-metadata">

**Author:** ![bruno\_aa](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/bruno_aa/32/35697_2.png) [@bruno\_aa](https://www.thethingsnetwork.org/forum/u/bruno_aa)\
**Post date:** [December 26, 2024, 3:04pm UTC](https://www.thethingsnetwork.org/forum/t/sx1262-loramac-node-wrong-frequency/69737/3 "2024-12-26T15:04:51Z")

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Thank you and sorry for responding late.

Issue was fixed. Problem was that I forgot to remove the load capacitors from the crystal of the 1262 (I reused a design with 1272), 2 15pF were mounted, once I removed, all good.

Thank you for the help!