# LimeSDR-USB frequency shift on 70cm

**URL:** <https://discourse.myriadrf.org/t/limesdr-usb-frequency-shift-on-70cm/3940>\
**Category:** LimeSDR\
**Created:** [31 December 2018 13:41 UTC](https://discourse.myriadrf.org/t/limesdr-usb-frequency-shift-on-70cm/3940 "2018-12-31T13:41:37Z")\
**Posts on this page:** 9\
**Page:** 1

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**Author:** ![Yume](https://avatars.discourse-cdn.com/v4/letter/y/d9b06d/32.png) [@Yume](https://discourse.myriadrf.org/u/Yume)\
**Post date:** [31 December 2018 13:41 UTC](https://discourse.myriadrf.org/t/limesdr-usb-frequency-shift-on-70cm/3940/1 "2018-12-31T13:41:37Z")

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Getting strange frequency offset on 70cm, for example my local DMR tower is on 439.312500 but with lime it shows up at 439.318600 (with my rtlsd+tcxo shows up in right place.) It’s constant, whatever I tried (eg. another laptop, gqrx, sdrsharp, sdrconsole, windows/linux as host, cooling check, vco/nco tuning, antenna change etc. Also the FM band seems ok. Any suggestions pls?

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**Author:** ![Yume](https://avatars.discourse-cdn.com/v4/letter/y/d9b06d/32.png) [@Yume](https://discourse.myriadrf.org/u/Yume)\
**Post date:** [2 January 2019 16:19 UTC](https://discourse.myriadrf.org/t/limesdr-usb-frequency-shift-on-70cm/3940/3 "2019-01-02T16:19:46Z")

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Hmm, still not perfect, but if I downgrade from 2.19 to 2.18 fw, getting less shift…

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**Author:** ![Yume](https://avatars.discourse-cdn.com/v4/letter/y/d9b06d/32.png) [@Yume](https://discourse.myriadrf.org/u/Yume)\
**Post date:** [7 January 2019 08:20 UTC](https://discourse.myriadrf.org/t/limesdr-usb-frequency-shift-on-70cm/3940/4 "2019-01-07T08:20:43Z")

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Anyone on this? I can reproduce it if anyone wants to debug… @andrewback ?

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**Author:** ![adim](https://avatars.discourse-cdn.com/v4/letter/a/8edcca/32.png) [@adim](https://discourse.myriadrf.org/u/adim)\
**Post date:** [7 January 2019 08:51 UTC](https://discourse.myriadrf.org/t/limesdr-usb-frequency-shift-on-70cm/3940/5 "2019-01-07T08:51:10Z")

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This is probably within the specified internal clock deviation. You can correct clock offset in software with an adjustment expressed in parts per million (ppm). I think the device also has an input for external GPSDO if you need such precision, although usually just correcting the deviation in software is enough for most applications of this type.

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**Author:** ![andrewback](https://avatars.discourse-cdn.com/v4/letter/a/22d042/32.png) [@andrewback](https://discourse.myriadrf.org/u/andrewback)\
**Post date:** [7 January 2019 09:56 UTC](https://discourse.myriadrf.org/t/limesdr-usb-frequency-shift-on-70cm/3940/6 "2019-01-07T09:56:39Z")

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Pinged @Zack.

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**Author:** ![Yume](https://avatars.discourse-cdn.com/v4/letter/y/d9b06d/32.png) [@Yume](https://discourse.myriadrf.org/u/Yume)\
**Post date:** [7 January 2019 11:56 UTC](https://discourse.myriadrf.org/t/limesdr-usb-frequency-shift-on-70cm/3940/7 "2019-01-07T11:56:15Z")

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…with 2.18 gw I think it’s within the specs, but with 2.19 it seems much worse.

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**Author:** ![Zack](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/zack/32/89_2.png) [@Zack](https://discourse.myriadrf.org/u/Zack)\
**Post date:** [23 January 2019 09:47 UTC](https://discourse.myriadrf.org/t/limesdr-usb-frequency-shift-on-70cm/3940/8 "2019-01-23T09:47:42Z")

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Hi @Yume,

Could you read VCTCXO DAC value using LimeSuiteGUI (board related controls menu item) for both gateware version, please.

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**Author:** ![Yume](https://avatars.discourse-cdn.com/v4/letter/y/d9b06d/32.png) [@Yume](https://discourse.myriadrf.org/u/Yume)\
**Post date:** [23 January 2019 18:32 UTC](https://discourse.myriadrf.org/t/limesdr-usb-frequency-shift-on-70cm/3940/9 "2019-01-23T18:32:42Z")

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With the 2.18 gw 125/7  
2.19 gw it’s 7/7  
Same temp around 40C’

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**Author:** ![Zack](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/zack/32/89_2.png) [@Zack](https://discourse.myriadrf.org/u/Zack)\
**Post date:** [24 January 2019 06:51 UTC](https://discourse.myriadrf.org/t/limesdr-usb-frequency-shift-on-70cm/3940/10 "2019-01-24T06:51:30Z")

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Enter “125” value to “VCTCXO DAC (permanent)” edit box and push “Write” button next to it. This will fix the issue.