# A strange phenomenon

**URL:** <https://discourse.myriadrf.org/t/a-strange-phenomenon/2490>\
**Category:** Uncategorized\
**Created:** [20 March 2018 15:31 UTC](https://discourse.myriadrf.org/t/a-strange-phenomenon/2490 "2018-03-20T15:31:34Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Xiegg](https://avatars.discourse-cdn.com/v4/letter/x/7993a0/32.png) [@Xiegg](https://discourse.myriadrf.org/u/Xiegg)\
**Post date:** [20 March 2018 15:31 UTC](https://discourse.myriadrf.org/t/a-strange-phenomenon/2490/1 "2018-03-20T15:31:34Z")

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A strange phenomenon occurs on my LIMESDR. FM signals can be received at the HF frequency. For example, a 90M FM radio can be received at 3M frequency. Is this a hardware problem? My LIME version is 1.4S.

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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:** [20 March 2018 15:35 UTC](https://discourse.myriadrf.org/t/a-strange-phenomenon/2490/2 "2018-03-20T15:35:20Z")

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No, this is to be expected with an SDR and strong signals, due to aliasing. If it causing you problems you can reduce/remove this with filtering. There are vendors that sell e.g. “band stop” filters for broadcast radio and TV bands, which are the most common source of problems.

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**Author:** ![Xiegg](https://avatars.discourse-cdn.com/v4/letter/x/7993a0/32.png) [@Xiegg](https://discourse.myriadrf.org/u/Xiegg)\
**Post date:** [20 March 2018 15:37 UTC](https://discourse.myriadrf.org/t/a-strange-phenomenon/2490/3 "2018-03-20T15:37:08Z")

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Thank you very much

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**Author:** ![AA7QQ](https://avatars.discourse-cdn.com/v4/letter/a/13edae/32.png) [@AA7QQ](https://discourse.myriadrf.org/u/AA7QQ)\
**Post date:** [20 March 2018 17:12 UTC](https://discourse.myriadrf.org/t/a-strange-phenomenon/2490/4 "2018-03-20T17:12:45Z")

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Bandpass filtering will help in all regions that you recieve in. It filters out frequencies higher & lower than the ones you are interested in.

Ed