# Input & output transformers

**URL:** <https://discourse.myriadrf.org/t/input-output-transformers/4629>\
**Category:** LimeSDR\
**Created:** [26 April 2019 14:19 UTC](https://discourse.myriadrf.org/t/input-output-transformers/4629 "2019-04-26T14:19:11Z")\
**Posts on this page:** 5\
**Page:** 1

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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:** [26 April 2019 14:19 UTC](https://discourse.myriadrf.org/t/input-output-transformers/4629/1 "2019-04-26T14:19:11Z")

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I am looking to alter the TX1 & RX1\_L for a lower frequency response.  
Problem is that the schematic does not match the part numbers at all.  
TX1, RX1\_L, RX1-W all use the TC1-1-13MA+.  
TX2 & RX1\_H use TCMI-63AX+  
Neither looks to be right part by the schematic, although may be the correct part number.  
I just want to be sure of the units, so as to swap them out.

Thank you,  
Ed  
AA7QQ

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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:** [26 April 2019 14:38 UTC](https://discourse.myriadrf.org/t/input-output-transformers/4629/2 "2019-04-26T14:38:50Z")

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Also, found the TX impedance at the output pin of the LMS7 to be 40 ohms. I could not find the RX input impedance. Could that be supplied?

Thank you,  
Ed  
AA7QQ

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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:** [30 April 2019 14:41 UTC](https://discourse.myriadrf.org/t/input-output-transformers/4629/3 "2019-04-30T14:41:03Z")

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Bump for the new week…

Ed

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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:** [30 April 2019 14:50 UTC](https://discourse.myriadrf.org/t/input-output-transformers/4629/4 "2019-04-30T14:50:20Z")

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> [@AA7QQ](#):
>
> Also, found the TX impedance at the output pin of the LMS7 to be 40 ohms. I could not find the RX input impedance. Could that be supplied?

@Zack?

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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:** [2 May 2019 07:01 UTC](https://discourse.myriadrf.org/t/input-output-transformers/4629/5 "2019-05-02T07:01:33Z")

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Hi @AA7QQ,

For RX check this:  
[https://limemicro.com/?attachment\_id=8453](https://limemicro.com/?attachment_id=8453)