# 50 MHz Tx performance, LimeSDR Mini 2.4

**URL:** <https://discourse.myriadrf.org/t/50-mhz-tx-performance-limesdr-mini-2-4/8763>\
**Category:** LimeSDR\
**Created:** [12 April 2025 05:08 UTC](https://discourse.myriadrf.org/t/50-mhz-tx-performance-limesdr-mini-2-4/8763 "2025-04-12T05:08:52Z")\
**Posts on this page:** 10\
**Page:** 1

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**Author:** ![dave\_VK1DJA](https://avatars.discourse-cdn.com/v4/letter/d/cab0a1/32.png) [@dave\_VK1DJA](https://discourse.myriadrf.org/u/dave_VK1DJA)\
**Post date:** [12 April 2025 05:08 UTC](https://discourse.myriadrf.org/t/50-mhz-tx-performance-limesdr-mini-2-4/8763/1 "2025-04-12T05:08:52Z")

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I am seeing low Tx output from my LimeSDR Mini 2.4 at 50 MHz. My intent is to use this device in a 6M transceiver.

The outputs measured with a spectrum analyser (good to only 500 MHz) are:

450 MHz, -8.7 dBm  
350 MHz, -10.4 dBm  
250 MHz, -16.8 dBm  
150 MHz, -27.2 dBm  
50 MHz, -46 dBm

The test software is LimeSuiteGUI (V23). Frequencies set manually in SXT. Gain set in TBB (Frontend gain). Input source set in TxTSP (Test signal, TSGFC -6 dB).

The fall in output hints at filtering in the Tx chain?

Does the test procedure look OK, please?

Am I missing some filter settings in LimeSuiteGUI, please?

Thanks

Dave

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**Author:** ![dave\_VK1DJA](https://avatars.discourse-cdn.com/v4/letter/d/cab0a1/32.png) [@dave\_VK1DJA](https://discourse.myriadrf.org/u/dave_VK1DJA)\
**Post date:** [12 April 2025 12:43 UTC](https://discourse.myriadrf.org/t/50-mhz-tx-performance-limesdr-mini-2-4/8763/2 "2025-04-12T12:43:09Z")

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I’ve found  
[LimeSDR HF Performance - Myriad-RF Wiki](http://wiki.myriadrf.org/LimeSDR_HF_Performance)

From the Tx curves in that report, it looks as if a LimeSDR Mini 2.4 performs like the LimeSDR TX1-2.

Is it sensible to think about mods to the Tx matching on the Mini 2.4 to get usable performance on HF, please? In my case, to drive my power amplifier I need 26 dBm of drive. 72 dB of gain in a driver amp would not be easy.

Dave

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**Author:** ![dave\_VK1DJA](https://avatars.discourse-cdn.com/v4/letter/d/cab0a1/32.png) [@dave\_VK1DJA](https://discourse.myriadrf.org/u/dave_VK1DJA)\
**Post date:** [14 April 2025 05:40 UTC](https://discourse.myriadrf.org/t/50-mhz-tx-performance-limesdr-mini-2-4/8763/3 "2025-04-14T05:40:25Z")

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I apologize for not have been done more homework before posting.  
Looking at the schematics, I see TX1-1 and TX1-2 are present. I also see Band1 and Band2 as options for TX RF port path in LimeSuiteGUI/Board Related Controls.  
From the schematic, I expect Band 2 is the path for the lower frequencies.  
However, choosing Band 2 gives even lower output:

- Band 1 chosen: 450 MHz, -9 dBm; 50 MHz -46 dBm;
- Band 2 chosen: 450 MHz, -46 dBm; 50 MHz, -67 dBm.

Does this narrow down the possibilities, please?

Dave

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**Author:** ![dave\_VK1DJA](https://avatars.discourse-cdn.com/v4/letter/d/cab0a1/32.png) [@dave\_VK1DJA](https://discourse.myriadrf.org/u/dave_VK1DJA)\
**Post date:** [16 April 2025 12:57 UTC](https://discourse.myriadrf.org/t/50-mhz-tx-performance-limesdr-mini-2-4/8763/4 "2025-04-16T12:57:34Z")

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After digging into the doc (including an old performance assessment), my Mini generates the expected output on 50 MHz. With LimeSuiteGUI, Band 2 must be selected in the Board Related Controls panel, and as the TXFE setting in the TRF panel.

Dave

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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:** [16 April 2025 15:01 UTC](https://discourse.myriadrf.org/t/50-mhz-tx-performance-limesdr-mini-2-4/8763/5 "2025-04-16T15:01:48Z")

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I checked with a colleague and he suggested that it sounded like the correct RFIC transmit port had been selected, but the RF switch on the SDR wasn’t set correctly.

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**Author:** ![kapuita](https://avatars.discourse-cdn.com/v4/letter/k/fbc32d/32.png) [@kapuita](https://discourse.myriadrf.org/u/kapuita)\
**Post date:** [29 May 2025 17:56 UTC](https://discourse.myriadrf.org/t/50-mhz-tx-performance-limesdr-mini-2-4/8763/6 "2025-05-29T17:56:16Z")

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Dave, did you ever solve the Low TX power? I am having teh smae problem and wanted to understand what you did that got the TX output power at 450MHz closer to the spec of 10dBm?

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**Author:** ![dave\_VK1DJA](https://avatars.discourse-cdn.com/v4/letter/d/cab0a1/32.png) [@dave\_VK1DJA](https://discourse.myriadrf.org/u/dave_VK1DJA)\
**Post date:** [30 May 2025 07:35 UTC](https://discourse.myriadrf.org/t/50-mhz-tx-performance-limesdr-mini-2-4/8763/7 "2025-05-30T07:35:46Z")

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In LimeSuiteGUI ,

- select Default;
- In the TRF panel. set “TXFE output selection” to Band2;
- In the SXT panel, enter the desired frequency and tap Calculate;
- In the TRX Gain panel, tap on Alternative TRX gain source.  
With Frontend gain of 37, I see 2.5 dBm of output.

If you’re running limeGUI (Lime Suite NG), the same sequence. Note that the reset action is found in the menu item LMS7002.

However, I am yet to generate a signal using the LimeSuiteNG sink. I can see the device go through calibration but only an unsteady, small signal where I expect it.

Any advice on LimeSuiteNG sink would be appreciated.

Dave

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**Author:** ![dave\_VK1DJA](https://avatars.discourse-cdn.com/v4/letter/d/cab0a1/32.png) [@dave\_VK1DJA](https://discourse.myriadrf.org/u/dave_VK1DJA)\
**Post date:** [1 June 2025 02:30 UTC](https://discourse.myriadrf.org/t/50-mhz-tx-performance-limesdr-mini-2-4/8763/8 "2025-06-01T02:30:29Z")

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I have the GNU Radio LineSuiteNG Sink performing as expected. I used LimeSuiteGUI to configure as in the previous post and to save the configuration. The configuration is then specified in the parameter for the Sink block.

There is a remaining puzzle. The Sink block throws an error if the NCO offset is specified as more than half the Sample Rate. From posts here (see Max NCO, relation to sampling rate, and NCO effect), the maximum NCO offset is the product of the Sample Rate and the RF Oversampling.

The LimeSDR Sink accepts an NCO frequency offset more than half the Sample Rate.

Any advice, please?

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**Author:** ![ricardas](https://yyz2.discourse-cdn.com/flex034/user_avatar/discourse.myriadrf.org/ricardas/32/86_2.png) [@ricardas](https://discourse.myriadrf.org/u/ricardas)\
**Post date:** [2 June 2025 05:32 UTC](https://discourse.myriadrf.org/t/50-mhz-tx-performance-limesdr-mini-2-4/8763/9 "2025-06-02T05:32:04Z")

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> [@dave\_VK1DJA](#):
>
> There is a remaining puzzle. The Sink block throws an error if the NCO offset is specified as more than half the Sample Rate. From posts here (see Max NCO, relation to sampling rate, and NCO effect), the maximum NCO offset is the product of the Sample Rate and the RF Oversampling.

Fixed it. Now NCO can be set up to the sampling rate.

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<div class="post-metadata">

**Author:** ![dave\_VK1DJA](https://avatars.discourse-cdn.com/v4/letter/d/cab0a1/32.png) [@dave\_VK1DJA](https://discourse.myriadrf.org/u/dave_VK1DJA)\
**Post date:** [4 June 2025 08:46 UTC](https://discourse.myriadrf.org/t/50-mhz-tx-performance-limesdr-mini-2-4/8763/10 "2025-06-04T08:46:09Z")

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The GNU Radio block now shows no diagnostic if the NCO offset is greater than half the sample rate.

However, execution throws an error:

LimeSuiteNG :info: version: 0.3.0-unknown build 2025-06-04  
LimeSuiteNG :info: Connecting device: “LimeSDR Mini, addr=0403:601f, serial=1DA13CDBCB3B1C”  
LimeSuiteNG :info: Reference clock 40.00 MHz  
pagesize :debug: Setting pagesize to 4096 B  
top\_block\_impl :debug: Using default scheduler “TPB”  
LimeSuiteNG :error: config error: Tx ch0 NCO offset (800000) must be less than half of sample rate(960000)

sdrdevice\_sink :critical: Failed to configure device. config error: Tx ch0 NCO offset (800000) must be less than half of sample rate(960000)

thread\_body\_wrapper :error: ERROR thread[thread-per-block[4]: \<block sdrdevice\_sink\>]: Failed to configure device. config error: Tx ch0 NCO offset (800000) must be less than half of sample rate(960000)

I was hoping that the test was the NCO offset was less than the samplimg rate times the RF oversampling. This appears to be the case with the LimeSDR sink.