TX Matching for frequencies below 100 MHz

Projects LimeSDR
1

Hi All,
We are using the LIMESDR-USB and transmit using the TX1_2 port as it is said to be optimized for frequencies above 10 MHz upto 2 GHz.
There is a modification to enable HF Reception at the port RX1_L.
Is there a modification to enable optimized TX at frequencies below 100 MHz?
Thanks in advance…

2

I have asked the same question with no answer.
If you look up the balun transformer series, you will find the same unit, but with lower frequency response. I am going to try it in the RX side & if I can get better performance, I will use it in the TX side.
Of course, it will take some work with capacitors.
I look forward to seeing if you get an answer.
My original question was if the RX & TX of the ports impedance acted the same.

Ed

3

I doubt the Transformer is the Culprit. TC1-1-13M+ is a 4.5 - 3000 MHz Transformer.
I am getting extremely bad VSWR results below 400 MHz.
The S11 parameters below are stuck at 0.7 dB!

4

If you look up that TC! series of transformer, you will find a much lower rated balun that is wired the same.
I have not tried, because, I am not a programmer & am trying to get Simon to bring back HF TX on SDR-Console.
I also have never received a response if the TX & RX of the LMS chip have the same impedance.
I would thing that it would work better for receive & transmit, if so.

Ed

5

I think this is the one.
https://www.minicircuits.com/WebStore/dashboard.html?model=TC1-1T%2B

Ed

6

@Karolis perhaps you could advise?

7

Hello,

LMS7002M impedance (S11, S22), matching overview is described in the " LMS7002M S-parameters" section (http://www.limemicro.com/?attachment_id=8453).

Regards,
Karolis

8

Hi Karolis,
I am using QUCS Studio for S parameter analysis. I try to place the S parameters file a a 2-port device but have no idea how to do it as the inputs of the LMS7002m are differential.
Do you have any idea of how to use the provided S parameter file in a simulation?