I greatly appreciate the posting by Ricardas of plots for the RXn_L and RXn_H antenna ports. I would like to see a similar plot for the RXn_W port. I would also like to see a similar set of plots for the TXn_1 and TXn_2 output ports, so that I could make a maximally intelligent choice of which of the 10 Rx/Tx ports to use for a variety of applications.
Once again, thank you very much for the work done so far.
John Toscano, W0JT/5, EL09vu20
That is very bad news.
It was promised to have a broadband matching network instead of the very narrow UMTS/LTE optimized one.
Please post detailed analysis of how the final HW and the âHF fixedâ HW behave when a signal is sweeped on the 3 RX antenna ports from 100 kHz to 3.8 GHz.
The interesting thing is the behaviour from the antenna input plug to the final I/Q output on the computer.
And then sweeping a signal on the 2 TX ports and look at the output signal on the antennas.
These are the optimized frequencies for the current matching network:
RX1 L = 700 MHz - 900 MHz
RX1 H = 2 GHz â 2,6 GHz
RX1 W = 700 MHz â 2.6 GHz
What does that mean.
How much attenuation do I see if I am in a non optimized frequency?
RX1L is optimized for 700-900 MHz (veeeery small frequency band)
What behaviour will I see if I go outside of that optimal band?
0.95% or 0.05% of the signal that would have made it in the optimized band? something in between?
How does the âHF Fixâ worsen the behavior on higher frequencies?
We need information that we can decide weather to cancel the purchase, or go for the HF fix or go for unmodified HW v1.4.
Please give detailed answers, as we need a basis for the decision if we want to cancel or not.
Out of curiosity what were the motives to break the promise to change the matching network to be much more broadband??
How does the frequency sensitivity compare to Ettus USRP and the BladeRF and HackRF.
They use 1 matching network for the entire frequency spectrum they support. How does their sensitivity on certain bands compare to the LimeSDRâs? (when taking into the account everything from the antenna plug on)
Personally I find it sad that we have not been informed earlier that the promise of a more broadband matching network has been broken.
I think all your questions are answered on this forum already, multiple times. And for those specifics, you can find in the documentation. As for comparing the other SDRs you can look at the docs and find that info and there was a table with some of those comparisons on the crowdsupply page.
No promises were broken and you would know if you read through just a few of the posts here. There was a lot of discussion also with beta testers that were interested in HF last year. So you may want to contact those testers.
And a lot of the other HF fans that were threatening to cancel have changed their minds.
I was refering to this promise made in this very thread:
âCurrently we are using components on LNA inputs to fine tune for some cellular bands. On the final version of the LimeSDR we shall match the receivers for the optimum broadband performanceâ
The final LimeSDR hardware is still optimized for cellular network bands, and was not made more broadband.
Anyhow ⌠at the moment I think I will do nothing, and when I have the HW I can still decide if I want to remove MN18 or leave it as it is.
Hello all,
I just received my version 1.4s board and purchased it to primarily receive and transmit satellite signals (primarily receive) in the 440 MHz ham bands. Can anyone give an update on the issue described above relating to the matching network on this board? Either way, can someone suggest which connector I should use for receiving a 24 kHz wide signal on this band? If the matching network is still in place, can someone point me to a board modification to fix the limitations and allow me to maximize on the 440 MHz frequencies? I have not used the board, can I return it? Very new at this and appreciate any help or comments.
Best Regards,
Fred - KF4FC
You can find that info here. I suggest the EasyFix1 wich is done just by removing the MN18 inductor.
For 440 MHz you can use RX1_L as isâŚ
73
@RicardasVadoklis Very nice chart! Could you please explain how to draw a chart like this, e.g. for RX*_W? If I understand correctly the NF could just be seen in Gqrx or similar software. But how did you measure Gain? Just by sending a signal on given frequency or somehow else? In other words could you please explain the experiment conditions in a little more details.
The Noise Figure measurements I would assume used one of the following methods:
( ref: https://www.maximintegrated.com/en/app-notes/index.mvp/id/2875 and Noise Figure Measurement Accuracy: The Y-Factor Method PDF Asset Page | Keysight )
My assumption would be that Lime Microsystems used an expensive noise figure meter, tuned the LimeSDR from 100 MHz to 3650 MHz in say 50 MHz steps, and then from data collected, generated the two graphs (system gain and noise figure).
There is also CANFI (Cheap Automatic Noise Figure Indicator), which I only mention because it is probably closer to the price range of most individuals. It is an open source program written in C# (that uses the Y method) which relies on a RTL-SDR, a calibrated noise source (and a noise source calibration file or an uncalibrated noise source with a calibration file - which is not easy to generate without access to expensive calibrated equipment) and a 50-ohm terminator. The source code could probably be adapted to use a LimeSDR.
http://www.canfi.eu/index.html
GitHub - dl2alf/CANFI: (C)heap (A)utomatic (N)oise (F)igure (I)ndicator with DVB-T stick