Where did the 100 KHz go?

@dean,

Pavel is a genius…He turned that Red Pitaya into a Metis radio completely compatible with OpenHPSDR. I wish some of the LimeSDR alumni here would get a clue and be more like Pavel - head down all the time and working on making that radio great…If that happened with the LimeSDR it would be phenomenal right now…Yet, we wait for that to happen…

73 de Marty, KN0CK

I will certainly buy another Lime SDR but will wait and buy one for 50c on the $ from the HF guys HiHi. That is why I set the other page up so people can make positive comments on how to set Lime up on HF. I love SDR Console very much but also wish the Lime would talk to PowerSDR too. I am not seeing any thing that I class as a problem with the Lime on 6/2/222 and agree with you. Time to only discuss positive things about getting the Lime running. I am so looking forward to when I can try it on JT65 TX.

Paul,

I can’t really say anything right now, but let me assure you that there’s motion in the background that’s gonna make that wish of yours come true for two channels of transmit and receive for the Lime…Stay tuned…

73 de Marty, KN0CK

I look forward to reading more when more information is released. Just an easy way to create a SSB (DIGI) TX input will be fantastic as my main reason for supporting Lime is the same. A 10GHz SDR rig.

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Marty - agree 100% with you there! Oh, and I currently have 3 Red Pitayas - one is a dedicated multi-band WSPR box, the others aren’t dedicated to anything specific, although they get used for SA, 'scope, SDR and logic analysis as required :slight_smile:

John

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Perhaps we should try to persuade Pavel over to ‘the Dark Side’? :wink:

John

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The sensitivity of the receiver of the LimeSDR has been measured.

Frequency

The sensitivity of the receiver of the LimeSDR has been measured.

Frequency Noise Figure
3 GHz 28 dB
1 GHz 8 dB
300 MHz 9 dB
145 MHz 8 dB
100 MHz 8 dB
30 MHz 8 dB
10 MHz 28 dB
3 MHz 52 dB
1 MHz 68 dB
300 kHz 86 dB
100 kHz 105 dB

This is far from beeing state of the art.
The measured noise figure of a good receiever (SDRplay, RSP2) is 2dB at 145 MHz, without a significant drop at the upper or lower end of its frequency range.

The system antenna+receiver need not be optimized as long as the antenna noise overrides the receiver noise.

The Lime LMS 7002 has not been designed for a wide band application and for frequencies below 30 MHz.

Do you mind to explain your measurement method and equipment used :wink:
Also please keep in mind that RSP2 have two band stop filters and bunch of band pass as well.
I have here 2 pcs of RSP 1 so was able to compare a bit and if you provide your method that can
be useful for all.
73
Dj

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Adding a filter will reduce sensitivity and not improve it. Without the filter the RSP’s would be even more sensitiv.

Ok, than please take your RSP2 or any low or high end SDR near the top of any hill populated
with FM and TV broadcasting and RF links GSM base stations etc. and than let me know about
sensitivity and reception of any HAM band :smiley:

BTW Measurement method? Equipment?

[quote=“9a4db, post:215, topic:690, full:true”]
… high end SDR near the top of any hill populated with FM and TV broadcasting and RF links GSM base stations etc. and than let me know about sensitivity and reception of any HAM band :D[/quote]
If you had a 100kW (80 dBm) FM transmitter sitting on that hill, the only hardware that I can think of that might have some chance would be the, soon to be released AirspyHF+ (There is a device driver in the latest release of SDR#, so I’m guessing it will be soon). On paper it has 18-bits of dynamic range (~110dB) and if you decimate the bandwidth from 600 kHz down to 37.5 kHz that would be ~122.2dB of dynamic range. It would be deaf as a post sitting beside a FM transmitter, but it might still pick up something. It is different from the LimeSDR, it stops receiving where the LimeSDR starts in ernest, and it only does RX, so totally different markets for both devices, but it is the only device that I can think of that might meet your challenge.

Nope, my HPSDR (a machine that keeps up with the best of them) has better snr with filtering.
Loss of 1-2dB of signal is trivial against the gains of not flooding the front end with a full 64MHz.
Not having filters on SDR’s is rather foolish and counter productive, they are practically a requirement for the platform.
Just using my antenna tuner in front of my HPSDR before I set it up with band pass filtering produced excellent results, when it comes to SDR some losses are preferable to running barefoot.

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What equipment and measurement method were used?

So far that is well hidden secret… :smiley:

Equipment: highly professional. And the most relevant part of it is experience…

The measurement of the noise figure always is based on an absolute power reference such as:

Signal generator -> 3dB method
Noise source -> Y method
Resistor at temperature T -> delta T method
Calibrated power meter -> S/N method
Calibrated receiver -> S/N method

Without the need for a ±0.1dB accuracy the NF has been measured using the 3dB method here.

BTW: a very elegant way to measure NF with a reasonable accuracy is to to apply the dBm indication of the RSP/SDRuno setup.
The dBm value is the absolute and real total power within the well defined IF channel! It is S+N, its tolerance has been measured to be within ±0.5dB within a wide range of the receiver spectrum.