Problems with HF, multiple questions

Due to the situation with getting a limesdr, I bought a ‘once used’ unit online. It passes self tests. I’ve removed MN18, 402 size is a little beyond my comfort level. But it’s removed. I didn’t get the results I hoped for, so I resoldered the 2 caps next to it to be sure I didn’t disconnect them. Ohm meter says they are connected, and confirms they are not shorted.

I’m native to Linux and use sdr++, but I have tried in windows with sdr++, sdrconsole, cubic, and one other. I’m using a amplified loop, 80M and 40M are dead during the day right now. But I receive nothing below 25mhz. I had an SDRPlay that worked quite well.

I do get a elevated noise level when selecting RX1_L

Nothing on the AM broadcast band.

I can’t receive any of the WWV stations.

I’ve found an FM broadcast station around 25mhz

I still have my limesdr on order from crowdsupply, but don’t know if I have a problem, this limesdr has a problem, or what is going on.

Thanks for any advice, Cory

Upped a setting to in sdrpp, now I’m getting lower frequencies, many are in the wrong place. I have a FM station at 750khz.


For HF operation you need very good BPF. What is your settings for HF (sample rate, RX LPF etc…)?

Thanks for the response. I’m kinda new to the RF world, really new to SDRs. But I can get around a tube receiver pretty well. The software I’m using is vague, so I have many unknowns. I have a pulldown menu that allows from like 100khz, up to around 56Mhz. The SDR must be stopped to change this. Upping this value made things way better. Bandwidth is 130 Mhz, also needs to be very high to get results.

Can you be more specific on very good BPF? I take it not just a passive filter? After changing the settings I found FM broadcast signals all over the bands. I was guessing I just needed a LPF to keep the higher frequencies out of the front end. Am I going to need multiple BPF for the HF bands?

You asked about the LFP, Is there a LPF in the LImesdr? If so I don’t see any options for turning it on in my software. Or any of the other software I tried either.

I’m in over my head here a little. But if you know what you’re doing, you’re not learning anything. lol

Thanks for any education is appreciated, any suggested reading? Cory

If you have WIndows good starting point is SDR# and LimeSDR plugin from:

Download and unpack (32 or 64bit version) into SDR# folder , read two xml files, modify original SDR# files (add lines for LimeSDR device) and run SDR#. In Source selection combo box must appear LimeSDR and in settings you will see all neccessary tweaks for RX to run HF (or any other band).

About BPF: LimeSDR is broadband device and to avoid oversampling effect you need good hardware BPF plus LimeSDR software RX LPF set correctly. RTL SDR DVB-T USB dongles have tracking BPF but overall noise figure is much worse. With low noise LNA and selective BPF LimeSDR can be used for extreme receive signal conditions like EME (Moonbounce comunications) or MS (Meteor scatter reflection) etc…

I tried the SDR# and plugin. There is no longer a frontend config file and I tried several options of putting the config in the .config and plugins file. Kept deleting and unzipping the folder fresh. I found a manual for sdr# that said all you have to do now is add the files to the plugins folder. I put the 3 .dlls in there, then tried the 64bit versions. Nothing allowed the limesdr to be seen. Maybe I’m missing something, but something has changed.

All sorts of Christmas stuff going on here, but I am going to try and build a LPF at around 45 mhz next chance I get. Really surprised how much broadcast FM is getting into the lime. The I have powered loop antenna that is only good to 30 mhz. The SDRplay I had before never would pick anything up above about 50 mhz.

Any suggestions on the SDR# issue? Thanks!

Just checked, new SDR# is built for .NET 5.0 with different frontend requirements. Try to download older version from:
I’m working with 32bit and 64bit versions.

Is the LPBW the software LPF? Sadly there’s a TV show messing up google searches.

Yep, that worked. Same results I"ve been getting elsewhere. I’m looking into building a LPF for fun soon and seeing what that will accomplish. If a BPF is needed for every ham band, or a LNA also, I need to get something like the SDRPlay I just got rid of. Horrible Linux drivers. Anyway, I’m eager to experiment with this. Thanks

From my experience:
Lime SDR USB with mod is useful down till 3,5 MHz with HF low pass and some preamp.
I used LNA4HF

Lime SDR mini or Lime NET micro, no mod, useful down to 7 MHz with LNA4HF

For any lower freq you need to up convert the signals.

Used SW SDRConsole , SDRAngel, CubicSDR

Thanks for the info. I’m building the LPF, my antenna is amplified. Going to do the wideband mod as soon as I get the parts ordered. Did simple mod #1 at this point.

Just to be sure I’m not working on a lost cause, is any of this seem correct?
I made my LPF today and it works, not sure how I got a little more than 14mhz cutoff instead of the 45mhz I designed for. Double sided board with some DIY vias to make the back a complete ground plane.


Nanovna results.

Here is the FM band with the LPF installed, it knocked the FM broadcast out as seen in the waterfall.

That got rid of the FM stations all over the HF band. Not sure why I didn’t try this earlier, but the HF bands seem pretty dead here tonight. Here is the receive with the input shorted.

Is this level of noise to be expected?
Again my antenna is amplified. I guess I’m going to need a lot more amplification, and only to get to 80M? Or is this limesdr broken?

The LPF filter helped a lot. Building a new loop with a LPF and more amplification. Thanks

Okay, the limesdr is a good receiver. Definitely weak in the HF bands. I really wasn’t trying to bad mouth it, I’m new to the SDR game and was out of ideas. The LPF helps a lot. I was able to boost the antenna gain and I’m getting decent results. One major issue I found is that MLA-30 antenna I’m using has a switching power supply in the bias T. It is getting through the LPF still. The SDRplay, and only other SDR i’ve used, had a built in bias T that isn’t full of noise. So this whole this whole post has been beginner error, bad hardware, and not having a second of anything to test against.