How about RX gain setting?
RX gain just increases the noise level.
Can you put the gain on 20 dB
freq 3600 kHz 750 kHz sample
than please put here:
one screen copy with your standard antenna on RX1_L
one screen copy with 50 ohm termination on RX1_L
3600 KHz 750 KHz sample rate with antenna on RX1_L
3600 KHz 750 KHz sample rate with 50 ohm termination on RX1_L
@Boult - David,
Something just occurred to me while I was thinking and also studying your latest picturesâŚDo you have a Low Pass Filter (LPF, DC to 30 MHz with a filter rolloff at 35 MHz and with suppression to 80dB in the FM band) applied in series with the RX1_L input? If you donât, chances are pretty good that all the energy to receive in the HF band is being taken completely away by strong, nearby FM radio stations. This issue DOES happen to the LimeSDR because itâs a wideband receiver and if you have the gain full up but are not on a Low Pass Filter this is why your HF receive is incapable of being strong - itâs all being sucked away by nearby FM stations that will diminish the front end sensitivity in HF. If you apply an LPF in front of the RX1_L port you will immediately find your HF receive performance to be better than what you have now because you attenuate the FM stations and effectively preselect for the HF range with better receive sensitivity.
Iâd strongly recommend it for that (receive sensitivity boost) as well as cutting away the FM radio station images you will find in the HF tuning range - again, because the Lime is a wideband tuner.
Give it a shot with an LPF and let us know your progress - I think this is a contributor to your issueâŚ
73 de Marty, KN0CK
Yes lots of strong FM signals nearby but not strong enough to interfere with my SDRPlay, RTL dongo or Funcube Pro. No I donât have LPF connected to RX1_L input. Maybe I can look around and buy one from Amazon. Could also look at an AirSpy upconverter to take the HF signal into the VHF band where it will be more suited.
Thanks for all your help and info and will let you know how things develop over the coming weeks.
I initially bought the LimeSDR to work Qatar EShail-2 sat QO-100 with 2.4GHz WIFI booster etc. but things are moving slow on that front so HF is a bonus if it works.
73 de David
@Boult both screens look normal.
My Lime act the same
Even you went low with freq to 360 kHz instead of one zero more
at 3,6 MHz where is useful fange on HF.
I am using for HF LNA4HF with Low pass bellow 35 MHz with Lime.
73
Djani
1 Like
@Boult - David,
Itâs true that the SDRPlay, FunCube and other SDRs are also wideband receivers, but they incorporate and were designed to have preselection filters to reduce the effects of strong nearby emitters and also improve receive for the selected band - The RTL and LimeSDR do not have preselection filters in their frontend design and as such are more prone to interference and undesirable effects due to strong nearby emitters. So please keep that in mind. Also, Djani is correct in that the receive gain below 80/75m will be challenging without some preamplification. Iâm capable of hearing broadcast AM stations pretty well with my LimeSDR without any modifications, but itâs not going to have the same receive sensitivity as an SDRPlay or other SDR that build-in preamplification and preselection into the frontend to give consistent performance where itâs specâed to operate. Adding an up-front Low Pass Filter (DC to 30 MHz) to the Lime will certainly improve your receive in the 80/75m band (I know - I have to do it, too) and will also eliminate the strong FM images youâd see falling into the HF band because of the frontend of the LimeSDR being wide open from (realistically) 4.0 MHz to 2.0 GHz.
Keep in touch - 73 de Marty, KN0CK
Thanks for you advice and will look to getting the same low pass filter.
73 de David
Thanks for all your advice Marty will be looking at ordering low pass filter this weekend and will let you know the results when fitted.
73 de David
Just for giggles, you may try reflowing the solder on the capacitors just upstream of the inductor you pulled. Just in case there is a stress crack from the procedure. One of mine was like that.
Ed
Glad to say the LimeSDR is now working perfectly on HF with just the EasyFix1 mod without any additional filters. I ordered LNA4HF, AM and FM band block filters last weekend but still waiting for them to arrive. But in the meantime i had a longer play with LimeSuiteGUI. I wasnât able to download the QuickTest files before using Windows 10 64-bit Pro for security reasons but have now been able to using dual-boot Win 7 32-bit Pro. After running self_test.ini, example.ini and waveform files everything checked out fine. I then did some TX1 and TX2 transmission test using SDRPlay and SDRuno for receive again everything checked out ok. I re-connected 85 foot end-fed long wire with 9-1 balun as before but now everything works just fine and pulling in more signals than my TS-2000. Canât for the life of me see what changed but glad something did. The difference after the mod is astounding.!!
HF bands are not good at this time but 40m band was best, heard signals on 10m, 20m, 15m, 17m and 80-160m was able to hear some QSOs.
AM broadcast stations now loud and clear as is VHF broadcast stations, 2m amateur band and aircraft frequencies.
The LimeSDR-USB Type-A board is fitted into Luftek enclosure with external LEDs and fan which runs stable at 48C on receive.
Now very happy and pleased with the performance.
Still waiting on other delivery items to work Esâhail 2 / QO-100 satellite which is what I wanted the LimeSDR for in the first instance.
Many thanks Marty and Djani for all your help and suggestions and yes Ed I did have a good
look at the other capacitors nearby with magnifying glass at the time but nothing looked untoward but thanks for you input.
73 de David
4 Likes
I bought a Mini-Circuits BPF-E16+ 2MHz to 30MHz band pass and put that in front of the Lime, and it made all the difference in the world. Once you get all the strong signals from FM out of the way, the part can do pretty well down load.
Mini-Circuits now has a DC-30MHz filter that would probably be even better, but I havenât tried it.
Mouser has them.
2 Likes