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Why Lousy Signal to Noise? I'm using a NooDElect SDR & Upconveter

Discussion in 'Software Defined Radio (SDR)' started by K4BDA, Nov 7, 2020.

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  1. K4BDA

    K4BDA Ham Member QRZ Page

    I'm new to SDR and have a NooElect R820T SDR & DVB-T and a NooElect Upconverter aka Ham It Up

    I'm using SDRsharp software and I have it all working on HF and above.

    I'm using a wire antenna that goes out the door by my desk and runs about 30 feet along the ceiling of our front porch.

    On 75, 40, and 20 meters the noise floor is the same level as the ham radio signals. I can barely hear the stations because of the high noise or because of the low signal level.

    1 - Any tips on how to get more of the radio signal into the radio?
    2 - I'm wondering if the high noise level is coming from my computer... the SDR is plugged directly into the USB connector on the front of the PC. What do you think?
    3 - Any tips welcome.
    Thanks for the help.
     
  2. N6YWU

    N6YWU Ham Member QRZ Page

    There are at least 3 strikes against your setup.
    1) The NooElect RTL-SDR device only has a 8-bit ADC, which has a fairly high quantization noise floor. Other SDR dongles (Airspy, SDRPlay, Lime, etc.) can sample more bits and thus have better S/N performance.
    2) Your antenna on the porch is likely too near EMI/RFI sources inside the house.
    3) Your antenna is too low to have much gain in the direction of interesting signals. Low wires tend to have a near vertical pattern.

    First thing I'd try is running coax to an antenna higher and farther away from electronic noise (appliances, chargers, LED lights, solar panels, etc.). Or, if you have a portable laptop computer, you can try taking your NooElect and antenna wire to a park away from power lines and houses, and throw the wire up into a tree.

    Another thing to try is experimenting with ferrite chokes on all the network and USB connections and power cables around your office.
     
    Last edited: Nov 7, 2020
  3. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    -What is your antenna, precisely? Please describe it.
    -What is the feedline?
    -Does it have radials/counterpoise? How many?
    -What efforts are there to reduce Common Mode Current and pickup on local electrofog/noise? Feed point choke/isolator/balun? Entrance point isolator/balun?
    [edit]-Have you previously swept your house for offending electronic devices?
    -Have you connected the SDR to another antenna?
     
    Last edited: Nov 7, 2020
  4. NM7G

    NM7G Ham Member QRZ Page

    In a word, antenna, antenna, antenna. OK, so it was three words.

    On a porch ceiling makes me think its not high enough, and thus its close to manmade noise sources (utilities, PCs, appliances). At 30 feet long, its way too short for 75m and 40m. Get some wire way up in the air, match antenna impedance to the SDR input, and you'll be much happier.
     
  5. K4BDA

    K4BDA Ham Member QRZ Page

    N6YWU... Thanks for the quick reply.
    Roger on the antenna and the NooElect RTL-SDR device.
    I've got an Eagle One vertical I'm going to hookup later this week. If not that a better long wire outdoors.
    On the NooElect RTL-SDR device... You listed Airspy, SDRPlay and Lime devices. Which of these would be the best choice?
    What SDR device would be a cut above those... without spending a fortune :)
    Thanks again for the help.
    K4BDA
     
  6. K4BDA

    K4BDA Ham Member QRZ Page

    KA0HCP, thank you for the reply.

    As mentioned in the original post I'm just using a long wire down the ceiling of our front porch for an antenna.
    It is connected directly to the Up converter RF input.
    I will be putting up a better antenna outside next week so hopefully that will help.
    Regarding "sweeping" the house for offending electronic devices... what device would you use to do that?
    I guess I could put together a broadband simple RF device signal strength meter but time tells me to just buy one :)
    Thanks.
    K4BDA


     
  7. KA9JLM

    KA9JLM Ham Member QRZ Page

    Yes.

    The Upconverter needs to have a well filtered power supply also.

    All of the computer signals mix and add up.

    A 6 foot usb extension like this should help.


    upload_2020-11-7_13-41-50.jpeg
     
    KA0HCP likes this.
  8. N6YWU

    N6YWU Ham Member QRZ Page

    The Lime devices are more for microwave experimentation, as they work above 2 GHz, but are not very sensitive for MF and HF listening.
    The SDRPlay RSPdx and the Airspy HF+ Discovery are both excellent for amateur radio HF and VHF reception.
    The RSPdx also supports UHF frequencies, and it has a wider bandwidth than the HF+.
    But the HF+ Discovery is a bit less expensive and has more open source software support available.
    I have and use both SDRPlay and Airspy receivers.

    But whatever device you choose to use, you may want to first spend your money on a better antenna systems and/or household EMI suppression instead.
     
  9. TJNII

    TJNII QRZ Member

    I have a NooElec upconverter and one of their RTL2838 based SDRs. I've found the upconverter to be fussy to the point of uselessness. I've only been able to get it working once with a longwire monopole antenna and a good ground through a desktop chassis. I haven't been able to get it to work in any other configuration. Personally after many hours of faffling with it I've given up on the upconverter for HF, and am looking into other SDRs for HF listening.

    Anyway, my point is, in my experience, the upconverter & VHF SDR combo is marginal in the best case. Don't spend too long chasing your tail if it doesn't work for you.
     
  10. VE7BPB

    VE7BPB Ham Member QRZ Page

    I'll throw my two cents in.

    I have multiple SDRs such as the SDRPlay RSP2 and Pluto SDRs and multiple RTL dongles .

    Doing WSPR receive tests with an RSP2 versus an RTL-SDR dongle and a Noolec Ham-it-UP converter on the same station, on the same band and the same antenna at the same time, I find that the signals levels that get reported by WSPR are typically within 1 DB of each other.

    The potential overload of the RTL dongle on HF is mitigated very nicely by the Noolec converters built-in 10 DB conversion loss. As long as you run the RF gain on the dongle at a reasonable level (not full out) it does a fine job.

    Having said that, your problem is entirely due to a poor antenna picking up lots of local noise and not enough signals. Make the antenna longer, higher, further away. All or any of these will help.

    There is no point spending money on a higher end SDR until you deal with the antenna issue, and you current equipment can be used to achieve that.

    Good luck.

    regards, Roy
     

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