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What's Your Noise levels?

Lasse MoellLasse Moell Member
edited July 2019 in New Ideas
Just saw a post regarding noise levels.. Lets see what others measure. Use 100 Hz BW and read the average level in dBm (I'm using DDUtil), make sure it's an empty spot! Do note time when sample is taken.
---------------------------
28 MHz -132 dBm 2el Yagi
24 MHz -133 dBm   "
21 MHz -130 dBm   "
18 MHz -128 dBm   "
14 MHz -123 dBm   " (ant to northwest)/-117 dBm (ant to southwest)
10 MHz -122 dBm   Dipole
7 MHz -108 dBm     Dipole statics/thunder
3,5 MHz -108 dBm inv L
1,8 MHz -104 dBm inv L

All measured at 21 local, still daylight. QTH just outside of city center (suburban).
Anyone care to share your levels? Do not forget to mention where you are located i.e. city/suburban or rural. Remember increasing RF gain can improve readings!

Comments

  • dlwarnbergdlwarnberg Member
    edited July 2019
    40 meters, DX Engineering 4 square receive array... pic.. rural 


  • dlwarnbergdlwarnberg Member
    edited July 2019
    How about 80 meters no RF Gain?



  • Lasse MoellLasse Moell Member
    edited July 2019
    David, thanks for posting. maybe you misunderstood what I want... Setting a 100 Hz wide passband filter makes it easy to calculate and compare to other settings, and of course not having a station/signal in the passband only noise, and use dBm rather than S-units. What I forgot to account for is the "antenna factor" i.e. a receive only antenna may have good SNR but pick up lot less energy, hence very low noise floor. By using the transmitting antenna (and telling what type) it is possible to compare with others.
  • dlwarnbergdlwarnberg Member
    edited July 2019
    simply trying to help get the conversation started
  • Mark_WS7MMark_WS7M Member ✭✭
    edited July 2019
    All with 80m loop, coax feed, 2.5:1 balun and PalStar HF Auto tuner with antenna tuned:

    12:00Z, location is suburban/rural.  IE on the edge of town near a large open space.  Underground utility wiring.

    3.5: -100
    7: -110
    10: -119
    14: -116
    18: -119
    21: -117
    24: -119
    28: -126
  • Lasse MoellLasse Moell Member
    edited July 2019
    Mark, that is some 10 dB worse than me! I have spent a fortune on ferrites to make sure it's just the antenna and not the feeder that is receiving. BTW today 7 megs are a bit more normal here reading  -116 dBm.
  • John KB4DUJohn KB4DU Member ✭✭
    edited July 2019
    So, at 1700 UTC, Inverted V at 25ft, Tuner set to matched condition, I get:
    80M  -105
    40M   -105
    20M   -115
    15M   -120
    10M  -122

    Living right next to an Army post doesn't help.

  • Lasse MoellLasse Moell Member
    edited July 2019
    John, I live just next to air force base. See the jets taking off from my kitchen all day long :) Helicopers can be a bit annoying as they hover for hours. I had a problem with 9th overtone on 14.040 hitting one of the tower comms channels, causing thie squelch to open and close as I was transmitting this drove the ops nuts, distance to their ground tx/rx-site is 1/4-mile  This was lilkely due to passive intermod, and I never found the non-linear source. Spent several days running all over with portable spectrumanalyzers, directive antennas and such.So I often try to avoid this frequency, just to keep them happy. They know where I live....
  • K3DCWK3DCW Member ✭✭
    edited July 2019
    Here's my numbers for my 6700 tested here in Maryland in a large-lot (avg. 2 acre) suburb in rural area at 1645 local time / 2045 UTC.

    Antenna is a Marconi T with the vertical element going up about 90' and a 265' top over radials and a 500 sq ft. ground screen. All utilities underground and house apx. 130' from antenna base.

    All measurements done in CW mode, 100Hz bandwidth, no preamp and with antenna tuned using internal ATU.

    Band        Measurement           
    10m         -124dBm
    12m         -118dBm
    15m         -125dBm
    17m         -124dBm
    20m         -126dBm
    30m         -123dBm
    40m         -117dBm
    60m         -121dBm
    80m         -114dBm
    160m        -112dBm

  • Lasse MoellLasse Moell Member
    edited July 2019
    Looks pretty quiet to me, especially the low bands! I am sure your numbers would be even better on 20-10 meter if you invoked the preamp, as I bet you are limited by the radio NF. I do hear/see a big improvement by using the pre-amp, especially on 10,12 and 15 meter.
  • K3DCWK3DCW Member ✭✭
    edited July 2019
    Indeed, some of the numbers are around -140dBm with the preamp on. However, I wanted to give a good even baseline knowing that I can always improve from that if needed.

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