Is there a source of data for natural and man made noise, as pick up by an isotopic antenna (or dipole which will be about 2dB higher) in dBm value, either
a) based on 'fixed paper model" as page 5 of ITU-R document, R-REC-P.372-13-201609 b) actual measurement or 'daily' prediction of 'atmospheric conditions' Does the natural noise level vary with air temperature, season, geographic location, sun spot, etc.? I was under the impression that the HF (unlike VUHF) noise floor will be some what higher and the HF receiver sensitivity cannot be use to its lowest level, specification is 0.3uV, -117dBm for the RSP1A. I used decimation 8, so may be noise floor is a little bit lower. Presumably, it will be 10 dB SINAD and -127dBm noise floor The SOTA test show noise floor at -130dBm and the HF receiver can work at its lowest level as in the case of VUHF. The SDRPlay RSP1A is calibrated to show real dBm value. 73 Simon On 12/29/18, Simon <[email protected]> wrote: > Is FT8 and psk31 generally use around 20 to 30 watts maximum, as a "social > rule", so that one station would not be too strong as to mask out other > station, due to agc of rig? > > On Saturday, December 29, 2018, Jim Brown <[email protected]> > wrote: > >> On 12/28/2018 4:54 PM, Simon wrote: >> >>> Hi K9YC, >>> >>> Many thanks for the detailed analysis. >>> >>> 1. Sorry, I do not understand why u said, quoted, "Gauging by the FT8 >>> signals centered around 7075 kHz, I'd call this QTH pretty noisy". This >>> is >>> the FT8 band at 7074kHz, usb and wsjt-x decoded good copy of traffic. >>> Those are wanted ft8 signals. >>> >> >> I'm using their strength as a guide to the strength the noise sources I >> identified. >> >>> >>> Ft8 Traffic was busy, 4 decodes per 15 seconds cycle. Strongest signal >>> is >>> 4 dB snr. Most are better than -4dB snr, rare one was weakest at -19 >>> dB. >>> From call sign, many are from Indonisia, Australia and new zealand, >>> 4000km >>> from Hong Kong sota qth. So, it was good received signal from 4000 to >>> 6000km away. It was healthy signals. >>> >> >> That's not a lot of decodes -- I regularly decode several dozen signals >> on >> each pass on the HF bands. >> >>> >>> 2. The sota site has no AC utility electricity and no street lamps, it >>> is >>> a laws protected country park area where they preserve nature. >>> >>> 100 meters away is a public toilet with solar panel and pir triggered >>> led >>> lighting, which should be off as there is likely no one in toilet. Solar >>> panel was zero output as it was dark, 30 minutes after sunset. No >>> charging >>> pwm noise. >>> >>> 500 meters away, and blocked by hill profile, as 100 meter lower, is a >>> ranger office. Should be all person off duty at that time. Sure, there >>> may >>> be some smps still running. >>> >>> Up 150 meters, are two airport long range survilance radars, one >>> primary, >>> one secondary radar, with Powerful smps inside. Radar range about 700km >>> for >>> the hong kong fir, flight information region, from hong kong to taiwan >>> to >>> philpines. >>> >>> There is a residential estate, 500 homes, 30 floors buildings, 2 km >>> away, >>> with all kind of smps inside, computer, fluroresent lighting, led >>> lighting, >>> vfd motor drive for lift, etc. >>> >> >> It's hard to get away from noise. In essence, all of these noise sources >> are added together to form the noise floor. To find a dead quiet band, >> you >> almost need to be tens of miles from sources. One of the few times I've >> encountered that was a county expedition for the California QSO Party >> three >> years ago in a very remote part of Trinity National Forest. No homes, no >> radio sites, nothing as far as the eye can see from our site looking out >> from about 1,000 ft above the ground sloping away from us. >> >> 73, Jim K9YC >> >> >> _______________________________________________ >> wsjt-devel mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/wsjt-devel >> >
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