n6gn
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WD does not allow moving the reference plane as far as the antenna. Alone, the kiwi with a -16 calibration factor is pretty accurate, within a dB at 14 MHz. It reads high above that and low below. With WD's correction that frequency un-flatness is…
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https://github.com/jks-prv/kiwiclient/tree/master/tools but Rob and all need to explain broadly where things are found. I'm not at all sure the latest versions are here. Rob?
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Ulli, A great many things to be said about what you wrote, perhaps too much and annoying to this forum. Let me just say a couple of things. For constant ERP from a distant source, available power follows a perfectly-matched antenna's aperture. At…
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Measuring it when you can is great but even with a crude (optimistic model) you can see the general problem. It's not possible to match to the radiation resistance of a monopole far from resonance, this means that there is effectively (room temperat…
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As a first approximation, presume that the ground losses are zero. This isn't quite correct but other issues are bigger, mainly mismatch loss at most frequencies for a 6m vertical radiator. Its 'radiation resistance' only rotates to a good match (~…
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Ulli, You don't necessarily need to wait until spring. The characteristics of a short dipole are known and so are those of a short monopole. If you can characterize your preamp, its input impedance as well as its voltage gain then you can obtain a…
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My thought for absolute calibration is roughly this: The noise measurement at the KiwiSDR SMA connector is generally quite close to correct when "-16" is entered into the calibration value on the admin page. This seems to be true for both…
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There may be one more, /tmp/wsprdaemon.conf, that is created by the program. I think it has to do with schedule updates and probably should be left alone.
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Ulli, If you are referring to residual coherent ingress on KPH's noise floor, here's a current spectrograph (Image) yes, there is still some very low level ingress but do recognize that this is a calibrated system and those levels are quite low. I…
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ITU P.372-8 Figure 2 shows "quiet receiving site" as having ~50 dB excess noise due to "man made" sources near 160m. I'll let Rob describe the current distribution, it may be that 160m, unlike higher bands, is not calibrated to …
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There seems to be a correlation between bursty noise, e.g. relatively close lightning strikes, and spread. It's probably not simple though...
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I just looked at an in-circuit SP4203. Driven from 1-30 MHz from a 50 ohm source and terminated with 50 ohms it nicely catches peaks greater than 7V. Actually it catches at 7V and then drops back to ~6 V peak at the top/bottom of a sine wave. Adm…
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Do the 'normal' TVS parts not work, e.g. SP4203 ?
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Pin 28 of the LTC2248 is behaving just as I'd expect. At -15 dBm it is low while at -14.9 dBm there are infrequent 15 ns wide pulses. By -13 dBm or higher power they are very common. I can believe that integrated they follow the percentage of the ti…
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Thanks for the clarification. I'm still having difficulty seeing any effect from changes to the number of 0's. Also what I observe doesn't look to me like inductor saturation. Things are well behaved in the waterfall until the instant of onset -…
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If you have enough low noise preamp gain to have raised the noise floor by 10 dB the Kiwi noise will then be degrading the result by less than a half dB, IF IMD or other factors haven't made things worse. But it does depend upon signal and noise l…
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On v 1.320 with a pulse modulated 14MHz input at -10 dBm the OV indicator flickers the same whether I enter "0xffff" or "0x0001" in the first field of the devl extension. The flicker on/off ratio is much less than the 50% duty cy…
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Is there a way to determine the results of the new/masked OV determination remotely from kiwirecorder.py?
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As mentioned elsewhere, it would be useful to have rx# utilization along with that tuning available from kiwirecorder. The WSPRdaemon still occasionally hogs a '"full feature" rx when a lesser one is free.
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"Fun fact: The GPS's coax was radiating common mode noise originating from the kiwi." and thereby also providing a lower impedance path for CM currents from other sources, both within (LAN) and outside the Kiwi on other lines, LAN, PS, ant…
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HB9TMC writes: "I get -10 to -5 dBm "bare foot" on my L-antenna. Only during gray line or sporadic-e though. Culprits are Woofferton (300 kW) and Issoudun (500 kW), both at good skip distances. The noise floor from 8.5 MHz to 28 MHz …
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It does depend on what noise floor you are striving to achieve. This morning, 0500 local time, http://kphsdr.com:8076/ located at a very quiet site with a well calibrated system from the known antenna efficiency and 'ground noise' through an LNA a…
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The ground path through the wire connector is worse than the SMA in terms of common mode paths that can increase the noise floor. This is true whether or not leads are short since the coupling mechanism isn't due to slightly increased series inducta…
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Watch out if you use the wire-antenna connection on the kiwi - it is not nearly so good as the SMA and you will very possibly have increased spurious coupled in, at least that's what I've concluded from experience and measurement.
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If your noise floor is reasonably high at LF, you should be able to see the tuning of the notch as a local minimum, a "noise-stimulus scalar network analyzer". Look at the percentage error and adjust the capacitance by the square of that n…
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Isn't it already there? (Image) and the precise frequency can be manually adjusted after the band selection has been made in the extension.
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Thanks for the biconical reference, I really haven't looked at any yet. The issue isn't (just) the feedpoint impedance, essentially I think it is the Q of the structure. To get a reasonably good match over a broad band the issue is not only the rea…
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Martin, FWIW, I played a little with your suggestion of matching to a 'slimmer' antenna at a higher impedance. Broadband matching is a never-ending story. I spent some time trying relatively simple approaches to match the S Parameters that NEC2 sa…
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Martin writes "You should be able to make the whole structure active and a lot slimmer. The problem with a lot of E-Probe antennas is that they tend to use a very small plate antenna, which only has a capacitance of a few pF. If you use a fat …
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As I usually think about it, the problem is about noise/QRM floor. For a more-or-less omnidirectional antenna, an antenna's aperture is roughly the same, a short dipole or monopole over perfect ground 'catches' the same power irrespective of its el…