G8JNJ

Ooops, I should also have added this YouTube link which shows you how to use them.



Although this shows them being used with a printed circuit board, you can do the same thing with power supplies, cables, PC's etc.

Just be aware that the KiWi takes time to process the signals, so there will be a delay of 1-2 seconds between you moving the probe and seeing a change occur on the waterfall or spectrum display.

Regards,

Martin - G8JNJ

Yeh, I see the variation in signal levels, somethings not right with the antenna, the KiWi doesn't have any auto gain control.

I heard the signal, but to be honest it sounds like local interference. I think sorting out the antenna problem is the first priority, then see if you can minimise the wideband interference. I suspect that your mystery signal may be an artifact associated with some of the other interfering signals I can see / hear on your KiWi.

Unfortunately reducing unwanted interference tends to be a full time occupation in its own right, as soon as you get rid of one lot, you then hear a weaker set that was previously hidden :-(

Regards,

Martin - G8JNJ

Hmm, that look like interference too.

If you zoom out you can see lots of reguarly spaced signals that are almost certainly local interference.

I'm not saying that it isn't genuine, but I'm still not convinced.

The 15-25MHz region is generally fairly quiet and you don't hear many genuine signals unless propagation is good, especially wihen using a Mini.Whip type antenna, as they typically run out of steam on frequencies above anout 10MHz. This frequency range is also prone to Ethernet and other computer related interference, and the signals can sound modulated and come and go like genuine signals, depending upon what data is flowing at the time.

When you hear modulation on this frequency your KiWi, does it exactly match the other KiWi ?

Regards,

Martin - G8JNJ

Can you hear it on any other KiWi's that are near to you ?

If you can't, it's likely to be local interference, especially on the higher frequency bands.

Regards,

Martin -G8JNJ

@ Lonecrow

Looking back over some past notes, I think it's likely to be noise from Ethernet data. I was reminded about this when I tried my KiWi around 18MHz and found some weak signals similar to what you are observing, as I'd previously manged to reduce these to a fairly low level.

http://forum.kiwisdr.com/discussion/778/noise-at-roughly-60-khz-intervals

If you look at some of the screenshots that I'd attached to my post, they look a lot like what you are seeing and hearing.

The exact frequencies at which some of these signals are strongest will depend upon your Ethernet cable lengths and any switch / hub you are using.

Make up some simple 'sniffer' probes to use with your KiWi in order to locate local noise sources.






Copied from Keith Armstrong's excellent EMC notes.

http://www.compliance-club.com/archive/keitharmstrong/emc_testing1.html

http://www.compliance-club.com/archive/keitharmstrong/emc_testing2.html

Regards,

Martin - G8JNJ

@Hugobmf

I have just tried editing and saving a configuration on the admin pages and it worked OK for me running v1.216

When you enter a new value in to a text box, and then press 'enter', do you see the text box turn green for a short period ?

Regards,

Martin - G8JNJ

Should have said, these are the bursts centered on 4785KHz

See

http://www.hfindustry.com/meetings_presentations/presentation_materials/2017_sep_hfia/presentations/THALES_HFXL_HFIAsept2017_Presentation_final2_Bernier.pdf

Regards,

Martin - G8JNJ

Hi Dave,

I've just managed to perform four runs using different KiWi's (fortunately Emerald was available.

I used the widest I/Q filter bandwidth to straddle two sets of databursts that had no other transmissions at low level in the background.

The best (narrow red band) 'pairs' of plots from all four runs intersect St Eval and the composite best guess location is just off the West Cornish coast in the Irish sea.

Regards,

Martin - G8JNJ

Hi Dave,

See

http://forum.kiwisdr.com/discussion/comment/2631#Comment_2631

NVIS makes a real mess of TDoA on the LF bands.

You may have to try TDoA at a few different times if day, before you find stable propagation.

Regards,

Martin

Hi John,

This week I've been trying to use a number of KiWis to perform some antenna field strength measurements, but its been a somewhat frustrating process.

So I'd also like to echo Jim's request for an option to allow the the S-meter logging period to be even slower, perhaps up to 24hrs, so that I could also use it to monitor changes in my noise floor, signal levels from BC stations and other propagation related monitoring.

It's currently a real pain to have to derive this information from the graph image and the subsequent visual resolution is only about 3dB or so, it's also difficult to check for max values over a period of time or try to determine the signal average level. I know there is already a request to provide this functionality, but I also know that there are more pressing or higher priority fixes to be implemented first.

I wondered if it would be possible to add a function to store and be able to download the graphed dBm values as a CSV file. Each value to be timestamped and the header to the contain frequency and RX bandwidth.

This would permit much more detailed off-line analysis of max /min values, averages and other trends, which wouldn't need to be added to the existing graphing option. Maybe sampling intervals could be defined or automatically selected as a function of logging period so that huge files are not generated. Each time the S-meter restarts the file could be overwritten, perhaps a bit like the fax image files ?

Regards,

Martin - G8JNJ