Kiwi 2 less sensitive then the Kiwi 1 with the same antenna seperately [freq cal problem]
Hello, received my Kiwi 2 and i noticed that my Kiwi 2 is less sensitive overall then the Kiwi 1. I used the same antenna for both seperately, and for example i receive messages on DSC frequentie 8414.5 on my Kiwi 1 but nothing on the Kiwi 2. see picture.
Can anyone confirm it is less sentive or is it possible my Kiwi 2 is defect, ofcourse strong signals are receiving oke. Can i do a full reset of the Kiwi 2? On the picture left Kiwi1 and right Kiwi 2
and still my Kiwi 1 is powered through the mini-usb because the original power conection is broke it is working perfect.
Comments
My KiWi 2 is the same as the KiWi 1.
I have them fed from the same splitter and the performance is identical.
http://wessex.zapto.org:8073 KiWi 1
http://wessex.zapto.org:8074 KiWi 2
You may need to check that they have the same S-meter and waterfall calibration settings. But this won't affect their actual performance.
Also check the KiWi 2 attenuator setting.
Regards,
Martin
@G8JNJ Thanks for reply , i quite new with the kiwi's (bought the defect Kiwi 1 2 months ago and Kiwi 2 i get 3 weeks ago) , perhaps stupid question how calibrate the s-meter and waterfall. The attenuator setting is 0db.
You can set the calibration in the admin / config GUI.
Ideally you should use an external calibrated signal generator, but I have found that :-
S-meter calibration (dB) -13
Waterfall calibration (dB) -10
This is a good starting point, and pretty close to actual values I have measured.
Regards,
Martin
Thanks Martin, i will look into that. I have now conected the two kiwi's on one antenna with a splitter and get the same results. I hope the caibration will do something but i think honestly that my Kiwi 2 is really less sensitive.
First calibration... 🙏
The example you gave for differing sensitivities is not very good because it relies on a single DSC decode. There's nothing else to compare to: how the waterfall looks, spectrum, S-meter, etc.
Because of random factors the decoder can fail for weak signals on one Kiwi but not on another (assuming both fed from the same antenna).
So I would really need to compare these myself. Are they both accessible from the Internet? Could this be the "26 dB" problem mentioned in the first thread on the forum?
They are not for public internet at the moment, i shall try this in the next week. Ill let you know, thanks in advance. I have read the 26 dB problem and try this also.
The 26 dB is not the problem at the moment. I testet it. Thanks
One test is to use the strongest station in the AM broadcast band. Use CW or CWN mode when tuned exactly on the carrier frequency. Check the dBm value shown in the right part of the S-meter. The values should be very close. The carrier will not have much fading.
This depends on the calibration values on the admin page, config tab
S-meter calibration (dB)being set the same, e.g. -13.@jks Done the test, 648 Khz Radio Caroline UK both kiwi’s give the same reading on the s-meter. Almost s9 but on the CWN mode the Kiwi 2 drops to s7 and the Kiwi 1 s8. Send you a mail with my ipadres.
To make a comparison such as this, the frequency, mode, receive bandwidth and RF parameters need to be set exactly the same as each other, including the waterfall and S-Meter calibration values.
Don't use the S-Mater value, the scaling is too coarse.
Use the digital dBm reading, as John suggested, which has 0.1dB resolution.
Ideally, you need a signal that is constant. If you are in Europe or the UK try 198kHz BBC radio 4, or better still 162kHz the old France international frequency, which is now just transmitting a carrier with little modulation. Both of these are subject to less variation in level than signals on higher frequencies.
Regards,
Martin
@G8JNJ Hello, i did the test , strong signal. Kiwi 2 between -85.8 and -86 dBm and the Kiwi 1 -84.41and -84.7 dBm. All settings the same. That is almost equal i think.
The answer is quite simple, and I should have thought of it sooner 🙄
Your Kiwi-2 is way off frequency. It needs a manual calibration if you're not going to use GPS frequency correction. I looked at RWM (Moscow) 9996 kHz. Kiwi-1 is about 10 Hz low. Kiwi-2 is 470 Hz high!
Follow the procedure on the admin page, bottom of the "config" tab to do the manual calibration.
470 Hz is outside the DSC spec (150 Hz I believe). So that explains why many decodes were failing. I don't know why your Kiwi-2 is so far off.
BUT then I looked at the IQ extension of the Kiwi-2. It already has a manual calibration. But with a huge value that is way off! The Kiwi-1 manual calibration is zero. So please repeat the Kiwi-2 manual calibration and make sure it is correct by looking at a time station like RWM or WWV etc. at 10 MHz or above at the highest zoom level (14).
@jks thanks, i will study this. I am not a expert with this. I connect the GPS in the coming week. Hope i can resolve this.
The manual calibration procedure is very simple. I am happy to do it for you. Just email your admin password to the support email (set a temporary admin password if you like).
@jks send you the mail. Again thanks.
@jks Sorry to inform you that after the perfect calibration of the Kiwi 2 there is no decoding and no messages are incoming. I try with the gps later and hope this works.
for test i logged in a another Kiwi 2 server in my hometown who has a stronger signal but there i saw no messages incoming on the DSC frequency. Could it be that the debian version that is higher affect the plugin because my kiwi 1 has the old debian version.
Just now I did a test on your Kiwi-1 and Kiwi-2 using the FT8 decoder on 30m (10 MHz). This is an excellent way to compare the receiving ability of two co-located Kiwis.
Look for the "FT8 decoded N" messages after every 15 second decoding period. In all cases the two decoding counts ("N") agreed or differed by only one.
Your noise situation there is not so great. The 2 and 4 MHz DSC channels are pretty much useless due to the noise level. I didn't hear any DSC at all on the other channels in a few minutes of tuning around.
You antenna might not be so great as well. LW-198 was only an S7. And MW-648 only S8. I would have expected more for your location. On the other hand you have good VLF reception. What kind of antenna is it?
Hello, i use the original youloop indoor antenna from RTL-sdr blog shop. I live in a apartment so an outdoor antenna is forbidden. I know it is not good but for the most receptions i wil do.
Maybe Martin will comment here about the YouLoop. As I recall he was not very impressed by it, at least when used with the Kiwi.
I have severe reservations about the YouLoop, and personally I think it is a triumph of marketing over actual performance, but your mileage may vary.
It was designed for use with the Airspy products, which have a very low noise floor and are incredibly sensitive. It also ideally requires a receiver with a higher than 50 ohm input impedance, and some of the Airspy range have been designed in this way.
It's OK when used directly in conjunction with that range of receivers, but as soon as you connect it up via a reasonable length of coax you will hit problems.
The Chinese MLA-30 is marginally better, but once again in my opinion, not by much.
Personally, I'd say that if you want a wideband loop for use with the KiWi, then look at LZ1AQ or Cross Country Wireless designs.
But before any of that, join the Loopantennas IO group https://groups.io/g/loopantennas read through the previous posts, and save yourself a lot of money, especially if you can construct basic electronic circuits.
PCB's, either blank or populated and working, are often available too.
Regards,
Martin
Hello, I have the MLA-30 but sadley the reception with it was very bad. Even on the LW and MW is was terible. I have also a indoor Loop from Wellbrook but htis is picking up the noise badly. So only the Youloop was good for me. Thanks for your remarks and i will look into this. For now suddenly the meassages from the DSC on freq 8414.5 coming through and decoding on the Kiwi 2. for now i am happy. Thanks everyone.
Some antennas seem to pick up less noise simply because they have lower gain and are less sensitve.
As a test, I suspect that the Wellbrook will produce similar results if you use the attenuator cintrol on the KiWi 2 to reduce the signal levels to match those produced by the YouLoop.
In an indoor environment with lots of noise, all three loops you have mentioned should perform approximately the same, as long as they are sensitive enough to be performance limited by the electrical noise that is present.
Regards,
Martin