Messages

136

North American Shortwave Pirate / Re: WDOG 6925 USB 0125 30 April 2023

« on: April 30, 2023, 0243 UTC »

0239 - Suddenly off during "Get a Grip On Yourself".

I think that this was a replay of this from Thursday evening: https://www.hfunderground.com/board/index.php/topic,113220.0.html

From MDK2's notes that evening. Note the exact same song order.

0152 "In the City" The Jam
0154 OM with English accent saying "I'm not trying to impress anyone but myself" into "Trash" New York Dolls
0156 "Chinese Rocks" Johnny Thunders & The Heartbreakers
0159 "Fall Out" The Police
0202 "(Get a) Grip (On Yourself)" The Stranglers

137

The RF Workbench / Re: Class D audio amps - protection circuits

« on: April 28, 2023, 0318 UTC »

Yes, familiar with it. In fact, I mentioned it over here: https://www.hfunderground.com/board/index.php/topic,89881.msg348346.html#msg348346

How do you know that it is "DC Detect Fault" and not simply the overcurrent protection turning on? Overcurrent is simply drawing too much current from the output(s). This could be that you have an inappropriate load (likely too low impedance) or you are just asking for too much output based upon the load that is attached. In the latter case, you just have to turn the gain down or reduce the input.

If we are talking about the same thing, I generally I observe it as momentary drop in audio; basically just asking for too much from the amp. This is most likely to happen when there is heavy bass content to the program material. Not many alternatives for immediate relief other than reduce the bass content, turn down the gain or reduce the input. Also, it is important to note that these transmitters do not look like a pure resistor to the Class-D amp output; they will look like a complex impedance, especially below some arbitrary audio frequency. The Class-D amp may be "happy" with the load that the transmitter looks like at 1 KHz but very "unhappy" with the (probably) different impedance at 50 Hertz, for example.

The reason why bass tones are more likely to cause a problem, is for one thing, bass tones are low frequency, which means longer period and thus the Class-D output is on for a comparatively longer period of time. The overcurrent protection is only going to be triggered when the output is on, so, if there is an impedance problem that would trigger an overcurrent fault, it's more likely to occur on bass than treble just by sheer probability.

Beyond that, I have noticed some interesting turn on characteristics. If I have an audio input present at turn on that is too strong, it can create some sort of fault condition that is difficult to clear without turning off the amp, lowering the input and trying again.

138

SDR - Software Defined Radio / Re: KiwiSDR future/replacement?

« on: April 20, 2023, 2322 UTC »

John, the developer of the Kiwi, posted on the Kiwi forum some time back that he was also ready to sunset the project as he was pursuing other projects.

Which is curious because he keeps cranking out software revisions. Of course, hardware revisions have a longer timeline than software revisions.

The software the Kiwi user interface is based on, OpenWebRX https://www.openwebrx.de/ can be configured to work with a host of SDRs. It's not as feature packed.

You can say that again. For one thing, frequency resolution is lacking, IMO.

139

The RF Workbench / Re: Using LM7805 regulators for AF / RF amps?

« on: April 20, 2023, 2316 UTC »

You're modulating the DC (at an audio frequency) not RF.

You're confused and simultaneously confusing, as usual. Let's clarify.

Forgetting about which circuit we're talking about for a second, if you modulate the DC that is fed to a final amplifier, then you will amplitude modulate the signal. That's pretty fundamental. You can do this with a Class-A modulator, such as shown here or you can do it other ways, like a Class-D modulator and LPF. Either way, you're making the DC fed to the final amplifier wiggle up and down and that produces amplitude modulation on the RF at the "wiggle frequency".

In the case of the circuit from the OP, it only produces RF (without AF modulation, unless the RF already has modulation on it) riding on the DC. In the case of the second circuit, the one that I posted, it probably won't work very well at RF because it needs an inductor that the first circuit has.

140

The RF Workbench / Re: Using LM7805 regulators for AF / RF amps?

« on: April 20, 2023, 1805 UTC »

Yes. In that circuit, its upper frequency limit is likely defined first by the internal parasitics of the silicon die, the package and the physical PCB layout than so much the internal circuit design.

Also, you folks seeking a simple AM modulator for your <15 Watt transmitter can do as shown in the applications section of the L78xx data sheet:
https://www.alldatasheet.com/datasheet-pdf/pdf/22615/STMICROELECTRONICS/L7805.html

Page 22, figure 34, “Power AM Modulator”.

The concepts of the two are similar. The regulator does exactly what it is supposed to do: regulate a voltage. In the case of these circuits, ground voltage is being brought up and down by the AC or RF input. Therefore, the user is impressing that AC or RF voltage on the output of the regulator, which is forced to follow.

141

North American Shortwave Pirate / Re: Sycko Radio 6950 USB 0110 UTC 20 APR 2023

« on: April 20, 2023, 0145 UTC »

Look at the lightning map and weep. https://www.blitzortung.org/en/live_lightning_maps.php?map=30

Listening on an SDR in VT and it's noisy but we're doing it.

0233 - Waving a hand at you too. Pretty reasonable signal for only 40 Watts.
0309 - I switched to an SDR in Michigan. OMG, what an improvement. S9+20 on peaks, mostly well above the noise which is S9+10.
0354 - signal is fading out and the static is dominating. I need to go anyway. Good night.

142

North American Shortwave Pirate / Re: KAT re-broadcast via NAPRS 6935 AM 0040 UTC 19 APR 2023

« on: April 20, 2023, 0144 UTC »

I heard myself as Garfield Morris from an old KAT cassette that I sent out to people who reported my broadcast from my friend Pam's house on the rock river in Edgerton WI (25 miles SE of Madison) back in the 1990's,

I am unfamiliar with this concept of outing yourself 30 years after the fact.

143

North American Shortwave Pirate / Re: UNID 6935 AM 0130 UTC 18 APR 2023

« on: April 18, 2023, 0136 UTC »

This should be its own topic since it was a separate broadcast.

Off suddenly at 0133.

Was it really 6936? I had it on 6934.96 or so.

144

Software / Re: Black Cat ALE Vacuum Cleaner 0.3.0

« on: April 17, 2023, 2126 UTC »

You hear that "giant sucking sound?"

https://youtu.be/VRr60nmDyu4?t=89

145

The RF Workbench / Re: Common mode supression

« on: April 17, 2023, 2035 UTC »

My english still very bad, but i should tell here about my experiments.

Your English is good enough to write this, which is reasonably high. I can see that you paid attention in English class. 

Common mode noise i measure between PC case and grounding in 9 floor building via 10:1 voltage divider - almost 13 volts.
http://hoshinokoe.ru/files/0ARTICLES/common_mode/interf_pc_case.jpg

OK, understood, however, I don't think that this is completely unusual and don't take this as positive proof that you have "a lot of noise". Your photos of the SDR screen do indicate that there is quite a bit of 1-30 MHz noise but I would not say that the oscilloscope image is indicative of the SDR waterfall images. That is, one does not necessarily lead to the other.

A few things to note:
1) Oscilloscope probes that are not grounded will often pick up (receive) noise like this.
2) I believe that you have connected the oscilloscope probe to a AC to DC power inverter output (but without a ground connection?). Understand that this output should be a high impedance node for anything above ~10 KHz (because the parasitic L increases the output impedance at higher frequencies), making the DC cable a very nice antenna, so the oscilloscope (which also has a high impedance input) will pick up quite a bit of noise from everything in the general area.
3) I think that the oscilloscope may not be connected to the same AC mains outlet (220V outlet) as some of the other items on your desk. This can create a ground loop that can create enough noise to show up on an oscilloscope by virtue of the different ground voltages at frequencies greater than DC.
4)  The oscilloscope probe is ~30 cm from the computer screen and there are likely many power inverters within ~1 meter of the probe.

So, again, it looks ugly but I wouldn't make a lot of decisions about what to do about it based upon this measurement that you show.

I still not measure this long balun, but it seems t be its better then only miniature transformer.
Today i made a Austin tranformer for HF to measure its reactance for common mode.
http://hoshinokoe.ru/files/0ARTICLES/balun_for_SWL/Austin_trans_isolation.jpg
...
Now i use "long" balun with my personal sdrs and parallel with web-sdr on my personal webpage.

You may want to consider using two antennas (e.g., the 8m wire and the 30 m wire) and a variable phasing network to be able to rotate (change) the phase of the two wires relative to each other to attempt to partially cancel some of the noise by making it out of phase.

146

European Pirates and Private Stations / Re: Deltracks International 6285 AM 0727 UTC 16 APR 2023

« on: April 16, 2023, 0816 UTC »

Deltracks, rarely adding 'International'

Indeed. They have not used that since then.

147

European Pirates and Private Stations / BeneLux Radio 6260 AM 0755 UTC 16 APR 2023

« on: April 16, 2023, 0757 UTC »

A bit overmodulated when I tuned at 0755 and I could hear the Op turn down the audio gain at 0757. Still a bit distorted. Otherwise, a very good signal in France: SINPO 44454.

I'm hearing maybe a sung ID at 0757 but can't understand it.

0758 - The Monkees, "The Last Train to Clarksville"
0802 - Possible sung ID in Dutch?
0805 - "Hier is BeneLux Radio" in the middle of spoken announcements, some in German and some in Dutch.
0806 - "Hotel California".

148

European Pirates and Private Stations / UNID 6295 AM 0732 UTC 16 APR 2023

« on: April 16, 2023, 0732 UTC »

C&W at tune in. SINPO 34343 on an SDR in France. A little bit of splatter from Deltracks on 6285 KHz.

149

European Pirates and Private Stations / Deltracks International 6285 AM 0727 UTC 16 APR 2023

« on: April 16, 2023, 0730 UTC »

SINPO 44444 on an SDR in France.

0727 - "Bittersweet Symphony'
0731 - ID in Dutch and English
0744 - Deep Purple, "Child In Time"

150

SDR - Software Defined Radio / Re: Adjusting bandwidth on Kiwi SDR ?

« on: April 16, 2023, 0726 UTC »

You may want to become acquainted with the entire list of shortcuts. Type 'h' or '?' anywhere on the screen to see the list of keyboard shortcuts. (The passband shortcut mentioned is on that list.)

You can also enter passband choices into the frequency selection screen, which might be easier in your situation: http://www.kiwisdr.com/quickstart/#id-freq-entry

To make things easier with the touchscreen, you may want to try mobile mode: http://www.kiwisdr.com/quickstart/#id-user-mobile
You can force mobile mode when you connect to a kiwi by adding " /?m " or " /?mobile " at the end of the URL. Example: http://echofox.fr:8073/?mobile (This is from the list of all the parameters that you can specify in the URL, including passband: http://www.kiwisdr.com/quickstart/#id-user-tune )