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I am new to this forum. I do a lot of reading of other forums especially on the SDR Radios and in particular to CW operation. The one common thing I am finding is as the speed exceeds about 15WPM the built in Keyers are not able to keep up. who would have thought that an old mode such as CW requires more computer time transom of the more advanced digital means of communications.
This explains why the CW Decoders have some difficulty as the noise increase and the speed increases above about 15WPM. Again proving the human ear connected to a brain wired (years of training) for CW is still faster and better at copying CW, than a current day processor. |
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Re: High pitch whine on 20-10 meters
#sBitx
Hi David,
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Yes I have tried filtering the high pitch whine out with caps on the 5 volt supply, they have had no effect at all. I believe the noise is from the I2C buss, because with the RTC unplugged in I can still hear the same noise only very lightly, (still a vast improvement). As far as I know there is no way to filter the I2C buss without affecting it's performance. If anyone has any ideas on how this can be cleaned up, I would love to hear it, meanwhile I will run without the RTC.
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Joel
N6ALT |
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Re: A long long video on building feedback amplifiers
Thanks, Farhan. I was hoping an assembly manual might give info on shielding requirements and so on, plus more explanation of how it works. I was somewhat perplexed as to how square wave excitation could work without use of DSP, as in the nanoVNA for example. But I think I get it now as far as the superhet design with sharp filtering to reject the harmonic components.? It's very clever! On the ugly FBA - I got inspired enough to give it a shot and managed to create a functional amplifier in an hour or so. I have those somewhat stringy equations from EMRFD in my "everything" excel ham workbook to assist in designing these things. 73 Nick, WA5BDU On Tue, Sep 24, 2024 at 10:26?PM Ashhar Farhan via <farhanbox=[email protected]> wrote:
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sBitx calibration, and flattening power out
I wanted to check the actual power output on my old (serial #118) sBitx. I built a simple RF detector using a 1N4007 diode and a 10nF capacitor, with the rig running into a 50 ohm dummy load. I found a very helpful note from Hans Summer that described this measurement.
After all the caveats in his note, I decided my setup might "still be used nicely for ballpark and for relative measurements of RF power level." Making some meaurements and preliminary calculations, I decided to try to set "scale" values in hardware_settings.ini that gave me 5 watts out on every band, with the sBitx drive control set at 50. I used CW mode for my tests. 5 watts was an attractive taget because I can claim to be running QRP on all bands, and it might be a good level for driving a higher power amplifier. I made a table to collect data, and started to experiment with scale values in hardware_settings.ini. I worked out several formulas to predict new values based on measurements, but they were not really helpful. It did lead me to collecting power measurement over a range of scale values though, and then I just eyeballed the data and got to the final numbers. This table shows I can now set the drive to 50, and get just over 5 watts out on 80 through 10 meters. (see drive_50.jpg) With the same hardware_settings.ini scale values, I can turn the drive up to 90 and get the following power out. (see drive_90.jpg) With drive level = 90, power output is no longer flat across all bands. But I am satisfied that I am still under the rated power output for my sBitx on all bands. This graph shows the scale value in hardware_settings.ini, and the power output at the two different drive levels across the bands. (see sbitx power cal.jpg) -- Mike KB2ML |
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High pitch whine on 20-10 meters
#sBitx
Hi all,
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Today I decided I've listened to this high pitch whine on the 20 meter through 10 meter band long enough. Through a process of elimination I determined that the RTC module is causing the offensive noise in the background. With it unplugged everything is nice and quiet. My questions are, do I even need a RTC if I don't do digital stuff, does anyone know of a fix for this to quiet it down? BTW, I tried the exact same module out of my V2 board and it sounds the same with it plugged in, so It's not a defective module. Is anyone having this high pitched whine? Maybe some bypassing of the module is in order?
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Joel
N6ALT |
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Re: replacing V2 board with V3 ???? DOES NOT DROP IN
Bill,
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I'm not sure whats going on. I noticed you have SN 0045, mine was a V2 radio also, SN 0042 so built at the same time yours was and my new V3 board just dropped in very easy. Maybe the heat ink is slightly bigger, IDK. Maybe someone from HFSignals can give some help here. A picture might help also.
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Joel
N6ALT |
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Re: A long long video on building feedback amplifiers
That was a very informative video. I'm primed to try some ugly construction for the first time (more or less) since I build the Ugly Weekender back around 1999.
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I wonder if anyone happens to have the manual for the Antduino, assuming there was one. If so, I'd love to have a copy of it.
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73
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Nick, WA5BDU
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Re: any hints on replacing V2 board with V3 ????
On Tue, Sep 24, 2024 at 03:57 AM, Michael Saladino wrote:
I replaced my V2 with a V3 board.?? Moved the Pi4 over and used the new SD card.? Works great except for the V3 SWR not really reading.? I replaced the finals ( 4th time ) in my old V2 board with the IRF 510's and installed an old Pi 3B on it and now have a second sBitx that works great also! Michael,
could you tell the forum readers why the final stage fets had to be replaced 4 times? What antenna, what power supply did you use and in what modes did you use the device so that this could happen?
We want to learn from others' descriptions to avoid similar stories.
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Gyula HA3HZ |
VE6LX
Joel Caulkins/N6ALT
Nick Kennedy
HA3HZ