Re: Sbitx finals replacement
Art, I had this problem with fake LM338s. Most of them are simply relabelled LM317 that give up on current peaks. We, unfortunately, wiped the LM338s cleab from Mouser for our own production. The switching regulators that I mentioned in a earlier email work best. - f
On Sun, Aug 14, 2022, 2:15 AM Art N2AJO < olson339@...> wrote: back again. Replaced the LM338 and the 2-IRFZ24N finals. checked to ensure the final and the LM338 tabs to ensure no ground connectivity and in contact with the heat sink. Measured the DC voltage of the LM388 tab 5,4 volts. Final tabs 13.8 volts. Put it all back together and receive works fine. Tried FT8 and within a second or 2 the rig shuts down and reboots. I also updated the firmware. So any suggestions on what next to check.?
I did order the voltage regulator Farhan suggested awaiting their arrival.
Art
N2AJO
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looking to buy ubitx motherboard v3,4,5
Hi,
Looking to purchase a v3, V4 or v5 motherboard (prefer 3 or 5 because of v4 audio design). Best if it has not been messed with "too much".
Please reach out to be via private email (also I am good on QRZ). if you have one. I am doing some work on KD8CEC's screens and software, so it will be put to good use.
73
Mark
AJ6CU
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Hi Jerry,
Boy, do I fell stupid.? In your earlier message, it was the first thing you said.
Sorry about that.
Thanks again, Scott
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Re: sBitx Display--bigger monitor via HDM1
Here¡¯s the screen 
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Re: sBitx Display--bigger monitor via HDM1
Thanks! The GUI currently occupies precisely 1/4 of the screen.
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Re: Daylight radio - PTO notes
They are trifilar wound, 10 turns on FT37-43 cores. Use any gauge. I used 28. - f
On Sun, Aug 14, 2022, 4:33 AM David R. Hassall WA5DJJ < dhassall@...> wrote: Dear Ashhar,
Can you give me the core and winding details for the two RF transformers? T? .... I couldn't find it listed anywhere.
Thanks,
Take care and have fun.
73 Dave WA5DJJ
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Low pass.? You can use larger values if you wish. I was just following the advice from a design paper by TI.
Hi Jerry,
Thank you very much for the starting point.? I think I've got some 2.2uf caps.? I know I have some 22 and 14AWG (overkill) wire.? I'll see what I can wind.
Oh, almost forgot: high pass or low pass filter?
Thanks, Scott
--
Jerry, AC9NM ÊÖÖеÄÄñÔÚ¹àľ´ÔÖÐÖµÁ½¸ö
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Re: sBitx Display--bigger monitor via HDM1
It is a simple scale up. First, determine the stretching factor in x and y directions as x_scale and y_scale. In sbitx_gtk.c, the user interface is an array of controls held in the pointer active_layout.? You have to loop through all the controkss, multiplying x, y, width and height elements by x_scale and y_scale. I will do this today if I can find the time. - f
On Sun, Aug 14, 2022, 5:18 AM John Terrell, N6LN < N6LN@...> wrote: Ashhar Farhan wrote
"However, the screen layout is not dynamic and rather than cutting out anything, most of the gui is stuffed in the upper left quardant.?
It is an easy fix to rewrite a layout() routine that will measure and stretch out the controls to be bigger."
I am using a bigger monitor as well and I'm fairly familiar with Unix, Linux and the Raspberry Pi but I need a few hints about how to do this.
Hints?
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Re: sBitx Display--bigger monitor via HDM1
Ashhar Farhan wrote "However, the screen layout is not dynamic and rather than cutting out anything, most of the gui is stuffed in the upper left quardant.?
It is an easy fix to rewrite a layout() routine that will measure and stretch out the controls to be bigger."
I am using a bigger monitor as well and I'm fairly familiar with Unix, Linux and the Raspberry Pi but I need a few hints about how to do this.
Hints?
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Re: sBitx antenna-first warning
On Thu, Aug 11, 2022 at 07:11 AM, Jerry Gaffke wrote:
The uBitx has a forward transformer at the output which develops 24 volts (roughly) across the push-pull FET's
regardless of how it is loaded.? The IRF510's have a Vds max of 100 volts.
Should be fine with or without an antenna.
Interesting explanation of why the uBitx should survive without an antenna load. As far as current limiting, could there be any advantage to placing low value resistor(s) in the drain connections of the finals and measuring the peak voltage to determined the peak current flowing through the finals? Should just require a?Schottky diode(s) and a small filter cap to get the peak current. The reason for measuring the current at the drains is a mismatched load that is capacitive could cause the final mosfets, as ether one is turning on, draw more peak current than what may be measured on the main power supply.? Using poly fuses is a very interesting idea, also.? Tom, wb6b
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Hi Jerry,
Thank you very much for the starting point.? I think I've got some 2.2uf caps.? I know I have some 22 and 14AWG (overkill) wire.? I'll see what I can wind.
Oh, almost forgot: high pass or low pass filter?
Thanks, Scott
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and a bigger coil and cap should not hurt ;-)
so you could use a 100uF cap and a 10uH coil or more ... not?!?
dg9bfc sigi
Am 14.08.2022 um 01:17 schrieb JerryP:
toggle quoted message
Show quoted text
Digikey has a low pass filter calculator you can use to
determine the values for a LC filter. If you use a MP2307
based buck converter which runs at 350kHz, you'll want to put
the filter on the input side of the buck converter. A 2.2uF
capacitor with a 1uH inductor will have a -3dB point of
100kHz. You should test the LC filter to make sure it doesn't
make the buck converter unstable. Also, the wire used for the
inductor should be able to handle the current, in this case
3A, 24AWG wire will do.
--
Jerry, AC9NM
ÊÖÖеÄÄñÔÚ¹àľ´ÔÖÐÖµÁ½¸ö
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Re: #sbitx blowing up of the finals and the LM338
#sBitx
Hi Scott.
Yes, they screw in above the transistor and press down on the body of the transistor.
The picture is of the ones from Jaycar here in Australia but they should be available from the likes of Digikey, Mouser etc in the US.
Search for TO-220 single mounting clip (I mistakenly put TO200 in my original post, should be TO-220).
--
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Digikey has a low pass filter calculator you can use to determine the values for a LC filter. If you use a MP2307 based buck converter which runs at 350kHz, you'll want to put the filter on the input side of the buck converter. A 2.2uF capacitor with a 1uH inductor will have a -3dB point of 100kHz. You should test the LC filter to make sure it doesn't make the buck converter unstable. Also, the wire used for the inductor should be able to handle the current, in this case 3A, 24AWG wire will do.
--
Jerry, AC9NM ÊÖÖеÄÄñÔÚ¹àľ´ÔÖÐÖµÁ½¸ö
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Re: Daylight radio - PTO notes
Dear Ashhar,
Can you give me the core and winding details for the two RF transformers? T? .... I couldn't find it listed anywhere.
Thanks,
Take care and have fun.
73 Dave WA5DJJ
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Re: Daylight radio - PTO notes
Dear Musa,
That looks like a workable solution. Should do the trick if you don't have a way to print them.?
Well Done!
73 Dave WA5DJJ
SUPER QRSS GRABBER https://www.qsl.net/wa5djj/
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Re: Daylight radio - PTO notes
Dear Ashhar,
I have a NANOVNA and I know how to use it to build the filters.?? I have the crystals on order and they should be here soon.? Right now I am kitting up 10 PTO's for my builder's group at the local clubhouse. I think we are going to do this modular.? That way I will have time to build one or two ahead and also kit up a parts kit for the group.? They build each module and then we test them and add them to the project board.? That way it is manageable for me and them. The PTO 3D fixture is very well done and makes the reproduction of that module easy to get the desired results.? It tunes very smoothly and is a great design.?? It was easy and quick to print.?
Looking forward to see how my group handles the PTO module.
Take care and have fun.
73 Dave WA5DJJ
SUPER QRSS GRABBER https://www.qsl.net/wa5djj/
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Hi Niels,
Thanks for sharing your filter experiments.? I know it will be somewhat "individualized" for each buck converter but a starting point would be nice on the design and component selection.
It looks like you used a small toroid a simple choke (about 13 turns) and a electrolytic (47uf 50vdc?) to make a "L" type filter.? I'm not sure if it's configured as a high pass or low pass.
Can you pass along some details?
Thanks, Scott
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Re: #sbitx blowing up of the finals and the LM338
#sBitx
Dean
I just went through the same as you with Amazon by buy lm338s. Wen to Mouser and they are on backorder
Art
N2AJO
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Re: Sbitx finals replacement
back again. Replaced the LM338 and the 2-IRFZ24N finals. checked to ensure the final and the LM338 tabs to ensure no ground connectivity and in contact with the heat sink. Measured the DC voltage of the LM388 tab 5,4 volts. Final tabs 13.8 volts. Put it all back together and receive works fine. Tried FT8 and within a second or 2 the rig shuts down and reboots. I also updated the firmware. So any suggestions on what next to check.?
I did order the voltage regulator Farhan suggested awaiting their arrival.
Art
N2AJO
|
John Terrell, N6LN
JerryP