Re: sBitx antenna-first warning
I am building a stockon add on for the sbitx. I will add a raspberry pico as the measuring device that you can plug into the usb port. - f
Another way NFETs can be destroyed is exceeding Vgs limits (voltage from gate to source).
This could be due to a long source lead to ground, or a poor ground plane.
This could be due to capacitance from the drain to the gate yanking the gate around
when the drain zips up and down some 24 volts, if the gate is not being driven by a source of low enough impedance.
An NFET designed for RF makes things easier because:
1)? The source lead is often connected to the heat sink tab, which is handy because we usually want to ground the source.
?On the IRF510, it is the drain that is connected to the heat sink tab.
2) An RF NFET is designed to have lower internal capacitances, making the gate easier to drive.
3) AN RF NFET comes with app notes describing a recommended design for an RF amp.
The IRF510 was meant for blinking automotive turn signals, does not have an app note for operation at 30 mHz.
Even when following app notes describing a well thought out design,
building an RF amp that works well can be tricky.
Jerry, KE7ER
On Thu, Aug 11, 2022 at 07:11 AM, Jerry Gaffke wrote:
I'd be more worried about shorts at the antenna, as it is excessive current (and subsequent heating) that will destroy the IRF510's.
|
Re: sBitx antenna-first warning
Another way NFETs can be destroyed is exceeding Vgs limits (voltage from gate to source).
This could be due to a long source lead to ground, or a poor ground plane.
This could be due to capacitance from the drain to the gate yanking the gate around
when the drain zips up and down some 24 volts, if the gate is not being driven by a source of low enough impedance.
An NFET designed for RF makes things easier because:
1)? The source lead is often connected to the heat sink tab, which is handy because we usually want to ground the source.
?On the IRF510, it is the drain that is connected to the heat sink tab.
2) An RF NFET is designed to have lower internal capacitances, making the gate easier to drive.
3) AN RF NFET comes with app notes describing a recommended design for an RF amp.
The IRF510 was meant for blinking automotive turn signals, does not have an app note for operation at 30 mHz.
Even when following app notes describing a well thought out design,
building an RF amp that works well can be tricky.
Jerry, KE7ER
toggle quoted message
Show quoted text
On Thu, Aug 11, 2022 at 07:11 AM, Jerry Gaffke wrote:
I'd be more worried about shorts at the antenna, as it is excessive current (and subsequent heating) that will destroy the IRF510's.
|
Re: Do you hate to wind toroids?
I use one of these to hold the toroid ? As long as you're careful they don't scratch the enamel.? They are nice and thin so you don't hog wire space.  --
|
Re: Ubitx Ver 6 need PTT circuit for Linear AMP
?Now to determine which of the six pins is #1. Schematic uses different numbering sequence than the data sheet for the relay. K3, KC1,KB1 and KA1 all show the numbering on the Schematic that the product data sheet shows.? According to the diagram below, Pins 1 & 16 are the Coil.? Again, this does not match K1 on the Schematic as it shows the coil as pins 8&9. The schematic of K1 is the same in board versions 4,5 and 6.? --  KG5UMH Michael - DM93am
|
Re: Do you hate to wind toroids?
Currently it's $30 for just two of the winders, or $40 for the kit with two winders plus the toroids and a tuna can to?hold it all. At current pricing from kitsandparts, the toroids would cost $11.40 if you use the quantity 25 prices and divide down to quantity 10.
For the $30 you also get a selection of 50 toroids, so not a bad price.
In a pinch, could probably use a pair of springy forceps in a vice on small toroids,
Or cut something vaguely like what he has out of plastic or wood.
The really tough toroids are the ones that are completely full of wire
where this tool might not be such a good idea.? Solution then is to use a larger toroid
of the same core material, adjusting the number of turns to give the same inductance.
Jerry, KE7ER
|
Re: Do you hate to wind toroids?
For many, the hard part isn't winding the toroid, it's keeping track of the counts. I rarely get phone calls, but when I do, it's while I'm winding a toroid. I just keep my camera handy and when I think I have it done, I take a picture, put it in Paint, increase its size, and then count the turns.
Jack, W8TEE
On Thursday, August 11, 2022 at 09:47:43 AM EDT, Jerry Gaffke via groups.io <jgaffke@...> wrote:
For the $30 you also get a selection of 50 toroids, so not a bad price.
In a pinch, could probably use a pair of springy forceps in a vice on small toroids,
Or cut something vaguely like what he has out of plastic or wood.
The really tough toroids are the ones that are completely full of wire
where this tool might not be such a good idea.? Solution then is to use a larger toroid
of the same core material, adjusting the number of turns to give the same inductance.
Jerry, KE7ER
-- Jack, W8TEE
|
Re: Ubitx Ver 6 need PTT circuit for Linear AMP
Dan,
A little off topic, but
If you might have an idea on how to do that, private message me. I looked at the amplifier that you mentioned in your post. I looks a lot like the Palomar TX-100 (uses same transistors) that I had acquired. I was going to use it with an LPF but could not figure out how to do that.
--
KG5UMH
Michael - DM93am
|
Re: sBitx antenna-first warning
I could be proven wrong, but I doubt a zener is needed on the uBitx.? 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. The Bitx40 with the flyback transformer at the output is a different story, but the Miller effect is there to catch you. You do often see zener's on single NFET finals like the Birtx40 and the ones Demaw often used. /g/BITX20/message/84987I'd be more worried about shorts at the antenna, as it is excessive current (and subsequent heating) that will destroy the IRF510's. Some way of limiting current (perhaps just a fuse or polyswitch, or a wimpy power supply) might be sufficient, as it will take a second for the heat to build up enough to destroy the IRF510.? I think. Don was burning up his IRF510's when operating with 24 volts into the final.? Keep things at 12 volts and add a polyswitch if you want something reasonably bulletproof. Some RF NFETs claim to tolerate any SWR. They assume you use their circuit design recommendations and don't exceed the recommended supply voltage. Any NFET can be bulletproof if used conservatively. Any NFET can be blown away if you push things. Jerry KE7ER
On Thu, Aug 11, 2022 at 06:19 AM, Anthony Good wrote:
On an aside, could a strategically placed zener diode or two on the finals prevent damage? ?Doug Demaw recommended this on NPN finals in his books.
?
|
Re: Do you hate to wind toroids?
For the $30 you also get a selection of 50 toroids, so not a bad price.
In a pinch, could probably use a pair of springy forceps in a vice on small toroids,
Or cut something vaguely like what he has out of plastic or wood.
The really tough toroids are the ones that are completely full of wire
where this tool might not be such a good idea.? Solution then is to use a larger toroid
of the same core material, adjusting the number of turns to give the same inductance.
Jerry, KE7ER
|
Re: sBitx antenna-first warning
LOL :-D
Last night I was messing around and had the 40m dipole connected to another rig and had the sBitx unterminated. ?I bumped the CW key and put out 10 watts momentarily and nearly screamed. ?I quickly hooked up a wattmeter and a dummy load and was relieved to see RF power still coming out.
I’m going to implement an SWR sensor and RF power foldback mod as soon as one becomes available, or I get the gumption to develop it.
On an aside, could a strategically placed zener diode or two on the finals prevent damage? ?Doug Demaw recommended this on NPN finals in his books.
73 Goody
toggle quoted message
Show quoted text
As an experimenters/makers playground, the lack of self protecting circuitry became apparent.
I’d mess around with multiple antenna systems and tuner/switches/cables/CMC balun/etc. ?and 1 out on 10 “hookups” would be an open/error. Hey I’m a relative newbie and a liberal art major — what would you expect. Hahah. ?
Then there were many experiments playing with uBITX final PA voltage levels, and countless other goofy “experiments”?
it got to the point where my favorite radio accessory was a fire extinguisher, and my fastest repair was irf510 appendectomies. ?I’d line up the dead and abused 510s and praise them for their brave service and contribution to my belated understanding ?of Ohm’s Law. ?And the effects of rapid heat build up under sketchy situations.
These confessional stories make the point that for many of us curious hacks, goofy experimenters, newbies, or the just bone headed folks in general, self protective circuits in the sBITX, and any BITX, would be welcome.
On the other hand, blowing stuff up is a learning methodology. So thanks much for the chance to play and repair (often).
Don the Incendiary?
km4udx ?
|
Re: sBitx antenna-first warning
As an experimenters/makers playground, the lack of self protecting circuitry became apparent.
I’d mess around with multiple antenna systems and tuner/switches/cables/CMC balun/etc. ?and 1 out on 10 “hookups” would be an open/error. Hey I’m a relative newbie and a liberal art major — what would you expect. Hahah. ?
Then there were many experiments playing with uBITX final PA voltage levels, and countless other goofy “experiments”?
it got to the point where my favorite radio accessory was a fire extinguisher, and my fastest repair was irf510 appendectomies. ?I’d line up the dead and abused 510s and praise them for their brave service and contribution to my belated understanding ?of Ohm’s Law. ?And the effects of rapid heat build up under sketchy situations.
These confessional stories make the point that for many of us curious hacks, goofy experimenters, newbies, or the just bone headed folks in general, self protective circuits in the sBITX, and any BITX, would be welcome.
On the other hand, blowing stuff up is a learning methodology. So thanks much for the chance to play and repair (often).
Don the Incendiary?
km4udx
?
|
Re: Do you hate to wind toroids?
Raj,
And this seems to be the PDF file
Thomas
Dennis, a link please.
On 11/08/2022 5:43 PM, Dennis Zabawa
wrote:
I have discovered a great set of tools to make this process
quick and easy!
?
Go to the QPRME website and click on Toroid EZ Tools in the
sidebar.? Then read the documentation provided in the link.
?
While they seem a little pricey, $30.00, they make the task
of winding a toroid SO MUCH EASIER!
?
--
--
Support@...
|
Re: Do you hate to wind toroids?
Raj,
I think it's this link,
Thomas
Dennis, a link please.
On 11/08/2022 5:43 PM, Dennis Zabawa
wrote:
I have discovered a great set of tools to make this process
quick and easy!
?
Go to the QPRME website and click on Toroid EZ Tools in the
sidebar.? Then read the documentation provided in the link.
?
While they seem a little pricey, $30.00, they make the task
of winding a toroid SO MUCH EASIER!
?
--
--
Support@...
|
Re: Do you hate to wind toroids?
Dennis, a link please.
On 11/08/2022 5:43 PM, Dennis Zabawa
wrote:
toggle quoted message
Show quoted text
I have discovered a great set of tools to make this process
quick and easy!
?
Go to the QPRME website and click on Toroid EZ Tools in the
sidebar.? Then read the documentation provided in the link.
?
While they seem a little pricey, $30.00, they make the task
of winding a toroid SO MUCH EASIER!
?
|
Do you hate to wind toroids?
I have discovered a great set of tools to make this process quick and easy!
?
Go to the QPRME website and click on Toroid EZ Tools in the sidebar.? Then read the documentation provided in the link.
?
While they seem a little pricey, $30.00, they make the task of winding a toroid SO MUCH EASIER!
?
The kit actually came with three tools to wind T25, T30, T37, T50, T80 and T105 toroids.
|
Re: Nextion Display "File Version is too low"
Hi Ulf,
I haven't tested the QR code backup yet..I should probably do that.? I'll try it and get back to you.
73,
Tim A. King Jr.
Amateur Radio Station AG4RZ
Hi Tim,
have You tested using the "QR code backup"?? I have the same problem as you "... The remaining memory is not enough to run the temporary use of QR code (-261)..." I succeeded complie but I can't use the QR backup function, getting "Error- data file is short". Do You have the same problem ?
73 de SM0TRY, Ulf
|
Re: Ubitx Ver 6 need PTT circuit for Linear AMP
This is correct and simple!
Thanks Evan.
Raj
On 10/08/2022 10:32 PM, Evan Hand
wrote:
toggle quoted message
Show quoted text
Michael,
I would not connect the PTT to that point on the v6 uBitx.? On
the mainboard, K1 has a TX tag on pin 1 of that relay.? You want
to tap into that signal and connect to the new PTT relay.? Here
is the section from the v6 schematic:
I would connect that TX signal to one side of the new PTT relay,
ground to the other side, and then a protection diode across the
new relay coil with the band (cathode) going to the +side of the
relay, and the anode connected to ground.
Suggestion on my part.
73
Evan
AC9TU
|
Re: Ubitx Ver 6 need PTT circuit for Linear AMP
No no, partly yes. The amp side is correct but on uBitx side
connect one end of coil to ground
and other end to TX (12V on TX).. simplest. I usually dont
recommend connecting to PTT line
as any mishap will let out the magic smoke of the nano.
Raj
On 10/08/2022 9:42 PM, Michael wrote:
toggle quoted message
Show quoted text
Raj
I sometimes am a visual guy - Attached diagram what you envision?
--
KG5UMH
Michael - DM93am
|
with calculator
On 10/08/2022 7:45 PM, John Clark
wrote:
toggle quoted message
Show quoted text
I see that there are converters using this chip are listed on
Amazon.
Do you know if the frequency is easily adjustable on these
boards?
John
On 8/10/2022 7:48 AM, Raj vu2zap
wrote:
Then I stumbled on this one (see attached pdf) MT3608 that
runs at 1.2MHz and will have
3.6/7.2 blips. Tweak it to 1.15 Mhz and this can be avoided.
Raj
On 10/08/2022 6:47 PM, Ashhar
Farhan wrote:
Neils,
Many of these switching regulators have a 50
KHz switching frequency. This has images inside the
passband of the audio codec.
I arrived at LM338 only after experimenting
with various switching systems (including building one
from discrete components). These new generation of
switchers move the frequency to 500 KHz. That's what makes
them useful.
- f
On Wed, Aug 10, 2022, 6:27
PM John Terrell < N6LN@...>
wrote:
The
smallest ones have a small cheap potentiometer which I
would not trust in the long run to maintain a stable
output voltage. Some have a secondary means of choosing
between four or five fixed voltage levels and bypassing
the fickle potentiometer by cutting a pcb trace with a
hobby knife. Loupes help. But in any case a buffer
capacitor ought to reduce a noisy output p.
|
Only experimentation will tell John!
Mt3608 is the boost version, mp2331h is buck version.
For some reason I am not able to open those net pages
to share with you all. Some problem since last night.
Raj
On 10/08/2022 7:45 PM, John Clark
wrote:
toggle quoted message
Show quoted text
I see that there are converters using this chip are listed on
Amazon.
Do you know if the frequency is easily adjustable on these
boards?
John
On 8/10/2022 7:48 AM, Raj vu2zap
wrote:
Then I stumbled on this one (see attached pdf) MT3608 that
runs at 1.2MHz and will have
3.6/7.2 blips. Tweak it to 1.15 Mhz and this can be avoided.
Raj
On 10/08/2022 6:47 PM, Ashhar
Farhan wrote:
Neils,
Many of these switching regulators have a 50
KHz switching frequency. This has images inside the
passband of the audio codec.
I arrived at LM338 only after experimenting
with various switching systems (including building one
from discrete components). These new generation of
switchers move the frequency to 500 KHz. That's what makes
them useful.
- f
On Wed, Aug 10, 2022, 6:27
PM John Terrell < N6LN@...>
wrote:
The
smallest ones have a small cheap potentiometer which I
would not trust in the long run to maintain a stable
output voltage. Some have a secondary means of choosing
between four or five fixed voltage levels and bypassing
the fickle potentiometer by cutting a pcb trace with a
hobby knife. Loupes help. But in any case a buffer
capacitor ought to reduce a noisy output p.
|
Shirley Dulcey KE1L
Raj vu2zap