Well, you just need four contacts, but I see your point.
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On Mon, Sep 23, 2024 at 02:53 AM, Jeff Duce wrote:
Let me know if I've made any major mistakes here.? I figure I'll make a short run of boards to test and verify I didn't mess up the board design.? If that's all good, then I'll run do a larger order and put them up for sale on the etsy page.? Downside is that this process could take a month or so.?
?
Jeff
Jeff,
?I know this connector as XT60, but that's a minor problem. The bigger one is that there is a 10A fuse at the input that connects to the radio, while it can be seen on the opposite side in the conceptual drawing. So I see this as a faulty design, the pcb needs to be rearranged a bit. In the conceptual drawing, the left side is the input from the power supply, the right side is connected to the radio.
--
Gyula HA3HZ
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If you are going to operate UHF or higher, you might be interested in a satellite tracking program.? GPREDICT is available for Windows or Linux on x86 processors.? I don't know about the Pi or Macs.
Gerry Sherman
Sent by the Windows 11 Thunderbird
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Looks pretty nice to me!!!? ? Gordon KX4Z
On Sun, Sep 22, 2024 at 8:53?PM Jeff Duce via <jefe_de_estado= [email protected]> wrote:
So here's the latest.? My thought is that this would more or less replace the existing plug on the radio.? Can't really do that inside the radio without a lot of effort.? Here you would just plug in the board into the existing plug, which means you can now
only plug power into the board. The enclosure would have some sort of lid, but I haven't drawn it yet.? It uses a single existing screw from the bottom of the case to keep it from getting torqued too much when you unplug.? The box would need to be 3D printed,
it's a bit awkard and needs way more support that I'd like, but it's pretty small, so shouldn't be too bad.
From Left to right:? F1 would be a 10A fuse. D1 is a TVS diode to filter out fast high voltage transients (ESD protection).? The middle section (C1 to D3) is a crowbar overvolt circuit.? When voltage is below 16v, no current goes through these devices.? The
gate to the SCR is at 0V, so nothing happens.? When voltage is above 16v, the zener D2 allows voltage to pass, which turns on the gate on the SCR.? The SCR then creates a high current short to ground, which then pops the fuse.? Caps and ferrite for filtering
so you don't induce a current and pop the fuse from RF. Next section is reverse polarity protection.? After some going back and forth, I've picked a mosfet that is very low Rds, (1.6mOhm).? If power is connected with the correct voltage, it passes the current
with only a maximum power loss of 0.16w.? If polarity is reversed, Vgs will be 0v, and the mosfet won't turn on, no voltage at the output.
So you get ESD, overvolt, overcurrent, reverse polarity protection with no voltage drop at very low power loss.?
Let me know if I've made any major mistakes here.? I figure I'll make a short run of boards to test and verify I didn't mess up the board design.? If that's all good, then I'll run do a larger order and put them up for sale on the etsy page.? Downside is that
this process could take a month or so.?
Jeff
Andy,
if you have already brought up the topic here, I will answer here, although the title of the topic does not indicate this. I, who am only a radio user and cannot code, am told by others that it is not too late to learn. The sBitx developers settled on Discord
because many other devices are discussed in this forum. Besides, you also know that the direct answer option is given there, not here. In this way, developers can immediately find the questions that concern them and can answer them. So it is not so easy to
distinguish between the two servers, because each has advantages and disadvantages, you just have to consider them.
Just as no two people are the same, no two thoughts are the same. You can be confrontational and you can come to an agreement.
It is not necessary for everyone to go there, anyone who is interested in the matter and has an idea to share can do so.
--
Gyula HA3HZ
|
So here's the latest.? My thought is that this would more or less replace the existing plug on the radio.? Can't really do that inside the radio without a lot of effort.? Here you would just plug in the board into the existing plug, which means you can now
only plug power into the board. The enclosure would have some sort of lid, but I haven't drawn it yet.? It uses a single existing screw from the bottom of the case to keep it from getting torqued too much when you unplug.? The box would need to be 3D printed,
it's a bit awkard and needs way more support that I'd like, but it's pretty small, so shouldn't be too bad.
From Left to right:? F1 would be a 10A fuse. D1 is a TVS diode to filter out fast high voltage transients (ESD protection).? The middle section (C1 to D3) is a crowbar overvolt circuit.? When voltage is below 16v, no current goes through these devices.? The
gate to the SCR is at 0V, so nothing happens.? When voltage is above 16v, the zener D2 allows voltage to pass, which turns on the gate on the SCR.? The SCR then creates a high current short to ground, which then pops the fuse.? Caps and ferrite for filtering
so you don't induce a current and pop the fuse from RF. Next section is reverse polarity protection.? After some going back and forth, I've picked a mosfet that is very low Rds, (1.6mOhm).? If power is connected with the correct voltage, it passes the current
with only a maximum power loss of 0.16w.? If polarity is reversed, Vgs will be 0v, and the mosfet won't turn on, no voltage at the output.
So you get ESD, overvolt, overcurrent, reverse polarity protection with no voltage drop at very low power loss.?
Let me know if I've made any major mistakes here.? I figure I'll make a short run of boards to test and verify I didn't mess up the board design.? If that's all good, then I'll run do a larger order and put them up for sale on the etsy page.? Downside is that
this process could take a month or so.?
Jeff
toggle quoted message
Show quoted text
Andy,
if you have already brought up the topic here, I will answer here, although the title of the topic does not indicate this. I, who am only a radio user and cannot code, am told by others that it is not too late to learn. The sBitx developers settled on Discord
because many other devices are discussed in this forum. Besides, you also know that the direct answer option is given there, not here. In this way, developers can immediately find the questions that concern them and can answer them. So it is not so easy to
distinguish between the two servers, because each has advantages and disadvantages, you just have to consider them.
Just as no two people are the same, no two thoughts are the same. You can be confrontational and you can come to an agreement.
It is not necessary for everyone to go there, anyone who is interested in the matter and has an idea to share can do so.
--
Gyula HA3HZ
|
Re: A long long video on building feedback amplifiers
Minus seven for the pre-release QC fail.? The page lives in an open tab.
?
I'll add that the more about amplifiers I understand, the more fun they're becoming. Fun is good!
?
73
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Re: A long long video on building feedback amplifiers
Farhan,
?
? ?Your feedback amp page lives in a tan on my phone that's been open for more than a year now. Truly - thank you for the vid and calculator.
?
? ?Thank you for your observations - I will add them to my notebook and work to internalize them!
?
? ?Best,
? ? Andy
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Re: A long long video on building feedback amplifiers
On Sat, Sep 21, 2024 at 04:37 PM, AndyH wrote:
Terminations as farhan says is important!
?
Also Rf (feedback resistors) vs bias...?
Sometimes that resistor can be juggled to be the bias value.? Often
its too low for that so series resistance bypassed with suitable value
cap gives a valid DC bias with correct feedback.
?
Additionally many devices the FT and Beta vary with emitter current.
Some like the 5551A show curves that improve with increased current
also same for 2n2219A.? Others like the frequently used 2n3904 actually
decreases above about 12-15ma (best peak is 10ma).? Searching for
detailed datasheets helps with getting that information. Some vendors
have notably sparse datasheets making that harder to know.? Looking
at the same device from a different vendor often results in a more
detailed datasheet.
?
One thing seen with very high FT devices is oscillation at vhf or uhf
(usually well above frequency of interest) and usually in multi stage
amplifiers that often shows as reduced gain or less than expected
power.? For example the FT for the 2sc5551A 3.5ghz!? ?With a gain
bandwidth product layout and construction is a factor.? Sloppy long
leads and poor grounds will bite back.
?
At the other extreme the usual 2n3904 the FT is 300mhz which varies
from 250 to 380mhz or more.? The problem with that is; build a gain
of 17DB for use at 28mhz...? it does not net the correct gain in practice
due to low FT, it has more than enough beta.? The test is
FT/frequency-max. so for a gain of 20 (13db) at 28mhz the FT must
be more than 560mhz (500mhz will likely do)!? ?Conversely the best
a 300mhz part can do?across many samples is about 10 (10db!).
?
Resistive feedback can also be used with jfets and mosfets as well
The calculations are different due to the gain nature of the devices.
FETs are voltage to current so the calculations need some math
translation.? Generally it works the same and FETs (mos or junction)
do not for the most part exhibit FT.
?
Building wideband amplifies is actually more difficult than the
basic calculations from W1ZOI suggest as they hold well for
small signal at below VHF.? ?As we go up the reactive properties
and unintended feedback become a more significant factor.
?
--
Allison
------------------
Please use the forum, offline and private will go to bit bucket.
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Re: A long long video on building feedback amplifiers
Andy,
It is a pleasant surprise that you sat through it all!
These amplifiers need 'strong' terminations at both ends. If two amps cascade, this is usually lost. A trick is to add a 6dB attenuator between the stages. However, I havent noticed such a drastic drop of gain. There is a catch though.
Are you sure the second stage is not saturating? This is where a step attenuator is really effective tool to have. Reduce the input power by 10 dB and check?
The isolation resistors are chosen for a compromise between sufficient isolation and the current draw.
If your amplifier is drawing 20mA current, then a 220 ohms resistor will show 4 volts of drop! I usually gey away with 10 ohms unless the amp will draw more than 50mA. Usually with higher current, you have to increase the bypass capacitance and decrease the isolation resistance to keep the RF from leaking in and out of the DC line.
A more elaborate technique, often used with power stages is to use an inductor in place of the resistor. This is not a casual choice. You must not use the cheap molded chokes. They have a self resonance frequency well below the RF frequencies of our operations. This means that they are behaving more like capacitors rather than inductors! Instead, choose an inductance that has around 50 ohms reactance at the lowest operating frequency and wind it on a ferrite toroid. Remeber to bypass both ends of the inductor.
Farhan - it's still an excellent video and calculator - thank you!
?
Are there any rules of thumb about selecting the isolation resistor for the power input? I've seen from 10 to 220 Ohms. Is it calculated like a current limiter, or??
?
I've been experimenting with connecting multiple stages of amplifiers together.? I was surprised at the interaction between transformer coupled stages designed for 50 Ohms in and out. After tweaking a W8DIZ 2SC5551A amp for 17 dB of gain, gain of the first stage jumped about 5 dB after connecting? the second 17 dB stage. Does that sound normal?
?
There's art and science in this RF stuff.? Thanks for your work, and for easing the transition to W7ZOI'S feedback amp models.
?
73, Andy
?
On Sat, Jun 20, 2020 at 10:20 AM, Ashhar Farhan wrote:
Gang,
I have recorded a video on how to build feedback amplifiers. It is little?long. Do take a look if you are into homebrewing. I explain what a feedback amplifier is, how to choose the component values, how to build it and how to measure all the aspects like gain, input and output impedances and IIP3.
- f
|
Re: A long long video on building feedback amplifiers
Farhan - it's still an excellent video and calculator - thank you!
?
Are there any rules of thumb about selecting the isolation resistor for the power input? I've seen from 10 to 220 Ohms. Is it calculated like a current limiter, or??
?
I've been experimenting with connecting multiple stages of amplifiers together.? I was surprised at the interaction between transformer coupled stages designed for 50 Ohms in and out. After tweaking a W8DIZ 2SC5551A amp for 17 dB of gain, gain of the first stage jumped about 5 dB after connecting? the second 17 dB stage. Does that sound normal?
?
There's art and science in this RF stuff.? Thanks for your work, and for easing the transition to W7ZOI'S feedback amp models.
?
73, Andy
?
On Sat, Jun 20, 2020 at 10:20 AM, Ashhar Farhan wrote:
Gang,
I have recorded a video on how to build feedback amplifiers. It is little?long. Do take a look if you are into homebrewing. I explain what a feedback amplifier is, how to choose the component values, how to build it and how to measure all the aspects like gain, input and output impedances and IIP3.
- f
|
Would the keyer ever be able to handle the Ultimatic Mode rather than Iambic Mode. Or will I have to use my external ?keyer if I want the Ultimatic Mode?
|
Andy,
if you have already brought up the topic here, I will answer here, although the title of the topic does not indicate this. I, who am only a radio user and cannot code, am told by others that it is not too late to learn. The sBitx developers settled on Discord because many other devices are discussed in this forum. Besides, you also know that the direct answer option is given there, not here. In this way, developers can immediately find the questions that concern them and can answer them. So it is not so easy to distinguish between the two servers, because each has advantages and disadvantages, you just have to consider them.
Just as no two people are the same, no two thoughts are the same. You can be confrontational and you can come to an agreement.
It is not necessary for everyone to go there, anyone who is interested in the matter and has an idea to share can do so.
--
Gyula HA3HZ
|
JJ - I've already posted what I use here. Feel free to scroll up the thread on the web interface.
?
You could have PMd me as well. Maybe some of this history will be useful for the new folks though, so I'll entertain your query.
?
This is the only official support location for Farhan's projects.? Many have tried slack and discord groups in the past - going back to at least 2017 - and...well, they've become very tiny fiefdoms or abandoned lots.
?
Folks can do as they wish, of course - I was in uniform way too long to believe or suggest? otherwise. As a former serial business owner that used IRC and discord as support channels, and as a gamer and dad to a gamer, I'm familiar with the strengths and weaknesses of discord. That's ultimately why I'm against it for this group.
?
People are still scratch building BITX20 and 40 radios - try pulling relevant info from a Discord channel from 6 months ago, much less from 2005. Good luck with that!
?
There was a time when we agreed.
?
?
73, Andy
?
?
?
?
?
?
?
?
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Please just put what you want us to look at HERE....please don't force us into yet ANOTHER venue, OK/ Thanks Gordon KX4Z
On Fri, Sep 20, 2024 at 12:08?PM Jeff Duce via <jefe_de_estado= [email protected]> wrote:
Check out what I'm working on here, feedback would be appreciated.
We’ve got three instances of destroyed radios in our local group alone. Connectors are nice, but that doesn’t stop people from putting clips on storage batteries backwards. ??
It can be done with series diodes in low power devices ;
P channel mosfets in medium power ;
And in diode controlled relays in really high-powered devices?
Dc-powered radios that ?I consider valuable to me , I generally provide protection for!
Our local group just did an Arduino based Winkeyer ?project, and putting a series diode in there before the voltage regulator was easy ; most of my HF go boxes have mosfet ?protection?
Gordon kx4z?
On Sep 20, 2024, at 11:40, Gary Eldridge - KC8UD via <gary.video=[email protected]> wrote:
?
Yes, I see how that will work. But for a QRP rig such as sBitx one certainly doesn’t really need such a big bundle of connectors to carry the load. I understand that it is simply for making the polarity foolproof.?
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... unless the -ve O/P from the PSU shares the same ground as the rig or ATU!!!!!!!
toggle quoted message
Show quoted text
On Thu, Sep 19, 2024 at 10:31 PM, David Lacey wrote: I am surprised no one so far has used the simplest way of protection.
Use a suitably rated (amps) bridge rectifier, hard wire + to rig +
hard wire -ve to rig -ve? the two AC tags of the rectifier then connect
to the power supply.......either way round makes no difference, the rig
will always see the correct polarity.? Fuse as you normally would.
My 2 cents worth from this side of the pond.
Dave G4JBE
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Re: Advice and Opinions on the next iteration of the sBitx
On Fri, Sep 20, 2024 at 03:20 PM, IU0KVG wrote:
- push button to shut down the PI
- three position power switch (to limit draw when just fiddling with the sw):
? ? ? ?1 : OFF
? ? ? ?2: digital (PI) only ON
? ? ? ?3: both digital and analog ON?
- 5W VHF (possibly with separate antenna input)
- dedicated split for repeaters offset
- 100W HF
- fan (with speed monitor / alarm)
Interesting post. How long have you been using this device and reading the developments here?
--
Gyula HA3HZ
|
Check out what I'm working on here, feedback would be appreciated.
toggle quoted message
Show quoted text
We’ve got three instances of destroyed radios in our local group alone. Connectors are nice, but that doesn’t stop people from putting clips on storage batteries backwards. ??
It can be done with series diodes in low power devices ;
P channel mosfets in medium power ;
And in diode controlled relays in really high-powered devices?
Dc-powered radios that ?I consider valuable to me , I generally provide protection for!
Our local group just did an Arduino based Winkeyer ?project, and putting a series diode in there before the voltage regulator was easy ; most of my HF go boxes have mosfet ?protection?
Gordon kx4z?
On Sep 20, 2024, at 11:40, Gary Eldridge - KC8UD via groups.io <gary.video@...> wrote:
?
Yes, I see how that will work. But for a QRP rig such as sBitx one certainly doesn’t really need such a big bundle of connectors to carry the load. I understand that it is simply for making the polarity foolproof.?
|
We’ve got three instances of destroyed radios in our local group alone. Connectors are nice, but that doesn’t stop people from putting clips on storage batteries backwards. ??
It can be done with series diodes in low power devices ; P channel mosfets in medium power ; And in diode controlled relays in really high-powered devices?
Dc-powered radios that ?I consider valuable to me , I generally provide protection for!
Our local group just did an Arduino based Winkeyer ?project, and putting a series diode in there before the voltage regulator was easy ; most of my HF go boxes have mosfet ?protection?
toggle quoted message
Show quoted text
On Sep 20, 2024, at 11:40, Gary Eldridge - KC8UD via groups.io <gary.video@...> wrote:
? Yes, I see how that will work. But for a QRP rig such as sBitx one certainly doesn’t really need such a big bundle of connectors to carry the load. I understand that it is simply for making the polarity foolproof.?
|
Yes, I see how that will work. But for a QRP rig such as sBitx one certainly doesn’t really need such a big bundle of connectors to carry the load. I understand that it is simply for making the polarity foolproof.?
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Sorry: "Just use it in an hermaphrodite, REVERSIBLE, configuration"
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HA3HZ
VE6LX
Gary Eldridge - KC8UD