Re: A long long video on building feedback amplifiers
Farhan - it's still an excellent video and calculator - thank you!
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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??
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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?
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There's art and science in this RF stuff.? Thanks for your work, and for easing the transition to W7ZOI'S feedback amp models.
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73, Andy
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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
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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?
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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.
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Gyula HA3HZ
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JJ - I've already posted what I use here. Feel free to scroll up the thread on the web interface.
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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.
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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.
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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.
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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!
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There was a time when we agreed.
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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:
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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!!!!!!!
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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?
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Gyula HA3HZ
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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:
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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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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.?
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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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@Gary you CAN use PowerPole connectors to prevent reverse connections.
Just use it in an hermaphrodite configuration.
I suggested this as a standard in the Italian ham bullettin (2019, Vol 7/8)
Unfortunately the article (attached below) is in Italian, but looking at the pictures should suffice.?
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Re: Advice and Opinions on the next iteration of the sBitx
- 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)
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Thanks, Ragav. I think I carried the files forward from V2 as delivered to V3 64bit. However, I did not realize that setting were by unit. I will go to my backups, find the original, and check the values.
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Bruce,
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Each unit is individually tested and calibrated with it's own values in the hw_settings file. That said, there is usually very minor deviation from the values in a given batch.
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As OM Gyula suggested, it's a good idea to backup the settings for your device before you make any modifications.
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73,
Ragav
VU3VWR
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There's a whole bunch of ways to do the same thing.? This would work just fine and be cheap.? But you'd also see a voltage drop across 2 diodes, so upwards of 1.4v drop.? Lets say the radio draws 7A through the diodes, that's a power loss 9.8W.? When you're
running on a battery, that's a pretty large power loss and a fair amount of heat to have to reject.? Of course that's only at full-duty and on SSB it wouldn't be a big deal, but if you're running digital modes, that would be a lot.
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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: Discord communication
On Thu, Sep 19, 2024 at 01:39 PM, JJ - W9JES wrote:
Hi Nick. I sent you a private message to your email. I am willing to help.
Nick is all set. Feel free to contact me at w9jes@... if you need help.? w9jes ATarrl.net in case the group redacts my email.
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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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The keyer in JJ's dev branch feels promising. Played around with it on a dummy load and it seems to key correctly at 25 wpm. Planning to activate with it over the weekend and will report back.?
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On Thu, Sep 19, 2024 at 08:17 PM, Bruce W4BRU wrote:
I've seen comments that implies the contents of? hw_settings.ini are individual by serial number, that is by unit. That means that each? board was tested at the assembly point and the setting entered for that unit at that point. Is that true or is it the same for all the units of that model? It's important to me because I have V2 hardware slightly modified but with JJ's 64bit V3 software. This weekend I plan to see if I still have the original hw_settings.ini file and compare it to what I have on my V3 installed version. I need to determine what is correct.
The manufacturer can give you the correct answer to your question. I received the v2 device at the beginning of production, when we had not yet received an adjusted device (April 2023), I had to do this myself. The description of the setting can be found on the sbitx.net page.
This setting is not required for v3.
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Gyula HA3HZ
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VE6LX
HA3HZ
Gary Eldridge - KC8UD
Bruce W4BRU