On Mar 30, 2019, at 7:14 PM, Gordon Gibby <ggibby@...> wrote:

Bravo! ? I used to read the back of the Heathkit book to try to figure out what the heck was my radio doing

I think that’s where most of us learned electronics?

Read a bit on biasing a transistor, it is fascinating stuff. ? And then how the cathode resistor acts like negative feedback—-oops, I meant emitter resistor....

This is where ham radio gets a lot more fun than just pushing on Mike Button

On Mar 30, 2019, at 18:07, Joe Puma <kd2nfc@...> wrote:

Thanks Gordon,

I have been making good progress. Using transistors as switches and now amplification either for audio or RF. The last year has taught me more then I ever learned in that tech school 30 years ago. We did learn OHM’s law and voltage law but I didn’t spend much time being hands on with it where I seem to learn from the best. ?

As silly as it seems I guess I just didn’t know where to get current readings that bias the transistor or that I would even need to worry if I followed Allison’s steps, guess I was expecting the easy route ?. This is where things get interesting because I am getting familiar with what the components are doing in the circuit. I’m still lost in certain areas like how the clock and mixer circuits work.?

I am about to sit down and take some readings from what I’ve leaned in this thread and I’m confident I can get the drivers running right.?

Joe

KD2NFC?

On Mar 30, 2019, at 4:46 PM, Gordon Gibby <ggibby@...> wrote:

Joe, I was excited when I read that you were starting to figure this out! ? Applying ohms law to the emitter resistor to figure out the current is a crucial skill. ?

I know it’s embarrassing to us all, but this is just technician level ohms law. ? It’s the same stuff that we teach and test on in the technician license; what is different is that it is inside a circuit and we never really realized that this cool Ohms law can help us measure a zillion things.

As I’m sure you are starting to realize, whatever voltage the base terminal ( of a common emmiter type amplifier) is at...... The emitter will be about .6 or .7 V lower.

And whatever that voltage is, drives current through the emitter resistor!!!!!!!!! ? So once you know any part of this, you can kind of figure out how hot that transistor is going to get. ? Allyson is telling you what the correct currents are, so now you just have to make the voltage divider on the base side cause all of this to work properly

Set that base voltage too high, and you’re going to have a really hot transistor because now the voltage across the emitter resistor is really high! ? The amplifying action of the transistor will pull enough current through the collector to run that emitter right up to .7 V below the base..... and if that means 50 mA asked to flow, so be it! ? Short-lived transistor!!!

The DC biasing of transistors is well worth getting a good handle on. ?

I’m just starting a three or four part series in my local amateur radio emergency service group to teach common emitter amplifiers (or common cathode vacuum tube amplifiers)

I hope I did not bore you to tears

Gordon

On Mar 30, 2019, at 15:57, ajparent1/KB1GMX <kb1gmx@...> wrote:

Joe, it wasnt you.

There are a number of readers that do not write here and maybe read the emails.
So posting where he wiki is was needed as I get the feeling that anything posted
more than a few days ago are lost to the wind for many that only interact via email.
Yet despite that it is preserved in the web based copy.

Allison

Thanks Gordon,

I have been making good progress. Using transistors as switches and now amplification either for audio or RF. The last year has taught me more then I ever learned in that tech school 30 years ago. We did learn OHM’s law and voltage law but I didn’t spend much time being hands on with it where I seem to learn from the best. ?

As silly as it seems I guess I just didn’t know where to get current readings that bias the transistor or that I would even need to worry if I followed Allison’s steps, guess I was expecting the easy route ?. This is where things get interesting because I am getting familiar with what the components are doing in the circuit. I’m still lost in certain areas like how the clock and mixer circuits work.?

I am about to sit down and take some readings from what I’ve leaned in this thread and I’m confident I can get the drivers running right.?

Joe

KD2NFC?

On Mar 30, 2019, at 4:46 PM, Gordon Gibby <ggibby@...> wrote:

Joe, I was excited when I read that you were starting to figure this out! ? Applying ohms law to the emitter resistor to figure out the current is a crucial skill. ?

I know it’s embarrassing to us all, but this is just technician level ohms law. ? It’s the same stuff that we teach and test on in the technician license; what is different is that it is inside a circuit and we never really realized that this cool Ohms law can help us measure a zillion things.

As I’m sure you are starting to realize, whatever voltage the base terminal ( of a common emmiter type amplifier) is at...... The emitter will be about .6 or .7 V lower.

And whatever that voltage is, drives current through the emitter resistor!!!!!!!!! ? So once you know any part of this, you can kind of figure out how hot that transistor is going to get. ? Allyson is telling you what the correct currents are, so now you just have to make the voltage divider on the base side cause all of this to work properly

Set that base voltage too high, and you’re going to have a really hot transistor because now the voltage across the emitter resistor is really high! ? The amplifying action of the transistor will pull enough current through the collector to run that emitter right up to .7 V below the base..... and if that means 50 mA asked to flow, so be it! ? Short-lived transistor!!!

The DC biasing of transistors is well worth getting a good handle on. ?

I’m just starting a three or four part series in my local amateur radio emergency service group to teach common emitter amplifiers (or common cathode vacuum tube amplifiers)

I hope I did not bore you to tears

Gordon

On Mar 30, 2019, at 15:57, ajparent1/KB1GMX <kb1gmx@...> wrote:

Joe, it wasnt you.

There are a number of readers that do not write here and maybe read the emails.
So posting where he wiki is was needed as I get the feeling that anything posted
more than a few days ago are lost to the wind for many that only interact via email.
Yet despite that it is preserved in the web based copy.

Allison

So, I just finished wiring up my ver3 board to sunil 3.5" nextion case. Have an audio line and agc line off (not sure where to connect). Plugged it in and popped the LA4225 on the audio amp. Took power off of audio and agc board and nextion/rig still work fine.

On top of that, where should I get audio in from the board for the audio amp and agc? Pics are from ver4 board.

Joe, I was excited when I read that you were starting to figure this out! ? Applying ohms law to the emitter resistor to figure out the current is a crucial skill. ?

I know it’s embarrassing to us all, but this is just technician level ohms law. ? It’s the same stuff that we teach and test on in the technician license; what is different is that it is inside a circuit and we never really realized that this cool Ohms law can help us measure a zillion things.

As I’m sure you are starting to realize, whatever voltage the base terminal ( of a common emmiter type amplifier) is at...... The emitter will be about .6 or .7 V lower.

And whatever that voltage is, drives current through the emitter resistor!!!!!!!!! ? So once you know any part of this, you can kind of figure out how hot that transistor is going to get. ? Allyson is telling you what the correct currents are, so now you just have to make the voltage divider on the base side cause all of this to work properly

Set that base voltage too high, and you’re going to have a really hot transistor because now the voltage across the emitter resistor is really high! ? The amplifying action of the transistor will pull enough current through the collector to run that emitter right up to .7 V below the base..... and if that means 50 mA asked to flow, so be it! ? Short-lived transistor!!!

The DC biasing of transistors is well worth getting a good handle on. ?

I’m just starting a three or four part series in my local amateur radio emergency service group to teach common emitter amplifiers (or common cathode vacuum tube amplifiers)

I hope I did not bore you to tears

Gordon

On Mar 30, 2019, at 15:57, ajparent1/KB1GMX <kb1gmx@...> wrote:

Joe, it wasnt you.

There are a number of readers that do not write here and maybe read the emails.
So posting where he wiki is was needed as I get the feeling that anything posted
more than a few days ago are lost to the wind for many that only interact via email.
Yet despite that it is preserved in the web based copy.

Allison

Brings up a point that I have noticed: there really isn't a "before you post" guideline like there is on most email portals.? Would be nice if there was a general guidelines on the first page of the group.? It would go into the suggested search for your issue starting in the wiki, then the files, and finally the Topics(threads).? The would reduce, though not eliminate, the number of repeats on the topics.? I do know that I have posted about using an AF spectrum analyzer for BFO adjustment numerous times.? I have also read many topics on Arduino issues that are repeats.? I do not believe it is laziness on that part of (most of) the participants, just no clear direction on how to use the site. I know that I am still going through a learning curve on how to search, and what content is where (the first set of topics are very broad, and then no further grouping below the first level).

Above are my opinions, yours may differ, and that is OK
73
Evan
AC9TU

Joe, it wasnt you.

There are a number of readers that do not write here and maybe read the emails.
So posting where he wiki is was needed as I get the feeling that anything posted
more than a few days ago are lost to the wind for many that only interact via email.
Yet despite that it is preserved in the web based copy.

Allison

On Mar 20, 2019, at 11:05 PM, Raj vu2zap <rajendrakumargg@...> wrote:

That could a date code or batch number.

At 20-03-19, you wrote:

Looking closely at the photo, I see the inductors are marked
T
R68K
1144
while the ones I have "look" the same and appear to have the same manufacurer's logo, but are marked
T
R68K
1145

Any idea what the difference is between 1144 and 1145?

=Vic=