Re: [SoftwareControlledHamRadio] Rob Sherwood Presentation Slides on Amateur Radio Transceiver Performance

#6029

开云体育

For those who are interested…. Here is a tutorial on Class-A operation of transistor amplifiers:?

?

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

?

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

Show quoted text

From: [email protected] <[email protected]> On Behalf Of K9HZ
Sent: Monday, February 10, 2025 1:34 PM
To: [email protected]; [email protected]
Subject: Re: [AmateurRadioBuilders] [SoftwareControlledHamRadio] Rob Sherwood Presentation Slides on Amateur Radio Transceiver Performance

?

A couple comments on Rob’s talks… there are plenty more of them in addition to these.

?

Rob has done a wonderful job of evaluating radio transceivers… I’ve been to his house/ lab and he has the perfect location for his evaluations.? He will always give you an honest evaluation answer but never recommend a radio.? He does have some peculiar operating habits, like all of us, that causes him to identify waterfalls and knobs that he likes… that might not be your cup of tea.? In the past 5+ years Rob has been on an SSB IMD tirade, pushing predistortion accommodations with the top commercial radio manufacturers.? It’s all good stuff but he tends to extend that to the builder and hobbyist level at times that doesn’t always resonate with some of us.? In any case, he does tout using class-A final RF amplifiers in the transmit stages of radios because they, by shear design, will generate less IMD.

?

If any of you want to join the “Class-A” club, my 20W and 100W amplifiers will operate in Class-A operation.? The amps have plenty of head-room in terms of dissipation to perform this task, but at a reduced power and efficiency.? My original PA designs contained hardware to adjust the bias to perform this, but I was worried that people would try to keep the PA at the 20W level while in this pseudo class-A operation at about 28% efficiency.? Now will this be of use with the T41… hmmm that is left to the reader.

?

I will publish instructions on how to put the 20W PA in class-A operation by readjusting the bias.? Have fun with this but also have a extra set of transistors laying around!? Expect about 5 watts out for a safe level of performance.

?

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

?

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

From: [email protected] <[email protected]> On Behalf Of Greg KF5N via groups.io
Sent: Monday, February 10, 2025 8:15 AM
To: [email protected]
Subject: [SoftwareControlledHamRadio] Rob Sherwood Presentation Slides on Amateur Radio Transceiver Performance

?

The slides are here:

/g/SoftwareControlledHamRadio/files/Sherwood_Presentations

I attempted to video the presentation at Hamcation.? Unfortunately the acoustics and noise at the venue were quite bad.
Here are the videos:

?

--

73 Greg KF5N

Re: [SoftwareControlledHamRadio] Rob Sherwood Presentation Slides on Amateur Radio Transceiver Performance

#6028

开云体育

A couple comments on Rob’s talks… there are plenty more of them in addition to these.

?

Rob has done a wonderful job of evaluating radio transceivers… I’ve been to his house/ lab and he has the perfect location for his evaluations.? He will always give you an honest evaluation answer but never recommend a radio.? He does have some peculiar operating habits, like all of us, that causes him to identify waterfalls and knobs that he likes… that might not be your cup of tea.? In the past 5+ years Rob has been on an SSB IMD tirade, pushing predistortion accommodations with the top commercial radio manufacturers.? It’s all good stuff but he tends to extend that to the builder and hobbyist level at times that doesn’t always resonate with some of us.? In any case, he does tout using class-A final RF amplifiers in the transmit stages of radios because they, by shear design, will generate less IMD.

?

If any of you want to join the “Class-A” club, my 20W and 100W amplifiers will operate in Class-A operation.? The amps have plenty of head-room in terms of dissipation to perform this task, but at a reduced power and efficiency.? My original PA designs contained hardware to adjust the bias to perform this, but I was worried that people would try to keep the PA at the 20W level while in this pseudo class-A operation at about 28% efficiency.? Now will this be of use with the T41… hmmm that is left to the reader.

?

I will publish instructions on how to put the 20W PA in class-A operation by readjusting the bias.? Have fun with this but also have a extra set of transistors laying around!? Expect about 5 watts out for a safe level of performance.

?

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

?

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

Show quoted text

From: [email protected] <[email protected]> On Behalf Of Greg KF5N via groups.io
Sent: Monday, February 10, 2025 8:15 AM
To: [email protected]
Subject: [SoftwareControlledHamRadio] Rob Sherwood Presentation Slides on Amateur Radio Transceiver Performance

?

The slides are here:

/g/SoftwareControlledHamRadio/files/Sherwood_Presentations

I attempted to video the presentation at Hamcation.? Unfortunately the acoustics and noise at the venue were quite bad.
Here are the videos:

?

--

73 Greg KF5N

Display Board evaluation help

#6027

开云体育

I have a couple of the 3.3V ONLY display boards prebuilt and I want a couple of volunteers to test them out.? They have to be: 1) people with working radios, and 2) have displays that misbehave (meaning if you move them around, elongate the cable, etc… the processor locks up).

?

I don’t really have the problem so its hard for me to fully evaluate if the display driver boards completely solve this issue.

?

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

?

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

Re: V12 RF Board

#6026

开云体育

Yes I have a couple hundred of the off-set boards.? They are $0.50 plus shipping and can ship in a regular first class envelope for a couple of stamps.

?

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

?

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

Show quoted text

From: [email protected] <[email protected]> On Behalf Of Tim via groups.io
Sent: Monday, February 10, 2025 8:43 AM
To: [email protected]
Subject: Re: [AmateurRadioBuilders] V12 RF Board

?

Display freezes buttons and encoders stop working.

Do you have some extra Audio Hat extender boards?

I would like a few.

Tim W4YN

Re: V12 RF Board

#6025

Display freezes buttons and encoders stop working.

Do you have some extra Audio Hat extender boards?

I would like a few.

Tim W4YN

Re: [SoftwareControlledHamRadio] Display driver board reality

#6024

开云体育

Sorry Phil,

I have no idea now. Never bothered keeping records. Should have as there seem to be muliple versions.

I just ordered the 5" in the minimum configuration suggested on the group.

Glenn

vk3pe

On 8/02/2025 7:50 am, Phil Taylor via groups.io wrote:

Show quoted text

What model number did you order Glenn.

?

I did see a picture somewhere like yours too though.

?

?

Regards?

Phil

VK2KKZ

Re: Conductive Paint

#6023

On 2025-02-09 13:52, Wes Plouff via groups.io wrote:

The resistance of a flat surface is called sheet resistance, measured
in ohms per square. Not square inches or square cm, just per square.

*** I had to look that up. How can a big square have the same
resistance
as a little one? It's because as you add length - increasing the
resistance - you
also add width - decreasing it.

- Jerry, KF6VB

Re: Conductive Paint

#6022

On Sun, Feb 9, 2025 at 01:04 PM, Doug W wrote:

I am probably oversimplifying something I may not fully understand but is there a general rule of thumb for knowing if a material may be suitable? ? Such as if it measures x ohms per square cm or something like that.

The resistance of a flat surface is called sheet resistance, measured in ohms per square. Not square inches or square cm, just per square. After that, it looks like things get complicated. The amount of shielding depends on the conductivity of the shield material, its thickness, and the frequency in question. The reason is skin depth of RF currents, which varies inversely with frequency. They pay engineers good salaries to figure out the details.

?

One alternative to painting on a conductive coating would be to add a metal coating to a plastic case using a chemical process called electroless plating or electroless deposition. There are YouTube videos of hobbyists doing it. Using copper or nickel metal, this ought to provide good RF shielding.

?

It seems to me there is no easy solution for a hobbyist wanting to shield a plastic enclosure. That may be why the 4SQRP T41-EP kit used copper clad printed circuit board material for a case.

?

73,

?

Wes Plouff AC8JF

Re: Conductive Paint

#6021

开云体育

Copper tape is one of the better ways to shield. Solderability is a feature you won’t get with aqua-dag or silver-dag, and these paintable solutions are quite costly, meant more for small areas with difficult geometries. I prefer to not rely on the conductivity of the adhesives, but use solder bridges or wires to ensure continuity.?

There is one aspect you need to think about and that is the possibility that you may end up creating a slot antenna inadvertently; two conductive layers that don’t touch and connect properly leaving a long gap can be trouble. I learned this lesson while working on a 70cm linear and there was what seemed like a minimal gap between aluminum panels. The glow from a nearby fluorescent tube should have us in, but nobody thought that far ahead. A simple continuity test won’t reveal the gap either. Finger stock is a ‘must’ for this kind of structure when panels are removable.?

Before applying the tape, make sure that the surface is really clean. You can improve the rigidity of the tape layer by putting a piece of wire under the tape so as to form a small ridge in the tape when pressed down, which will reduce the tendency to buckle or curl up. Forming an X shape on the two diagonals will help to stop the corners from detaching on a larger flat segment.?

Good luck with the shielding tasks,

Roland AE6VL?

Show quoted text

On Feb 9, 2025, at 11:11?AM, jerry-KF6VB via groups.io <jerry@...> wrote:

?On 2025-02-09 10:58, K9HZ wrote:
Have a look at msg #5998 from Chris Corcoran… He shows a number of
plots that show the resistance of the coating. You can use that to
figure out the attenuation for the coating.
** Yeah, the attenuation for the cheap carbon stuff doesn't look too
good
around 20M.

I bought a roll of self-stick copper tape that claims that their
adhesive
is conductive.

I figure I can put that tape on the easy places, and then coat the
innards
- including the tape - with the carbon paint.

In principle, I like the fact that the carbon paint is *resistive*.
So it
should be able to attenuate EMI without necessarily having to be
grounded.

- Jerry

Re: V12 RF Board

#6020

开云体育

Hey Tim… when you say it shuts down… what do you mean?? The signal stops or the power goes off?

?

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

?

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

Show quoted text

From: [email protected] <[email protected]> On Behalf Of Tim via groups.io
Sent: Sunday, February 9, 2025 1:15 PM
To: [email protected]
Subject: Re: [AmateurRadioBuilders] V12 RF Board

?

My bad I had left off Jumpers 18 and 19. I can now rx fine, but only for short period then it shuts down.

Not up long enough to do RX calibration.?

Tim W4YN

Re: V12 RF Board

#6019

My bad I had left off Jumpers 18 and 19. I can now rx fine, but only for short period then it shuts down.

Not up long enough to do RX calibration.?

Tim W4YN

Re: Conductive Paint

#6018

On 2025-02-09 10:58, K9HZ wrote:

Have a look at msg #5998 from Chris Corcoran… He shows a number of
plots that show the resistance of the coating. You can use that to
figure out the attenuation for the coating.

** Yeah, the attenuation for the cheap carbon stuff doesn't look too
good
around 20M.

I bought a roll of self-stick copper tape that claims that their
adhesive
is conductive.

I figure I can put that tape on the easy places, and then coat the
innards
- including the tape - with the carbon paint.

In principle, I like the fact that the carbon paint is *resistive*.
So it
should be able to attenuate EMI without necessarily having to be
grounded.

- Jerry

Re: Conductive Paint

#6017

开云体育

Have a look at msg #5998 from Chris Corcoran…? He shows a number of plots that show the resistance of the coating.?? You can use that to figure out the attenuation for the coating.

?

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

?

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

Show quoted text

From: [email protected] <[email protected]> On Behalf Of Doug W via groups.io
Sent: Sunday, February 9, 2025 12:04 PM
To: [email protected]
Subject: Re: [AmateurRadioBuilders] Conductive Paint

?

I am probably oversimplifying something I may not fully understand but is there a general rule of thumb for knowing if a material may be suitable? ? Such as if it measures x ohms per square cm or something like that.

Re: [SoftwareControlledHamRadio] Calibrate S meter?

#6016

Hmm - at 14.2 MHz with the gen set to -72dBm ( as low as it'll go
without
an external attenuator ), I'm seeing just a hair under S9. Not bad!

7.2Mhz - just a hair under S8. Well, on that band the BPF is not well
tuned.
I need to get back to that. It's also down on transmit power, but since
I
use it with my homebrew linear, I still get 800W out, which is IMHO
plenty.

3.9Mhz - S7.5

10.1 MHz - S8.5

18.1MHz - S8.5

21.1MHz - S8.5

24.9MHz - S7.5

28.35MHz - S9

- Jerry, KF6VB

Re: [SoftwareControlledHamRadio] Calibrate S meter?

#6015

I didn't say that right. The calibration of the s-meter sets the ZERO point
(well... -73 db point) on the meter. That is the intercept of the equation
for "S" units. You also have to calibrate (eg determine) the SLOPE of the
curve using the attenuator (because we know the attenuator is correct).

S-units (an any input) = S-meter calibration point at fake -73 db +
"Detected signal strength in S units above zero"

So above S=0,

"Where Detected signal strength in S units above s=0" = gain(S=full scale
- S=0) * received signal strength in fake dbs.

You need to set the attenuator at two different points to resolve the slope.

This is very crude so don't kill me... just fix it...

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ
VP2EHZ

Owner - Operator
Big Signal Ranch – K9ZC
Staunton, Illinois

Owner – Operator
Villa Grand Piton – J68HZ
Soufriere, St. Lucia W.I.
Rent it: www.VillaGrandPiton.com

Moderator: North American QRO Group at Groups.IO.
Moderator: Amateur Radio Builders Group at Groups.IO.

email:? bill@...

Show quoted text

-----Original Message-----
From: [email protected]
<[email protected]> On Behalf Of K9HZ
Sent: Sunday, February 9, 2025 12:25 PM
To: [email protected]; [email protected]
Subject: Re: [SoftwareControlledHamRadio] Calibrate S meter?

Yeah and make sure you do it with the attenuator at ZERO! THEN go ahead
and calibrate the RX attenuation control.

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ
VP2EHZ

Owner - Operator
Big Signal Ranch – K9ZC
Staunton, Illinois

Owner – Operator
Villa Grand Piton – J68HZ
Soufriere, St. Lucia W.I.
Rent it: www.VillaGrandPiton.com

Moderator: North American QRO Group at Groups.IO.
Moderator: Amateur Radio Builders Group at Groups.IO.

email:? bill@...

-----Original Message-----
From: [email protected]
<[email protected]> On Behalf Of jerry-KF6VB
Sent: Sunday, February 9, 2025 12:23 PM
To: [email protected]
Subject: Re: [SoftwareControlledHamRadio] Calibrate S meter?

On 2025-02-09 10:11, jjpurdum via groups.io wrote:

No. It is an approximation based on comparing S signals on commercial
rigs with the T41 reading. At the time the S-meter was coded, its
accuracy was pretty far down the list of things to do,

*** Makes sense. That's actually what I figured :). I think such
calibration would need to be per-band.

- Jerry, KF6VB

Re: [SoftwareControlledHamRadio] Calibrate S meter?

#6014

Yeah and make sure you do it with the attenuator at ZERO! THEN go ahead
and calibrate the RX attenuation control.

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ
VP2EHZ

Owner - Operator
Big Signal Ranch – K9ZC
Staunton, Illinois

Owner – Operator
Villa Grand Piton – J68HZ
Soufriere, St. Lucia W.I.
Rent it: www.VillaGrandPiton.com

Moderator: North American QRO Group at Groups.IO.
Moderator: Amateur Radio Builders Group at Groups.IO.

email:? bill@...

Show quoted text

-----Original Message-----
From: [email protected]
<[email protected]> On Behalf Of jerry-KF6VB
Sent: Sunday, February 9, 2025 12:23 PM
To: [email protected]
Subject: Re: [SoftwareControlledHamRadio] Calibrate S meter?

On 2025-02-09 10:11, jjpurdum via groups.io wrote:

No. It is an approximation based on comparing S signals on commercial
rigs with the T41 reading. At the time the S-meter was coded, its
accuracy was pretty far down the list of things to do,

*** Makes sense. That's actually what I figured :). I think such
calibration would need to be per-band.

- Jerry, KF6VB

Re: Conductive Paint

#6013

I am probably oversimplifying something I may not fully understand but is there a general rule of thumb for knowing if a material may be suitable? ? Such as if it measures x ohms per square cm or something like that.

Re: Calibrate S meter?

#6012

开云体育

Yeah… we need a calibration procedure for this too…? Looks like you have volunteered Jerry!

?

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

?

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

Show quoted text

From: [email protected] <[email protected]> On Behalf Of jerry-KF6VB
Sent: Sunday, February 9, 2025 11:44 AM
To: [email protected]
Cc: [email protected]
Subject: [AmateurRadioBuilders] Calibrate S meter?

?

I was just doing this for one of my other radios, and wondered: Is the S
meter display
on the T41 calibrated?

S9 is defined as -73dBm, or 50 microvolts @ 50 ohms. I think I'll try
it out with a signal generator.

- Jerry, KF6VB

Calibrate S meter?

#6011

I was just doing this for one of my other radios, and wondered: Is the S
meter display
on the T41 calibrated?

S9 is defined as -73dBm, or 50 microvolts @ 50 ohms. I think I'll try
it out with a signal generator.

- Jerry, KF6VB

Re: V12 RF Board

#6010

开云体育

That is on the “TO DO” list.? Since this is an open/ community project… I would ask that someone with a working radio… please step up… do this as a contribution to the project if… people want it in the short term. ??I know there are guys on channel that did this for a living… that could bang it out in about 10 minutes.

?

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

?

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

?

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it:

?

Moderator: North American QRO Group at Groups.IO.

Moderator: Amateur Radio Builders Group at Groups.IO.

?

email:? bill@...

?

Show quoted text

From: [email protected] <[email protected]> On Behalf Of Tim via groups.io
Sent: Sunday, February 9, 2025 11:09 AM
To: [email protected]
Subject: [AmateurRadioBuilders] V12 RF Board

?

I see lots of test points on the RF board, is there a list of expected voltages and signal data for each point somewhere?

Trying to trouble shoot my RF board issues.

Tim W4YN