On Mar 28, 2025, at 5:28?PM, jerry-KF6VB via groups.io <jerry@...> wrote:

?Mine is oscillating too. But only with the later software.

- Jerry

On 2025-03-28 12:24, D Solt via groups.io wrote:
Today, I checked v50.2 and v66.4 after putting my T41's back together.
Both versions have a 33-45MHz oscillation at the higher bands. I
have pretty low isolation PA Out to PA In at those frequencies on the
12-6 meter bands. I am thinking that I must have a hardware issue
since I am not getting the isolation numbers that Oliver posted. I'm
going to set this aside for a while.
dave, n3ds
Links:
------
[1] /g/SoftwareControlledHamRadio/message/33281
[2] /mt/111852470/243852
[3] /g/SoftwareControlledHamRadio/post
[4] /g/SoftwareControlledHamRadio/editsub/243852
[5]
/g/SoftwareControlledHamRadio/leave/10484476/243852/1943518115/xyzzy

Today, I checked v50.2 and v66.4 after putting my T41's back together.
Both versions have a 33-45MHz oscillation at the higher bands. I
have pretty low isolation PA Out to PA In at those frequencies on the
12-6 meter bands. I am thinking that I must have a hardware issue
since I am not getting the isolation numbers that Oliver posted. I'm
going to set this aside for a while.
dave, n3ds
Links:
------
[1] /g/SoftwareControlledHamRadio/message/33281
[2] /mt/111852470/243852
[3] /g/SoftwareControlledHamRadio/post
[4] /g/SoftwareControlledHamRadio/editsub/243852
[5]
/g/SoftwareControlledHamRadio/leave/10484476/243852/1943518115/xyzzy

On Mar 28, 2025, at 4:36?PM, Steve Umans via groups.io <umans@...> wrote:

?

I completed my RF board last fall based upon the BOM "T41_RF_Board_BOM_V012.6_02-25-24.xlsx".? My RF board seems

to work OK although "how well" is still a question.? I have not followed properly the various messages about possible/suggested

changes to the RF board and I am wondering if there is a single location where one can find a complete summary of

the "latest and greatest" upgrades/modifications since the February 25, 2024 bill of materials was issued.

?

Thanks,

Steve

K8ZBE

On Mar 20, 2025, at 5:33?AM, Albert Peter via groups.io <albertfpeter@...> wrote:

?

Bill,

My system is working and without freeze-ups, but I will try out your board.

Al

On Mar 27, 2025, at 11:58?AM, D Solt via groups.io <davesolt@...> wrote:

?

I've continued looking at isolation as it relates to a PA oscillation at ~33MHz on the higher bands when the PTT is engaged.? Below is the first page of my attached report.? I have time to test any ideas to improve isolation.

Ignore my previous report of 3-24-25.? I had a blown RF switch.
I have had an oscillation at ~35MHz in the K9HZ 20-watt power amp in my T41 V12 (SW ver 66.4) when I press PTT in the higher bands.? It appears to be caused by low isolation between the PA Output, J8 and PA Input, J7, on the LPF-Control board.? Below are several plots from my NanoVNA showing the isolation at 28MHz and 50MHz.? On my two systems, the feedback oscillations only occur above 22MHz.
Some of my initial testing was with the BPF and LPF out of the circuit.? Whether or not they are in the circuit did not affect isolation much.? They are in the circuit in all of the attached plots
The plots below show the isolation at 28MHz and 50MHz and with version 50.2 and with version 66.4.? Results are the same in CW or SSB.? Results are the same in version 50.2 and 66.4.

Conclusions:
? RX_SEL_BPF does not switch state between transmit and receive in SSB in version 66.4 when PTT is engaged.? RX_SEL_BPF switches state in version 50.2.? TX_SEL_BPF in both versions changes state in CW with key down.

? RX_SEL_BPF not changing state doesn’t seem to affect isolation.

? Results are the same in version 50.2 and 66.4 of the software. ?

? Any suggestions on what to do to improve isolation are welcome

On Wed, Mar 26, 2025 at 6:46?AM Oliver KI3P via <oliver=[email protected]> wrote:

Thanks Dave! Do you mean that RX_BPF_SEL does not change state?

Can you point me to the source of the 66.4 code you're running? I want to try to figure out why this is the case.

On Tuesday, March 25th, 2025 at 9:48 AM, D Solt via <davesolt=[email protected]> wrote:

In ver 50.0 in SSB and CW modes, TX_BPF_SEL and TR_BPF_SEL both switch states when PTT or Key engaged

In ver 66.4 in CW mode, TX_BPF_SEL and TR_BPF_SEL both switch states when Key engaged. In SSB mode, only TX_BPF_SEL switches state.

I am going to sweep the RX and TX paths to try to find blown MASWSS0179's

dave, n3ds

On Tue, Mar 25, 2025 at 6:44?AM Oliver KI3P via <oliver=[email protected]> wrote:

By comparing your final plot (Isolation PA Out to PA In, LPF Cntl SN1, 25 MHz SSB, ver 50.0) to the plot of the same configuration with oscillating software loaded (Isolation PA Out to PA In, LPF Cntl SN1, 25 MHz SSB, ver 66.4), we see that the isolation is different between these two versions even though they have nominally identical configurations. Are you able to probe the control signals on the LPF board to see how they might differ?

I did notice that the Ver 66.4 CW isolation (which does not oscillate, IIRC) is identical to the Ver 50.0 SSB isolation (which also does not oscillate). So that is the configuration we should be seeking to replicate.

Regardless, the isolation is a lot worse than it should be, regardless of the configuration. Something is not right. We should expect about 48 dB of isolation from the MASWSS0179 switch alone:

<image.png>

This makes it seem like the TR switch is not working -- we should measure the TR switch performance on its own outside of the control board circuit.

On Monday, March 24th, 2025 at 3:55 PM, D Solt via <davesolt=[email protected]> wrote:

I ran some isolation tests today. Below is the first page of my report (attached).

I have had an oscillation at ~35MHz in the K9HZ 20-watt power amp in my T41 V12 (SW ver 66.4) when I press PTT in the higher bands. It appears to be caused by low isolation between the PA Output, J8 and PA Input, J7, on the LPF-Control board. Below are several plots from my NanoVNA showing the isolation between 21MHz and 25MHz. On my two systems, the feedback oscillations only occur above 22MHz.

The first plot shows the isolation with C18 removed from the PCB. This capacitor is the path between the transmit and receive RF switching circuits on the LPF-Control board. So is C7, but I didn’t bother removing that. Isolation is better than 65dB with C18 removed.

The next two plots show the isolation at 25MHz in the CW mode (key down) and SSB mode (PTT) engaged. Isolation is in the 35dB range. Additionally, the poor return loss in the SSB mode indicates that the LPF is not being connected properly.

The next plot shows isolation at 50MHz in SSB mode with PTT engaged. This is so bad (<25dB) that I must have a bad RF switch.

The final two plots are done with version 50.0 at 21 and 25MHz. Performance in CW and SSB is identical.

Conclusions:

· I may have a hardware problem or a test equipment problem. Could someone else duplicate this test?

· There is a software change in how CW and SSB are controlled between version 50.0 and 66.4, but that bug doesn’t seem to affect isolation.

On Sun, Mar 23, 2025 at 7:36?AM Oliver KI3P via <oliver=[email protected]> wrote:

I found that the 25 MHz and 30 MHz bands oscillate, but the lower bands don't, matching what others have found.

To figure out why I measured the insertion loss from the output of the PA to the input of the PA. i.e., I connect port 0 of my NanoVNA to J8, and port 1 to J7. What this measures is the magnitude of the feedback loop.

<inline.0.part>

What I found is that this is a lot higher than it should be, particularly at the higher bands.

| 7 MHz | 14 MHz | 21 MHz | 24 MHz | 28 MHz |
|-------|--------|--------|--------|--------|
|<-80dB | -63 dB | -53 dB | -48 dB | -47 dB |

I would expect roughly 40dB of insertion loss each through the T/R switch and the BPF selection switch U8. Clearly, I'm not getting that. It seems that the feedback amplitude is getting high enough at the higher bands to cause oscillations. What I would like to do next is:

1) Repeat this measurement for a known-good version of the code as identified by Jerry. Is this feedback path amplitude different?

2) Find the reason for the change in the feedback amplitude path by examining the LPF control signals between known-good and known-bad code.

Unfortunately, I am tied up for the week and won't be able to do this until next weekend.

<20250327 Isolation on the LPF-Cntl Board.pdf>

It would be interesting to know what consumer devices like smartphones and tablets are using.

?

--

73 Greg KF5N

On Mar 27, 2025, at 8:47?AM, John V Lundberg via groups.io <johnvlundberg@...> wrote:

?Great! I was hoping someone else would try it as a check on what I did.

On 3/27/2025 6:18 AM, Oliver KI3P via groups.io wrote:

Thank you for sharing your work John! That is a quick and easy method for finding EMI sources -- I think I'll try to do the same with my radio.

On Wednesday, March 26th, 2025 at 9:00 AM, John V Lundberg via groups.io <johnvlundberg@...> wrote:

Hello, I discovered this project last Fall and this reflector even more

recently. I have been reading the discussions about "Display Noise'

and"SPI issues" with much interest and since my experience is a bit

different I will share it here.

I have built a V12 radio with RF, Main, and Front panel boards in an

AI6YM chassis, using STDVer050.2 software.

I originally built the radio with a TFTM070A3-5 v4.0 (7") display and

immediately noticed significant amounts of noise not normally heard from

a radio with the antenna disconnected. This noise was below the level of

the noise coming from my antenna on bands up through 15M, but above that

the radio's internal noise was higher than antenna noise.

I made a simple probe from a piece of coax by removing 1 " of the shield

from the end, connected the other end to my spectrum analyzer, and

probed around the inside of my T41. I discovered what I believe to be a

smps in the upper right corner of the rear of the display running at

about 1.15 MHz. This smps exists in both the 5" and 7" displays. The 6th

harmonic of this can be heard at the bottom of 40M and the 12th harmonic

at the bottom of 20M; neither can be heard with my antenna connected but

are very noticeable with the antenna disconnected.

I discovered very high levels of EMI radiated from the middle area of

the circuit card on the back of the display. The spectrum of this EMI

starts in the HF band, peaks around 160 MHz and has very significant

strength in the 6M and 2M bands. I then noted that the layout of the

boards in my chassis places the receive input circuitry about 2" from

both the smps and the display EMI source. Not good!

I then clamped my coax to the chassis such that the 1" "probe" was right

next to the receive RF input circuitry. I then made a simple

shield/cover for the 7" display. In doing so, I discovered a few issues

with the displays. First, the pads around the four mounting holes are

not connected to the circuit ground, nor are they even connected to each

other. On the 7" display, the four oblong, exposed, pads across the top

are connected to the circuit ground, but the four across the bottom of

the board are not, nor are they connected to each other. When I then

measured the noise from the probe with and without the shield in place

on the 7" display there was some improvement, most noticeably on the

smps noise, but the noise on the upper HF bands was still higher than

the noise from the antenna.

I then looked at the 5" display. All four of its exposed, oblong, pads

are connected to ground. I soldered small clips (from a Harmon EMI kit)

to each of those four pads and made a shield to fit in those clips (see

attached picture). I had to run a short wire from each clip to the

closest mounting post to tie the shield to the chassis. This provided a

very significant reduction in the level of noise present at the receive

input circuitry.

To quantify the improvement, I measured the radio's sensitivity on each

band and converted that to a receive noise figure. That can be compared

to the level of noise that I measure from my antenna. This data is shown

and graphed in the attached Excel file. The T41 receiver is very quiet

now up through 10M. 6M is much improved, but further improvement is

desired. Perhaps the cable..., perhaps moving the RF board away....

73,

John W2TX

Thank you for sharing your work John! That is a quick and easy method for finding EMI sources -- I think I'll try to do the same with my radio.




On Wednesday, March 26th, 2025 at 9:00 AM, John V Lundberg via groups.io <johnvlundberg@...> wrote:

Hello, I discovered this project last Fall and this reflector even more
recently. I have been reading the discussions about "Display Noise'
and"SPI issues" with much interest and since my experience is a bit
different I will share it here.

I have built a V12 radio with RF, Main, and Front panel boards in an
AI6YM chassis, using STDVer050.2 software.

I originally built the radio with a TFTM070A3-5 v4.0 (7") display and
immediately noticed significant amounts of noise not normally heard from
a radio with the antenna disconnected. This noise was below the level of
the noise coming from my antenna on bands up through 15M, but above that
the radio's internal noise was higher than antenna noise.

I made a simple probe from a piece of coax by removing 1 " of the shield
from the end, connected the other end to my spectrum analyzer, and
probed around the inside of my T41. I discovered what I believe to be a
smps in the upper right corner of the rear of the display running at
about 1.15 MHz. This smps exists in both the 5" and 7" displays. The 6th
harmonic of this can be heard at the bottom of 40M and the 12th harmonic
at the bottom of 20M; neither can be heard with my antenna connected but
are very noticeable with the antenna disconnected.

I discovered very high levels of EMI radiated from the middle area of
the circuit card on the back of the display. The spectrum of this EMI
starts in the HF band, peaks around 160 MHz and has very significant
strength in the 6M and 2M bands. I then noted that the layout of the
boards in my chassis places the receive input circuitry about 2" from
both the smps and the display EMI source. Not good!

I then clamped my coax to the chassis such that the 1" "probe" was right
next to the receive RF input circuitry. I then made a simple
shield/cover for the 7" display. In doing so, I discovered a few issues
with the displays. First, the pads around the four mounting holes are
not connected to the circuit ground, nor are they even connected to each
other. On the 7" display, the four oblong, exposed, pads across the top
are connected to the circuit ground, but the four across the bottom of
the board are not, nor are they connected to each other. When I then
measured the noise from the probe with and without the shield in place
on the 7" display there was some improvement, most noticeably on the
smps noise, but the noise on the upper HF bands was still higher than
the noise from the antenna.

I then looked at the 5" display. All four of its exposed, oblong, pads
are connected to ground. I soldered small clips (from a Harmon EMI kit)
to each of those four pads and made a shield to fit in those clips (see
attached picture). I had to run a short wire from each clip to the
closest mounting post to tie the shield to the chassis. This provided a
very significant reduction in the level of noise present at the receive
input circuitry.

To quantify the improvement, I measured the radio's sensitivity on each
band and converted that to a receive noise figure. That can be compared
to the level of noise that I measure from my antenna. This data is shown
and graphed in the attached Excel file. The T41 receiver is very quiet
now up through 10M. 6M is much improved, but further improvement is
desired. Perhaps the cable..., perhaps moving the RF board away....

73,

John W2TX

On Mar 25, 2025, at 5:51?PM, Robert Luken W3RDL via groups.io <now.w3rdl@...> wrote:

?

Bill, I don't have any oscillations, but then I don't have a LPF or PA built yet. I lost over a week trying to get back to where I could compile a running version.?

I attached the spectrum of the 10m & 6m outputs from the RF board. The output on 6m is down significantly.

On 3/24/2025 12:08 AM, K9HZ via groups.io wrote:

Any oscillations on 10M or 6M?

?

?

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 Robert Luken W3RDL via groups.io
Sent: Sunday, March 23, 2025 10:51 PM
To: [email protected]
Subject: [SoftwareControlledHamRadio] SDTVer66.9 results

?

After totally scrubbing and rebuilding the IDE and libraries, I can compile and run everything again. However Ver66.4 and 66.9 only run at 600MHz if TCXO is defined. They both freeze if compiled with 528MHz.

The Receive I&Q Cal worked quite well, except the button assignments don't agree with the directions.

Compiled with: Faster with LTO, 600 MHz, Dual Serial

SDTVer66.4
Memory Usage on Teensy 4.1:
? FLASH: code:308228, data:132408, headers:8892?? free for files:7676936
?? RAM1: variables:194528, code:284488, padding:10424?? free for local variables:34848
?? RAM2: variables:483744? free for malloc/new:40544

SDTVer66.9
Memory Usage on Teensy 4.1:
? FLASH: code:312196, data:132408, headers:9020?? free for files:7672840
?? RAM1: variables:194784, code:288584, padding:6328?? free for local variables:34592
?? RAM2: variables:483744? free for malloc/new:40544

--

73

<image001.gif>

Bob W3RDL

?

Virus-free.

--

73

<73cw.gif>

Bob W3RDL

<10M CW M2.png>

<6M CW M2.png>

On Mar 26, 2025, at 12:15?PM, John V Lundberg via groups.io <johnvlundberg@...> wrote:

?

I am interested in getting a 3.3 V board to see if it will further improve the receive noise on 6M by reducing radiation from the cable between the Main and Display boards. I have an AI6YM chassis with V12 Main, RF, and Front Panel boards. I use a 5" display in a shielded enclosure which greatly improved the RX noise floor on 80M through 10M (see the attachment).

John W2TX

<T41_NF.xlsx>

On Mar 26, 2025, at 12:15?PM, Tom Schulte via groups.io <tomschulte9@...> wrote:

?

Bill.?

? ?
Would like 4 encoder boards. Let me know cost and will pay through pay pal.

?

?

Tom?
AB9EK

Hello, I discovered this project last Fall and this reflector even more
recently. I have been reading the discussions about "Display Noise'
and"SPI issues" with much interest and since my experience is a bit
different I will share it here.

I have built a V12 radio with RF, Main, and Front panel boards in an
AI6YM chassis, using STDVer050.2 software.

I originally built the radio with a TFTM070A3-5 v4.0 (7") display and
immediately noticed significant amounts of noise not normally heard from
a radio with the antenna disconnected. This noise was below the level of
the noise coming from my antenna on bands up through 15M, but above that
the radio's internal noise was higher than antenna noise.

I made a simple probe from a piece of coax by removing 1 " of the shield
from the end, connected the other end to my spectrum analyzer, and
probed around the inside of my T41. I discovered what I believe to be a
smps in the upper right corner of the rear of the display running at
about 1.15 MHz. This smps exists in both the 5" and 7" displays. The 6th
harmonic of this can be heard at the bottom of 40M and the 12th harmonic
at the bottom of 20M; neither can be heard with my antenna connected but
are very noticeable with the antenna disconnected.

I discovered very high levels of EMI radiated from the middle area of
the circuit card on the back of the display. The spectrum of this EMI
starts in the HF band, peaks around 160 MHz and has very significant
strength in the 6M and 2M bands. I then noted that the layout of the
boards in my chassis places the receive input circuitry about 2" from
both the smps and the display EMI source. Not good!

I then clamped my coax to the chassis such that the 1" "probe" was right
next to the receive RF input circuitry. I then made a simple
shield/cover for the 7" display. In doing so, I discovered a few issues
with the displays. First, the pads around the four mounting holes are
not connected to the circuit ground, nor are they even connected to each
other. On the 7" display, the four oblong, exposed, pads across the top
are connected to the circuit ground, but the four across the bottom of
the board are not, nor are they connected to each other. When I then
measured the noise from the probe with and without the shield in place
on the 7" display there was some improvement, most noticeably on the
smps noise, but the noise on the upper HF bands was still higher than
the noise from the antenna.

I then looked at the 5" display. All four of its exposed, oblong, pads
are connected to ground. I soldered small clips (from a Harmon EMI kit)
to each of those four pads and made a shield to fit in those clips (see
attached picture). I had to run a short wire from each clip to the
closest mounting post to tie the shield to the chassis. This provided a
very significant reduction in the level of noise present at the receive
input circuitry.

To quantify the improvement, I measured the radio's sensitivity on each
band and converted that to a receive noise figure. That can be compared
to the level of noise that I measure from my antenna. This data is shown
and graphed in the attached Excel file. The T41 receiver is very quiet
now up through 10M. 6M is much improved, but further improvement is
desired. Perhaps the cable..., perhaps moving the RF board away....

73,

John W2TX