Re: Oscillations on high bands
Since its a SWAG… explain why it happens with V69 of the software but not with V50. ?
Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton - J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com
email:??bill@... ?
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On Mar 25, 2025, at 9:19?AM, Greg KF5N via groups.io <greg.electricity@...> wrote:
? So that would be a reason for the isolation to degrade versus increasing frequency.
Because the module has common ground inductances on the input and output.
Just a SWAG here, it's hard to tell without having a good visualization of the hardware.
But it's a common problem with any RF thing which has an input and an output and connectors.
?
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73 Greg KF5N
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Re: Oscillations on high bands
So that would be a reason for the isolation to degrade versus increasing frequency.
Because the module has common ground inductances on the input and output.
Just a SWAG here, it's hard to tell without having a good visualization of the hardware.
But it's a common problem with any RF thing which has an input and an output and connectors.
?
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73 Greg KF5N
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Re: Oscillations on high bands
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On Mar 25, 2025, at 8:45?AM, Greg KF5N via groups.io <greg.electricity@...> wrote:
? This switch is a plug-in module?
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73 Greg KF5N
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Re: Oscillations on high bands
This switch is a plug-in module?
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73 Greg KF5N
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Re: Oscillations on high bands
It is here:
https://github.com/DRWJSCHMIDT/K9HZ/blob/main/K9HZ_LPF_Module/K9HZ_LPF_V1.00_Schematic_PDFs/K9HZ_LPF-Carrier_Relay_Board_Schematic_V1.00_07-25-24_KiCad.pdf
-------- Original Message -------- On 3/25/25 5:59 AM, Greg KF5N via groups.io wrote: Hi Oliver, where is the schematic of the TR switch?
I would like to see the circuit topology.? A few decades ago(!) I was designing TR switches and I'm curious about this one.
?
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73 Greg KF5N
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Re: Oscillations on high bands
Hi Oliver, where is the schematic of the TR switch?
I would like to see the circuit topology.? A few decades ago(!) I was designing TR switches and I'm curious about this one.
?
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73 Greg KF5N
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Re: Oscillations on high bands
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:
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 groups.io <davesolt@...> 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.
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.
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.
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Re: boards and kits and stuff
Years ago I worked for Niles Audio, and we produced a product that used plug in cards on a short bus.? The interconnect was via SPI between AVR ATmega128 and ATmega32 processors.? The bus had a buffer at the master side (mega128), the mega32 mcus on the cards were connected unbuffered.? The bus had the usual 3 SPI signals plus one? CS for each of the cards, IIRC there were a max of 4 cards on the bus.? We never had any issues with communication on the bus, I don't recall what the clock speed was, I think it was around 500khz.
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Working with the Version 66.9 T41 software.
This particular weirdness affects nobody but me....
I use four unused i/o bits to control my homebrew linear amplifier. They tell the amplifier what band the transceiver
is on.
These bits ( 28,29,30,31 ) were used in the V11 system to control its four-band LPF. There was an 80M pin, a 40M pin etc.
They are not used at all in the V12 system.
So I hooked them up to some transistor buffers and hence out to the linear.
V12 does have internal Yaesu codes in the LPF control card, but they are the wrong polarity. Instead of adding hardware
inverters, I just used those other four pins.
Now - with the V66.9 software, I am unable to write to those pins! The linear stays at its default - 6M. The reason
for that particular default is that it minimizes the risk of transmitting on the wrong band. If you use an LPF that is
too high, you run the risk of annoying the FCC. If OTOH you transmit through an LPF that's too low, you run the risk of
frying the expensive LDMOS final. I do have protection against that in the linear, but I am a "belt & suspenders" guy...
Back to the problem: I have verified that the code to write to those pins is being executed. ALSO, I wrote separate code at the top of loop() to write to them. No joy, no output.
BUT - I wrote a throwaway sketch - not a radio at all - to just write to those pins - actually an incrementing count. Yup, they work fine. And the linear cycles through its bands.
SO; Something in the code is preventing me from writing those pins. Gotta be one of two things: 1. Something else is writing to them. or 2) Something is pinMode-ing them to INPUTs.
Darned if I can find it though. There are some legacy places where those pins are written, but I'm pretty sure I found them all. It has worked on other versions, just not this one.
- Jerry, KF6VB
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Re: Oscillations on high bands
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.
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.
?
?
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.
?
?
?
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Re: boards and kits and stuff
On 2025-03-24 09:29, K9HZ wrote: Well the lesson i get from this category of devices is that mounting
the processor on the display board is preferred. But thinking about
it, all of my commercial have the processors mounted within an inch of
the processor that drives it. I guess there is some degree of
obviousness here. *** A main board bolted to the back of the display would get that cable length effectively to zero. We could use the parallel interface. Wonder if it's faster than SPI? OTOH, that would marry us to buydisplay... not sure that's where we want to go. HDMI? - Jerry, KF6VB
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Re: boards and kits and stuff
On 2025-03-24 08:39, rebruhnke via groups.io wrote: This may be sacrilegious, but I've been using the UART ports for a
long time as the comm interface between all the processors in my
radio. *** You are not alone. I recently built a little gadget for my Elecraft K2 to let it control my linear amplifier. The radio has a connector on the back for the internal "aux bus" with which all the pieces of the radio communicate. It's proprietary and undocumented. I stuck a logic analyzer on the aux bus output and discovered that it was async (aka UART ). I wrote code on a raspberry pi Pico to sniff it and figure out when the band was being changed, and to inform the linear via the 4-pin Yaesu "BCD" code. - Jerry, KF6VB
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Re: boards and kits and stuff
Well the lesson i get from this category of devices is that mounting the processor on the display board is preferred. ?But thinking about it, all of my commercial have the processors mounted within an inch of the processor that drives it. ? I guess there is some degree of obviousness here. ?
Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton - J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com
email:??bill@... ?
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On Mar 24, 2025, at 11:24?AM, Greg KF5N via groups.io <greg.electricity@...> wrote:
? It would be interesting to know what consumer devices like smartphones and tablets are using.
?
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73 Greg KF5N
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Re: boards and kits and stuff
It would be interesting to know what consumer devices like smartphones and tablets are using.
?
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73 Greg KF5N
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Re: boards and kits and stuff
This may be sacrilegious, but I've been using the UART ports for a long time as the comm interface between all the processors in my radio. You even could set it up as 485 multi-drop. I mainly use command/response type of protocol; the only information that is constantly sent is the S Meter value on a timer at about 10 times a sec. Unless tuning, then the frequency information is sent for each interrupt of the tuning knob. . I've used this concept for over 30 years in my professional career as UART has been around forever. It is inherently bi-directional with the current hardware implementation and processors have a very good interrupt system for this.? Of course, this idea won't pan out if you need to stream gobs of info. The newer implementation of the UART can go to over 1Mbaud.
?
Russ
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Re: boards and kits and stuff
I need to investigate how some of the commercial radios are doing this. ?They habe experts that have spent their entire careers on just display ops so ots good to learn from them. ?
Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton - J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com
email:??bill@... ?
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On Mar 23, 2025, at 5:25?PM, ken WA2MZE <wa2mze@...> wrote:
?I guess one could use a pico (RP2040) to drive the display via the parallel interface, and talk to the Teensy via SPI.? If much of the actual graphical processing is done on the pico, then the I2C interface might be fast enough.
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Re: boards and kits and stuff
Of course there are lots of questions, and also misunderstanding of the limitations of SPI at the PJRC forums.
SPI never had a standard, but it is considered a "de facto" standard.? It was originally intended for short physical distance communication between
ICs on a PCB.? That is probably 99% of what it is being used for today.? It can be expanded with more data lines to create a serial-parallel bus.? You can
see that being used to interface to the external memory chips.
?
When you start pushing SPI off the board or increasing the clock frequency, that is where problems can begin.? For example, with the T41 pushing the SPI
through a ribbon cable and also running the clock at the maximum possible speed.? This is territory where the SPI bus shows weakness and it is up to
the designer to work around the limitations.? This is not because SPI is bad; it is because it was not designed to do this.? So if you want to make it work,
you need to be very careful with driving long cables (shunt capacitance), PCB routing, and all of the EMI implications.? This is why SPI driver chips
exist.? Same comments apply to I2C.? If you want to push the envelope with these inter-IC busses, you will need to do something extra.
?
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73 Greg KF5N
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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@... ? ?
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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  Bob W3RDL
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K9HZ