How anybody can be bored during the man made 2020 China virus Covid-19 pandemic?
Dr. Anthony Fauci paid for Wuhan virus with "Gain-of-function". China worked to disseminate viruses over the whole world. One of my friends passed away due to Covid-19. The second friend was on the edge of minutes.
The courts will take care. There is no valid pardon for these criminals. Any employer that mandates the evil vax should be gut shot and drug down the road behind a truck.

Don't sit idle, move your butt.
Think about Common Sense book from the country founders. Due to force majeure, choose your government that works. Now.

Digital modulations are fun. With PSK31 and 10 Watts you can work the whole world. It is narrow band. It has long range communication properties as Morse code. It requires human interraction and brain. Type on keyboard. Your neighbor won't hear annoying FT8 sounds from Mars, operated by Bio-robots. FT8 is fully automated, and used by Windows25 zombies. RTTY is an optional mode to test longevity and temperature of your device in full power.

Before you start, prepare your station.
Try the audio link between computer FFT decoding program and radio speaker output. How does it work? No noise? Set your decoding program and try to read messages. The computer ventilator creates discrete audio noise spurs. You can try online SDR receiver with the program. Try also wire link from trx speaker to the computer. Watch how much interference you see.

Major problem is usually RF interference noise from computer, mouse, display backlight switcher, leaking to the antenna. The CPU, RAM memory, keyboard, power supply, and display radiate RF noise covering wide RF spectrum. Some computers cause HF interference up to 30MHz, different ones disturb 2-meter band and UHF bands (144.001MHz). By theory and practice, rectangular signal has infinite spectrum. Switched power supply works like transmitter switching 120V power. All devices should be tested for FCC certification for maximum levels of interference with different devices. Usually the imported production version has relaxed filters, to make more money. What the heck? It is simpler. Fix it by replacing FCC people - this was here multiple times. Replace technical people with lawyers. Bingo! This goes forward for decades. Fake FCC certifications. At the end, these people only harm themself. Some machines are good. Some machines are bad apples. Try it.

Try the directly-wired interface between your radio and computer. Then you can make further innovation steps and improvements.

Directly wired interface. TX path loss is about 100:1. (from ham radio resources)

The system grounds are not separated. The computer noise propagates over the grounds, via resistors, and by "air". Test with wired interface confirmed it is not usable (Toshiba). The decoding program saw only spurs and background noise.

Try to run PC machine from battery in "low power mode" without Ethernet. Wired Ethernet connection usually adds multiple "S" of noise. Somebody has it S7. If this works, you can use audio transformer interface between your computer and radio. The question - "Why to repeatedly charge batteries with 500 cycles?"

Better than wire connection is interface with audio transformers. If you see an improvement, -great. The following transformer interface made many nice PSK31 contacts to South America, Pacific, New Zealand, VK, Japan. If you still have 59+ interference, it can be "in the air". ISP providers add a lot of noise, plasma TVs, and power LED lights.

Transformer based PSK31 interface

Notes:
1) Notice the "Radio Shack" transformer ordering numbers.
2) The grounds are not fully separated.
3) The transformer has capacitive coupling for PC noise.
4) The PTT switch rarely works, or PTT state is inverted. Use foot switch.




Transformer interface for Yaesu, Icom, Elecraft, kits
MAKE it great again!   - Free, available for postage


Summary of specs

We want DC-isolated interface for 200Hz to 2800Hz range.

Use magnetic or optical interface. Feedback can improve the performance and linearity.

Microphone computer connector (3.5 mm jack)
There is no microphone standard. Two types of PC microphone connections are used.
The built-in microphone is electret, requiring about 180uA 2.5V.
Computers with USB microphone connector - return it to China.

Microphone Connections:
a) Two wire. (Ground and signal+power). 3V, 2-5 kOhm resistor.
b) Three wire. (Ground-signal-Vcc pin).
c) Try mobile phone with software.

Wall outlet interference filters
Experimenting with ground wires haven't brought any improvement to my setup. (Toshiba notebook)
The AC line filter suppresses noise from wall outlet. Typical cutoff is -3dB @5kHz. Town PLC is catastrophe. When the noise is in the "air", there is no help. Last 25 years the level of ambient noise generated mostly by China shit products in North America is amazing. Government (will pass), FCC (lawyers seated), ARRL (limited activity). Common divider is people.
Check:

AC line filters

Computer power supply

RX noise with computer ON/ OFF

RX power supply

PC power supply

Computer mouse, different monitor,

Move your PC away from the receiver. At least three feet.

Some locations are helpless with RF smog everywhere.

One guy gave up and solved the noise by trips to hills (Connecticut).

Take the stuff to an inhabited area. You will notice the difference.

Things start to work, hey !


New Plastic Case for PC Interface



John used 3D printer to print the case. Prusa 3D printer.
The second case finally fits (?) Will see.
There is the center lid and bottom battery holder.
Finally top lid arrived!
The input and output are physically and DC electrically separated.



New bidirectional interface by VA3DIW.
Works like charm.
This, we got it also right. :-)
Make your radio stuff Great Again!

Fully standalone device.
No dependency.
Cellphone Lithium batteries are under the board.
The Gerber files are available.
Will you build, or your club will build?

Performance examples:

WEFAX The mariner's weather and iceberg fax
(HF WEFAX graphic maps)






Nice DX. WEFAX 7880 kHz LSB, BW=850 Hz

Pacific ocean:
WEFAX Pt. Reyes CA, 8682 kHz USB, BW = 800 Hz. The carrier is 1.9 kHz below
WEFAX Boston MS, 9110 kHz
WEFAX Wellington New Zealand, 9459 kHz


NAVTEX text data, marine weather reports
(Readable RTTY characters, text)
There are still proprietary encrypted data in specific time slots.



Baud =50 Shift= 850Hz. RTTY 4583kHz 7646kHz 10100.8kHz
Lost anchor with chain, pipeline works, torpedo exercise, ...

Sound Card clock calibration
It is not expected to tweak your sound card crystal frequency with caps and inductors..
Every computer is different.
The crystal clock drifts with temperature, aging, and during machine warm-up. There is a better idea to measure the computer clock drift versus reliable reference and compensate the clock difference in software.
Tune to WWV on 10MHz, 15MHz, 20MHz, or use different broadcast with cesium frequency reference, strong enough. Tune RX to get the selected modulation tone e.g. 1kHz. Compensate in software in [ppm] steps up or down, till you get straight vertical line without any slant to the left, or right side. Usual difference is about (0 to +- 40)ppm. It takes a "while". Most of the computers do not need any compensation if the decoding software is well written. You can compare with any software written only for woke Win12 and Win25.. The software clock compensation feature for soundcard and calibration interface is built in MMSSTV and MMVARI je3hht' programs. !!!

Operating PSK31
"Overmodulated" signal takes 1kHz BW spectrum. The spectrum should be about 50Hz wide.
You can see the moment when TX-ALC load control kicks-in. It is overmodulated power glitch.
Some commercial transceivers have TX power glitches.

Interesting observation of commercial receiver behaviour. However, nothing new. When there is a single strong signal in the SSB RX bandwidth, the receiver AGC (automatic gain control) kicks-in and wipes-out all weak dx neighbour signals. What is it? Commercial design. You don't see the signals you want to see. It is wrong receiver architecture. The design flaw with absurd 38/73MHz first IF frequency flooded all Kenwood, Icom, Yaesu products. They want easier manufacturing. All you get is TFT display with colors. Same symptoms are seen on the online SDR receivers. Is there a cure? No Sir. Try front end attenuator, if it helps.

Well informed people. Bio-robots run FT8 program.

Now, they don't need any language, have no discussion, make no mistakes. Robots.
Pick a stray dog. Street mongrel can do FT8, FT4.


Summary
There are decoding programs for WEFAX, NAVTEX, PSK31, RTTY, MFSK, SSTV, and so on. Some programs offer chat and keyboard rug chewing, some not. Weak signal throughput via QRM and sudden phase shifts, echo, of MFSK clones is better than PSK31 (bw<= 50Hz). There are better modulation techniques than PSK31. But there are not users, and there is limited number of decoding programs. PSK31 suffers with phase shifts, echo from the short and long path propagation, and needs exact tuning.
PSK31 is good enough. PSK31 is Better than traing my dog howling with FT4.

The PSK31 upper case letters "CQ DE" message takes 3 times more bits than "cq de" lower case letters.
Upper case letters are prone to generate more errors.
Check your modulation level on remote SDR receiver, if the problem is overmodulated TX. Do not overmodulate - take care of your fellow neighbours 300Hz away. You can tweak it to a really nice signal. Weak good quality signal cuts through ionosphere much better than overmodulated signal 700 Watts.
Recent years, watch how much the phase noise goes up during contests. The devices transmit phase noise. disgusting.

Do your RX suffer from strong signals, intermodulations, and AGC?

AGC is automatic gain control for strong signals. Any linear mode modulation receiver use it. (not FM). Try the input attenuator. 8dB, 10dB, 15dB attenuator. PSK31 needs about 8dB S/N ratio. Narrow crystal filter might help. It is hardly possible to make any narrow filter on 38/70MHz etc., compared to the low frequency filter 500Hz-300Hz wide. Elecraft use 8.8xxMHz IF filters. Orion II use 9MHz IF filters. Older Yaesu use 8.2xx MHz IF filters. DSP receiver (FFT) without front end band pass filters behaves the same way, as analog receiver without any filters. IT creates intermodulations, and you hear signals artificialy created by the silicon, that are in reality not "on air". The DSP technical principles of signal processing are different, but the final results are same as analog approach. (Frequency bin to bin spectrum leakage, aliasing, intermodulations, and so on). There is same silicon FET or bipolar transistor inside the chip (analog versus DSP ADC) to process input signal levels from micro-volts to volts. Use of 40MHz IF makes filtering for manufacturer easier. The customer carry the burden. HF RX (short-wave up to 30MHz) architecture concepts with first IF of 73MHz are completely wrong. Single strong signal activates the AGC and kills sensitivity for weak signals 200Hz away. Use receivers with narrow low frequency crystal filters. The performance counts. Concepts, such as short-wave RX DSP brick without any analog blocks, without any RX front end filters, without AGC, attenuator, IF crystal filters, harmonic filters, are also wrong. Check the online SDR receivers during contest when somebody is transmitting few miles away. Anomalies? Hmm. Radios with built-in "Windows25" where you can spend the whole day setting software colors, fonts, font size, guessing what this stupid icon means, rebooting every 2 minutes, reboot when it cashes or freezes, with built-in web browsers, and performing infinite IT tasks, are useless. Way to nowhere. In terms of resilience, there is no reliability. When you see built-in CMOS battery and worn-out flash memories, it is a problem.

Hal, set it up for the weekend!

Resources:
[1] HamScope for PSK31, RTTY from Texas. Friendly UI user interface.
[2] The Sorcerer program. Wefax is semi-functional.
[3] MMTTY for RTTY. Work of JE3HHT. Great user interface, Great programming habbits.
[4] MMVARI for PSK31. Work of je3hht. Great features, great user interface, and great performance.
[5] MMSSTV for SSTV. Work of je3hht. Another great software package.
[6] Fldigi.exe from w1hkj. Crashing and buggy program. The user interface disaster. Received ARRL medal for Windows promotion. The Linux version is screwed up, as well. Security holes.
[7] Linux notebook. Avoid Win10, Win11, Win25
[8] Dell computer
[9] optocoupler with feedback
[10] LM358
[11] lithium batteries

Have fun,

MADE BY VA3DIW
DAT Consulting Cons. W6