Saturday, 9 November 2019

Virtual Audio Cable (VAC) by Eugene Muzychenko [Review]

Virtual Audio Cable Control Panel

Having a good Virtual Audio Cable program is indispensable in the ham radio shack. Especially if you own SDR receivers like SDRplay or any RTL-SDR based dongles, one time or another you will need to pipe the audio from the SDR software into another software. For example, you may need to pipe FT-8 signals into WSJT-X decoding software, stream IQ output signal from SDR software into CW skimmer program for reverse beacon network spotting. Perhaps, you would like to output ACARS signal into an ACARS decoder or set up an APRS iGate station with a sound card based APRS decoder.

If you have a decent condenser microphone attached to a computer, you could also set up a software based mixer and equalizer and pipe the audio into a ham radio transceiver.

There are many Virtual Audio Cable software on the Internet, albeit all with the same name to lure customers into their own product. Beware of fake websites providing paid VAC software for free, there's no free lunch out there. You may be unwittingly introducing malwares into your computer.

Having used several virtual audio cable software, I came into conclusion a few points a good vac software should have.

1. Being able to add as many virtual cable as you need
2. Supports a wide range of audio sampling rate
3. Supports the maximum sampling rate your application requires
4. Low latency
5. Easy to use

The virtual audio cable software by Eugene Muzychenko is my choice for all my virtual audio routing application. It is easy to create additional cables just by selecting the number of cables needed and pressing the set button. The additional cables will be installed automatically and appears in Windows sound setting. It also supports 48kHz of audio sampling rate so I could achieve full 192kHz bandwidth from SDRuno IQ output. Overall, the software is simple to use so I could allocate precious time for the project in hand. Trust me, having to fiddle with supporting software while halting the main project is not only time consuming but ruins the fun when it doesn't work at all. No one likes show stoppers.

You may visit the software main website here.
The trial version can be downloaded here.
If you are interested in purchasing the software, go here.

For a small fee, the software is definitely worthwhile. Some paid virtual audio cable software support up to 4 cables only while Eugene's vac supports more than that with a click of a button! If you do not need any support from the software author, you could even get the software at a bargain price.

Have you seen SDRPlay Multiband WSJT-X Skimmer + VAC [Eugene Muzychenko]?

Sunday, 20 October 2019

SDRPlay Multiband WSJT-X Skimmer + VAC [Eugene Muzychenko]

SDRuno with Multiple VRX Enabled

WSJT-X Multiple Instances FT-8 Decoding

The procedure to operate a multiband FT-8 skimmer with a SDRPlay receiver is complex but not difficult. Firstly, it involves setting the Sample Rate so that SDRuno covers the intended monitoring bands. Secondly, we will create multiple 'Virtual Receivers' (VRX). Next we will setup WSJT-X so that it could run multiple instances. Last but not least, we will need to pipe the audio output from SDRuno to WSJT-X using multiple virtual audio cables. The recommended software to accomplish this is Virtual Audio Cable by Eugene Muzychenko. I recommend this software due to its ease of use and supports up to 256 Virtual Cables! More than what you need for this application. It is not free and I am using the trial version right now but will consider purchasing the full-featured version soon. Apart from WSJT-X multiband skimming, CW skimming is also possible with CW Skimmer if you have enough computing power to spare. Enabling multiple VRX will require significant amount of CPU resources. Running multiple decoding softwares will also demand CPU power based on the number of instances running simultaneously. For reference, my Intel Core i3-6006U CPU @ 2.00 GHz maxed out at two VRX (9.0MHz Sample Rate) and two instances of WSJT-X with some breadcrumbs left for minor computing tasks.

Let's get into business.

SDRuno Multiple VRX Setup

The folks from SDRplay has written an excellent tutorial on setting up SDRuno for monitoring multiple bands. Please use their reference for the best information available. I will only provide a summarised outline herewith.

Deciding Band Coverage and Sample Rate

The RSPduo has a sample rate of up to 10MHz in Zero IF (ZIF), single tuner mode. Low IF (LIF) only has a maximum bandwidth of 2MHz and is not usable for this application. Okay, now let's decide what sample rate to use.

Popular DXing band is 40m - 20m band. (7.0MHz - 14.3MHz)
The span is 7.3MHz, the closest available option is 8MHz
Local Oscillator shall be locked at mid span, that is 10.6MHz.

Another example for understanding.
Band Coverage, 80m - 40m. (3.5MHz - 7.2MHz)
The span is 3.7MHz, the closest available option is 4MHz
Local Oscillator shall be locked at mid span, that is 5.4MHz.

When possible, avoid having the LO falling inside the amateur band. Modulation might be affected if there is no separation between VFO and LO due to cancelling algorithm applied. Explanation available here.

Once you grasp the concept, go ahead and set that SR and LO lock. Pay attention to the 'fall off' zone at the beginning and end of the spectrum. If any part of your intended spectrum is inside or beyond the fall off zone, increase sample rate by a notch.

80m - 20m coverage is not possible as it would have exceeded the 10MHz maximum sample rate. The more powerful redpitaya from StemLab would work for that application. (40MHz bandwidth!)

Adding Multiple VRX

Now create additional VRX. For 40m, 30m and 20m coverage you would probably need 3 of them in total. For FT-8 skimming, the main spectrum window (SP1) of subsequent VRX is not necessary. The main SP1 would suffice. The AUX spectrum window (SP2) would be useful though. Create a new workspace. Then press 'CTRL+W' to save this arrangement to your workspace list. Rename your new workspace.

AUX Spectrum Window (SP2) Showing FT-8 Signals in 3000Hz Bandwidth

Setting Up WSJT-X for Multiple Instances

Moving forward, the steps are getting easier. First, make a copy (or multiple copies) of the WSJT-X shortcut icon. Next, right click on the icon(s) and select properties. Edit the target line as follows:

Multiple Shortcuts

Default target line: C:\WSJT\wsjtx\bin\wsjtx.exe
Modified target line: C:\WSJT\wsjtx\bin\wsjtx.exe --rig-name=20m

Target line may differ according to your installation location.
Just add --rig-name=[text here] behind the target line.
Rename the copied shortcut(s) accordingly.

Additional Steps in WSJT-X

1. Set Callsign & Grid
2. Enable Reporting
3. Choose Audio Input Source (next step)
4. Adjust the waterfall
5. Manually set the band and decoding mode

[Waterfall Settings Guide]
Bins/Pixel - Make sure you have 3000Hz viewable bandwidth
N Avg - Waterfall scroll speed
Spec - Spectrum size. Not really useful, set to smaller scale.

Piping SDRuno Audio Output to WSJT-X

Now let the magic begin! The most important link between SDRuno and WSJT-X is the Virtual Audio Cables. Since we are skimming multiple bands, we would certainly need more than one VAC. My choice of software for this important task is 'Virtual Audio Cable' by Eugene Muzychenko. I prefer this over VB-Cable for its ease of use and flexibility. The virtual audio cable control panel allows you to change the number of virtual cables, modify cable settings and monitor signal levels all at once. That explains its ease of use and flexibility.

Creating additional cable is simple, first make sure the program is started in administrator mode. Choose the number of cables that you desire, click set and that's it. Simple, isn't it? Of course, there are more advanced settings which are useful for other applications such as IQ steaming (audio stream bandwidth). The maximum sample rate is 192kHz! That's needed for maximum IQ streaming bandwidth. Beware, some virtual cable does not support up to 192kHz.

Additional Virtual Audio Cables Setting

Virtual Audio Cable Control Panel

If the steps are done correctly, additional virtual audio cables will appear in Windows sound settings. I suggest making a short note which cable belongs to which VRX and WSJT-X instance pair. Example:

Line 1 (Virtual Audio Cable) - 40m
Line 2 (Virtual Audio Cable) - 30m
Line 3 (Virtual Audio Cable) - 20m

Almost done! Next, we need to configure the sound output (SDRuno) and sound input (WSJT-X) settings accordingly. This will channel the correct VRX audio to WSJT-X. Pay attention to the VRX frequency and the WSJT-X band selection.

Sound Output Settings in SDRuno

Sound Input Settings in WSJT-X

For optimal decoding in WSJT-X, adjust the volume in SDRuno VRX panel so that the green level bar in WSJT-X floats in the middle of the scale.

Volume Adjustment for Optimal Decoding

That's it, you're done! The audio from SDRuno should be piped to WSJT-X by now if you have followed the steps correctly. Repeat the steps for subsequent VRX and WSJT-X pairs. Remember to double check the VRX frequency and band selection in WSJT-X, otherwise you would be spotting on the wrong band!

The procedure above remains the same for channeling audio from SDRuno to CW Skimming software. I may cover that in another post.

SDRplay Multiband WSJT-X Skimmer (Real Life Images)

Dual Monitor Setup for Easy Monitoring

Core i3 2.00GHz CPU Load with 2 VRX Enabled & 2 WSJT-X Instances

Core i3 2.00GHz Maxing Out with 3 VRX Enabled (WSJT-X Unstable)

SDRplay [RSPduo] SDR Receiver with MLA-30 Active Receiving Loop


Software Source

Saturday, 31 August 2019

RSPduo + Diamond HF-40FX : WSJT-X

Diamond HF-40FX : 40m Monoband Mobile Whip [Magnetic Base]

I was curious how would an electrically short mobile whip for the 40m band performed on receive. Will it be picking up signals only from the Asia region or further than that? I left the antenna out for 3 nights and collected some data with WSJT-X. I piped the audio from SDRuno to WSJT-X with a virtual audio cable. I will touch more on the RSPduo next time. Initially, I thought this little black box was nothing but a toy receiver. I was left dumbfounded after fiddling with it for awhile now. It could possibly match other high performance receivers in my opinion.

SDRuno : Spectrum Display of the 40m Band

The Diamond HF-40FX is a narrow bandwidth antenna. This could be seen on the waterfall above. The shades are darker from 7.10MHz and above. I adjusted the whip for the lower portion of 40m band. Adjusting for good workable SWR is easy. The only adjustable part is the length of the antenna whip. I did note a change in SWR whenever I relocate the antenna to a different place. Ground condition and adjacent objects played an important factor. For reference, I could get perfect SWR just by adjusting the whip length. Otherwise, you will need to improve the ground beneath the antenna. It is recommended to use an antenna base with electrical continuity to whatever metal object it is mounted on. Attaching radials will also improve the antenna transmit performance.

WSPR Receive : 27th August 2019, Night Time

On the first night, I used WSPR mode. Furthest heard was a transmitter from South Africa. Subsequent nights, I switched to FT-8 mode and results were fantastic. Spots from EU were packed. Japan, Indonesia and the Asian region, returned high density spots. Scattered spots from west coast of the USA, South Africa, and Australia. However, I would not say 'if you can hear them, you can work them' for this particular antenna. Transmitting efficiency is still questionable for a small antenna like this. I had no trouble working one hop DX within Asia on a good day using FT-8 with this antenna. Signal reports returned from Indonesia and Japan were usually good on FT-8. I made some SSB phone contacts from West Malaysia, fabulous signals.

FT-8 Spotting : 28th August 2019, Night Time

FT-8 Spotting : 29th August 2019, Night Time
For apartment dwellers, this could certainly work out as an excellent apartment antenna or balcony antenna. A poor antenna is better than a non-existent antenna. You can always use FT-8 mode to overcome the shortcomings of living in an antenna restricted environment. When propagation is available, SSB and CW contacts will be possible when you least expect it. 

Sunday, 25 August 2019

9M2LMF : Weekend Trip to Kuala Lumpur

Last Friday night when the plane's landing gear touched down on the tarmac at KLIA2, I was contemplating between playing with the radio or calling it a day. My body was fatigued from a long day at work and travelling. When I reached home, I decided to setup the antenna for 40m and made a few calls using CW. I have left some of my radio equipment in Kuala Lumpur so I do not need to bring them back and forth Singapore. Air travel security screenings at the airport can be difficult sometimes.

After several calls, I checked the reverse beacon network. Not even 9V1RM's skimmer picked me up. There wasn't much station heard by 9V1RM to start with. I went to my bedroom to grab the SignaLink so I could work FT-8. Made a handful of exchange with Indonesia and some Japanese stations. Occasionally I made a few CW calls but to no avail. Perhaps the CW ops are sleeping or majority of hams decided to hang out at the FT-8 segment. I went to bed at around 2 hours past midnight when the Indonesian's signal became weaker. I couldn't work any of the Euro stations.

I woke up rather early the next morning and set the antenna for 20m band. Again, no replies on CW and hence I turned to FT-8. Made a handful of contacts within the Asia region. It was still early for any considerable DX to happen. I reckon the band would get lively around 3pm local time onwards but I do not have the entire day to spend on radio. Well, I wish I could but there were errands to be done. After all, that was the reason I'm back in KL. I had to catch up with family and friends.

Before I tore down the station, I reconfigure the antenna to a J-pole configuration for 2m band. The main element was about 1 meter long. The shorter element was a telescopic whip that isn't extended. First you tune the long section to resonate at the intended frequency, then if SWR is not satisfactory you can adjust the short section to fine tune the SWR. I always get a near perfect SWR with this configuration. Made some new friends through Marts national linked repeaters. I used the repeater on Ulu Kali. I could even hear one station on the repeater's reverse frequency. He's from Semenyih, situated about 20km away from my location. His incoming signal was literally off the scale on my S-meter, perhaps he was transmitting on medium power or he has a really good antenna system. Nevertheless with the FT-818ND, I was delighted to be able to jump from HF to VHF swiftly. Albeit, 5W output was the limiting factor. Not too bad if you have good repeaters within reach.

JPC-7 Multiband Dipole

If you ask me to choose between the Elecraft KX-2 and Yaesu FT-818, I'd say this to you. There's always the best tool for every circumstances. The right tool, for the right job. The razor blade is sharp but can't cut a tree; the axe is strong but can't cut the hair. Ultimately, you should understand what is best for your circumstances. If I had a Yaesu FT-891, I'd use that in this case. I could stand a better chance being heard with 100W of transmitting power. Power supply is not an issue as the mains supply is within reach. Its portability is advantageous for me too as I travel frequently. One thing I'd like to note about the FT-891 is the detachable front panel. This feature is excellent when passing through security screenings. When the front panel and microphone is detached, it doesn't look like a radio at all when being scanned through the X-ray machines. I would keep the front panel in a separate place.

J-Pole Configuration for VHF

Sunday, 11 August 2019

Learn Morse Code : The Quick & Easy Way

I will be starting a series of bite-sized lessons to help beginners who have zero knowledge in Morse Code gain proficiency in the language. This series of lessons is aimed at people who wish to learn Morse code to upgrade their amateur radio license and also amateurs who do not need to sit for the code exam but aspire to be a CW operator someday.

In each series, I will first teach you the fundamentals to help you master the code in an easy yet effective manner. I will also introduce the tools and software used for each learning sessions. Then, I will formulate a practice drill to drive the codes deep down into your brain. The drills will be explained in a detailed step-by-step manner. All you have to do is set aside 30 minutes a day for practice. We will learn to recognize the characters by sound and not as patterns of dots and dashes. Throw away that imaginary reference chart in your head and decode Morse by reflex not memory.

Use every opportunity to practice. See that chalkboard at the supermarket, turn them into Morse code in your head. Seeing license plates while riding on the bus, decode them into Morse. In a boring meeting? Transform the meeting minutes into a secret Morse message silently. Write it down, type it out, say it out loud, use different methods to build that link between a morse character and an alphabet in your head. Soon, it will become reflex without you knowing it. Reflex is instantaneous! Counting the dots and dashes, translating it into an alphabet, thinking of the word, these should all be avoided as it will only slow you down. Without reflex, you will always be in an anxious state. Always worrying about the next character, worrying about making mistakes, worrying about not being able to decode. Certainly, that is the source of frustration and why many gave up learning Morse code. Ultimately, we shall learn the code by reflex and this is the objective of this part series.

Repetition and practice is the key to success. Now let's embark our journey in learning the Morse code!

Part 1: Learn Your ABCs
Part 2: Learning Numbers (In Progress)
Part 3: Practice Drills (In Progress)
Part 4: Decoding Callsign & Words (In Progress)

About the author,
Benjamin Koe is an amateur radio licensee with the callsign 9V1KB (Singapore) and 9M2LMF (Malaysia). He is an avid Morse code enthusiast ever since he found interest in ham radio. He started learning Morse code by himself in 2008 when he mistakenly thought it was a pre-requisite for a Class B amateur license. He employs systematic learning approach to learn the code in a quick and easy yet effective way. He strongly believes that practice is the key to success. Today, he stills practice the code with routine drills to gain speed and proficiency. Being able to decode on the fly is his ultimate goal.

Sunday, 28 July 2019

Pulau Ubin Field Day : IOTA Contest 2019

On the Saturday morning of 27th July 2019, we set sail to Pulau Ubin (AS-019) on a bumboat from Changi Point Ferry Terminal. Pulau Ubin is only accessible by boat and it costs S$3.00 per journey. We were required to report ourselves to the coast guard office before heading to the campsite and set up our ham radio portable station.

Bumboat to Pulau Ubin

Inverted-V Dipole (20m/40m)

PAC-12 Multiband Vertical Antenna

We erected two HF antennas for the portable station. The inverted-V dipole provides medium-range coverage primarily within the Asia region. Signals from Malaysia, Indonesia, Australia, Philippines, China, and Japan came in strong.

For long-range DX, the vertical antenna is the way to go for its low take-off angle. The PAC-12 used here is fitted with a 5.6m extended length telescopic whip. No loading coil needed from the 30m band above. Ground wires are laid on the ground surface for efficiency. Our team will switch between the two antennas as and when band condition changes throughout the day.

Portable Station Setup

YAESU FT-891 and Standby Auto Tuner

Radio check and casual DX

We tested our dipole with the 20m band configuration. Made a few calls using CW and had quite some stations coming back at us with strong signals. We even managed to make contact with Dr. Klaus in the Philippines who offered a signal report. The contacts I made on 20m:

[27.07.2019 de 9V1KB] UTC Time
JA3CJO 08:27 599
VK6WX 08:31 599
N6TI 08:32 599
JA1JXT 10:10 599
4E1A 10:12 599
JA6ARM 10:13 599

Vintage Lionel J38 Straight Key

Vibroplex Square Racer Paddle

As we begin to make CQ calls using Morse code, curious campers came by to find out what we were doing. Peter with his excellent public speaking skills gave our visitors an introduction to Ham Radio basics. Coincidentally, the gentleman was responsible for sending and receiving Morse codes while he was serving in the army. He was rather amazed by our ability to work the codes by heart. According to him, he had to rely on charts to decode while we could do it in our head or with pen and paper. We turned off the transmitter and let our visitors have a hands-on experience touching the Morse keys and they were delighted with it. They left the site with a better understanding of ham radio. It's definitely not something you do to contact aliens or talking to your deceased ancestors. As the sun begins to set down the horizon, Daniel prepares the bonfire to provide some light in the dark. The campsite has minimal lighting and you could end up in pitch black darkness if not adequately prepared.

Peter explaining Ham Radio to other campers

Daniel prepares firewood

Hao Yuan and Peter working the station

Berend diligently spreading the ground wires

Berend, from the Netherlands, reached the campsite later in the evening. At the time of writing, he has returned to the Netherlands after working in Singapore for a couple of years. His home call is PA3FAL and his Singapore callsign was 9V1AW. His 9V1 callsign has been returned to the authorities. I remember how we shook hands with each other for the second time when we came to know that we are both pure CW operators. There's an indescribable linked when I meet other CW enthusiasts amidst the vast code bashers in our hobby.

It's a darn pity I would say, that Berend did not have much field days during his tenure in Singapore. As with most flat dwellers, his base location was filled with man-made interference and he wanted to operate portable but was set back by all the restrictions we had here. I wished we met earlier so we could go to operate portable at the park often. Nevertheless, I believe he had a memorable experience camping with us on a field day before his departure!

That being said, we have lots of work to do to get the amateur radio hobby alive and kicking in Singapore. The general mindset that radio hobbyist is always up to no good has to be eliminated from its roots. On the contrary, speeding e-scooters on pedestrian paths are worse. Yet, we have riders whooshing pass us within dangerous proximity every day and we took it with a grain of salt.

Mind you that one needs to sit for an exam to be a licensed ham radio operator. The same thing one would need to do before getting behind a steering wheel or to fly a civilian airliner. One must prove competency before being allowed to own radio communication equipment.

Starting the fire before sunset

Bonfire begins

From the operating deck

Berend, 9V1AW(ex) / PA3FAL begins DXing

Yours truly on the J38 Straight Key

As night falls the IOTA Contest begins...

Working hard on CW (Morse Code)

While the team was busy contesting with the dipole, Daniel and I tuned the PAC-12 for the 30m WARC band. Generally, contesting is not advisable on the WARC bands. Supposedly, some hams seek peace on the WARC bands during contesting periods. We connected the PAC-12 to my Elecraft KX-2 and made a few calls. The transmitted signal was boosted to about 25W with a linear amplifier. Guess what? We have the USA coming back at us. The low noise floor and the KX-2's sensitivity made that QSO possible I guess. The signals were weak yet legible.

The next day..

The next morning, Hao Yuan and Roland worked as many stations as they could while Daniel prepares light meals for breakfast. The sealed lead-acid battery lasted throughout the night with a little bit more to spare on the next day. We used medium power, about 60W and below most of the time. After breakfast, we packed our stuff and cleaned the campsite before heading back to the mainland. All in all, it was an enjoyable field day. Glad to see a handful of hams dropping by to give their support. I have learnt many things that I never knew before from the other hams. Albeit, I confess I was not spending enough time behind the radio during this field day.

Alright, will be looking forward to the next one! 73's.

Time to head back to civilization

9V1KB, 9V1CL, 9V1WO, 9V1FL, 9V1AW(ex), 9V1HY, 9V1PK