Kendall Amateur Radio Society

KB5TX


Six Meters (50mHz), the Weak Signal World and Digital

It seems the digital world of weak signals is the fastest growing segment of our hobby.  Each month that passes sees new operating modes and new software.  The purpose of this section is to try as best we can to keep readers aware of what is happening in this segment, to show you examples, and where to find more information.

Rocks a Flying

Dave Moore, N7RF, March & April, 2018.

With yagis up now, I found time on March 18th to check out the 6 meter meteor calling frequency (50.260).  I immediately started hearing strong bursts of raspy MSK144 signal.  I started up the WSJT-X software and then logged in to the Ping Jockey web site to see what was happening (https://www.pingjockey.net/cgi-bin/pingtalk).  As it seemed pretty busy, I announced on PJ that I would be calling CQ.  Almost immediately, K8LEE came back.  The QSO exchange was rapid since the meteors were hot and heavy.  During the final "73" exchange, I saw an uncommon 4-1/2 second burst from Wayne in Indiana.  Here's the record of that burst on the 15-s long waterfall trace. Wow.

 

After that, I conducted QSO's with KE5RV (Arkansas), K2DRH (Illinois), and W5TN (Texas).  The next morning, I added WB4JWM (Georgia), and W8BYA (Indiana).

March 24th update:  Another good morning for meteors.  I called CQ and was called by two stations, one after the other, WB4JWM again (Georgia) and K0TPP (Missouri).  Several times, I saw bursts from 2 or 3 stations within the same 15-second frame.  At 1427Z, I worked AK5QR (Alabama), and then was cold-called by XE2YWH.  My first new country on meteor scatter.  Jose is 535 miles south of here in Zacatecas, Mexico.  Here's the "Roger" and "73" transmissions at 1430Z and 1431Z:

And, finally, I asked W5LDA to give it a shot via the PingJockey web site.  We connected within 3 or 4 sequences.  Big signal from Oklahoma City!  

March 31 update 

I turned on the 6m station this morning and immediately decoded a meteor CQ from XE2JS in Chihuahua (449 miles).  After calling him for several minutes, someone broke in on SSB.  It was XE2OR in Coahuila, 151 miles away, with a 59+ ground wave signal.  After that QSO, I returned to calling XE2JS, and we finally connected.  He is my second Mexico QSO on meteor scatter.  A few minutes later, I worked N0LL in Kansas (693 miles).  I switched over to 2 meters to see what I could see.  On 2m, I'm only running 60W barefoot until I get the PTT cable made up for the linear..  The first decodes I received were from XE2AT in Aguascalientes, Mexico (689 miles).  I pointed the beam south and, after 10 minutes or so, I worked him, my first 2m meteor QSO (of recent times), and my first 2m DX entity at the same time! 

American Meteor Society

Meteor Shower Calendar

Meteor activity picks up a bit during April as the Lyrids become active during the month. They are active from the 14th through the 30th, with a pronounced maximum on the 22nd. Sporadic rates during April are steady as seen from both hemispheres with southern observers enjoying twice the activity that can be seen from the mid-northern hemisphere.

During this period the moon will reach it’s full phase on Saturday March 31. At that time it will be located opposite the sun and will remain above the horizon all night long. As the week progresses the waning gibbous moon will rise later in the evening but will still hamper the more active morning hours making meteor observing difficult at best. The estimated total hourly meteor rates for evening observers this week is 2 as seen from mid-northern latitude (45N) and 4 from the southern tropics (25S). For morning observers the estimated total hourly rates should be near 5 as seen from mid-northern latitudes (45N) and 8 from the southern tropics (25S). The actual rates will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity. Rates are reduced during this period due to interfering moonlight. Note that the hourly rates listed below are estimates as viewed from dark sky sites away from urban light sources. Observers viewing from urban areas will see less activity as only the brighter meteors will be visible from such locations.

The radiant (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning March 31/April 1. These positions do not change greatly day to day so the listed coordinates may be used during this entire period. Most star atlases (available at science stores and planetariums) will provide maps with grid lines of the celestial coordinates so that you may find out exactly where these positions are located in the sky. A planisphere or computer planetarium program is also useful in showing the sky at any time of night on any date of the year. Activity from each radiant is best seen when it is positioned highest in the sky, either due north or south along the meridian, depending on your latitude. It must be remembered that meteor activity is rarely seen at the radiant position. Rather they shoot outwards from the radiant so it is best to center your field of view so that the radiant lies near the edge and not the center. Viewing there will allow you to easily trace the path of each meteor back to the radiant (if it is a shower member) or in another direction if it is a sporadic. Meteor activity is not seen from radiants that are located far below the horizon. The positions below are listed in a west to east manner in order of right ascension (celestial longitude). The positions listed first are located further west therefore are accessible earlier in the night while those listed further down the list rise later in the night.

These sources of meteoric activity are expected to be active this week.

Details of each source will continue next week when lunar interference will be much less.

SHOWER

DATE OF MAXIMUM ACTIVITY

CELESTIAL POSITION

ENTRY VELOCITY

CULMINATION

HOURLY RATE

CLASS

 

 

RA (RA in Deg.) DEC

Km/Sec

Local Daylight Saving Time

North-South

 

Anthelion (ANT)

13:36 (204) -10

30

02:00

2 – 2

II

Zeta Cygnids (ZCY)

Apr 06

20:04 (302) +40

40

09:00

<1 -< 1

IV

 

FT8 Digital Mode

Dave Moore, N7RF, March, 2018

On a separate note, I have worked quite a bit of DX on FT8.  To me, it seems a lot easier than fighting the CW and SSB pileups you hear when a rare one comes on.  It's hard to compete with the super stations with multiple towers, stacked beams on every band, and full legal limit amplifiers.  There is a distinct advantage when the DX station can pull your weak signal out of the noise and get a perfect copy in the presence of lots of other stations.  Software has now replaced the human ear.  Yeah, it almost sounds like cheating, but you can't look at it that way.  Technology keeps improving the hobby.  I bet very few of you run vacuum tube radios anymore, nor are most of your solid state rigs without modern Digital Signal Processing.  Think of it this way:  instead of aspiring to be like the muscle stations and overpower everyone on frequency, you don't need to any more.  IMHO, this opens up the door for many, many more hams to make more contacts rapidly without the mega-buck expense.  (Note by Webmaster.  Be sure to use the latest version, WSJT-X v2.0.1 or later.)

Nevertheless, as the popularity of FT8 grows, we are starting to see DX pileups.  The problem is, you can have dozens of signals spread across the 2 kHz wide FT8 channel and the software decodes and displays all of them every 15 seconds.  A DX station sees all the stations calling him but the software only lets you respond to one station at a time.  Until now.  The ARRL reported that a beta version of a new FT-8 contest mode software was tested recently.  A DX station (the Fox) can now conduct multiple QSOs simultaneously.  Fox can select the number of responses (Hound stations) he wants to deal with.  He can also call region-selective CQs.  When Fox responds, his transmission consists of multiple simultaneous signals sent to selected Hound stations, each on their own frequency.  Sounds crazy.  And it's not simple.  Users are encouraged to study the operating guide and not try to wing it (http://physics.princeton.edu/pulsar/k1jt/FT8_DXpedition_Mode.pdf ).  Contest mode will never be used in established FT8 channels, rather a specific frequency to be announced beforehand. On 20m, the FT8 channel is 14.074-14.076 MHz.   During the recent beta test of contest mode, they used 14.105 MHz.  The test results were positive.  Expect to see this used by real DXpeditions.  But get some some conventional FT8 time in before you try it.

Updates, N7RF, May 2020 – New FT4 contest mode and other useful how-to information

The above was written over two years ago.  A lot has changed.  The interest in low signal-to-noise digital has not waned at all.  FT8 seems to be the de facto go-to mode of choice now.  DX stations use it in abundance, DXpeditions use it as their main mode as they can handle a large number of QSOs in a short period of time. 

FT4 Contest Mode:  FT8 frame times are still 15 seconds long, and 5 or 6 frame are still required to complete a QSO.  Not fast enough for you?   Now we have FT4, a 4-tone MFSK modulation with a faster baud rate and is designed for contest operations.  Here is how Joe Taylor, et al, describe the new mode:

Introduction: FT4 is an experimental digital mode designed specifically for radio contesting. Like FT8, it uses fixed-length transmissions, structured messages with formats optimized for minimal QSOs, and strong forward error correction. T/R sequences are 6 seconds long, so FT4 is 2.5 × faster than FT8 and about the same speed as RTTY for radio contesting. FT4 can work with signals 10 dB weaker than needed for RTTY, while using much less bandwidth.

Basic parameters: FT4 message formats are the same as those in FT8 and encoded with the same (174,91) low-density parity check code. Transmissions last for 4.48 s, compared to 12.64 s for FT8. Modulation uses 4-tone frequency-shift keying at approximately 23.4 baud, with tones separated by the baud rate. The occupied bandwidth (that containing 99% of transmitted power) is 90 Hz. Threshold sensitivity for 50% decoding probability is S/N = –16.4 dB, measured in the standard 2500 Hz reference noise bandwidth. A priori (AP) decoding can push threshold sensitivity down to –18 dB or better.

REF: https://physics.princeton.edu/pulsar/k1jt/FT4_Protocol.pdf

Bottom line:  FT4 is 10 dB better than RTTY at the same baud rate.  By comparison, the decoding threshold for FT8 is about 4 dB better.  FT8 is better for DXing and working weaker stations, but FT4 is perfect for racking up high contest scores.

Try it out!  FT4 can be found any time of day or night, but not on every band.  Although there are nominal frequency channels suggested for FT4 (ie, they are programmed into the WSJT-X software), most of the daytime activity is found on 20m (14.080 MHz). In the evenings, 30m, 40m, and 80m become more active as the propagation changes.  Meanwhile, FT8 rules on every band, when its open, including 6m (watch for summer sporadic E propagation, 50.313 MHz), and even 2m (morning tropospheric ducting, 144.175 MHz) 

Current WSJT-X software version:  Be sure you get the latest.  Today it is Version 2.1.2.  Go to Joe Taylor’s web site to download the one for whatever computer platform you are using (for most people, it is Windows): 

https://physics.princeton.edu/pulsar/K1JT/wsjtx.html

How to Digital Ops.  I have purposely not tried to get into how to connect up a station for digital operation.  With the variety of radio types out there, the “how” is “it depends.”  But here are the basic requirements:

1.     A 2-way audio interface between radio and PC (or iMac.  Or Linux computer.  Or even a Raspberry Pi3). This can be:

a.      An analog cable pair from radio speaker/mic to the audio port of a computer (uses the internal CODEC of the computer).

b.     A third-party CODEC interface such as a SignalLink USB device (they also sell custom cables that connect up your specific radio port).

c.      Or a single USB cable interface to the later generation of radios that handle both CAT and audio.  My FTDX-3000 does this and most other new generation radios (Icom 7300, FT101, etc.).  But my older FT950 requires use of a SignalLink USB.  The newer the radio, the easier it is to make it happen.

d.     Or buy a FLEX radio.  The radio IS the computer.

2.     A CAT (Computer Aided Tuning) connection between radio and computer.  WSJT-X software can control the frequency of the radio, although this is not a hard requirement.  But it is a nicety.  A new generation of USB-serial port cables actually makes this pretty easy.  But be sure you order one that specifically says it uses an FTDI chip set, under $15 on Amazon (Other cables use a Prolific chip set, but Windows has a hard time with these - ask me how I know). 

3.     A means of executing PTT.  The best way is to do it through the CAT control.  But, again, not necessary, as most radios have a VOX mode that will key the transmitter when an audio signal presents itself.  (Webmaster note:  If SignaLink to Icom, one must use VOX.)

4.     A computer system clock that is synchronized to a time standard.  Usually this means installing free Network Time Protocol software on the computer that and “disciplines” the PC system clock.  You can check your time synch by typing time.is in a browser window and it will tell you how close you are to real time. Next time your FT8 seems to have gone south, check your time, or
better yet install a service that will sync the time when you boot up.

Having your clock more than a few tenths of a second off time can result in lost QSOs.  I use the free Meinberg NTP: https://www.meinbergglobal.com/english/sw/

Logging QSOs.  If you still insist on writing down contacts in a logbook, then maybe digital isn’t for you.  You cannot possibly keep up with all the QSOs you will make without using click-and-go logging software to expedite the process. 

What does logging software produce?  There is a standards committee that decides the proper format for digital ADIF QSO files (ADIF = Amateur Data Interchange Format).  They are found here:  https://www.adif.org/ along with the latest ADIF format description, currently version 3.1.0. 

In theory, this common file structure allows different platforms to pass information back and forth.  For example, if you are striving to obtain the various operating awards that ARRL issues, you want your resident logger to be able to send new QSO ADIFs to ARRL’s Logbook of the World (LOTW) to get credit for Worked All States, DX Century Club, etc.  Depending on how and what you are doing, make sure you always have the latest version of software.  I had some initial problems logging FT4 contacts until I installed v.2.5 of LOTW tQSL, and v.6.7.0.277 of Ham Radio Deluxe.

When a QSO completes on WSJT-X, a small logging GUI pops up on the screen.  When clicked, it saves ADIF data in a master file on your hard drive, and sends the same data to whatever logging software you told it to use.  In my case, Ham Radio Deluxe.  Here is a map showing what happens to digital logging data and the results of submitting it:

HRD Logbook is the main repository of my QSO information.  At the close of an operating session, I manually highlight all the new QSO’s of the day and send the ADIF information to LOTW, QRZ and eQSL.  There are other destinations possible too, like Club Log or HRDlog. LOTW is probably the most used logging service.  The stations you contact will be sending their data in to their favorite services too.  Each service compares your data to their data and confirms the QSO if there is a close match.  This is how you collect credits for operating awards.  eQSL is a bit different – confirmed contacts allow you to download an image of a real QSL card and print it for display in the shack.

Of course, you may not wish to collect awards, or digital QSL cards.  There is still U.S. Mail!

Hope you try out FT4 or FT8.  You will enjoy it!

 

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