| Ham Radio Ghost stories? | |
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03/02/14 |
          
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Reprinted from December 2008 issue of QST with permission from A.R.R.L.Ghost QSOs — Olivia Returns from the Noise Olivia — the magic mode written by Gary L. Robinson, WB8ROL* * * * * * * * * * * * * * *
It was a chilly foreboding fall evening when I fired up the Yaesu FT-100D, started my DM780 software (part of the Ham Radio Deluxe suite) and parked my dial frequency on 1.808 MHz. The waterfall was as empty and devoid of signals as a sunspot starved ionosphere. After listening for almost half an hour without hearing any signals, I decided to set the program up to call CQ automatically once a minute. I set my mode as Olivia 500/16 (500 Hz wide using 16 tones format) — a digital mode I had recently "discovered" and was intrigued with — and double checked the frequency to make sure it was not in use. I engaged the auto-CQ and reached for my low G Irish whistle — another favorite endeavor of mine — and commenced playing a short lively jig. I routinely play tunes when sending auto-CQs and keep the receiver audio at a low level. With one ear on the receiver, one eye on the waterfall and both hands on the whistle I multitasked merrily. I had not heard all that much Olivia digital mode in use on 160 meters (or on the other bands) so I often found that calling CQ in that mode was more effective than just listening for activity. As I was slogging my way through O’Carolan’s Concerto for the second time, whistling like a piper on fire, the auto-CQ already had finished five calls. So far I had not heard the cacophony of tones signifying an Olivia signal or noticed anything at all in the waterfall window. It was at this moment that I entered the world of the paranormal. I chanced to glance at the text box that displayed received (decoded) text and I saw characters appearing. My call letters appeared as if a ghostly presence was typing them and answering my CQ. I screeched to a halt on my whistling, immediately disabled the auto-CQ and turned up the receiver volume. With the volume all the way up, all I could discern was the usual S8 hiss and static typical of nights on 160 meters. The waterfall still did not show any signal at all — but the characters kept appearing! What was going on here? Was it time to shut the rig off and consider bed rest and rehabilitation? Was it a bad piece of meat or an uncooked portion of potato I had for dinner that was causing hallucination? Or should I attempt to answer the ghostly call?
There’s No 0 for Signal Strength Well, I am a ham first and foremost so I cautiously clicked on the transmit button and began to tap out my reply — only hesitating when I had to consider just what I should give as a signal report. I finally banged out a 519 RST (Readability, Signal Strength, Tone) report (only because there is no zero for signal strength) and sent it back to my ghostly friend to see what would happen next. Close-up of an Olivia 500/16 average format
Well, we went back and forth for several transmissions as we exchanged all the usual information and then we ended the QSO passing friendly 73 to each other. My ghostly friend appeared to be a real ham in Texas and checked out okay on the Internet Web site QRZ.com. My sanity was preserved and apparently intact (my wife doesn’t totally agree on this point), though I was still slightly confused and filled with wonderment by what had just transpired! Since that day I have had several more of what I refer to as "Ghost" QSOs using the Olivia mode and have done a little online research to reassure myself that this is not all that uncommon. For the previous three and a half years I had mostly operated on PSK31 (a digital mode using phase shift keying at 31.25 bits/sec) and a little MFSK16 (Multiple Phase Shift Keying; a digital mode using 16 tones) and yet I had never experienced this type of ghostly phenomenon with either of these excellent digital modes. Apparently Olivia is one of the few modes that can actually decode signals that are at or below the noise level. That is why I never use the squelch with this mode because it could cut off signals below the noise floor that would otherwise be decoded. The Internet resource Wikipedia.org says, "Olivia MFSK is an Amateur Radio teletype protocol developed by Pawel Jalocha, SP9VRC, in late 2003 to work in difficult (low signal-to-noise ratio plus multipath propagation) conditions on shortwave bands. A signal can still be properly copied when it is buried 10 dB below the noise floor (ie when the amplitude of the noise is slightly over three times that of the signal)." The Wikipedia entry includes several paragraphs describing the technical details of the mode. Now, I am neither a technical whiz nor an expert in any field but I found myself smitten. I don’t have a giant tower with humongous beams, run high power or even live at a great ham location, but Olivia in particular has made it possible for me to chase DX and have quality ragchews like no other mode I have ever used. It has really ignited my activity level and fun factor to heights that rival my early Novice days and later DX chasing when I did have a big tower and massive antennas.
Let Me Introduce You Olivia mode can be set to various formats that are labeled using the particular format’s bandwidth and number of tones. Bandwidths of 125, 250, 500, 1000 and 2000 Hz are typical. The number of tones can be set anywhere from 4 to 256 depending upon the propagation conditions. Different combinations of tones and bandwidths provide for slower or faster transmission rates. Commonly used formats are 125/4 (125 Hz bandwidth using 4 tones), 250/8, 500/16, 500/8, 500/16, 1000/32. The 500/8 format seems most popular at this moment, though I have had several QSOs on the 125/4 and 250/8. The 1000/32 format seems to be popular on 20 meters. Each of the Olivia formats has advantages and disadvantages. Obviously, the bandwidth differences make the more narrow formats attractive because they will fit in available open spectrum space more easily. They also will likely get through slightly better since all the power of the transmitted signal is concentrated in a smaller bandwidth — much the way CW gets through better than wide phone signals. The speed of Olivia is an issue also. Olivia is generally not as fast as PSK31 or MFSK16. Olivia 500/16 sends text at approximately 20 wpm. The 500/8 format speeds that up to nearly 30 wpm. Fewer tones results in more speed while less bandwidth results in slower speed. Olivia 1000/8 and 2000/8 are often used by Military Affiliate Radio System (MARS) traffic nets because these formats are fairly fast, accurate and get through when the MT63 mode (a digital mode using 64 tones phase shift keyed in a 1 kHz bandwidth) fails. Most of this information and more pertaining to Olivia are available at the HFLink and DXZone Web sites. 2, 3 Many hams find Olivia slower than they like and prefer to use other modes, while many others find the accuracy and ability to get through an acceptable trade off. Also, many of us, including myself, are not fast typists and actually find "slower" to be a positive attribute and allows for more comfortable overall operation. Another advantage to the mode is that it’s not quite as critical for it to be tuned exactly on frequency as it is with PSK, MFSK and many other modes. If you click on the waterfall with your mouse and the indicator doesn’t get exactly on the signal it may still decode properly. Most implementations of Olivia are set to search for signals to either side of your center frequency by a fixed percentage of your signal’s width.
Pioneers Wanted The activity level of Olivia can be described as somewhat sparse, especially compared to PSK and CW. That is partly explained by the fact that only a few programs support Olivia at this time and that Olivia has not been around quite as long as other established modes. MixW (newer versions), MultiPSK, Ham Radio Deluxe’s DM780 (latest Beta versions)4 and OliviaMFSK support Olivia operation and are available for Windows based computers, while the FLDigi program is available for Linux and Windows. All, except MixW, are available free. There are a few other things worth mentioning about Olivia. Since it does incorporate some error correcting, it is not totally a ‘real time’ mode. It is essentially a real time mode in the sense that you do not ‘connect’ to a station and it is not duplex or bulletin board (BBS) type operation. Like PSK, you go back and forth in a typical ham QSO fashion. The difference is when you click on the waterfall of a PSK signal it starts decoding very quickly. When you do the same on an Olivia signal it may take 3 to 6 seconds before it starts decoding. The opposite happens at the end of a transmission. When the station you are listening to stops transmitting — your Olivia software program will continue to decode for 3 to 6 seconds. Typically that will result in a 6 to 12 second gap when passing transmissions back and forth.
This varies depending on the format and the software implementation in the program you are using. I see less of a gap using FLDigi than with DM780 for instance. What this means is that when you click on a signal if you don’t see anything right away — be patient! It takes a few seconds. When you send it back to the other station — again, be patient. It may be a few seconds before you start to see his printout or even hear him.
The QSO is on the Calling Frequency Another aspect of Olivia operation that is slightly different from most other digital modes is a loose voluntary channelization of the frequencies used by many operators. Since it is possible to copy signals that you cannot hear or that you might not see on the waterfall, it makes sense to use specific designated frequencies for calling and meeting other stations. Otherwise, if you just tuned all over the place looking or listening for an Olivia signal you could miss a lot of stations. A few of the popular frequencies are 14.107.50 MHz (20 meter calling frequency 1000/32 format generally), 7072.50 MHz (40 meter calling frequency 500/250/125 Hz bandwidth formats generally) and 10.133.65 MHz (30 meter calling frequency 500/250/125 Hz bandwidth formats generally). These frequencies are dial settings — meaning the frequency that your transceiver would display on upper sideband. For the 500/250/125 Hz bandwidth formats the waterfall position (center marker) should be set for 750 Hz. On the 1000 Hz bandwidth format the waterfall position should be set at 1000 Hz, and with the 2000 Hz bandwidth format it would be set at 1500 Hz. These "channels" and settings are not cast in stone and are certainly not mandatory or used by all Olivia stations but they are useful especially to help facilitate weak signal QSOs. For a much more complete set of voluntary frequencies see the charts at the HFLink Web site.
Better Than CW? After months of operating Olivia and having many QSOs (over 1,190 in 20 months), I have found it to be more reliable and more fun than any other mode that I have ever used on ham radio — including CW. It gets through noise (QRM), static (QRN) and fading (QSB) better than most and is excellent for DXing, rag chewing and even VHF weak signal QSOs. The faster Olivia formats are very useful for handling message traffic. The only place where it fails to shine as brightly is during contests. With many of the Olivia formats being slower and with the "not quite 100%" real time quality (4 to 6 second delay) it is probably not well suited for contesting. So in the end, it turns out that a really great communications mode and not ghosts were responsible for my extremely weak and spooky QSOs. I will put away my ghost busting tools, discard the books about Area 51 and fire up the rig to see if I can scare up some more Olivia activity! Give it a try and discover the magic and mystique of Olivia! Notes 1 http://en.wikipedia.org/wiki/Olivia_MFSK 2 http://hflink.com/olivia 3 http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=20015 4 http://hrd.ham-radio.ch Gary L. Robinson, WB8ROL, was first licensed in 1963 as WN8GIG at the age of 13 and obtained his Extra class license in the mid 1980s. He is semi-retired and living in a small town in rural Ohio with his spouse Nancy. During his active work years he wore many hats — including Corrections Officer for 14 years, computer technician and C, C++ and C# programmer. Currently he focuses on his five loves — ham radio (digital, especially Olivia, DominoEX FEC and THOR modes), computers and programming (primarily but not exclusively on Linux), playing Irish whistles, five cats and his wife. An ARRL member, Gary can be contacted at wb8rol@arrl.net or look for him lurking in the digital subbands of 160 meters through 70 cm.
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