How does chirpsounding work? First summary of the "Automatic Propagation Monitoring Project (APMP) Principles of ionospheric sounding and description of a simple reception for automatic passive monitoring of commercial and military jonosounders in the frequency range 2-30 MHz, and data processing and presentation of data in near real time. The project is conducted within SIG1 which is a Special Interest Group of the Association Experimentation Swedish Radio Amateur. Automatic Propagation Monitoring Project (APMP) Project Participants: Richard Niklasson SM7OHB programming, Kent Hansson SM7MMJ GPS systems, Bengt Falkenberg SM7EQL HF-parts and antennae, Jan-Olof Bergstén SM7ETW digital technology and programming, and Krister Ståhl SM7LXC web graphics and CAD. Ionosondes were invented 1926. In the '50s and '60s, about 200 ionosondes were in continuous use throughout the world. Based on observations from these, radio forecasts were prepared to determine the appropriate frequencies for radio. Two main types of ionosondes can be distinguished, namely the system of vertical sounding, and another system for so-called oblique sounding. Vertikal sondering används primärt i forskningssyften för att undersöka jonosfärens egenskaper. Vertical sounding is used primarily for research purposes to investigate IONOSPHERE properties. There are several different systems with different characteristics. Transmitters and receivers are usually co-located or located very close to each other. Oblique sounding is used mainly for commercial and military radio users for monitoring of radio channel between two remote locations. The results from oblique probes no underlying radio forecasts and provides input for the ALE-based radios. Transmitters and receivers may be located in the same country, or in different countries or continents. ESR's APMP is based mainly on listening and analyzing the signals from this type of transmitter, designed for oblique sounding. Vertical ionosounding - general basic principles An ionosonde is basically a kind of HF radar. Short pulses are sent in the coming straight up against the ionosphere. Transmission power may vary from perhaps 50 W to 10 kW or more, depending on the equipment and what purpose the sounding serves. The time difference between the signals reflected from height h is measured (Dt), as the time between the reference signal from the transmitter and the reflected signal via ionosphere. If we assume that the signal propagates with light speed c, and transmitters and receivers are located at the same place (or very close to each other <1 km), we obtaine the layer height h with the formula: h = 0.5 c Dt h = 0.5 c Dt Figure: Schematic description of the principle of ionospheric sounding with the presentation of the results on an oscilloscope screen as used until computers took over in the 70's. Ionosondes measure the layer height h at different frequencies, typically between 2-30 MHz. With increased frequency increases the time before the signal reflected back to the ground. The frequency at which the singal completely penetrates ionosphere E-layer is called the critical frequency (for the E-layere) and called f0E. Similarly, the critical frequency, which penetrates the F layer, is called f0F. The results from ionosounding presented graphically are usually called ionograms where the layer height h is shown as a function of frequency. Figure: Shows what can be deduced from an ionogram obtained by vertical sounding. The figure above shows that, for frequencies up to just above 3 MHz, the signals are reflected at about 100 km altitude. At about 3.2 MHz signal breaks through the E-layer (f0E). From 3.2 MHz up to about 5 MHz we get an echo from about 200 km altitude, ie. from the F1 layer. At about 5 MHz and at a height of about 250 km, the signal breaks through parts of the F-layer. We have a new reflection of up to about 7.5 MHz at 400 km altitude. At frequencies above 7.5 MHz is no reflections is detected. These signals disappear into space. Layer height h is read off at the lowest points in each curve, ie. before the bend of strong upward. Sometimes signals are reflected more than one time between ionosphere and the ground surface. Those are registered as a 2nd or higher order echo in the ionogram. Such echoes can be seen in the figure as a short line at the double height of the 1st-order echo. Sometimes signals may echo at the same height as the E-layer (between (100-150 km), but at frequencies much higher than f0E, and continuing completely up to 30 MHz. Such echoes come from so-called sporadic E-layer (Es) that occur during special conditions on these heights. Vertical ionosounding is now also done from satellites (top side sounding) to examine the layers from the above. Such measurements have yielded many new research results in the height range above 400 km. Oblique sounding The basic principles of vertical sounding also apply for oblique sounding. The geometry of oblique sounding makes the analysis of results more complicated. The reason is that the radio signal reflected in oblique angle is very sensitive to horizontal gradients and variations in the ionosphere. The situation becomes even more complicated by the fact that the radio signal from a transmitter can reach the receiver via multiple propagation paths, (so-called multi-way propagation) and each one brings different types of phase and amplitude distortion and reflection losses. Figure: The geometry of oblique sounding with a jump. The height h denotes virtual height of an imaginary geometric reflection point. The solid curve shows the signal in practice bending of the layer. Despite the increased complexity, oblique sounding method offers considerable advantages over vertical sounding, in order to explain and describe radio spread between two points. First and foremost, because the technology allows monitoring ionospheric properties in close to real time, at both remote locations and over long distances. Another advantage is that one single receiver can monitor multiple transmitters and thus gather information between different locations and continents. Conversely, a single transmitter of course be monitored by multiple recipients. Oblique sounding, where the outcome is presented as high-resolution ionogram providing important information on the frequency bands that are most suitable for communication between selected locations. The system used for commercial and military radio communications. The picture shows an ionogram for the line Boden - Eksjö, received with ESR's receiving equipment. The vertical axis represents the duration and the horizontal axis the frequency of 2-30 MHz. The bottom curve shows the first jump up to about 14 MHz (500 KHz per line, beginning at 2 MHz). The next graph (above) shows the 2-hopping spread up to about 8.5 MHz. The sharp break in the curve in the middlem is 3-hopping spread, and reaches up to approximately a 6 MHz. Finally, the 4th and 5th hops end at about 4 MHz. From the chart above can be deduced that the radio communications between Boden and Eksjö and at that time is possible from 2 MHz to 20 MHz. Best signal can be expected to just below 20 MHz for stations that have access to antennas with a low radiation angle, and between 2-6 MHz for antennas with high radiation angle. A diagram such as this clearly shows which frequencies are best suited for one radio path at a time. It also shows that it is not possible to make a connection between 20-30 MHz. However, it must be remembered that conditions in ionospher change very quickly. How do the transmitter and receiver devices work for oblique sounding? The emitted radio signal, typically 10-50 W output power, can be described as a continuous 100 kHz/s frequency sweep (called chirp) varying from 2 to The receiver works an ordinary shortwave receiver for amateur or commercial use. There are many military and commercial transmitters for oblique sounding we radio amateurs can use to get a free ride. The prerequisite to be able to benefit from them is that their geographical position is known and that we know the broadcasting schedule and start time when the frequency sweep begins. Here in Sweden there are such transmitters in Boden and Visby. Presentation of the prototype receiver in ESR's project APMP The received 2-29.9 MHz signal is mixed to a fixed intermediate frequency (IF) at 30 MHz. Block "CW RX" in the prototype device consists of an ordinary ICOM IC706 receiver is fixed at 29.95 MHz. The audio signal is fed into the sound card in a PC (lower right of picture) where all signal processing happens. A GPS receiver controls a 10 MHz frequency standard used to lock a 100 MHz reference clock in the DDS-oscillatorn. 1 PPS pulse from the GPS receiver branch is used to time synchronize the PC clock and start the frequency sweep. Figure: Schematic of the prototype receiver. Main Circuits and HF part The HF part in the "chir receiver" consists simply of a converter with few components and it coverts the range of 2-30 MHz to an IF of 29.9 MHz. The normal amateur receiver, used as IF, is connected to the PC whith FFT analysis software (waterfall type of program as used for PSK31, etc.). Antenna signals (left SMB connector) pass through a 5-pole low-pass filter with Fc 29 MHz. The local oscillator signal (nominally -5 dBm from the DDS VFO - lower right SMB connector) is reinforced in a MAR-3 to about + 9 dBm, as the mixer (SCM1LH from Mini Circuits) needs about 10 dBm. Conversion gain is measured at 7 dB. A 7812 voltage stabilizer is used to provide +12 V inter voltage to the two MAR-3 which need a total of 35 mA. A 4001 is used as protection against polarity errors of the supply voltage. This simple converter was intended as a temporary means to test the DDS sweeper and kick off the system. Therefore, little effort was spent on sharpening and optimizing filters, etc. A "modern" receiveconverter requires much better input filter, for example in the form of half-octave bandpass filter or the similar. Also, some filtering between the the LO signal and the filter or diplexer would be required. However, this simple converter is able to receive weak signals in the range of commercial receivers any time, down to about about -140 dBm. The weakness of the converter is a bad IM2, and lack of mirror frequency attenuation. As can be seen as the simple design is by no means optimized. For better performance, theLO signal must be filtered properly, so that its harmonics and out-of-band spurs do not reach the mixer. A LPF or BPF can be inserted between the MAR-3 output, and pin 8 on SCM1LH. The MAR-3 is slightly undersized for this work, and the reason for the low gain (9 dB) is that circuit nears the 1 dB compression point. If the best possible performance is desired, pin 8 must be adapted to a resistive 50 ohm load over all frequencies. Normally, this can be solved by introducing a 3 ... 6 dB attenuator pad. The disadvantage is that it will require a correspondingly higher LO injection. A better way is to use a diplexer. Sak samma gäller för MF utgången från blandaren (pin 4) Bästa lösningen är en diplexer så att alla frekvenser termineras i 50 ohm resistivt. The same applies for the MF output of the mixer (pin 4) The best solution is a diplexer so that all frequencies terminated in 50 ohm resistivt. Det finns inga genvägar om man vill ha ut maximal prestanda ur en blandare. There are no shortcuts if you want maximum performance from a mixer. Även RF-ingången bör känna 50 ohm och även här gäller diplexer, 3 dB pad och/eller i kombination med en pre-amp med bra storsignalegenskaper. While RF input should know 50 ohm and this applies diplexer, 3 dB pad and / or in combination with a pre-amp with good large signal characteristics. DDS (Direkt Digital Syntes) - lokaloscillatorsignal DDS (Direct Digital Synthesis) - lokaloscillatorsignal För att generera mottagarens lokaloscillatorsignal används en oscillator baserad på DDS kretsen AD9858 från Analog Devices. To generate the recipient lokaloscillatorsignal used oscillator based on DDS chip AD9858 from Analog Devices. Kretsen innehåller allt som behövs för att skapa en analog signal upp till c:a 50 MHz. The pool contains everything needed to create an analog signal up to c: a 50 MHz. Frekvensinställningen kan genom digital kodning göras i steg ner till 0.01 Hz vilket är mycket mer än vad som behövs i en applikation som denna. Frequency adjustment can be made through digital encoding in steps down to 0.01 Hz which is much more than needed in an application like this. AD9858 har lågt fasbrus men tyvärr ganska dålig undertryckning av spurioser. AD9858 has low fasbrus but unfortunately rather poor during the printing of spurioser. I mer avancerade mottagare låter man därför DDS-oscillatorn styra en lågbrusig VCO vilken faslåses till DDS-oscillatorn. In more advanced receiver allows therefore DDS oscillatorn control a low noise VCO which faslåses to DDS oscillatorn. Richard Hoskins VK6BRO har tagit fram en generell DDS-konstruktion som passar bra i den chirpmottagare som vi tagit fram. Richard Hoskins VK6BRO has developed a generic DDS design that fits well in the chirpmottagare which we have developed. Konstruktionen bygger på AD9854 från Analog Devices. The design is based on the AD9854 from Analog Devices. DDS ger hög frekvensnoggrannhet DDS provides high frequency accuracy Fördelen med DDS-oscillatorn är att frekvensen hos utsignalen blir lika noggrann som referensoscillatorn. The advantage of the DDS oscillatorn is that the frequency of the output will be as precise as referensoscillatorn. I prototopen används en temperaturkompenserad 100 MHz kristalloscillator (TCXO) med en noggranhet av 1/10 ppm. In prototopen use a temperature compensated 100 MHz kristalloscillator (TCXO) with an accuracy of 1 / 10 ppm. För att ytterligare förbättra frekvensnoggrannheten är det möjligt att faslåsa DDS-oscillatorn till en mer noggrann 10 MHz referenssignal. To further improve the frequency accuracy, it is possible to faslåsa DDS oscillatorn to a more accurate 10 MHz reference signal. Denna kan skapas med hjälp av signaler från GPS-mottagaren ovan. This can be created by means of signals from the GPS receiver above. DDS-kretsens frekvenssvep styrs digitalt från seriekanalen i en PC. DDS circuit frequency sweep is controlled digitally from the serial channel to a PC. Den höga frekvensupplösningen 0.01 Hz möjliggör extremst snabba och mycket exakta förändringar av frekvensen. The high frequency resolution 0.01 Hz extremst enables fast and very precise changes in frequency. GPS (Global Positioning System) GPS (Global Positioning System) GPS består av 24 satelliter i omloppsbana på 20000 Km höjd över jordytan. Systemet drivs och kontrolleras av USA:s Försvarsdepartement sedan 70 talet. Numera har dock civila organisationer fått stort inflytande eftersom den civila användningen ökat. GPS consists of 24 satellites in orbit at 20,000 km altitude above the Earth's surface. The system is operated and controlled by the U.S. Defense Department since the 70's. Now, however, civic organizations had a major influence since the civil use has increased. Den höga omloppsbanan och vinkeln mot ekvatorn (inklinationen) gör att man från varje plats på jorden alltid kan ta emot signaler från minst fyra satelliter över horisonten. The high orbit and the angle towards the equator (inclination) do that from any place on earth can receive signals from at least four satellites above the horizon. Omloppstiden för varje satellit är ca 12 timmar. Circulation time for each satellite is approximately 12 hours. Namnet antyder att systemet primärt är avsett för navigering och positionering. Systemet ger dessutom möjlighet för noggranna tids- och frekvensmätningar. Varje satellit har fyra inbyggda atomur, två cesium och två rubidiumur där varje enskilt ur är noggrant synkroniserat mot UTC ( Universal Time Coordinated ). The name implies that the system is primarily intended for navigation and positioning. The system provides an opportunity for accurate time and frequency measurements. Each satellite has four built-in atomic clocks, two cesium and two rubidiumur where each from is carefully synchronized to UTC (Universal Time Coordinated). Tidsskalan som används kallas för GPS-tid, det är en kombination eller medelvärde av varje satellits egen klocka och ett antal klockor på jorden bland annat UTC. Time scale used is called GPS time, it's a combination or average of each satellite's own clock, and a number of clocks on Earth including UTC. GPS tid är dock till skillnad från UTC en kontinuerlig tidsskala. GPS time, however, unlike a continuous UTC time scale. Därför skiljer sig GPS-tid från UTC förutom små variationer genom att man i GPS tid inte lägger till sk skottsekunder. Therefore, different GPS time from UTC in addition to small variations through the GPS time does not add so-called ballistic customers. Satelliterna sänder på två olika frekvenser benämnda L1 och L2. The satellites transmit at two different frequencies, called L1 and L2. Signalerna är modulerade med två olika unika koder för varje satellit, för att mottagaren skall kunna särskilja signalerna från de olika satelliterna. The signals are modulated with two different unique codes for each satellite to the receiver to distinguish signals from different satellites. Den ena koden den sk P-koden är krypterad och används av militären, den andra C/A koden är öppen och sänds bara på frekvens L1 och kan användas av alla. On the one code called the P-code is encrypted and used by the military, the second C / A code is open and broadcast only on L1 frequency and can be used by all. Båda bärvågorna är dessutom modulerade med ett navigationsmeddelande som innehåller information om var satelliterna befinner sig när de sänder ut en speciell del av koden, satellitklockornas tid relativt UTC m m. Eftersom C/A koden bara sänds på en frekvens så kan man inte korrigera för fördröjningar i atmosfären vilket gör att det endast är militären som kan använda GPS systemet med extremt god noggrannhet utan att använda markbundna referensstationer sk DGPS differentiell GPS. Both Carrier is modulated by a navigation message that contains information about where the satellites are located when they send out a special part of the code, satellite clocks time relatively UTC m m. Since C / A code is broadcast on a frequency you can not adjust for delays in the atmosphere so that only the military that can use the GPS system with extremely good accuracy without using ground reference stations called DGPS differential GPS. IC/A koden finns möjlighet att införa ytterligare onoggrannhet eller missvisning, detta kallas SA eller Selective Availability. IC / A code is the possibility of introducing additional accuracy or misunderstood view, this is called the SA or Selective Availability. Fram till maj år 2000 var SA påslagen i GPS systemet vilket gjorde att man med kommersiella mottagare inte kunde få bättre noggrannhet än ca +- 100 m utan SA blir precisionen ca +-10 m. Until May 2000, SA was turned on in the GPS system so that commercial receivers could not get better accuracy than about + - 100 m without SA is the accuracy around + -10 m. Egentligen behövs bara signal från en satellit för att kunna göra tids- och frekvensmätningar, men med flera satelliter kan noggrannheten ökas genom att bilda medelvärden från flera satelliter. Really needed only signal from a satellite to make time and frequency measurements, but with several satellites can accuracy be increased by forming averages of several satellites. Man kan i princip få en tid relativt UTC med en noggrannhet på några hundra nanosekunder om man mäter under flera timmar. One can in principle be a time relatively UTC with an accuracy of a few hundred nanoseconds of you measure for several hours. Med längre mättid och olika mätmetoder kan man få ännu högre precision, upp till 10E-10 och 10E-15. With longer measurement and different measurement methods can provide even higher precision, up to 10E-10 and 10E-15. 1 PPS standard 1 PPS standard I detta projektet har vi valt att använda en GPS mottagare Lassen LP från Trimble, anledningen är bland annat att den finns tillgänglig på surplusmarknaden och att den är enkel att använda och konfigurera. In this project we have chosen to use a GPS receiver from Trimble Lassen LP, the reason is that it is available on the surplus market and that it is easy to use and configure. Prototyp till 1 PPS standard För tidssynkroniseringen av chirpmottagarens frekvenssvep behövs följande signaler och information från GPS-mottagaren: Tid i form av NMEA meddelanden, 1PPS (1 Pulse Per Second), och en 10MHz referensoscillator låst till 1PPS. GPS-mottagare är en Lassen LP. Prototype to 1 PPS standard for time synchronization of chirpmottagarens frequency sweep, the following signals and information from the GPS receiver: Time in the form of NMEA messages, 1PPS (1 Pulse Per Second), and a 10MHz referensoscillator locked to 1PPS. GPS receiver is a Lassen LP . Mottagaren lämnar meddelandena GPGGA samt GPGLL där det senare innehåller tiden ner till 1/10 sek. The receiver leaves messages GPGGA and GPGLL where the latter includes the time down to 1 / 10 sec. Tekniska data Lassen GP Technical Data Lassen GP * Drivspänning 3.3 V Operating voltage 3.3 V * Effektförbrukning 180 mW Power 180 mW * Drivspänning till antenn , 3.3 Volt Operating voltage to the antenna, 3.3 Volt * TSIP, TAIP och NMEA 0183 protokoll på serieport 1 TSIP, Taip and NMEA 0183 protocol on the serial port 1 * RTCM SC-104 ingång för DGPS på serieport 2 RTCM SC-104 DGPS input for the serial port 2 * 1PPS puls för synkronisering 1PPS pulse synchronization För att konfigurera mottagaren och för att mottagaren skall kunna skicka tidsmeddelanden till datorn behövs ett programmeringsinterface. To configure the receiver and the receiver is able to send messages to the computer time needed a programming interface. De två serieportarna på GPS-modulen ger CMOS/TTL nivåer ut och kan därför inte anslutas direkt till serieporten på datorn. The two serial ports on the GPS module provides CMOS / TTL levels and can therefore not be directly connected to the serial port on your computer. För att klara detta har ett interface med en standardkrets från Maxim (MAX232) tagits fram. To do that has an interface with a standard chip from Maxim (MAX232) has been identified. Eftersom Maxim-kretsen drivs med 5 V och GPS mottagaren med 3.3 V så används en 7805 stabilisator för 5V, och göra 3.3V (3.6V) fås genom att seriekoppla två dioder. Since Maxim chip is powered with 5 V and GPS receiver with 3.3 V using a 7805 as a stabilizer for 5V, and 3.3V (3.6V) is obtained by series connecting two diodes. Lassen LP lämnar en mycket kort negativ puls, (1 PPS-puls) som inverteras och förlängs innan den omvandlas till RS-232 nivå för anslutning till CTS pinnen till datorn. Lassen LP leaves a very short negative pulse (1 PPS Pulse), which inverted and extended before it is converted to RS-232 level for connection to CTS pin to the PC. Tidssynkronisering mellan sändare och mottagare viktig Time synchronization between the transmitter and receiver are important GPS-systemet används för att tidssynkronisera sändarens frekvenssvep med mottagaren. GPS system used to time synchronize the transmitter frequency sweep with the recipient. Detta medger exakt mätning av löptiden eller den tid det tar för radiosignalen att nå fram till mottagaren. This allows for precise measurement of the duration or the time it takes for radio signals to reach the recipient. Svephastigheten 100 kHz/s motsvarar en teoretisk avståndsupplösning av 10 mS eller 1.5 km. Sweep rate 100 kHz / s corresponds to a theoretical range resolution of 10 mS or 1.5 km. Chirpsändarna i Boden och Visby startar sitt frekvenssvep på 2 MHz var 15:e minut, dygnet runt. Chirpsändarna in Boden and Visby starts its scanning frequency of 2 MHz every 15 minutes, around the clock. Ett komplett svep upp till 28 MHz tar 280 sekunder. A complete sweep up to 28 MHz takes 280 seconds. Genom att synkronisera ESR:s chirpmottagare i tid och frekvens kan både den mottagna signalens styrka och relativa frekvens (dopplerskiftet) registreras. By synchronizing ESR's chirpmottagare in time and frequency, both the received signal strength and relative frequency (Doppler shift) is recorded. Just dopplerskiftet är intressant eftersom det är är kopplat till signalens löptid och som påverkas av skikthöjden. Just Doppler shift is interesting because it is linked to signal duration and affected by the layer height. Genom bearbetning av signalen i ett FFT-program (vattenfallsprogram) presenteras resultatet som skikthöjden på den vertikala axeln och sändningsfrekvensen på den horisontella axeln. The processing of the signal in an FFT program (cataract program) presented the results as layer height on the vertical axis and the transmission frequency on the horizontal axis. Vad kan man utläsa ur jonogrammet? What can be inferred from jonogrammet? Radioenergi utbreder sig genom olika moder (t ex ett hopp. två hopp, E-skiktet F-skiktet etc) som har överföringsfördröjning, karakteristik och andra igenkänningsmärken. Radio Energy spreads through various parent (eg a jump. Two jumps, E-layer Q-layer, etc.) that has transmission delay, characterization, and other identification marks. Signalen från chirpsändaren tas följaktligen emot som flera olika signaler med olika frekvens och fördröjningar. The signal from chirpsändaren are therefore opposed to several different signals at different frequencies and lags. Dessa signaler processas av mottagaren och PC-n och visas grafiskt som en funktion av sondens svepfrekvens, med värden för signalens löptid på den vertikala axeln och för mottagningsfrekvens på den horisontella axeln. These signals are processed by the receiver and PC-n and is shown graphically as a function of the probe sweep frequency, with values of signal duration on the vertical axis and the reception frequency on the horizontal axis. Det resulterande diagrammet benämns jonogram. The resulting graph is referred jonogram. Diagrammet ger information om vilka frekvenser som vid en viss tidpunkt kan reflekteras via jonosfärskikten och som därför är användba för radiosamband. The chart provides information on the frequencies at a particular time can be reflected through jonosfärskikten and is therefore useful for the radio connection. Mätningen Boden - Eksjö gäller naturligtvis enbart denna sträcka, men kan ändå ge en fingervisning om möjligheterna för kommunikation t ex inom Sverige. The measurement Boden - Eksjö of course only that distance, but can still give some indication of the possibilities for communication such as in Sweden. Presentation av den mottagna signalen med hjälp av fft "vattenfall" Presentation of the received signal using fft "waterfall" På grafen nedan visas frekvensen i MHz längs den horisontella axeln och höjden där signalen reflekteras i km, längs den vertikala axeln. On the graph below shows the frequency in MHz along the horizontal axis and the height where the signal is reflected in km, along the vertical axis. foF2 kan läsas ut från jonogrammet. foF2 can be read out from jonogrammet. Denna frekvens är den högsta som reflekteras vid vertikalt infall och vid jonosfärförbindelser över mycket korta avstånd (NVIS) . This rate is the highest that is reflected at vertical incidence and jonosfärförbindelser at very short distances (nvisen). Om man önskar förbindelse över längre avstånd, kan högre frekvenser än foF2 användas. If you wish to link across longer distances, higher frequencies than foF2 used. Högsta användbara frekvens vid förbindelse över 3000 km betecknas i ionogrammet som MUF (Maximum Usable Frequency). Maximum usable frequency at the link across 3000 km designated in ionogrammet which MUF (Maximum Usable Frequency). Vid kortare avstånd än 3000 km ligger MUF för det aktuella förbindelseavståndet mellan foF2 och MUF(3000) som det presenteras här i exemplet. At shorter distances than 3000 km is MUF for the connection distance between foF2 and MUF (3000) as presented here in the example. Signal från sändaren i Boden mottagen i Eksjö. Bilden visar ett E-skikt på c:a 100 km höjd. Signal from the transmitter in Boden received in Eksjö. The picture shows an E-layer on c: a 100 km altitude. Vad kan resultatet användas till? What can the results be used for? Realtidsdata som vi använder här för att säga något om förbindelsemöjligheterna är baserade på mätningar som precis gjorts. Real-time data that we use here to say something about the connection possibilities are based on measurements just made. Begreppet realtid är därför inte helt korrekt, men nära nog. The concept of real time is therefore not entirely correct, but close enough. I jonosfärfysiken är där många processer som har olika varaktighet. In jonosfärfysiken is where many processes which have different duration. Till exempel varar en solfäckscykel 11 år, elektromagnetisk strålning från solen varierar med en period om ett dygn, medans en geomagnetisk storm kan vara från några timmar till ett dygn. For example, lasting for a solfäckscykel 11 years, electromagnetic radiation from the sun varies with a period of one days, while a storm geomagnetisk can be from few hours to a day. De realtidsdata och resultat vi talar om här kan vara till nytta för att bestämma förbindelsemöjligheterna är i ett visst ögonblick och troligen kommer att vara den kommande timmen. Resultatet är till för att visa trender, inte ge exakt information. The real-time data and results we are talking about here can be useful to determine the potential relationship is at a given moment and will likely be the next hour. The result is to show trends, not give accurate information. Eftersom Sverige li gger långt norrut har vi också större problem med HF-kommunikation än t ex stationer i medelhavsområdet etc. Detta beror på att vi är nära norrskenszonen med en mycket oförutsägbar jonosfär som ofta påverkas av solen och dess aktivitet. Since Sweden is far north, we also have major problems with the HF-communication than eg stations in the Mediterranean, etc. This is because we are near the northern zone with a very unpredictable IONOSPHERE, which is often influenced by the sun and its activity. Slutord Conclusion Som en fortsättning på projektet är det tänkt att komplett schema och konstruktionsbeskrivning skall läggas ut som pdf-filer så att fler kan bygga sin egen chirpsoundermottagare. As a continuation of the project is to complete construction schedule and description to be published as PDF files so that more can build their own chirpsoundermottagare. Du som är ESR-medlem och vill följa projektet kan läsa mer på medlemsavdelningen under rubriken SIG1. Projektet är öppet för alla som vill bidra med ideér och arbetsinsatser. You are ESR-member and want to follow the project can read more on their department under the heading SIG1. The project is open to all who wish to contribute ideas and effort. Anmälan till Richard sm7ohb (at) Notification to Richard sm7ohb (at)