System for Monitoring Weather Satellites:

FM Receiver For 134 - 141MHz  

(A double conversion  superhetrodyne with pll)

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Miroslav Gola OK2UGS





Receiving information from FM meteorological satellites has become an interesting hobby for thousands of radio enthusiasts all over the world. Those of you who have already tried internet searches using such keywords as
NOAA, METEOSAT, 137.5MHz, WEFAX, Meteor etc., will undoubtedly confirm that they have found hundreds of links to pages of receiver manufacturers, re-sel-lers, professional users and particularly ham enthusiasts.


Not long ago history...

It is worth noting that on 1st April 2010 we commemorated the 50th anniversary of the first transmission of images from the satellite TIROS 1.


Tiros 1 TV - day 01.04.1960

The pictures were of rather low quality, nevertheless, they started an era of space research of the Earth's surface. The resolving power of todays images is currently of the order 1 pixel = 1 m. You can find more detailed information on the internet pages of the NOAA agency . Quite and few hams tried successfully in the seventies to construct receivers. These obviously did not have the technical specification that can be achieved with modern components.



TIROS (Television Infrared Observational Satellite)  On April 1, 1960, TIROS 1, the first true weather satellite, was launched.  With each succeeding generation of satellites, remote sensing instruments became increasingly sophisticated and generated finer spectral and spatial resolution imagery.


The Television and Infrared Observation Satellite (TIROS) carried special television cameras that viewed Earth's cloud cover from a 450 mile orbit. By 1965, nine more TIROS satellites were launched.  They had progressively longer operational times, carried infrared radiometers to study Earth's heat distribution, and several were placed in polar orbits to increase coverage over the first TIROS in its near-equatorial "polar" orbit...


History ... in Czech republic


History ... Polar 1972 ( OK1BI photo front - back )


Images were not generated using high quality decoding programs for personal computers, simply because they did not exist at that time.

OK1BI HamShack 2001

The images were "decoded" using of technology of the seventies; plotting on oscilloscope with medium afterglow and then photographing using an instant Polaroid camera [9].

OK1BI & WXtoIMG ... stereoscopic study picture NOAA - 27. 08. 2005


Looking at earth from space...

NOAA POES ( NOAA POES (National Oceanic and Atmospheric Administration Polar Operational Environmental Satellites, USA ) and METEOR, OKEAN, RESURS (Russia) are the focus in this article. They are flying on polar orbits around the Earth at the distance of approximately 800 - 1200 kilometres passing over the same place at approximately same time every day [23]. Satellites pass the North or South pole on each orbit, that is why their orbits are called polar.

Satellite constellations [ movie_1 &  movie_2  wav_1 ]

It is possible to determine their trajectory precisely using "Keplerian elements", which describe the current orbit of the given satellite. Calculation of the exact time of a satellites orbit, from the moment when it appears at the horizon till the moment when it disappears behind the horizon, can be made nowadays using many programs for personal computers. I most frequently use a simple Windows program called SatWin [10, 24]. A version of SatWin was also written for MS-DOS and can be run on older personal computers of the DX486 type. Both these programs can be downloaded free of charge together with up-to-date Keplerian elements at the following address: . You will also find other information about the activities of satellites plus the signals that you can receive and decode using the receiver described in the following article.

Pictures are transmitted continuously from polar satellites without beginning or ending.




When the satellite appears over the horizon, the edge of the pictures is slightly cramped, gradually resolution of details in the picture improves. At the end of orbit the signal gets weaker and the picture begins to disappear in noise as the satellite slips behind the skyline.


Inclination is the angle made by the plane of satellites orbit and equatorial plane. A satellite that passes over both poles (on so called polar orbit) has the inclination of 90°. The inclination of American satellites NOAA 10-18 is 98°, their period is approximately 102 minutes and height of satellite is approximately 820 -850 kilometres.

Signals from the satellites are in WEFAX - APT format (Weather Faximile - Automatic Picture Transmission). This is an old, but still useful, system for transmission of black and white visual information using a standard audio channel where a change of amplitude of the 2400Hz sub carrier represents the level of the video signal brightness. Maximum modulation (black) is not zero, but approximately 5%, white is then approximately 87%. This audio signal is frequency modulated on the main carrier, e.g. 137.50MHz for the satellite NOAA 15.

APT is an analogue format: information is transmitted by means of AM/FM modulation of the carrier frequency in 137 MHz radio wave band with a bandwidth of about 40 KHz. Transmitted in the APT format are data of only two channels, with lowered spatial (to 3.5 km) and radiometric (to 8 bits) resolution.

After demodulation by the FM receiver we therefore obtain an amplitude modulated tone of 2400Hz. This signal is sent to the input of standard sound card in a PC and processed by a software decoder such as JVComm32 which can be downloaded from . JVComm32 even handles bad quality demodulated signals due to the efficient digital filters.

The result of this processing is shown in Fig as picture displayed on a computer monitor.

APT (Automatic Picture Transmission) format

Transmission of images from NOAA satellites are composed of lines lasting 0.5 second, which correspond with data from sensors. They provide one picture of the Earth surface containing data from two channels. Channel A transmits picture in the visible spectrum (VIS) and channel B transmits picture in the infrared spectrum (IR). Each line contains time multiplexed data from both channels and is composed of separation tones interlaced with picture modulation. Data from channel A is preceded by and short impulse of 1040Hz and similarly data from channel B are preceded by and short impulse of 832Hz. Each line also contains a calibration sequence. Thanks to this the decoding program can display only the chosen type of picture. You will find more detailed information at  .


You will find up-to-date information about Russian satellites METEOR, OKEAN, RESURS at  . These satellites have higher orbit than that of NOAA satellites (1200 km). For example inclination of satellites METEOR is 82° and their period is 115 min. The system of picture transmission from METEOR satellites is compatible, however slightly different, from that of NOAA satellites. Modulation is similar, but pictures contain only one photo with higher resolution. Edges of lines contain sets of phasing lines (alternately black and white), the lines mark end of picture and greyscale. Pictures in the infrared spectrum do not contain the greyscale. The pictures are also inverted as in comparison with NOAA pictures. Photos from NOAA satellites show warmer places by darker shade and colder places are brighter. The pictures from METEOR use inverse scale warm seas are white and cold cloud formations are black.

Summary of Russian Meteorological METEOR Satellites

Meteor 2-21
This is the last of the second generation Meteor satellite series. This and similar satellites are in a non sun-synchronous orbit, so the visible channel imagery is useful for only a portion of the year.

This spacecraft transmits on the 137.850 MHz channel with normal 120 line per minute visible mode APT. It can alternately transmit on 137.400 MHz. It continues to show very decreased signal strength during the approaching part of each orbital pass. This would be consistent with a improperly deployed VHF antenna or perhaps some damage to the antenna during launch. The second part of each pass (as the spacecraft passes away from the observer) has a much stronger signal, but is still weaker when compared to Meteor 3-5 or any of the NOAA series spacecraft.

Currently the spacecraft is in an orbital plane with early morning and mid to late afternoon passes.

Meteor 3-5
This satellite, launched in 1991, is in a slightly higher orbit than Meteor 2-21. It transmits on 137.300 MHz. Mechanically, it is similar to Meteor 2-21. Which satellite is in operation depends on the sun angles and consequently the seasons. Meteor 3-5 is usually the (Northern Hemisphere) "summer" satellite while 2-21 is in operation for approximately the half-year centered on winter.

Information about the APT operating schedule and frequencies of the Meteor 2-21 and 3-5 satellites can usually be found on postings to the WXSAT-L list. See our links page for more information about subscribing to WXSAT-L.

The Meteor-3M series of satellites is to be an advanced series of polar orbiters with one 1.4 km resolution visible channel and a ten-channel radiometer with 3 km resolution. An APT transmission was planned to only have a reduced resolution (2 km) visible channel data. The first of these, Meteor 3M-N1, was launched in December 2001. The status of any APT capability on this satellite is unclear, but it is thought not to have an APT transmitter. No APT transmissions have been received from this satellite.

Russia also launched the RESURS 01-4 satellite in July 1998. This satellite carries a meteorological package similar to what was planned for the 3M series, and may be a cost saving effort to have these capabilities without launching a separate satellite. APT-like transmissions from RESURS have been heard on 137.40 MHz.

OKEAN 4 and SICH 1 are radar imaging satellites that have been monitored as they dump recorded image data. Both satellites have a transmission frequency of 137.400 MHz. Reception has usually only been within Europe.

More information about these satellites can be found at the "Sputnik" site in Russia. (You will leave the NOAASIS web site and NOAA domain when following this link)


Have a look at active in-reference:  

Weather Satellite Images recorded at Tenerife, Canary Islands, Spain (on-line www) ...

It is also possible to decode visual information from the receiver any time. To do this it is necessary to save the received modulated signal as a WAV sound file on a high quality recorder (we had the best results with SONY Minidisk). If you take holidays in distant countries, it is recommended that you use a portable and easily mounted Quadrifillar Helix antenna, take the receiver described below and a Minidisk. During your trip you can record exotic pictures from any of the meteorological satellites. When you return you can decode the saved WAV sound files in the same manner as during direct reception


Description of the receiver RX-134(7)-141MHz

The RX137141MHz receiver has already been produced since 1998 and I have been gradually implementing various improvements of its technical parameters. The most recent modification of the service properties of the receiver consists in a possibility to connect it to a PC via the RS232 interface. This modification was initiated by the interest of the WXtoIMG decoding program  users. The WXtoIMG program has outstanding properties for decoding of the APT signals and it enables a completely automated operation and optionally also an automatic sending of the decoded image to the chosen web page. The WXtoIMG program sends a special code into the RX134141MHz receiver shortly before the rise of the satellite to the horizon, which will trigger the setting of the RX134141MHz receiver to one of the following ten frequencies ( 137.20 .. 137.10 .. 137.40 .. 137.50 .. 137.62 .. 137.9125 .. 137.30 .. 137.70 .. 137.80 .. 137.85 MHz ). The process is continuously repeated before each flyover of the satellite in the cycle, which is updated from the database of the current Keplerian elements. The selection of the frequency for the given satellite is substantially more reliable at present than it was in older models of this receiver, with the use of SQL SCAN or PLL 2400 Hz SCAN with the LM567circuit. The impact of interfering signals on the receiver’s input that afterwards caused a process of undesired repeated scanning never occurs now. 

At present I have started the production of a new model of the RX134141MHz receiver with an extended range that was inspired by the needs of users of the converter 1700MHz made in Italy, the output frequencies of which are 134.00 a 137.50 MHz. The new model of the receiver embodies all good properties, which were confirmed during a six-year-long practical use by numerous users in many countries.

The receiver RX-134(7)-141 MHz is designed to receive images of the Earth surface from polar-orbiting satellites in APT (Automatic Picture Transmission) format in 137 MHz band. The receiver RX-134(7)-141 MHz has been designed for high quality reception of signals form polar meteosatellites NOAA, METEOR, OKEAN and others. It is compatible with the converter from 1691.00 MHz to 137.50MHz which is suitable for reception from geostationary satellite METEOSAT 7.

Table: Satellite Status Information ( NOAA Operational Satellites )

Satellite Transmission Frequencies
NOAA-19 APT - ON 137.10 MHZ HRPT - 1698 MHz
NOAA-18 APT - ON 137.91 MHZ HRPT - 1698 MHz
NOAA-17 APT - ON 137.62 MHz HRPT - 1707.0 MHz
NOAA-16 APT - OFF since 11/15/00 HRPT - 1702.5 MHz
NOAA-15 APT - ON 137.50 MHz HRPT - 1702.5 MHz
NOAA-14 APT - OFF since 8/2/05 HRPT - 1707.0 MHz
NOAA-12 WEFAX/LRIT - 1691.0 MHz HRPT - 1698.0 MHz


Satellite Transmission Frequencies Notes

Not all the satellites given are always active. Some of them are still flying on polar orbits, but their transmitters have been switched off. Some others do not transmit due to a failure, e.g. the modern satellite NOAA 16 only transmits in the mode HRPT at the frequency 1.698 GHz due to a defect. This is the fate of all artificial satellites, when they fail they can only be repaired using very costly methods. Not all the satellites are as important as the Hubble space telescope, which was repaired by the space shuttle that we watched with excitement and admiration. See



NOAA-N  (NOAA-18) Rockets Into Orbit...

Looking at the Table 1, you will find that satellites in polar orbits transmit signals in the range of 137.10-137.62MHz, therefore a very narrow frequency range is sufficient. We have chosen, for practical reasons, a lower frequency of 134.00MHz and an upper frequency of 141MHz. No meteorological satellites transmit at frequencies above 137.85MHz but the frequency of 141MHz will make it possible to use the converter for the METEOSAT 7 satellite. This makes it possible to process information from both channels, the first channel (1691.00MHz) converts to 137.50MHz and the second channel (1694.50MHz) converts to 141.00MHz.


Since the design of the RX134141MHZ receiver will only accept frequency steps of 10 KHz, the new 137.10 frequency (NOAA-18) cannot be exactly programmed, so I chose the closest values above and below that frequency. The error is only 2.5 KHz, so either channel should be able to receive the APT signal with minimum degredation. Due to doppler shift, the recption may be slightly better on one channel while the satellite is approaching, and it may be better on the other channel as the satellite moves away from your location.

The circuit diagram of the receiver is shown in Fig 1. It was originally developed for the nearby ham frequency range of 144-146MHz [3]. The circuit of the receiver is designed for wideband FM (bandwidth 30kHz). The low-frequency APT/WEEFAX signal is sent from the output to the PC sound card. The frequency synthesiser PLL and LCD display are controlled by an ATMEL micro-computer ( UP-MODE-DOWN ).

The receiver is a double conversion superhetrodyne. Design of the receiver has been significantly simplified by using an MC3362P (IC1) integrated circuit made by Motorola [5], which comprises all main elements of modern FM receiver. All that is required to connect to the MC3362P is an input band-pass filter, a resonant circuit for the first mixer oscillator, 2 ceramic filters for 10.7MHz and 455kHz, a quartz crystal oscillator for the second mixer, a resonant circuit for the demodulator and few other passive components. We will thus obtain an excellent receiver with a rather simple circuit and with supply voltage of 2-5V [12].

Table: Specification of the receiver.

Frequency Range  134 - 141 MHz (infinitely adjustable, step by step 10 kHz)
 Frequency Synthesizer Step:  10,0 kHz
 Input Sensitivity:  0,25uV (rms-type) for 12dB SINAD
 Intermediate Frequency:  10,7 MHz and 455 kHz
Tone decoder/PLL SE567:  2400 Hz
 Pass band of the 2-st.IF filter:  30 kHz/ - 3 dB (or alternately 15 kHz)
 Power:  DC 12V (max.12 V)
 Current output:  70 - 90 mA, according to the loudness level setting
 Power Connector:  3 mm (+pole is inside of the jack pin,-pole is on its surface!!!)
 WXtoIMG Scanning  Yes / 10 -channel, controlled by the uP [ RS232 or USB ]
 Automatic Scanning:  Yes - 2400 Hz stop point - Squelch function controlled by the uP
 Noise Gate ( SQUELCH ):  Yes 
 Antenna Connector:  2x "BNC" or  SO239 type
 Display:  LCD 1 x 16 alpha - numerical  symbols
 Connection for Loud speaker:  (or Headphones) external 8-25 Ohms, CINCH connectors
 Connection for PC1:  2PIN connectorsor cable from the computer sound card
 Connection for PC2:  9PIN connectorsor cable from the computer COM/RS232 card
 Receiver Size:  Case Bopla: 225x200x70 mm


A requirement for assuring high quality reception of signals from meteorological satellites is the use of a high quality  antenna. Polar meteorological satellites are rotation stabilised and transmit circular polarisation. It is therefore impossible to use ordinary Yagi or ground plane antenna. When you listen to the signal from the loudspeaker it seems to be noise free, however when you observe the picture after it is decoded you will see that it is unusable. Anyone can build high quality antenna. Two basic types are used: Turnstile and Quadrifillar Helix.  

General view of a Turnstile antenna.

The turnstile consists of two crossed dipoles (Fig. 2) phased for circular polarisation. This antenna should be situated as high as possible above the horizon, preferably above the house roof or in an open air space. Experiments made with a turnstile antenna located on the  balcony of a blockhouse, satellites flying over at a low elevation angle were shielded by building or balcony. In short, it is only possible to receive signals that are "seen" by the antenna. Instructions  for building several types of turnstile antennas are on the authors homepage. Drawings describing the construction of  a simple antenna made from plastic tube and 8 - 12 mm aluminium tube are given in the literature [18].

  We have tested the antenna shown in Fig 3 with the receiver. The antenna was installed on a roof at 40m above the ground and gives high quality signal reception. The feeder connection for circular  polarisation is shown in Fig 4. Fig 5 shows the polar diagram for this antenna, particular attention should be paid  to the dipole to refelctor spacing because it changes the polar diagram, the author chose 3/8 lambda.




Practical design of a turnstile antenna.  

Details of feeder for turnstile antenna.

Polar diagram for turnstile  antenna

The manufacture of the Quadrifillar Helix antenna, which is shown in Fig. 6 can be done only in a well equipped machine  shop. 


General views of Quadrifillar Helix antennas.  QFHA KIT EMGO and Russia version

This antenna has slightly better reception of signals and moreover it can be used also in moving objects, such as  yachts cruising in Mediterranean Sea.The article [20, 21] contain many descriptions of simpler mechanical constructions  suitable, however, only for a shortterm seasonal use, or for antennas made of copper heating tubes.


If the distance of your receiver from the antenna will exceed 10m, I would recommend use of selective preamplifier for frequency range of 137MHz, preferably using bipolar transistor. Experience has shown that summer storms have a rather bad impact on MOS-FET transistors. In an environment with industrial interference it is often desirable to use a band pass helix filter in front of the preamplifier.

Power supply for the receiver

The receiver requires a stabilised power supply adapter with a voltage of 9 - 12V. It is highly that you pay special attention to the selection of a power supply adapter. 


If you have an oscilloscope, look at it's output when on load at 150mA and check that there is no ripple. The low-frequency  amplifiers IC2 and IC6 are fed directly from the adapter. The other supply voltages, 5V for receivers circuits and 5V for synthesiser and microprocessor, are stabilised by IC5 (LM7805). The supply voltage for the analogue part of  the receiver is also isolated by choke TL2. 

The input of the power supply is protected against reverse polarity by diode  D2. Bridging jumper JP2 enables the use the feeder cable to supply the antenna preamplifier or Meteosat converter. This requires a higher capacity power supply adapter, for connection of the OK2XDX Meteosat converter [16], I recommend a power supply adapter of 12V/500mA.


Description of software WXtoIMG

Source: WXtoIMG - setting WXtiOMG Version wxinst21010

Basic set-up for communication with the Interface EMGO RX134141MHZ/WXtoIMG/RS232


Communication with PC – setting of frequency of received signal

Quality reception of signals from NOAA satellites requires mutual collaboration of all the hardware and software components – preferably without any human intervention. That’s why the receiver’s features were extended by adding an RS232 communication channel, which is designed to work with an outstanding decoding program, WXtoIMG.

Condition: The program WXtoIMG must have the valid (most current) set of Keplerian data (e.g. NORAD Two-Line Element Sets Current Data). At the moment when satellite appears on the horizon,  the program WXtoIMG sends a code to the receiver, which will tune its frequency within the 137MHz band. The receiver then transmits a 2400Hz modulated signal to the computer (via the sound card), which is then transformed into an image by the WXtoIMG program. When the satellite disappears behind the horizon, the receiver and computer are switched into a standby mode and await the next code generated by the program WXtoIMG at the moment, when next satellite appears on the horizon.

The current code transmitted into the receiver will tune it to another frequency within the 137MHz band.  This new function of the receiver enables fully automatic unattended reception of images and storing them on computer’s hard disk or directly to the relevant web page. Inter-connection of receiver and computer is unidirectional (from PC to the receiver).

PIN 3 of the connector COM1 on PC is connected with the PIN_RS232 (the first conductor – e.g. a low-frequency cable) and PIN 5 of the connector COM1 on PC is connected with the GND of the receiver (the second conductor, preferably formed by shielding (braiding) of the low-frequency cable).

It is also possible to use a standard COM9PIN cable without crossover of the conductors RX and TX for this connection.

Testing program: RX134141MHZ/RS232/WXtoIMG CODE (ZIP file)



Configuration of the program WXtoIMG for reception of satellites NOAA or METEOSAT is very simple (www support - help) . Set the mode to NOAA or METEOR, and the Interface type to Sound Card. The help       with this program is also very user friendly, you will find all the details of setting and operation.

1. WXtoIMG: Options/Ground Station Locatinon


2. WXtoIMG: Options/Recording Options


2a. WXtoIMG: Options/Recording Options (alternate)

3. WXtoIMG: File/Record


4. WXtoIMG: Options/Map Overlay Options



Basic set-up for communication with the Interface EMGO RX134141MHZ/WXtoIMG/RS232 ( )

Program WXtoIMG has many functions, thanks to which it is a very powerful tool for reception and decoding of images from meteorological satellites. You can run the program in basic mode as freeware without necessity to pay any licence fee. Should you wish to use its extensive more complex functions, you can choose one of several licences for accessing full version of the program.

... two-colour glasses for stereoscopic study picture NOAA (part of licence WXTOIMG SW)

1. Set the exact QTH coordinates (geographical). Option-Ground station location1. Set the exact QTH coordinates (geographical). Option-Ground station location.
2. Setting of options in the system of reception of images and communication port for RX134141MHZ/WXTOIMG/RS232. “Option-Recording options”.
3. Set the type of satellite in the menu “Satellite” to “Autodetect”.
4. Set the satellite approach direction in the menu “Direction” to “Autodetect”.
5. Start recording of received images. “File-Record”.
If you do not want store the pictures on the web, do not check the item “Create web page”. By clicking the “Image Settings” you will set the spectre, in which you want the final pictures generated. After clicking the “Record” the program will be switched to the mode of waiting for approach of the satellite.
6. The received image can be either OK or it may consist only of more or less angled lines. If you see instead of the image just some skew lines, set the option “Options-Disable PLL”, afterwards choose the “Image-Slant correction” and draw by mouse a straight line over this skew line. Computer will re-calculate the „sampling“ frequency. In the “Options-Disable PLL” uncheck the option and everything should be now OK.
7. You can set outlining of contours of countries, rivers and towns in the final picture. Use the menu “Options-Map Overlay Options” to enable this feature.
8. If you do want to remove telemetric data from the images (vertical lines at the image sides), you can switch-off this option in the menu item “Options-Crop telemetry”.

Important final notice: It is absolutely necessary to update regularly Keplerian data (
 ), otherwise contours of countries can be shifted when the map is inserted into the images. I do it myself on a daily basis.

Shall reply here:         


[ BACK ]


[1 ] Günter Borchert DF5FC, Funkamateur 2/1995, str. 153 - 156 Der  Wetterfrosch - ein 137 MHz  Satellitenempfänger, continuation in Funkamateur 3/1995, p. 274 

[2] Ing. Radek Vaclavik OK2XDX, Prijimac a interfejs WXSAT (prijem snimku z orbitalnich meteosatelitu) [Receiver and interface WXSAT (receipt of images from orbital meteorological satellites)]. A-Radio Praktická elektronika, series of articles in issues Nos. 2-6/1997. 

[3] OK2UGS.: Prijimace FM v pasmu 144 - 146 MHz s obvodem Motorola  MC3362 [FM receiver for the band 144 -146  MHz with the circuit Motorola  MC3362]. A_Radio_Electus-99, pp.73-79 

[4] Marsik, V.: Kmitoctova synteza oscilatoroveho kmitoctu rozhlasovych prijímacu [Frequency synthesis of oscillator  frequency of radio receivers], Amaterske  Radio B3/1987, p. 88. 

[5] Motorola, Linear/Interface ICs Device Data, Vol.II, str. 8-82 

[6] Philips Semiconductors, SAA1057 -Radio tuning PLL frequency synthesiser, November 1983. 

[7] ATMEL, AT89C2051 8.bit Microcontroller  with 1kbyte Flash, catalogue  sheets August 1994. 

[8] DF2FQ: VHF Empfanger, CQ DL  1/1994 

[9] Borovicka, Jiri, OK1BI. Personal consultation history of receipts from the Meteosat, Antenna Turnstile 

[10] Our location database includes most  towns and villages in the entire world (over 2 million places!)  / 

[11] OZ1HEJ, Pedersen, Michael: Receiver with LCD readout:

[12] OK2UGS.: Prijimace FM v pasmu 144 - 146 MHz s obvodem Motorola MC3362 [FM receiver for the band 44 -146  MHz with the circuit Motorola MC3362]. Elektroinzert 5/97 p. 6. 

[13] Philips Semiconductors: SE567-Tone decoder/phase-locked loop, , 4/92 

[14] OK2UGS.:

[15] Ing. Radek Václavik, OK2XDX: Prakticka elektronika No. 7/1999 construction guide to building of converter LNC1700 MHz 

[16] L. B. Cebik, W4RNL: The Turnstile An Omni-Directional Horizontally Polarized Antenna 

[17] Martin DH7GL:

[18] Ruud JANSEN'S PA0ROJ: QFHA Skladaci antena na cesty za poznanim [Foldaway antenna for exploration trips] 

[19] Steve Blackmore: QFHA

 (step-by-step construction guide to building and QHFA) 

[20] Borre Ludvigsen: QFHA - More pictures and construction picture above is one of the designs on this site. 

[21] Josef Danes et al: Amaterska radiotechnika a elektrotechnika, 3. cast , Mereni na prijimacich [Ham radio and electrical engineering, 3rd part, Measurement on receivers], pp. 190  254, Nase vojsko, Praha 1988. 

[22] Kucirek, Petr: Program SatWin  predpovidi doby preletu satelitu nad  zvolenym uzemim [Program SatWin prediction of time of passages of satellites over the selected territory] 

[23] Eberhard Backeshoff, DK8JV e-mail address: , homepage:  

[24] WXtoIMG is a fully automated APT and WEFAX weather satellite (wxsat) decoder

[25] Vaclavik, R, OK2XDX: Easy down-converter  for Meteosat, VHF Communication 4/1999, page 196 - 207.

[26] Vaclavik, R, OK2XDX: Small receiver for Meteosat, VHF Communication  4/1999, page 208 - 217.


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