Useful links

Antennas, ground systems

• 472 kHz small loop experiment (VK1SV)
• 630 m 8-circle antenna (NO3M)
• 630 m loaded inverted L Antenna (VK5FQ)
• 630 m Loop On the Ground (LOG) RX antenna experiments (N6LF)
• 630 m RX vertical folded dipole (WB4JWM)
• 630 m transmit experiment with a baloon lifted antenna (SQ2BXI)
• 630 meter station TX antenna (WB4JWM)
• Antennas for 136 kHz (ON7YD) ^*
• A receive only vertical (WA3ETD)
• A receiving array for 160 m through 2200 m (N6LF)
• A small 500 kHz vertical antenna (G0MRF)
• A versatile 630m antenna (VE7SL)
• Design of some coupling circuits for aircraft transmitting aerials (W.W. Honor) Dated 1945, covers 140-500 kHz
• Ground Loss Measurement at LF (G3NYK & EI0CF)^*
• LF and MF transmitting antennas characteristics and diagrams (ITU)
• LF-MF antenna notes (N6LF)
• Low and medium frequency receive antennas (NO3M)
• Magnetic Loop antenna for 630m (DL6RCN)
• Multi-Turn LF/MF Receiving Loops (N6LF)
• N6LF 630m Transmitting Antenna Version 2 (N6LF)
• Radio antenna engineering (Edmund A. Laport, electronic edition by AE6EO)
• Receiving with wideband small active loops in NDB band (250 to 500 KHz) (LZ1AQ)
• Short low- and medium-frequency antenna performance (Valentino Trainotti et al.)
• Simplified calculation of ground losses in low- and medium-frequency antenna systems (Luis A. Dorado et al.)
• Skin Depth And Wavelength In Soil (N6LF)
• Some Comments on Laport (N6LF)
• Tee vertical antenna for the 630 m band (VK2XV)
• The AM umbrella antenna (K3LC, C. M. Beverage)
• The Low Noise Vertical (VE7SL)
• The PA0RDT Miniwhip antenna (PA0RDT)
• Universal curves for soil conductivity and permittivity (N6LF)

Antenna matching, loading coils

• 136/475kHz ATU (G0FTD)
• 250-400 µH variometer (G0MRF)
• A short antenna tuner (HB9DUL)
• Ball variometer (DL4YHF)
• Coil Length-to-Diameter Ratios For Maximum Q in LF/MF Antenna Loading Inductors (N6LF)
• Operating a longwire on VLF, 630 m and 160 m - 17 m via a simple matching circuit (SQ5BPF)
• Optimum Q LF/MF Antenna Loading Inductors (N6LF)
• The variometer – how to make (WA3ETD)
• Wet Inductor Tests (N6LF)

Books, magazines

• American Radio History Online library of old books and magazines (some starting 1920's)
• LF Today (G3XDV) A guide to success on the bands below 1MHz
• MF Down Under (VK5BUG) An edited VK-compendium of articles and projects for the 630m and 160m bands
• Volume 1 (2016) of the 630 m yearbook (W5EST) Analysis & commentary on a wide range of topics related to 630 m
• Volume 2 (2017-2018) of the 630 m yearbook (W5EST) Analysis & commentary on a wide range of topics related to 630 m
• Volume 3 (2019) of the 630 m yearbook (W5EST) Analysis & commentary on a wide range of topics related to 630 m
• Volume 4 (2020-2021) of the 630 m yearbook (W5EST) Analysis & commentary on a wide range of topics related to 630 m

Commercial rigs

• EME223 630m Band Transverter Kit
• JUMA TX500
• MF SOLUTIONS 630 Meter Transmit Converter

Measuring

• 630 m antenna matching measurements using an oscilloscope (VE7CNF)
• A long-wave SWR meter (HB9DUL) ^*
• LF VSWR meter (G0MRF) ^*
• LF-HF reflection coefficient bridge (G0MRF)
• Making a ScopeMatch for the LF / MF bands (VK5FQ)
• Simple 1PPS signal source and distribution amplifier (SQ5BPF)
• Tuning aids for the 136 kHz and 500 kHz Bands (M0BMU)

Modes, modulation

• Basic forward error correction (FEC) schemes (Mark Watson)
• The principle of forward error correction (Paul Nicholson)
• Weak signal modes (ON7YD)

Operating

• Some digital modes on MF & LF (VK5FQ)

Personal sites ^#

Propagation

• Longwave and mediumwave propagation (H. E. Farrow, BBC)
• Worldwide NDB list List of Non Directional Beacons around the world, useful to to check propagation

Receiving

• 136 kHz LF and 472 kHz MF Pre-amplifiers (G0MRF)
• 475 kHz bandpass filter (VE7VV)
• 500-515 kHz preselector (W1VD)
• 518 kHz elliptical 50 Ohm low-pass filter (W1TAG)
• A simple bandpass filter for 475 kHz (VK1SV)
• ADSL Filter for 630m (DL0ABR, German language)
• Making a 472 to 479 kHz bandpass receive filter for 630 m (VK5ZVS)
• Receive band pass filter (WA3U)
• RX 630m Preselector (DL0ABR, German language)

Software

• Argo (I2PHD) A DFCW and QRSS viewer
• Freeware for radio amateurs (DL5WSB, sk) Mini Ring Core Calculator, mini dB Calculator, ...
• Opera (EA5HVK) Opera receiving and transmitting software
• QRS (ON7YD) QRSS & DFCW transmitting software
• SlowJT9 (ON7YD) Supports the slow JT9 submodes (JT9-2, JT9-5 and JT9-10) as well as JT9-1
• Spectrum Lab (DL4YHF) Audio spectrum analyzer with waterfall display, for QRSS & DFCW reception
• Winrad (I2PHD et al.) SDR amateur radio program
• WSJT-X (K1JT et al.) FST4(W), FT4, FT8, JT4, JT9, JT65, Q65, MSK144 and WSPR receiving and transmitting software
• WSPR (K1JT) WSPR receiving and transmitting software
• WSQ (ZL2AFP, DL4YHF) WSQ2 receiving and transmitting software

Transmitting

• +28 dBm linear driver (WB4JWM)
• 0-500 kHz linear exciter (VK2XV)
• 1W QRP QTX (GW3UEP)
• 100 Watt CW transmitter for the 500 kHz band (N4ICK)
• 100 Watt MF CW TX (GW3UEP)
• 137/472 kHz transmitter (W1TAG)
• 225 Watt 630 meter non-linear amplifier (WB4JWM)
• 25 Watt 472 kHz PA (GW3UEP)
• 28 MHz to 472 kHz QRP transverter (DL8YCA)
• 4 watt class A amplifier (WB4JWM)
• 400 watt FET amplifier for 630 meters (W7IUV)
• 472 kHz 25W PA (GW3UEP)
• 472 kHz transmitter (M1GEO)
• 472 kHz transverter (G3XBM)
• 472 kHz VFO (GW3UEP)
• 472-479 kHz QRP linear amplifier & RX-preamplifier (DL8YCA)
• 475 kHz 7 pole elliptical low pass filter (VK5FQ)
• 475 kHz 40 W linear amplifier (DL8YCA)
• 500 kHz Class-D 500-Watt RF deck (W1VD)
• 500 kHz CW transmitter (M1BMU)
• 500 Watt output 4-400A linear amplifier for 600 meters (W5JGV)
• 630 m 100 watt transmitter (VK5FQ)
• 630m 200W PA (DL0ABR, German language)
• 630 m 5-15 W amplifier (IW3SGT)
• 630m 500W Class-C PA (DL0ABR, German language)
• 630m 800W Class-C PA (DL0ABR, German language)
• 630 m low power transmitter (VK5FQ)
• 630m Transverter using a bidirectional bigh-power mixer (VE7CNF)
• 630 m Wilkinson power combiner (VE7SL)
• 6AG7/807 transmitter for 472 kHz (VK1SV)
• A 100 to 200 watt linear amplifier (WB4JWM)
• A 300 W Class D amplifier for 630 m (G0MRF)
• A 630 m transverter (VE7CA)
• A simple amplifier for the Ultimate 3 for 136 & 472 kHz (HB9ASB)
• A small 'linear' power amplifier for MF (DL4YHF)
• Broadband 5 watt amplifier for LF and MF (G0MRF)
• Class E Power Amplifier Design (G3NYK, GW4HXO, EI0CF)
• HF to LF/MF linear transverter with 500 kHz Class D EER power amplifier (M0BMU)
• LF/MF, flexible, efficient, non-linear, transmit converter (VK1SV)
• Long-waves and medium-waves dual-band kilowatt CW transmitter (HB9DUL)
• Medium power linear power amplifier for LF/MF (G4JNT)
• Modifying an IC735 for the 630 m band (SQ5BPF)
• SoftRock RXTX - Modification for 2200, 630 and 160 metre operation (VE7VV)
• SWR protection circuit for FET amplifiers (WB4JWM)
• Third-Method Narrowband Direct Upconverter for the LF / MF Bands (G4JNT)
• Transverter for the 630 m band (VK6YSF)
• Using the Ultimate 2 on 472 kHz with an external PA (G8AGN)
• VXO controlled transmitter for the UK 500 kHz Experiment (G3YMC)

Web

• ON4KST chat (630 m) (ON4KST) 
• PSK Automatic Propagation Reporter Propagation reporter, unlike the name suggests also useable for JT9, FT8, Opera, ...
• Twente WebSDR (PA3FWM et al.) Wide-band WebSDR, includes 472-479 kHz
• WSPRnet WSPR propagation reporter

Other

• A survey of the 630-meter band for amateur radio (KB5NJD)
• Determination of soil electrical characteristics using a low dipole (N6LF)
• List of VLF/LF/MF grabbers (SQ2BXI)
• The ARRL 600 meter Experimental Group (W5JGV et al.)
• You, too, can work 630 meters (WD8DAS)

The missing link

Do you know one or more links that should be in the above list? Feel free to contact .
Broken links can be reported to the same e-mail address.

^*: Can be used for 630 m as well.
^#: Do you want your personal site added? Just let me know (). The only conditions are that the site is not commercial and at least partially related to 472 kHz.