630M
My Part 5 license callsign is WG2XJM. I am authorized to transmit on the following frequencies:
160.0 - 190.0 kHz 10 W ERP
460.0 - 480.0 kHz 100 W ERP
495.0 - 515.0 kHz 100 W ERP
I previously operated under the ARRL 600M Experimental Group license as WD2XSH/46 prior to acquiring my own Part 5 license.
My primary LF/MF transmit activities include CW and PSK-31 beaconing, WSPR (Dial 474.2 kHz or 495.4 kHz), and CW QSOs. My Part 5 license also permits use of SSB at 460-480 and 495-515 kHz.
Equipment
Three AMRAD based converters are used for frequency conversion using a 10 MHz LO derived from a GPS disciplined reference oscillator (modified Trimble Thunderbolt). An Elecraft K3 is used in conjuction with the transverter for dual receive and transmit capabilities, also disciplined using the 10 MHz reference (K3EXREF option).
For transmit, a W8DIZ 10W linear amplifier follows one of the AMRAD converters (down conversion) and feeds a modified (KN8AZN) Communications Concept EB-63A 100W amplifier. Maximum power is about 110W.
Three AMRAD-based converters, providing dual RX and TX. Modified W8DIZ 10W linear amp boosts converter output to drive 100W power amplifier.
Front view of LF/MF Transverter. Selectable low and high power ranges by switching a 10 dB Pi-attenuator at the transmitter IF port. Ten Tec enclosure.
Modified EB63A amplifier based on mods by KN8AZN. LMB Heeger Tite-Fit chassis.
Inside of modified EB63A amplifier. COR circuit in original EB63 design is only used for a front panel "TX" LED.
KN8AZN-design Elliptic LPF; T200-2 cores, Ten Tec enclosure.
A modified Heathkit SB-1000 amplifier (3-500Z) is used for operation up to the license power limit of 20W ERP. Modifications include:
- Input Pi-network; 10000pf, 20.8uH, 7400 pf (Q=2.5 @ 475 kHz)
- Filament choke; FT240-77 core, 24T bifilar #14 enameled wire - 1.7 mH
- Plate Choke; #30 enameled wire over a 1" x 6.75" ceramic insulator - 1.13 mH
- DC supply bypassing capacitors (cold end of plate choke); 2 x .0047 uF 6kV
- Replaced DC Blocking capacitors, 2 x .002 uF 6kV
- Output Pi-network inductor; T300A-2 toroid, 69T #14 enameled - approx. 108 uH
- Additional padding capacitors in parallel with both the plate and loading air variables.
Output pi-network Q is approx. 14 @ 475 kHz and 13.4 @ 495 kHz. The amplifier is run at about 300W output to reach the 20W ERP level. Output power starts low for the first several seconds as the plate tuning padder capacitors (upper left in photo) start to warm up from RF current and drift in capacitance until they settle. Currently the padders are 2 x 500 pF 5kV HEC 858 (HT58) doorknobs, 2 x 170 pF 5 kV HEC 850 (HT50) doorknobs. The 500 pF padders may be replaced when more suitable caps are acquired (probably 10 x 100 pF 5kV HT50s) to reduce or mostly eliminate the capacitance drift by distributing RF current over more caps and better temperature coefficient in the lower value, HT50 series doorknobs.
Inside the modified SB-1000 linear amplifier.
Antenna
The 600M antenna is a T-vertical; 19.4m vertical section and 128.6m top loading wire. There are currently 48 radials ranging from 80-130 ft. Estimated efficiency is 6%. With 100W input, ERP is around 7W. The feedline from the shack is 600 ft of LMR-400 equivalent coax.
Antenna Feedpoint
Series Inductance: 4-3/8 in "Bugcatcher" coil ; approx 64 uH @ 475 kHz tap
Shunt Inductance (impedance matching): 3-in AirDux coil approx. 13uH
Remote Tuning: Grey metal enclosure houses a Bias-T circuit for injecting relay activation voltage (13.8V); black ABS box houses relay that switches between two coil taps, centered at 475 kHz (CW/PSK) and 495 kHz (WSPR)
SWR: 1.03:1 @ 475 kHz, 1.04:1 @ 495 kHz
(Yes, that's old ladder line used as a pair of radials toward the rear of the photo!)
Reports
Please submit reception reports by visiting http://500kc.com/reportinfo.htm