WD8DAS 630-Meter Band Operations
Steve WD8DAS operated Experimental Station WH2XHY in the 630-meter band (472-479 kHz). This project was part of an effort to demonstrate that ham operation using practical rigs and suburban antennas would work on this band. This effort was recently rewarded with a new amateur band allocation from the FCC and now we can operate as hams on the 630-meter band! Here is information on the WD8DAS medium-frequency station...
JRC NSC-71M Shipboard "Reserve" Transmitter
Crystal-controlled CW transmitter 472-479 kHz with built-in matching for short antennas.
Front panel RF ammeter shows current into the antenna.
LPB "Carrier Current" Broadcast Amplifier driven by a Kenwood TS-990S on the main operating desk.
L-Network to the lower right provides the matching to the inverted-L antenna.
Meter to the upper right shows the RF current into the antenna.
Antenna System - Inverted-L wire, 40 feet up and 100 feet across.
The ground for the Inverted-L antenna system is just my regular station ground. The central
ground point is along a section of wall where the all the utility service
entrances are located. This central ground is a few feet of 1/2" copper pipe
with 1" copper straps connecting to the power entrance ground, an 8' rod driven
right outside the house, the iron and copper water pipes (before and after water
meter), and the metal HVAC ductwork in my house. To this ground system I have
connected (with more 1" copper strap) the operating desk star ground, my
two Gates BC-1T AM transmitters, the 630m transmitters, and the shields of all my
various antenna feedlines.
I made no special ground for the 630 meter antenna system - just made sure its
ground side was well-attached to my existing station ground. The outside of the
various coaxial cable shields form accidental counterpoises and radials I'm sure.
Receive antenna? My best choices are my 75-meter inverted vee dipole (with the receiver preamp turned on), or my
ground mounted 8' whip with a preamp at the base (preamp off in the receiver).
I've been very diligent about keeping noise sources in my house to a minimum,
but neighbors and powerlines do cause noises at times. I made a 10-foot
shielded loop active antenna out of coax inside PVC pipe but it is stored in the
garage right now - too unwieldy and has to be turned to peak signals or null
WSPR reports on a typical night:
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