[600MRG] WH2XTW in NorCal

[David Fannin]

Greetings,


I recently received the FCC exp license of WH2XTW for the 630 meter band,
so I've been diligently working to get on the air.
I'm based in Dublin, CA (around 25 miles east of San Francisco, 20 miles
north of San Jose).  The license grants me 20 W EIRP from 465-478 khz on
multiple modes.

For the first setup, I'm running CW at the present time, and switching to
QRSS today. I am currently transmitting on 475 kHz.  I will working to get
 WSPR  in the future.

Here's a summary of the current equipment setup:

CW keyer - k3ng keyer, home built arduino keyer using k3ng software , runs
the beacon http://blog.radioartisan.com/arduino-cw-keyer/

Transmitter - irf510 amp  , 13.8 volts power,  Cauer (Eliptic)  low pass
output filter .  Output is ~17watts, measured at the output of the
transmitter.  used this schematic for the design:
http://njdtechnologies.net/wp-content/uploads/2014/08/Schematic-for-25-watt.jpg
I replaced the output filter with a different one from
http://630m.net/dev/index.php?option=com_content&view=article&id=114:630m-transmit-low-pass-filter&catid=39:transmitters-and-amplifiers&Itemid=59.


VFO - arduino controlled AD9833 DDS module, with a small gain buffer amp.
The  buffer amp was a  design from a local RF engineer.  raises the output
of the DDS to a 10 volt square wave.

antenna -  coupled tuned loop.   1 meter  diameter loop,  13 turns of 18
awg wire in serial with a 20-180pf air var cap, tuned at 475khz.  1
coupling loop into a 4:1 balun to bring it to 50 ohms. around 3 khz of
bandwidth.  Great for receiving, but I plan on getting a larger antenna up
later.

My thanks to John WG2XIG and Neil WG2XSV for their help.


dave KK6DF/WH2XTW