From:
[email protected] (Mark Zenier) on Tues, Jan 24 2006 7:13 pm
For information on the WWV, WWVH, WWVB time codes and signal
strength, go to:
http://tf.nist.gov/timefreq/index.html
From the coverage diagrams (every 2 hours), most of the
contiguous states of the USA get sufficient signal from
WWVB in any 24-hour period. That has been observed here
(Los Angeles County) using a 2 1/2 foot diameter loop;
distance to Ft. Collins is roughly 800 miles (?).
By actual test, my LaCrosse radio wristwatch was able to
sync on WWVB on an auto trip to Wisconsin and back over
September to October. Typically such radio watches only
begin checking/syncing after midnight local time. The
internal quartz timing oscillator remains stable (for
time indication) within one second in 24 hours.
Radio clocks are consumer electronics items that typically
cost $20 to $30 (depending on display size and extras such
as local temperator). If all that is wanted is automatic
time setting, it may not be a good return on time
investment to build one's own automatic-setting clock.
Those radio clocks aren't much good for zero-beating a
local frequency standard except: If the local standard
is counted down to 1-second pulses for comparison with
the radio clock (arduous process to check).
There was once a KIT for a WWV time code receiver (Heathkit?).
As memory serves, it cost about $400 just for the kit! That
was in much older days before 25-cent 74LS00 chips.
The original requestor wanted a WWV receiver, presumably to
zero-beat a local crystal standard. ANY HF receiver will do
for that, but preferrably one whose S-Meter can show very
slow beats (well below 100 Hz). As another suggested, a
cheapo import SWL receiver can do that, adding only a
metering connection to the internal AGC line (for the slow
zero beat). Bandwidth of the IF is not of great importance
since the time-frequency bands are wider than the usual
cheapo receiver IF bandwidth.
In the northern Los Angeles area, I've never had a problem
picking up either WWV or WWVH on 5, 10, or 15 MHz, even with
a few feet of hook-up wire as an antenna. That's over a 42
year residence in this same house here. The time ticks are
good for checking progressive aging of local frequency
standards which are counted down to 1 second output...that
compared with the time tick in delay...and delay change (to
indicate very slow changes in the local frequency standard).
The time tick method was once the ONLY precise way to check
out local L.A. frequency standards when WWV was located
back east. That preciseness was to better than 1 part per
million.
A simple TRF arrangement tuned to 5 MHz will do the trick
for a receiver used solely for zero-beating and hearing the
voice announcements and time ticks. The interstage tuning
will be stable enough to pick up WWV or WWVH. To get 10
or 15 MHz carriers, add a mixer to the antenna input with
a local oscillator of 5 and 10 MHz. A local frequency
standard can supply that; no extra LO crystals required.
Four stages tuned to 5 MHz with Q = 100 will result in an
overall TRF/IF bandwidth of about 20 KHz, quite adequate
for WWV/WWVH.
[email protected]
