[SMCARA] WWV 25 MHz Signal Swapped to Circular Polarization, Reception Reports Invited

[JD Delancy]

 From the ARRL News:


    WWV 25 MHz Signal Swapped to Circular Polarization, Reception
    Reports Invited

07/11/2017

The resurrected 25-MHz signal of time and frequency standard station 
*WWV <http://www.nist.gov/pml/div688/grp40/wwv.cfm>* is now emanating 
from a circularly polarized turnstile antenna. WWV had used a vertically 
polarized antenna on 25 MHz in the 1970s. Silent since 1977, the 25-MHz 
signal returned to the air on an “experimental basis” in April 2014, and 
it’s been transmitting ever since — initially on a broadband discone 
until August 2015, when it switched back to a vertical, which it used 
until the July 7 switch to circular polarization.

“[W]e are broadcasting with 2 kW from a circularly polarized turnstile 
antenna,” WWV lead electrical engineer Matt Deutch, N0RGT, told ARRL 
this week. “It is just your standard plain-vanilla turnstile — two 
horizontal orthogonal dipoles with a quarter-wave phase-shifting coax 
linking them.”

Deutch has explained that when the 25-MHz transmitter was shut down in 
1977, the antenna’s radiating element was “tossed in the bone yard, and 
a new longer section put on the tower to make it a 15 MHz stand-by 
antenna,” Deutch recounted. When WWV first reintroduced the 25-MHz 
broadcast some 37 years later in response to requests, it used a 
broadband monopole. But, it was later decided to use that antenna for 
WWV’s 2.5-MHz stand-by transmitter and to rebuild the 25-MHz antenna. 
The old radiating section was retrieved and the antenna rebuilt, so that 
it looked like what was being used in 1977.

Deutch said it’s hoped that the latest antenna change to circular 
polarization might be helpful to anyone studying propagation during next 
month’s total solar eclipse, which will be visible across the US. “My 
effort right now is focused on getting the word out, just to make people 
are aware that [the 25-MHz signal] is available, if it can be useful to 
them.”

Before the change, Deutch said WWV had received reports on the 25 MHz 
signal from across the Atlantic. The 25 MHz broadcast includes the same 
information transmitted on all other WWV frequencies and at the same 
level of accuracy.

Located in Fort Collins, Colorado, WWV is operated by the National 
Institute of Standards and Technology (*NIST* <http://www.nist.gov/>). 
WWV has *invited* <mailto:wwv at nist.gov> listeners’ comments and reports 
on its 25-MHz signal.