ARLA/CLUSTER: Estação padrão WWV emite em 25 MHz / 2kW na polarização circular e solicita relatórios de recepção.

[João Costa > CT1FBF]

WWV 25 MHz signal swapped to circular polarization, reception reports
invited

The ARRL reprt the resurrected 25-MHz signal of time and frequency standard
station WWV 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.�

Read the full article at
WWV 25 MHz Signal Swapped to Circular Polarization, Reception Reports
Invited
<http://www.arrl.org/news/wwv-25-mhz-signal-swapped-to-circular-polarization>
-------------- próxima parte ----------
Um anexo em HTML foi limpo...
URL: http://radio-amador.net/pipermail/cluster/attachments/20170717/a3c6089e/attachment.html