AmateurRadio.com

New Turnstile Antenna / WWV - 25MHz

Last week's ARRL announcement regarding WWV's new circular polarized Turnstile antenna tests on their 25MHz transmitter quickly garnered my interest.




Their 25MHz signal used to be heard world-wide on F2 until it was dropped in 1977, but somewhat surprisingly, was resurrected in 2014.

I recall hearing its 2nd harmonic on sporadic-E very routinely on 50.000MHz when I first became active on 6m back in the late 60's. Back then it was also not uncommon to hear the 3rd and 4th harmonics of ship CW stations operating on 12 and 16MHz, at the very low end of 6m and just below the band edge on 49MHz.

6m Prop Indicator From The 70's!

They were often heard calling or working maritime land stations in Hawaii or Japan and the reception of these signals meant that the band was open out to the Pacific somewhere ... but of course there was no way of knowing just how far out they were and there were never any amateur signals to be heard.

Having not listened for WWV's 25MHz signal for several decades, I set up yesterday to see if it could be heard here in mid-summer. Using my Perseus SDR and my LF/MF inverted-L, self-resonant in the middle of the broadcast-band (gosh knows what the pattern looks like up on 25MHz!), I started monitoring just after lunch. I could detect their carrier which was very weak but steady, probably arriving on ionospheric scatter via the e-layer.

A few hours later I re-checked after hearing a few Colorado signals on 6m Es and sure enough, there they were with a fairly robust signal. It too, was no doubt arriving via sporadic-E as it was again today during another widespread Es opening from the PNW to as far south as Puerto Rico.

Here is a recording of the 25MHz signal made this morning with my Perseus SDR along with a comparison recording of their 20MHz signal, made about 30 seconds later.


There is not a lot of difference between the two and both run similar powers ... 2.5kW on 20MHz and 2kW on 25MHz. The 20MHz system uses a half-wave vertical on a 7.5m tower while the 25MHz outlet uses the crossed-dipole circular polarized Turnstile shown at the top of the blog.

Reception reports of their 25MHz signal are being sought and can be e-mailed to WWV at this address.