Are you getting ready for the upcoming winter’s reduced QRN on lower frequencies? Maybe preparing for the new LF band or planning a beacon in the 160-190 kHz “experimenter’s band”?
If so, I may be able to help you out with a freebie antenna. It even meets Mil-Specs.
On the ocean floor, in the northwestern part of the Pacific, there are a number of VLF floating wire antennas that are not currently being used. In fact, they’ve been abandoned. They exist elsewhere as well but I have first-hand knowledge of those in the area mentioned…
About that “floating” part – they only float when they’re in motion.
Here’s how they got there:
Normal submarine communications is via UHF satellites. This provides an extremely high data rate, reliability and two-way comms. The main disdavantage of this is that a submarine has to be at periscope depth (PD) since the main antennas are in one of the two periscopes.
But being at PD means a risk of detection, or worse – broaching, if the sea state is heavy. And, of course, being at PD is impossible while under polar ice.
For receive only, there are two antennas capable of receiving VLF transmissions – the “football” and the floating wire antennas.
The football gets its name from its shape and is about twice the size of an American football. It sits on a short mast next to the periscopes and can be raised hydraulically (though not nearly as tall as a periscope). And it can be just below the water’s surface and still receive. But theory is one thing and reality is another…to put this in Navy-speak, it’s a POS performance-wise.
Enter the floating wire antenna.
Only streamed out when needed, the floating wire is streamed from a spool in the sub’s bow compartment and then goes out the top of the sail (the modern word for what used to be called a conning tower). Several thousand feet are fed out and trailed behind the sub which is typically at a shallow depth. The Officer of the Deck (OOD) usually follows the radioman’s recommendations regarding which course to steer for maximum signal strength.
And then comes the problem.
The OOD has a million things to think about when the sub is shallow – particularly if under the ice “up north”. Once all the PD evolutions are completed, we all want to go deep where the seas are smooth. At this point, the OOD might say, “Dive, make your depth xxxx feet.” He may or may not specify a “down angle”.
If the down angle is steeper than a specified maximum (either accidently or due to a rough sea state), the screw can – and will! – sever the floating wire antenna.
All American subs carry several back-ups on every mission. They’d make a fine Beverage for 160 meters………..
For another story on a severed antenna (with a “life lesson” thrown in), check out this site.