Frustrated

[J0313]

Originally Posted by CaptBones

Well, since I was a Navy Communications Officer and Electronic Systems Engineer for nearly the first decade of my career...and I do have first person experience with submarine radio communications in GUPPY-converted Fleet Boats... I suppose I could make a couple of points here.

The discussion is, to some degree, mixing apples and oranges. In WWII, receiving broadcast messages and sending Contact Reports to HQ (which is the game "issue" that started this discussion), dealt with HF CW ("Morse code") radio communications. Tactical communications with other ships and aircraft was done with VHF and UHF voice radio as well as voice/CW at the low-HF/high-MF frequencies.

The primary Fleet Broadcast in the 60s and 70s was still the "Fox" broadcast, even though by then it was a machine-encrypted radio-teletype system and in WWII it was a Morse code, manually encrypted system (yeah, we had "Enigma" machines too). Yes, there were early TTY communication links being used during the war, but they were almost exclusively land-line (including transatlantic cable). Towards the end of the war, such technology was starting to be implemented in the forces afloat, but the equipment wasn't yet suitable for submarines.

There's a world of difference between transmitting and receiving equipment used in WWII and now-days. But, back when I started out, we were still using the WWII equipment and systems on the shore-side of long-haul communications. The long-haul system, both send and receive, was high frequency (the "HF" part of HFDF) 3-30MHz. HF is also commonly known as "short-wave" radio; the wavelength is 100-10m (higher freq = shorter wavelength). The full-wave transmitting towers at NAVCOMSTAs Washington D.C. (Annapolis), Wahiawa (Lualaulei), HI and Stockton (Dixon), CA were landmarks that I remember well.

I can assure you that an HF radio signal, of as little as 500W at the transmitter, can be received via sky-wave refraction, at a distance of some 6000 miles or more and at a receiving antenna depth (not keel depth!) of 33 ft (10m) or more. You're not pushing a signal through the water, you're bouncing it off an ionospheric scattering layer. The trick is that the receiving antenna is a bare long-wire, or two or three in parallel, insulated from ground and connected to an ungrounded receiver, the earth is the ground plane for the signal transmitter at the radio communication shore station. The signal strength that can be detected by a full-wave or half-wave wire antenna is incredibly small; a few milliwatts will generate a very solid signal voltage. Remember, you're picking up a radio wave that is between 10 and 100m long...it will definitely penetrate the water to a depth equal to the wave-length. We routinely had to practice establishing long-haul duplex terminations across the Pacific, between Japan, Guam, Hawaii, and California, with 100W transmitters (the really good operators could do it with 10W!).

It doesn't work in reverse, the transmitting antenna has to be high-and-dry, or at least not immersed in good old salt-water; that will definitely attenuate the outgoing signal, totally. You need to be well above the water's surface to use it as the antenna's ground plane. As I noted, the shore station transmitting antennas were 350ft tall full-wave towers. Typically, the shipboard HF transmitting antennas were both long-wire (10-50m or so) and base-loaded 8ft and 16ft whip antennas. In the case of WWII US submarines, the whips were retractable, but not nearly capable of being extended sufficiently above the water when at periscope depth or radar depth to keep from being grounded by passing waves (US subs also had rod antennas incorporated in the SD radar supports). Early-on, US subs also had retractable, vertical wire antennas, consisting of a mast with a cross-head that supported two or more wires per side.

Most of the 1/4 wave and dipole VHF and UHF tactical radio antennas were small and could certainly be attached to or incorporated into a periscope, radar antenna mast, the shears, or a snorkel mast. Those you could use while the boat was submerged at either periscope or radar depth; I can guarantee they don't work underwater though.

Although it's too late to make this long story short...getting back to the topic...for both US and German WWII submariners, receiving HF "broadcast" messages at shallow depths was possible and done routinely, but transmissions to HQ had to be done on the surface.

Thank you for this info. I have a question. Could it be done in calm sea's?