Marine Radios

[renpirate]

It sounds like a loud whistle and a mirror would be a better solution to that problem. A couple of aerial flares and dye markers would be helpful too.

Does anybody know what kind of radios that navy pilots are issued? I am sure they have thought this one through. The idea there would be for the downed pilot to be able to communicate with rescue aircraft.

 

[Don Burke]

Does anybody know what kind of radios that navy pilots are issued? I am sure they have thought this one through. The idea there would be for the downed pilot to be able to communicate with rescue aircraft.

Here is what is being touted as the latest and greatest.

http://www.gdds.com/press2002/0517hook2.html

I remember an older radio that worked on 121.5 and 243. It did not have GPS capability and I do not recall a 156.8 (marine channel 16) capability.

 

[miketsp]

Here is what is being touted as the latest and greatest.

http://www.gdds.com/press2002/0517hook2.html

I remember an older radio that worked on 121.5 and 243. It did not have GPS capability and I do not recall a 156.8 (marine channel 16) capability.

The focus here is on "line of sight" communications because they don't want everybody listening in. With omnidirectional antennae this only happens when one antenna is very low and the other is high (search aircraft).

 

[renpirate]

Here is what is being touted as the latest and greatest.

http://www.gdds.com/press2002/0517hook2.html

That is a very impressive radio, probably in the several thousand dollar range. Wee bit too pricey for me.

I did call up the coast guard in my area and they have towers set up that should be able to pick up the signal. According to them the marine radios are line of sight and as long as there are no obstructions they should be able to pick up the signal.

Also rescue planes would be able to pick up the signals, also they highly recommended the dye markers, just like you recommended.

 

[Don Burke]

I did call up the coast guard in my area and they have towers set up that should be able to pick up the signal. According to them the marine radios are line of sight and as long as there are no obstructions they should be able to pick up the signal.

You might want to borrow a handheld (or a scanner tuned to 156.8 for that matter) and take a walk on the beach. There is no point in buying a radio if you can't hear _them_.

It is illegal to transmit from land on marine VHF without a special license. Marinas and such have this.

Also rescue planes would be able to pick up the signals, also they highly recommended the dye markers, just like you recommended.

I have seen the training films where they go past an orange PFD within 500 yards without seeing it. It is pretty hard to miss a few thousand square yards of bright green water.

 

[renpirate]

You might want to borrow a handheld (or a scanner tuned to 156.8 for that matter) and take a walk on the beach. There is no point in buying a radio if you can't hear _them_.

That's a good idea, I was going to see if I could out and do a radio check. The CG said I could do that on channel 16 or 68.

 

[String]

If going to these extremes like building an antenna pole in situ etc then i think a personal EPIRB would be more effective.

 

[Sideband]

The focus here is on "line of sight" communications because they don't want everybody listening in. With omnidirectional antennae this only happens when one antenna is very low and the other is high (search aircraft).

Not really. Line of sight communication happens any time 2 radios are able to exchange signals without using atmospheric tunneling, skip, or bounce. As long as both antennas are theoretically visible, i.e., a line can be drawn from one to the other without a hill or the curvature of the earth being in the way, it's line of sight comms. LOS communications are greatly improved by one antenna being really high (makes the 'line' capable of being much longer) but it is not the definition. The same is true if the antenna is omnidirectional or a beam.
In your example, the search plane is probably the only one that will be able to hear the lower radio but the search plane would be heard for many miles.
I'm a ham and would be glad to go into this further if you'd like.

Joe

 

[O2BBubbleFree]

I was thinking a little more about the antenna business.
Probably the best solution would be a flexible antenna supported by a 9ft sausage.
Something like:
http://cap-es.airsmc.com/projects/antenna.html

Your idea has merit wrt improving the LOS by raising the antenna above the waves and chop. If I remember correctly from my Ham classes (which I’ve never used), the only antennae that don't need a ground plane are 1/4 wavelength, which is what the radio would come with. You can usually buy slightly higher-performance rubber antennae, but any ¼ wave antenna would be pretty much the same size as the one that comes with the radio. The one you referenced is generally referred to as a ‘long wire antenna,’ and would be much too long to try to string up while floating in the ocean.

HOWEVER, I remember reading several years ago about flexible ¼ wave antennae that railway operators used. Instead of sticking up from the radio, it just hung down. This type of antenna could be used as you described, on the top of a sausage, with a short piece of coaxial cable connecting the two. My concern would be the connectors. They would have to be waterproof at the depths you dive, or you’ll get water between the inside wire and the insulation. That would be bad.

Or, (I’m thinking on the fly here, correct me if I’m wrong) you could eliminate one of the connectors and the piece of coax interconnect connect cable by finding an appropriate cable a little longer than the sausage, put a connector on one end for the radio, and strip back the insulation from the other end far enough to make a ¼ wave antenna. (For optimum performance, it needs to be precisely ¼ wavelength.) However, you would have to find a real good way of sealing the connector and the bottom of the antenna section to keep the water out, even while the cable is in your pocket at depth.

 

[Sideband]

If I saw the link correctly it wasn't a long wire. What it showed was a 1/2 wave J-pole antenna with a 1/4 wave matching section, made from twinlead. It's a dang good antenna. I have one I made and it hangs on the wall in my apartment. Using it and my HT I can talk over 13 miles south to a repeater and always get good reports. I'd keep the coax length to a minimum though as it is a high loss point for VHF.
I'm not sure I'm sold on the need for a radio, but this antenna would work great with a sausage if you decided to use one.
Several fiberglass pole sections with the bungee through the middle, like used in dome tents, would also make a great small package antenna mast.

1/4 wave antennas do need a ground plane. The metal housing of the antenna serves this purpose. I doubt you will find a "higher performance" 1/4 wave antenna as all 1/4 wave antennas are nominally 0db gain. Rubber duck antennas suck.

Joe