eHam

eHam Forums => Antennas and Towers and more => Topic started by: KK4MYT on December 23, 2012, 02:32:43 PM



Title: vertical vs horizontal
Post by: KK4MYT on December 23, 2012, 02:32:43 PM
I am curious. When I was in the Navy I was running the mars station on board USS Briscoe NNN0CVN. I had all kenwood gear coupled to half of a navy hf antennae. This was of course mounted vertically. I was doing phone patchs from the Red Sea nightly and always had reports of how good my signal was to New Hampshire. From everything I read here and else where the antennae should not have been that good. So is it really that important when transmitting SSB as to which polarization you use. I think probably yes in FM but otherwise not so sure it matters. I would send and receive margrams on 5 watts power so I really do wonder.

Just curious.
Jason
KK4MYT


Title: RE: vertical vs horizontal
Post by: K7KBN on December 23, 2012, 03:04:43 PM
Propagation is dependent on frequency but not on mode.  As far as polarization, well, let's assume the shore MARS station you were ternminated with was using a multi-element beam and horizontal polarization.  For a contact by direct wave (not "ground wave", as some would call it), there would be about 20dB loss because of cross-polarization.  Once the transmitted RF gets refracted through the ionosphere and back to earth, there's no telling exactly WHAT its polarization will be.  If it works, it works, and you've proved it.

I used to run patches from USS Kitty Hawk when the ship was anywhere in the First Fleet (basically across the Pacific as far as 160 degrees west longitude) to San Diego, Bremerton and places in between (like Hawaii).  We had a Collins S-Line including a 30L1, feeding a TOP FED vertical hanging from the angle deck all the way on the port side of Kitty Hawk's flight deck.  Never a problem. 

This was an authorized ham station, though...we weren't affiliated with MARS, for some reason.  I was a Radioman on board from 1963-1966.


Title: RE: vertical vs horizontal
Post by: AA4PB on December 23, 2012, 04:29:05 PM
You might be getting confused with amateur VHF operations. FM stations typically use vertical polarization while SSB stations use horizontal polarization. The reason has nothing to do with different modes requiring different polarization however. Its mostly a matter of tradition. FM was used primarily for mobiles and a vertical antenna was easier to install. Fixed FM stations used vertical so they could talk to the mobiles. SSB stations were primarily fixed stations who were interested in weak signal work and needed directional antennas so the horizontal Yagi was easier to install.

What you don't want to do if you are using direct wave (the propagation mode usually in effect for local VHF work) is to have one station vertical and the other horizontal. That will result in a good deal of attenuation, in the area of -20dB.

Since HF propagation is usually skywave it really doesn't matter if you use horizontal or vertical polarization or if the two stations are cross polarized because the polarization typically gets changed during propogation anyway. The reason that you had such a good signal was probably that your vertical had a massive steel counterpoise (the ship) sitting in salt water, miles away from any obstructions. A vertical is a good solution for a shipboard HF installation. Think of the issues you'd have trying to keep a horizontal Yagi pointed towards the other station  ;D



Title: RE: vertical vs horizontal
Post by: K2OWK on December 23, 2012, 04:44:48 PM
When transmitting using a vertical antenna over salt water, you have the worlds best infinite ground plane. Ship to shore, ship to ship or shore to ship works great over salt water. Of course if the two antennas are line of site then both antennas must be the same polarization or very high attenuation will occur, but under skip conditions as said by K7KBM all bets are off and excellent signals can be heard by both the shore and the ship stations. When I was in the merchant marines we had a scheduled contact on 12.421MHZ between our ship in Indonesia and our home base in Texas. The ship had a vertically polarized antenna and the base station had a multi-element beam horizontally polarized. We were always able to get through. We were running a kilowatt at both ends which also helped.

73s

K2OWK


Title: RE: vertical vs horizontal
Post by: KI4SDY on December 27, 2012, 09:41:39 AM
I believe the reason they use vertical antennas on ships for HF SSB is quite simple. Ships are always in motion and change angles frequently. This makes aiming the broadside of a horizontal antenna temporary at best and not too reliable, especially if the direction of the station you want to contact is not in synchronization with your current course. Verticals, on the other hand, transmit and receive in all directions no matter what direction the ship is currently pointed. The excellent salt water ground plane is an added plus!   ;D



Title: RE: vertical vs horizontal
Post by: K7KBN on December 27, 2012, 11:17:30 AM
Aboard an aircraft carrier, the deck-edge antennas (normally vertical within a very few degrees) are lowered to 90 degrees outboard, or sometimes 120 degrees, depending on what's happening on the flight deck.  This includes both transmitting antennas and receiving antennas.

Since some time in the 1970s, when the Navy pretty much did away with HF (and CW >:( ), there hasn't been much in the way of studies done, AFAIK, concerning radiation patterns/interference on the HF side.  These days, the HF transmitting antennas are located primarily aft, both port and starboard, and the receiving HF antennas are forward.

We never had much of a problem with staying terminated with shore stations when we'd lower/raise the antennas.  At least not on the CW circuits.  I believe the "covered circuits" had a few problems now and then.  These days, however, they rely on satellite links for everything.  As I tell today's "Radiomen" (who now are called "Information Specialists" or "Information Technicians") when I was a Navy Communicator, the only "satellite" we had was called "the moon", and we didn't rely on it for help.  ;D


Title: RE: vertical vs horizontal
Post by: W9GB on December 27, 2012, 04:56:20 PM
Pat -

The newest Mobile User Objective System (MUOS) is an impressive satellite (15 year design life)
 heaviest comm sat payload launched by Atlas 5.
This system is the replacement for Navy's Ultra High Frequency Follow-On (1993-2003)
11 satellite constellation.
MUOS is a sky based cell-phone tower and comm shed !
http://spaceflightnow.com/atlas/av030/

One already in orbit (Feb 2012), next one goes up in July 2013;
 then the remaining 3 satellites by 2015.