vertical take off angles vs hor 1/4 wave and ground question

[ghutch]

i'm planning a beach trip during the next couple weeks.....been setting around think up antennas to take and setup as a portable DX antenna. The antenna must very portable (due to size) and the mast can be no more than 20feet. My plan is to take a 102 whips and a couple 10 foot fence top rails to use as a mast, some wire to use as radials(if needed).
thought about taking two 102 whips and making a hor. 1/4 wave dipole that can be rotated? or may just use the 102 on top as a vertical. I think the take off angle would be better for the vertical for DX as all the mast we can take is 20 feet of top rail....what do you guys think would be the better antenna with these limitations?? My question about grounding is, if the grounded end of the mast (top rails ) are buried into the sand a foot or so(wet sand) to stablize the base,(using rope as guys) will i need to run a ground wire from the 102 whip down the mast and attach to a ground rod or will the mast act as my ground?
second question is can anyone tell me the take off angle on such an antenna?

setup will be on the sand, at the beach feet from the gulf of mexico around 60 miles south of corpus christi tx
i'll post before we go and see if any members can make contacts the plan to work the station for 3 days.

 

[wavrider]

What frequency you wanting to work? That will make a diffrence in the vertical size.

 

[ghutch]

27 mhz DX will use 555 as the center freq..
had thought about a siro dipole mounted horizontal, easy to rotate but the 102's would give me the same thing. problem I thing will be the take off angle if the antenna is setup as a horizontal at 20 feet will be high....a vertical I think would be much lower mounted at 20 feet....for DX this may be the better way to go.

 

[W5LZ]

The simplest solution would be to take 2 - 3 feet of mast, and lots of wire for radials and ground mounting the thing. Considering the amount of mast you can take, that would probably result in a lower TOA than otherwise.
- 'Doc

 

[BOOTY MONSTER]

Height versus take off angle

 

[wavrider]

Research a MOXON antenna, easy to build, lightweight, portable if built out of PVC.

At 20' it will give you a decent TOA and it will also get some ground gain being horizontal polarized.

Next option would be a dipole in a tree, even a low tree will work.

Then slopers will also work.

If you are determined to work a vertical, then 18 to 20' of mast pipe, an Imax 2000 is light weight as is an A99. Either one will give you a decent TAO for DX.

But do not get hung up on TAO, as the arriving signals will vary as to what angle they arrive at.

The 102" whip will be fine, especially in a salt air environment. Need at least 3 or 4 raised radials for a counterpoise.

Have fun and good DX.

 

[Captain Kilowatt]

Research a MOXON antenna, easy to build, lightweight, portable if built out of PVC.

At 20' it will give you a decent TOA and it will also get some ground gain being horizontal polarized.

Next option would be a dipole in a tree, even a low tree will work.

Then slopers will also work.

If you are determined to work a vertical, then 18 to 20' of mast pipe, an Imax 2000 is light weight as is an A99. Either one will give you a decent TAO for DX.

But do not get hung up on TAO, as the arriving signals will vary as to what angle they arrive at.

The 102" whip will be fine, especially in a salt air environment. Need at least 3 or 4 raised radials for a counterpoise.

Have fun and good DX.

I have been trying to convince people of this for years.All too often people think that they absolutely need the lowest TOA they can get to work DX. The truth is that a very low TOA is really only needed when trying to work really long haul DX, like halfway around the world or further via longpath. For everyday DX within North America or to the Carribbean or South America from the Gulf of Mexico area TOA should not even be a consideration for a temporary antenna installation. You will work plenty of DX if you can hear it. The fact that the antenna will be next to salt water means that you will have a pretty decent TOA to begin with.

 

[HomerBB]

Easiest thing?

Your fence posts for mast. and a 1-1/4" piece of PVC on the top of it for an insulator.

Two pieces of wire for your dipole attached to the top mast insulator. Two stakes to drive in the sand. Two pieces of rope/cord to tie off the ends of you inverted Vee dipole to the two stakes. Allows for easy SWR match and high portability.

 

[ghutch]

First off THANKS! Guys, for the input and ideas.....I do not understand "counterpose" is it the same thing as radials attached to ground side of the coax?
If I use a 102 whip then 6-8-10 radials made of 12 gauge copper wire arranged in a fan pattern around the base of the mast and then attached to the mast would work as the counterpose? if this is correct then what length should they be? 102 inches?
i read somewhere ground wires need to be as short as possible so it brings up the question? if I use a 20 ft mast and have coax attached to the feed point of the 102 whip and the braid attached to the mast and ground wire running down to the earth. ....would i have a 1/4 wave vertical with a 20 ft counterpose? not trying to make this hard just dont fully understand the ground wire/countepose. seems to me a 1/4 wave antenna needs a 1/4 wave balance or counterpose? to be balanced?
if i used a dipole for example 102 whips on both sides then the mast and radials would connected but the whips would not have a direct connection to the mast or radials? thus a balance 1/4 wave dipole and then the attached mast and radials

 

[HomerBB]

ghutch, this drawing is crude, but it does demonstrate the connections related to a 1/4 wave GP (and any other antenna employing a counterpoise).
Braid to radials (or one half a dipole), and center conductor to the vertical.

An earth ground is not a counterpoise. A mast can behave as a counterpoise, but so does the coax when antennas lack sufficient counterpoise. Simply put, the counterpoise is the other half of the antenna.

In the setup you are asking about I see no need to worry with an earth ground. Your mast is enough.

 

[M0GVZ]

Go with the inverted V idea. One support, quite omnidirectional with more gain than a vertical antenna and no faffing around with radials.

 

[ghutch]

Thanks Homer i think I got it!! ....my mental issue is the radials and the ground wire that runs down the mast. they are much longer than the 1/4 wave whip used as a radiator. so i have a un balanced 1/4 radiator with an unbalanced "counterpose? right??....to make a balanced antenna i would need to cut the radials at the 1/4 wave and attach them just below the radiator as many GP commercial antennas are constructed.
the sand is wet down about 6 inches so the mast would be grounded to earth.....the radials could be buried or just spread out on the ground and the ends stuck into the sand.....they would be gronded to earth.....the radiator(whip) would connect to the center of the coax and the braid connected to the stud mount and mast. i know this would work as i have a 1/4 wave dipole made in this way....but it is balanced on both ends...1/4 wave radiator and 1\4 wave counterpose or ground connected to the coax braid. I may be putting to much thought into a simple antenna but the unbalanced radials and ground wire/mast cause me to go into antenna overdrive! :headbang

 

[Beetle]

You need to mount the vertical no more than a very few INCHES above the ground level and run radials out from there. Each radial wire at least 1/4 wavelength, at least half a dozen, maybe more, fairly equally spaced. You can bury the wires in sand with no problems.

If you simply MUST elevate the antenna, you'll have to elevate the radials to keep them close to the feedpoint. You'll still need at least four radials and more would be better (IMO) to act as the return path for the RF sent out by the vertical radiator. The antenna will be more sensitive to radial length than if it were ground mounted. Radials can double as part of a guying system.

Either way, be careful that no people or pets can come into contact with the antenna OR the radials.

 

[gamegetter]

To the beach?

i'm taking a cooler, my fishing poles, and sun tan lotion!

 

[Marconi]

Go with the inverted V idea. One support, quite omnidirectional with more gain than a vertical antenna and no faffing around with radials.

M0GVZ, in my experience with an inverted V, it worked fine the higher I could get it, and it didn't seem to work good at all when less than 20' feet, even for DX. I think ghutch would be better off under the circumstances he notes getting an end fed vertical up on a 20' foot mast.