Newbie Licensed Antenna Question

[popnokick]

If you're thinking about G5RV, consider the ZS6BKW. Even better, look at a Windom Off-Center Fed Dipole. Here's much more info on the Windom / OCFD antenna (and yes, I have two of them and they are fantastic... and can operate as an inverted vee if necessary) -
Windom Antenna Home Page, and Handbook
OCF Dipole - Whoa! Holy Cow! - Ham Radio

 

[Akozub]

It sounds like you're considering some sort of inverted V (which may be what you meant about 'downward V' in your post).

There's a lot that goes into making one of these things radiate (and receive) properly, partly having to do with height above the ground (higher ends make them more directional, lower ends make them much less directional) and the apex angle you propose, so if you could sketch out what you actually have in mind, that would help.

Given the stock ladder line length for the feed is about 30', will that be enough feed for you given the center point on the roof peak, and can you keep it away from metal gutters, etc, in the way to the rig? Something to consider.

A sketch of your overall terrain (house/lot/fence with compass orientation) and what you're proposing would be very helpful.

Here is a pic of the peak that I was going to attach the center of the antenna to. The next pic shows the view and right corner fence post, the left is the same. Rear of house faces south west and slopes down from my fence to the road. Fence is about 60' wide, peak of roof is about 28' high. This probably won't fly with my hoa but I'll give it a shot if the consensus is that it will work. I have an internal tuner as well as an external mfj tuner(not that I know how to use it yet, lol. Thanks
Edit: right under the right rear fence corner post is where the electrical box is.

 

[ecanderson]

With that much slope and angle, you won't be very directional, which can actually be a good thing if that's what you're after. What's the situation on making it in from the peak to your rig? The G5RV feed is a balanced line until you hit the coax, and you don't want to get it in close to anything that will disturb that. Same thing with the ZS6BKW recommended above. Though it uses a balun instead of a direct connection to the coax, there's still that same balanced feeder/matcher line to keep clear of things.

 

[Akozub]

With that much slope and angle, you won't be very directional, which can actually be a good thing if that's what you're after. What's the situation on making it in from the peak to your rig? The G5RV feed is a balanced line until you hit the coax, and you don't want to get it in close to anything that will disturb that. Same thing with the ZS6BKW recommended above. Though it uses a balun instead of a direct connection to the coax, there's still that same balanced feeder/matcher line to keep clear of things.

Ladder line would come down from the peak offset down the left side of the doghouse strait down 5" of roof, over gutter, under soffit, down the house and into the house above the first floor. Should I use all the ladder line if it extends into the houses as far as it will go and then into coax? Or cut the ladder line where it enters the house?

 

[ecanderson]

You should not cut the ladder line! That's part of the whole impedance matching game, and its length is relevant to tuning it up properly. You'll want to add some standoffs to keep the ladder line away from wet wood, metal gutters, etc. Conductive window frames must also be dealt with if that's what you have.

 

[wb6uqa]

Hf antenna

Cobra makes a short vertical dipole. It is 35 feet long and can be hung from a tree.A Ultra max end fed wire is 10-80 meters.A hex beam is nice. It works at 20 feet high and hasa 11 foot turning radius.

 

[popnokick]

One of the best things about the Windom / OCFD (ref'd in my previous post) is that it is fed with 50 ohm coax of any length you want. No ladder line to keep clear of anything, or to be sure it's a certain length hanging down, etc. HOWEVER, as its name implies, the Off-Center Fed Dipole feed line is located about 1/3 of the way from one end of the total length of antenna wire. So if there is a greater distance from the center peak of your roofline to some other object you can use as one of the ends (fence post, tree, etc.) then you are in luck. If your endpoints are equidistant from the peak of the roof, then it may be trickier to use the Windom / OCFD. All of this is detailed in the URLs I provided above. BTW - The OCFD wire antenna is going to be almost invisible, and the coax feed line is easily tucked away or neatly run in the seams around the roofline. Unless you are hosting parties for HOA members on your deck / at your house, it's not likely to be noticed from the road.

 

[ecanderson]

True enough on the Windom, but for that antenna, he's going to want to add some PVC or something to those fence posts to get it properly elevated. Even if he uses 'drop ends' to make it work as an inverted V, he's looking at 12+ feet above ground level on the ends to get it to work well.

 

[Akozub]

Thanks for all the suggestions. Still not sure what to do. Elevating the fence posts is not an option as I'm probably going to get busted by the hoa police just for stringing wires. How about my gutters? I have read about a guy in lewisville? That claims to have had great success with his gutters as an inverted L.

 

[GrayJeep]

Now I'm thinking about a G5RF HF wire from the peak of my roof to two fence posts on opposite ends of my back yard. On the right side of my back yard is one of those big electric boxes, and a comcast box sticking up about 2 feet each. First off will this type of antenna work in a downward "V" configuration and second, will the power boxes so close make the antenna useless? Thanks for any help.

Running RF right to the cable box may make cable useless and all the neighbors mad whenever you transmit. Not a good idea. In the olden days when hams could put up 50' towers with big beam antennas it was a given that the neighbors would complain about their TV problems being the fault of the ham. Even if he was on vacation somewhere else at the time. The cable guy who is called out will react the same way.

I had a V from roof peak to fence posts for awhile. Didn't get out very well and ice finally brought it down.
I'm not a very active ham and just listen only anymore so I never put it back up. Was never noticed by any of the neighbors and we have an HOA that prohibits antennas.

 

[ecanderson]

True enough. The lowest cable TV frequencies are located at almost exactly the same frequencies as the original broadcast frequencies for Ch 2~6 (starting down around 55MHz), so harmonics could certainly be an issue if he gets TOO close. Might be a great test to see if the cable company is using crap 40% aluminum braid coax though (grin).

 

[wb6uqa]

A dipole in a attic works great. 20 meters is open day and night. You might decide to upgrade.

 

[wb6uqa]

20 meters is open day and night. A half wave dipole is about 10 meters long. Eham dot net reviews many ham antennas.

 

[GrayJeep]

A dipole in a attic works great.

When my V came down I considered putting up a wire in my attic. I have a scanner discone up there already and removed a TV antenna that the original owners had installed up there but didn't understand that it was pointed 90 degrees away from all the TV transmitters because that's the only way it would fit in the space. (it never worked and we have cable anyway)

Upon close examination I found that my house power wiring runs in the attic. Was probably more quickly and easily installed than running thru wall studs. Even the heavy 220V oven wire goes up and over.

Given the amount of power wires and the very close proximity to where I could reach to put the transmitter antenna wire I decided they were incompatible. (and the power wires would de-tune the antenna or absorb the RF)

If this was the only solution there might have to be a power limit used to keep home life not interfered with.

Fellow ham in my neighborhood has a ground mounted vertical placed next to his two story chimney. I don't know how well it works but it's not very visible.

 

[Akozub]

Quick question. Can I use cable TV coax to feed a RECEIVE only antenna?

 

[popnokick]

Absolutely, assuming of course there will be no connection whatsoever to the active CATV system. But 75 ohm TV coax such as RG-6 works fine for receiving.... especially well up into the UHF and 800 mHz ranges. Makes a lousy match for transmitting, though. So no TX.
I have an abandoned CATV coax system in my house and converted it to scanning receiver use. Put an OCFD antenna in the attic and a splitter amp. Connected it to all the wall outlet drops in the house, and I have a scanner antenna jack now in many rooms of the house. The splitter amp provides the isolation between the multiple scanners I run on it.

 

[Akozub]

Thanks for all the help and suggestions. I guess I have 2 outside options. An end fed inverted "L" gutter system or an end fed semi vertical wire from the lawn in my back yard strait up to the railing of my deck (10') then angled up to the peak of my roof (27' tall from ground level, 28-29' of wire including the angle). If I try both of these to see which one works best, is it ok if the ground radials cross each other(insulated wire)? And should I use a ground rod at the base of each antenna where the radials all meet? Should I also have a ground rod and ground all my antennas including my vhf/uhf where they all come into the house(all come in at the same location)?

 

[GrayJeep]

Since you won't have a pure reproduction of any antenna you might as well just try it out.
Maybe try both?

Thing to watch for is introducing RF transmitted noise into stuff in the house. Start with low power and see what happens.

You'll have some fun figuring out the tuner settings. Be sure and write them down. Don't be surprised to get very narrow ranges where the antenna can be tuned for less than 2:1 SWR. or not.

You won't know until you give it a try. Do it with low power and you likely won't hurt anything. Just be polite and do your tuning when the band is dead and not on top of rare DX.

 

[Akozub]

Since you won't have a pure reproduction of any antenna you might as well just try it out.

Maybe try both?



Thing to watch for is introducing RF transmitted noise into stuff in the house. Start with low power and see what happens.



You'll have some fun figuring out the tuner settings. Be sure and write them down. Don't be surprised to get very narrow ranges where the antenna can be tuned for less than 2:1 SWR. or not.



You won't know until you give it a try. Do it with low power and you likely won't hurt anything. Just be polite and do your tuning when the band is dead and not on top of rare DX.

Thanks, can the insulated radial wires from each antenna cross over each other? Can they be shared?

 

[GrayJeep]

Thanks, can the insulated radial wires from each antenna cross over each other? Can they be shared?

If they are ground radials I expect they are fine.
Your antenna is going to tune with whatever is around it.
Your wire might be coupling into the gutters and vice versa.

As long as you get SWR below 2 your transmitter will be happy. Just don't expect to get whatever pattern "the book" says you'll get because you aren't radiating in a clear, unobstructed field.