Limited space & Inverted V's

[EDUK8TR]

Greetings,

In my plans for working HF I want to put up some inverted V dipoles in the trees in my backyard. These trees are spaced close together. How close together can I have these dipoles without them interacting with one another. What HF Inverted V's would one put up to make the best use of the active HF bands. Suggestions?

Thanks!!

Wayne C.

 

[W5LZ]

Wayne,
Just depends on how much room you have and what bands you want to have. One method is to connect a couple (or more) dipoles to the same feed point, then sort of space them around as much as you can. Takes longer to tune, cuz you have to tune each dipole and they all affect each other, but a really simple feed system, just one feed line.
There is a difference between a 'real' inverted 'V' and the more 'normal' drooping dipole that most people really have. Inverted 'V's are strung up so that the angle between legs is 90 degrees. The 'drooping' dipoles (the more common type) have an angle between the legs of more than 90 degrees. The biggest difference between the two types is the input impedance. An inverted 'V's input impedance isn't 50 ohms by any means, closer to 35 or 40 ohms, sort of. The smaller the angle between the legs, the less the input impedance. Also why you 'droop' the thing anyway, impedance matching as well as making it 'fit'.
Another way of doing the multiband thingy is by feeding with ladderline and a tuner. The input impedances just don't matter much, whatever they are (also depends on how 'good' a tuner you have).
What 'small' antennas all have in common is that they just are never going to be as 'good' as the full sized versions. What that difference in performance is 'worth' just depends on 'where' and 'what' you have to work with, or where you live.
- 'Doc

PS - To answer your original question, the distance between antennas should be as great as possible. The exception to that 'rule' is placing them 90 degrees from each other (or close to 90). At 90 degrees they can have the same feed point.

PPS - None of any of the above is 'carved in stone'.

 

[EDUK8TR]

Hey Thanks!

Gives me some more food for thought :!: I have a very large Oak that I have a 11m ground plane installed in. I was thinking that I could maybe do half-wave 20m? and 40m? inverted V's attached below the ground plane at right angles to one another. What bands would be most feasable in this configuration? I'm interested in HF DX so which band atennas would be the best ones to put up? Keep in mind I'm just sorting things out for now. My intention was to get some commercially made balums and hook them to the mast below the ground plane. The base of the 11m ground plane is right at 70 ft. So attaching the balums maybe 5 or 10 ft. below on the same mast would allow me to be able to get the wires at 90 degree angles for a proper inverted V. I'm also wondering how tunable the 11m ground plane would tune with a tuner for maybe 10m or 12m? Yeah, I know I can shorten the ground plane for 10m but I'm not at that point yet. I'm sure that I'll have to experiment with this but any pointers to cut down on pitfalls is apprieciated. Of course experimenting is part of the fun. Am I approaching this right? Right now weather permitting I'm installing pole steps going up the main trunk of the tree for easy access. I could probably put the inverted V's on the outer limbs if the mast attachement wouldn't work. The wheels are turning right now, I just want to get them going in the right direction

73's :!:

Wayne C.

 

[Switch Kit]

old Radio Shack used to sell a inverted V that had different lenghs for different freq's built in to one , I never used it for transmitting but it received very well on my Sony ICF-2010 Shortwave , Can you believe that ! I learned how to shut up for awhile and listen , man !! that was a great portable radio. I wish I still had. )-: sorry about that guys, the inverted V talk just brought me back a ways. I've heard guys over the years say that Radio Shack I-V was kind of decent for what it was. I through it away a few years back.

 

[W5LZ]

Wayne,
Sounds like it ought'a work.
DX in the daytime on 20 meters isn't unusual at all, same for 17 meters. On day time 40 meters, DX is measured in a few hundred miles . At night, it's a different story! I'd expect 40 meters to be the 'better' of the two (generally the way it works but don't bet on it). Not that 20 and 17 meters are 'dead', they aren't. (None of the bands are what they were several years ago.)
I would do it a little different than the way you described, but that's me. Low(er) antennas for the HF bands are not exactly directional, and the closer they get to a 90 degree 'angle of the dangle', they are even less so. 'Flattening' them out a little does give them some 'directionality', which can help at times. I'm not a big fan of baluns. Most of the time they just aren't needed. On HF baluns tend to 'do' more to keep the radiation pattern sort of 'regular' instead of being 'lop-sidded'. For beams, sure. For most wire applications, why bother? I've had several 'fail', so tend to shy away from them, in general. But that's just me.
Using that 11 meter groundplane on 10 meters, maybe 12 meters, just requires a tuner that can handle the mismatch. Won't be the 'best' in the world, but then it certainly won't be the worst either! Forget about running power to any extent. The feed line will suffer because of it (not much, but some, sort of).
Something else to think about is that DX (the foregn kind) tends toward the 'bottom' ends of the HF bands, especially 40 meters. Different countries, different freq allocations. 'Split' freq operations are sort of common. A real P.I.T.A., but oh well.
If you're really serious about DXing you might listen to some of the DX and WAS nets. DX sort of tends to frequency them, so are easier to find. 'Nuther one of those 'sort of' things. Also pay attention to what time it is in different places. In general, late here is early there. [Worked a 'ZL' last night, got a 5x7 from him at about 0800 UTC. Not all that exceptional, but different. Figure the UTC/CST conversion and you'll know why hams are sort of weird...well, one reason anyway.]
The saving grace of all this stuff is that there's nothing stopping you from making changes to your antenna arrangements. Nothing 'electrical' at any rate. Have fun!
- 'Doc

 

[Moleculo]

Edu:

You can buy an antenna that is basically what you are trying to accomplish from Alpha Delta, without all the trial and error. The Alpha Delta DX-CC is a 10,20,40,80 meter multiband dipole that uses varying lengths of wire for the different bands. The 80meter segment is shortened using loading coils for people like me that have to live with restrictions of city sized lots. You can use it in conjunction with a tuner to tune the WARC bands. I have one up that is 42' from the ground and use it regularly on most of the HF bands. I have mine in an Inverted V configuration with as close to a 90 degree angle as I could eye-ball. This antenna works great for me, and yes I use it on 80/75 meters with very good results.

 

[Switch Kit]

Multi-band Inverted V

 

[Hamin' X]

Also, look at these:

The All-Band Center-Fed Inverted-L

Straightening Out the Inverted-L

Also, consider feeding the antenna with ladder line, or open wire and place the balun just outside your shack. This will greatly increase the usefulness, bandwidth and efficiency of your antenna.

Rich

 

[EDUK8TR]

Thanks for all the info folks :!: If you think of anything else please add to what's already here.

73's :!:

Wayne C.

 

[Beetle]

Don't cheat yourself out of a good learning experience. BUILD the antenna yourself rather than spend three or four times the money for some commercial toy.

It's getting harder and harder to build your own equipment -- except in the antenna world.

 

[Hamin' X]

Beetle is correct. Also, don't wait for the "perfect" antenna to come along. Get something up now and dink with it. Experiment and learn. The signal from a poor antenna is many times better than the the signal from the one on the drawing board.

Rich

 

[N8ATS]

i usually use a inverted v cut for the lowest frequency ya would like to work feed it with ladderline and use a tuner on it. mine is cut for 75m with a length of roughly 120 feet. i use this antenna for usually 80 and 40, but it does tune well above those bands, but gets a little bit of a funky radiation pattern but they will show gain and will preform. and in total cost the antenna costs around 12 bucks to build and is a great preformer for the money. also i do not runs the legs straight becasue of size restrictions, my 1 leg looks like a z but the tuner makes it forgiving and have not really seen a drop in preformance. hope this helps you out. worked really well for me.