Worldwide DX Amateur Radio Forums - Ham - CB - HF - VHF - UHF

Well, after going through the thread about building a dipole out of different materials, I broke down and bought two Radio Shack 102s to build one. I was actually surprised Radio Shack had not one, but four 102s IN STOCK! $20/each.

I have the materials to make up the female 3/8x24 connectors with bolts (will allow me to use ring terminals for both center and shield) in place of the SO. I intend to use two mirror mounts bolted back to back and flipped (sort of like a "Z"). This will place the threaded ends about three inches apart.

This will allow me to "clamp" a piece of 1" pipe (yet be electrically isolated from it), and erect it probably 10 or so feet in the air (whatever a standard length of black steel pipe is). If I can get ten feet above the peak of my shed, that would put the tip around 25 to 30 feet above the ground.

I guess this is all experimenting, but since the 102 is "short", will the antennas need the added 6 inches to make it a 108?

Now I need to buy around 50 feet of coax...nothing big, just running a barefoot Grant XL. I may actually set it up in the shed temporarily just to see if it works!

I will take pictures next week when I get it together and possibly put in the air.

my homemade wire dipole came out to about 15 feet,i think that was channel 20.however if you need to add length try this cut the ball off at the top and crimp on 3/8s copper brake lines!i did this to my wilson 1000 to lengthen it for other frequencys.

I'm not worried about lengthening...nothing a piece of 3/8x24 all-thread can't be used for...

well hook up an swr meter and cut or lengthen it for whatever frequency you want it in.

Will it work? Absolutely! Basically just using different conductors for the antenna elements.
Here are the 'catches'. A 'flat' dipole never has an input impedance of 50 ohms, more like 75 ohms (not exactly, but close). 'Drooping' those two dipole 'legs' tends to lower the input impedance. Depending on everything around the thing, the amount of 'droop' varies, so experiment till you find the 'sweet spot'.
An SWR meter can tell you nothing about resonance. It can only make comparisons of impedances (and that set of impedances has to have 50 ohms on the input side of that SWR meter, otherwise, all bets are off). The easiest/simplest/cheapest way of determining resonant lengths is by formula. Set the length by the usual formula that takes things into consideration (468 instead of 492) and you're close enough. Then work on matching impedances, which is a totally separate thing. When you get both of those characteristics right, then you've got a 'tuned' antenna.
Did things just get harder? No, but understanding what you did might have. It's still the same as it ever was.
- 'Doc

I assume by "droop" you meant the antenna is horizontal...I was intending to mount it vertically, will that make a difference?

I can mount it either way just as easy, but figured to talk locally, vertical would be better? If I mount it horizontally, it will only be around 18 feet high to the top.

I know the calculator is to get you close...but the 102 with the short mount will be nearly 103. Through the calculators, I should be around 103.25. However, my mount will have around 2 inches of space between the two antennas...essentially making the overall length grow to 208.

So I guess that will make it a tad long, but probably still useable.

Horizontal or vertical, will it make a difference? Sure. That 50 ohm match will be just a bit harder to get close to, can't play with the droop to get it right. Actually, you can, but it isn't going to 'look' very good so I figure most people won't do it. That's basically what you are doing when you play with the 'angle of the dangle' with radials on a groundplane.

Length. That can be done several way. You've got some 'play in the amount of wire that makes connections to those two 102" whips. You can use that to make up for any shortness, just make them a little longer/shorter/whatever.

There's lots of 'wiggle room' with a dipole, they aren't all that 'exact' or critical in shape, sort of. They tend to work no matter how you shape them or position them. That doesn't always mean they will work well, but nothing does all the time anyway.
- 'Doc

So the feed point of any dipole is 70ohm, and you adjust that by the angle of the legs?

I could also turn this into an inverted V also...I guess I am trying to avoid being directional since I won't be able to turn this easily.

What's the angle between the two legs of an inverted V supposed to be? I am guess it typically around 90 degrees, or each leg roughly 45 degrees from horizontal?? With varying degrees in between (whatever works)??

I was reading and I assume the "angle" discussed is the one from vertical, and not the angle between the legs?

I'm probably better off with an inverted V configuration.