300ohm folded dipole

[channelcat]

hey guys i made this 300ohm tv twin lead folded dipole that i have sloping down from my window at a close to 45 degree angle. i cut it for ch38 (27.385) because i mainly do ssb at the house but sometimes i like to tune down to 19 and talks to the locals. The problem with that is the reception is horrible. the rx is very choppy sounding and only the drivers with the linears can really stand out. it works good for sideband cause ive made several contacts up and down the east coast with it on both 11 and 10 meters and it works good for SWL. is the polarity the problem? i know for dx polarity doesnt matter because the waves tumble around after being reflected from the ionosphere, but is 45 degrees too horizontal to pick up the local guys who are vertical?

['Doc]

channelcat,
The 'bad' reception is probably due to the polarity which can have quite an affect on things, as you are aware. The direction your antenna is 'pointing' in can also affect your reception, just like a directional antenna (beam), not as much, but some. Your antenna is typically called a '1/2 wave slopper' and tends to be bi-directional in the directions of the slope. That radiation pattern isn't very 'sharp' at all, and there's certainly not much 'gain', but there is more that a vertical in two directions. (Think in the shape of a watermelon, rather than a pumpkin.) It really isn't suprising that you can't hear all that well, if you think about it. No idea about the 'choppiness'.
I do have a question though. How did you do the matching, a balun?
- 'doc

[channelcat]

yea there is a 4:1 balun in my mfj-941e tuner. i mainly use it for the balun but when the weather gets wet i need to actually tune the antenna.

['Doc]

I sort of figured it had to be something like that, and the way you're doing it is probably about as 'normal' as any.
Depending on exactly what that 'choppiness' might sound like, it puts me in mind of a loose connection somewhere. Don't bother asking, I have no idea where or what it may be. That would be my first thought. Or, I want to say I think it might be connected to just how that twin-lead is strung up. Does it flutter in the wind much? And does that choppiness sort of 'follow' that fluttering? I know that sounds like quite a 'reach', but it's not as outlandish as you might think, sort of. I like to use ladder-line/twin-lead for feed lines. I've found that twisting them to look like a 'spiral'/twisted ribbon(?) tends to stop the wind from really flopping them around as much. If it's mechanically possible for you to do that, you might give it a try. That's one of those, nothing else helps so why not, thingys. Certainly not a definite 'cure' for it in a lot of cases, probably more 'miraculous' than anything.
I've also found that using a tuner for 'flattening' an almost 'right' input impedance is VERY "iffy", depending on the tuner (and NOT in by-pass mode). The closer it is to 'right' the harder it is to fine a combination that works. Easier to just accept a little mismatch than find the right @#$ settings.
Something else you might try if nothing else seems to help, is to just use plain wire for that dipole part of that antenna, keep the twin-lead feed line. Or, sort of 'spread out' that folded dipole into a loop. I like loops too! Make it sort of square, feed it at one corner and a horizontal loop turns into a vertically polarized antenna (feed it on one side and it's horizontally polarized).
Lots of options, none of them all that 'good', but then, what'cha got ain't exactly perfect either. Why not?
- 'Doc

[channelcat]

yea i have thought of a loop. i would go with the polarity explanation because of the awesome reception i get from shortwave stations, and ssb dx stations on 10-20meters. just when i tune into the locals who are groundwave, its bad. all my connections are good and the wind doesnt effect it really. the same thing happend to my friend when we freebanded his icom 746 pro and tried to talk to breakers with his 40m horizontal loop. the reception was horrible with an exception to people running linears

[Slowdraw]

I may have something to do with how the antenna is fed. A 4:1 balun at the feedpoint and coax to the tuner, may depending upon the actual SWR may be experiencing significant losses. I would recommend, if you are not already, running the 300 ohm line all the way to the tuner. The 300 ohm feedline will have much lower losses over the distance at high SWR than the coax would.

A delta loop is an awesome antenna if you want to give it a try. A full wave triangle fed from the side will have vertical and horizontal components. The typical feedpoint impedance is 100 ohms. Use 6' of plastic dielectric 75 ohm coax between the feed point and your 50 ohm coax for a near perfect match. The long length of the antenna and the use of the matching section work to give you a very wide "true" bandwidth. Be sure to waterproof the coax connections.

I've used delta loops on 20, 30 and 40 meters with very good results, even close to the ground. Always wanted to try one on 11 meters, but never got around to it.

Have fun and good luck,

Slowdraw