Tom, et al
Great webpage you have....Awesome Antennas!
Anyway, thanks for your informative reply. It was 10 years and a 100
antenna's ago that I did this(160m system), so you're most probably correct
in that I must not have had it configured that way.
It may have been a 1/4WL feed to one antenna and 3/4WL feed to the other,
switching in an extra 1/2WL of line into the shorter run.
Like I said, it was MANY many antennas ago. Some antennas here only stay
up a day or two before I rip it all apart and try something else. As I
recall, the phased vert's on 160m lasted a week or so before I went to a
single inverted L (but I digress).
I might try the DPDT switch for my new 6m mobile system--sounds like a good
idea.
I would just do the 1/4---3/4 feeds but 1/4wl is only a bit over 3FEET on
6m, so the coax will barely make it into the car
(front, passengers side) if I go that route.
BTW, I have it jury-rigged (just for today) to switch in either just one
antenna or BOTH antennas and it actually is directional in either posistion.
The other ant must be acting like a reflector. I suspect I am also getting
some interaction from my 10m whip and my 2m 5/8wl whip occupying the same
rooftop too.I know, I know, a 2m 5/8wl whip works on 6m, but removing the
whip altogether barely makes any difference whatsoever. (using my local
beacon as a signal source 5 miles away)
Anyway, thanks agn for the idea and I'll let you know how things pan out.
Mike VE9AA
Michael, Coreen & Corey Smith
(VE9AA, VE9AAA & Baby-VE9)
271 Smith Rd
Waterville, NB
E2V 3V6
Canada
http://members.tripod.com/~ve9aa/index.html
http://www.geocities.com/RainForest/Vines/2174/
----- Original Message -----
From: Tom Rauch <w8ji@akorn.net>
To: <towertalk@contesting.com>; Mike Smith VE9AA <ve9aa@hotmail.com>
Sent: Monday, November 05, 2001 12:44 PM
Subject: Re: [TowerTalk] phased verticals on 6m HELP!!
>
> > I am running 2, 1/4wl verticals,spaced 3/8WL apart (my car roof is
> > only so big) and feeding each antenna with an equal length of RG8X
> > (116" I think) I have a spdt switch with a jumper across the common
> > and one side(to make it a spst in actuality), so one antenna is ALWAYS
> > connected direct to a short length of RG8X to the rig. I then have a
> > 1/2WL of rg8x (77" aprox) which I short out or open up, introducing a
> > 180degree phase shift. No matter how many times I check and double
>
> If you short the ends of the 1/2 wl of cable together with a perfect
> short, you should have what appears as a short across the main
> transmission line! What that does is form two 1/4 open stubs that
> parallel the main transmission line, and each open 1/4wl line acts
> like a short between the shield and center at the connection point.!
>
> I don't see how that ever worked on any band.
>
> What you need to do is switch that line out, and that takes a DPDT
> switch.
>
> It also doesn't sound like the line is correct, because it looks like
> you used solid poly dielectric velocity factor of .66. A free-space
> half-wave is about 118 inches on six meters, and the Vf of most
> RG8X I've measured is about .75. .75 times 118 is 88 inches, not
> 77 inches! That still is a small error, unless the particular RG8X
> you have has a lighter foam than most RG-8X cables I have seen.
> In that case the error is larger.
>
> By the way, while it is true that solid poly cables are about .66 Vf,
> foam cables vary widely in Vf. I have cables as high as just above
> .9 Vf, and as low as .75 (the RG-8X I have)!
>
> Another problem is a 1/4 wl vertical over a reasonably good ground
> is about 35 ohms, and so there are usually standing waves in the
> system. With mutual coupling the antenna base impedances will
> be different than for a single antenna...but you have a BIG problem,
> because of the switch wiring.
> 73, Tom W8JI
> W8JI@contesting.com
>
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>
List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
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supporting towers up to 100 feet for under $1500!! http://www.anwireless.com
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