[TowerTalk] 160m project

[Roger (K8RI)]

Hi Lee,

Its from Onion wrote:
> Hello all,
>
> I am in the design stage of a dipole antenna for 160m and would like some professional input in case I missed something.  All input is appreciated and welcomed.  I'm a bi-lateral amputee so my time table is dependent on my friends time!  haha
>
>   
It all depends on what you want to do with the antenna.   A good DX 
antenna it won't be, although that doesn't mean you won't work some.  I 
had one up that was only 40' at the center and 10' on each end. I worked 
great for most of the US except the far western states. OTOH on a good 
night I could easily work California and the Pacific NW.  I even worked 
the occasional DX, but that was not common.  Performance was pretty much 
comparable to the same thing on 75.
> The jest of it:
> 260 feet of #12 wire suspended at or about 85 feet.
>   
I would want to use either hard drawn, or preferably copper clad steel 
for this long a span.
> 65 feet of 600 ohm ladder line feeding the wire directly.
>   
Good coax and a tuner might make for an easier installation unless you 
want to use it on more than one band.
Personally I don't like open wire, although it does work well. Ideally 
you'd run open wire to the remote operated tuner at the base of the 
mast/tower and coax from there to the shack. OTOH with a good balun at 
the base of the mast and coax to the tuner in the shack you'd get a 
slightly more loss, but an easier installation. The coax would be seeing 
a resistive load and would have very little additional loss due to SWR.  
Me, I'd run larger coax all the way to the antenna with a tuner in the 
shack unless it were a *long* run, which is what I do now. Using either 
LMR 400 or 600 the additional loss isn't all that much even with a 
relatively high SWR.
> A mil-spec balun from Antenna Products rated at 2-30M 4Kw PEP
>   
Mil spec?  The SM153 (50 - 600 or 12:1) is rated for 1 KW continuous and 
2 KW PEP which I'd assume is into a resistive load.
> http://www.antennaproducts.com/BINDEX.htm<about:blank> SM-153.
>   
Hmmm...my software doesn't like this site and blocks it.  Don't know 
why, but I had to intervene before I could get to the site.
> 50 feet of 9931 coax with a 6" PVC air choke made from 25 feet of 9931 wrapped. 
>   
I doubt this will give the isolation you desire, particularly being air 
core and solenoid. I use almost this much in a tightly wound bundle for 75.

I've forgotten the URL on baluns and particularly current baluns using 
ferrite cores with multiple turns would through them. I'm sure some one 
can point you to it as one of our posters has a lot of good information 
on baluns and isolation..

Also, I'd stay far away from 9913 (I assume that you, like I often do, 
transposed the 1 and the 3 and the coax is really 9913).  No matter how 
well you water proof 9913 that is its weak point.  I used to swear by it 
and a good water proofing job, but it only took one lightning strike to 
remove the seal from the far end and water actually running out of the 
rig onto the desk about 15 minutes later to change that from "swearing 
by" to "swearing at". The rig survived, but the desk top didn't.  After 
clean up, water (I didn't see) ran back under the rig and out onto the 
surface, soaking into the wood which required a complete refinishing of 
the top.
> This is tuned with an Ameritron ATR-15 "T" type tuner
>
> Legal limit when needed from a AL-1200 Ameritron.
>
> Will send a photo of the balun should you want to see.
>
> Thanks again an
Good Luck,

Roger (K8RI)