[KYHAM] Coax Question's

Fri, 23 May 2003 09:36:50 -0400

At 07:41 AM 5/23/2003 -0400, Jim Simmons wrote:
>Time to update the question; When I asked which was best, I meant best over
>all. The cable will outside subject to weather, but will have no stress/load
>on it. It will be completely supported. Max power will not be over 300 amps,
>normally it should be much less.

RG-58 A/U is probably best for your application. At HF almost no loss, it has
solid dielectric, and stranded inner conductor.  Foam dielectric may be 
lower loss but after
the wire is flexed  by the wind or a rotator mounted antenna the center 
conductor
tends to hollow out a space inside the soft foam and you get inconsistent 
impedances along
the length of the cable.

>   I am one of those "use the least power
>guys".  I do have a SB-200 that I bought and build about 25 yrs ago, I
>sometimes run it into a dummy load just to check it out.

To a dummy load you should have almost a perfect match. RG-58 will take a 
full gallon.
But as soon as you have some SWR over 1:1 the RF voltages in some areas may 
break
down the dielectric.

Probably the worst combination is a rotator mounted antenna and 9913 coax.

>  If I every use it,
>I will use a long wire.

Are you saying you will feed your longwire with a single conductor and not 
coax?
This is the best way to transfer RF from the antenna tuner and antenna.
But if you want to use coax with a long wire at any power level above
100 watts use the largest coax you can afford unless you want to do it by 
trial and error
(which is OK too). You may have very high voltages in the feed-line to a 
longwire antenna
at some frequencies due to high SWR.
     The only way to avoid this is and use coax to " get the RF out of the 
house" is to use
a remote antenna tuner.  If you are expecting to operate the longwire on 
only one frequency
you can make a weather protected fixed tuned tuner. However, the greater the
impedance mismatch the higher the Q will be of the antenna/ tuner system. 
That is to
say at higher SWRs the frequency range you can cover without retuning 
becomes smaller.

73
Bill wa4lav

>After reading all the reply comments, I think that I will go with RG-8x.
>What do you think?
>
>Jim
>
>----- Original Message -----
>From: "WA4QAL" <[email protected]>
>To: "Jim Simmons" <[email protected]>
>Cc: <[email protected]>
>Sent: Thursday, May 22, 2003 10:10 PM
>Subject: Re: [KYHAM] Coax Question's
>
>
> > How do you define best?  Is it the lowest loss?  Lowest cost?
> > Greatest durability?  Smallest size?  Most flexible?  Power
> > handling ability?
> >
> > For 25 feet at HF, loss is unlikely to be a concern.
> >
> > If properly supported, durability shouldn't be a concern.
> >
> > RG-58 should be good for a couple of hundred watts, so power
> > handling capacity shouldn't be a problem.
> >
> > For flexibility, a stranded center conductor will probably
> > be best, although coax with stranded center conductors tend
> > to be marginally more expensive.
> >
> > All RG-58s should be the same size, although there are smaller
> > coaxes, and larger coaxes.
> >
> > Personally, I usually buy mine from R&L (http://www.randl.com),
> > in Hamilton, Ohio, and I usually get RG-8/X (also known as Mini-8).
> > It's a little larger than RG-58, and has a little lower loss, but
> > it's quite a bit more flexible than RG-8, and it comes with a
> > stranded center conductor.  Oh, and it uses the same reducers for
> > a PL-259 that RG-59 would use, so they're easy to obtain.
> >
> > Dave
> > WA4QAL
> >
> > Jim Simmons wrote:
> > >
> > > Hello to all of you,
> > >
> > > I have a few questions and would appreciate your input!
> > >
> > > Which of the RG-58's do you consider the best to use for HF
>transmission?
> > > Total cable length is 25ft.
> > >
> > > Which coax cable would be best to use with a roof mounted, base loaded,
> > > vertical antenna?
> > >
> > > Where would be the best place to buy cable and have it shipped to you?
> > >
> > > Jim
> > >
>
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