[TowerTalk] Force12
Jon Ogden
jon.ogden@cain-forlaw.com
Thu, 4 Oct 2001 09:46:03 -0500
The fact is, DON'T worry about it.
2:1 SWR is not a magical number. It's a typical industry standard but when
a person gets over the fact that it's not a big deal then you can move on
and enjoy the antenna. Having a high SWR doesn't mean the antenna's
performance is not good. All it means is that the feedpoint impedance is
not a perfect 50 Ohms but rather another value. This value could be 25 Ohms
resistive, 100 Ohms resistive, 50 Ohms resistive with a purely reactive
content. The bottom line is it doesn't matter. In a 2:1 environment, 88.9%
of your power is still radiated by the antenna.
And anyhow, SWR is greatly affected by things such as proximity to objects,
height above ground, etc. Any of these could make your SWR better or worse
regardless of feedline length.
As far a specs go, SWR should be spec'd at the antenna feedpoint and based
on a free space environment. Of course, both of these are realistically
impractical and impossible, but they provide a standard basis that is
applicable everywhere. Real world values can come close but won't be exact.
So it matters not one little bit of the SWR is 2.1:1 with 20 feet of cable
and 2:1 with 100. Yes, the loss in coax makes the SWR look better. BUT WHO
CARES.
If the antenna works for you, then great. Use the minimum amount of
feedline possible. If the SWR isn't to your liking, then use a tuner. If
performance isn't to your liking, move the antenna or get a new one.
This crucifixion of a company because they recommended a 100 foot feedline
is ridiculous. Shame on F12 for ever suggesting it. They probably thought
it was no big deal since by the time you take cable runs into account and
any kind of height, 100 feet is a pretty good estimate for the average run
of cable that "most" hams may have.
73,
Jon
NA9D
-------------------------------------
Jon Ogden
Sales Engineer
Cain-Forlaw Company
847-202-9898 (Voice)
847-202-9896 (Fax)
jon.ogden@cain-forlaw.com
> -----Original Message-----
> From: Ed Wolf [mailto:n3ue@arrl.net]
> Sent: Wednesday, October 03, 2001 10:16 AM
> To: Guy Olinger, K2AV
> Cc: TowerTalk
> Subject: RE: [TowerTalk] Force12
>
>
>
>
> You ARE missing something.
> When I installed the antenna, I followed the
> mfgr's recommendations, which worked ok for where
> the shack was.
> Now that I have moved the shack closer to the antenna,
> I asked a feasible question concerning what to do with
> the 30+ feet of excess coax.
> I do not see how you answer contributed anything to the question,
> except...
>
> Ed Wolf - ars:N3UE - NA40+TR.PA
> http://members.home.net/wolfie132/
> http://www.breezeshooters.net
> http://www.breezeshooters.com
>
>
> -----Original Message-----
> From: owner-towertalk@contesting.com
> [mailto:owner-towertalk@contesting.com]On Behalf Of Guy Olinger, K2AV
> Sent: Wednesday, October 03, 2001 10:35 AM
> To: Ed Wolf; TowerTalk
> Subject: Re: [TowerTalk] Force12
>
>
>
> Ah, SWR. But then again, what else except SWR. Then there's SWR. How
> could anything else but SWR matter, after all, it's SWR.
>
> SWR trumps performance.
> SWR trumps efficiency
> SWR trumps price.
> ...
>
> How come no one ever gets on and gripes about the narrow
> matching range
> of an amp, or how the design of the amp (the tube, largely) causes
> extreme variation in grid current for variations in the load
> impedance.
> That's just a cost cutting exercise by the amp manufacturer.
>
> That's because SWR trumps ANYTHING.
>
> Or did I miss something.
>
> I'm going to make a deck of cards that has clubs, diamonds, hearts and
> SWR, and play bridge with it, except a rules modification:
> SWR is always
> trumps.
>
> What does an SWR look like? I need a picture.
>
> Does a car have SWR? Obviously someone has overlooked something. It
> would be revolutionary, given SWR's ability to transfix everyone. Move
> over Sexy, move over Sleek, here comes SWR. Cars will never
> be the same.
>
> 73
> -----------------
>
> Guy Olinger
> Apex, NC, USA
>
> ----- Original Message -----
> From: "Ed Wolf" <n3ue@arrl.net>
> To: "TowerTalk" <towertalk@contesting.com>
> Sent: Tuesday, October 02, 2001 11:20 PM
> Subject: [TowerTalk] Force12
>
>
> >
> > Force 12 recommends using a minimum of 100 feet
> > of coax for their C4SXL feed lines. I just moved my
> > shack to the second floor and now have over 30 feet
> > each of both of the feed lines. Has anybody used shorter
> > coax with their antenna? I was told by F12 that if I
> > use shorter coax, the BW would suffer.
> > tnx
> >
> > Ed Wolf - ars:N3UE - NA40+TR.PA
> > http://members.home.net/wolfie132/
> > http://www.breezeshooters.net
> > http://www.breezeshooters.com
> >
> >
> > List Sponsored by AN Wireless: AN Wireless handles Rohn tower
> systems,
> > Trylon Titan towers, coax, hardline and more. Also check
> out our self
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> http://www.anwireless.com
> >
> > -----
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> > Submissions: towertalk@contesting.com
> > Administrative requests: towertalk-REQUEST@contesting.com
> > Problems: owner-towertalk@contesting.com
> >
>
>
>
> List Sponsored by AN Wireless: AN Wireless handles Rohn
> tower systems,
> Trylon Titan towers, coax, hardline and more. Also check out our self
> supporting towers up to 100 feet for under $1500!!
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>
> -----
> FAQ on WWW: http://www.contesting.com/FAQ/towertalk
> Submissions: towertalk@contesting.com
> Administrative requests: towertalk-REQUEST@contesting.com
> Problems: owner-towertalk@contesting.com
>
>
>
> List Sponsored by AN Wireless: AN Wireless handles Rohn
> tower systems,
> Trylon Titan towers, coax, hardline and more. Also check out our self
> supporting towers up to 100 feet for under $1500!!
http://www.anwireless.com
-----
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 100 feet for under $1500!! http://www.anwireless.com
-----
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