[Elecraft] Re: [Icom] Opinions re: HF Verticals?

Tue Oct 15 02:48:00 2002

----- Original Message -----
From: <[email protected]>
To: "Hank Kohl" <[email protected]>
Cc: "Elecraft" <[email protected]>
Sent: Tuesday, October 15, 2002 12:39 AM
Subject: Re: [Elecraft] Re: [Icom] Opinions re: HF Verticals?

> that they claim 2:1VSWR over an adjustable 320Khz segment of 20m.  Am I
> just anal retentive of are there others out there that consider any
> supposedly resonant antenna that presents a 2:1 VSWR as a NON-RESONANT
> antenna?

What they are saying is that at no point over the 320 khz range does the swr
exceed 2:1. It maybe 1:1 at 14.160 and 2:1 at 14.000 and 14.320. Most
commercial antennas for 20 meters will have similar ratings and they are
resonant.

> I consider an antenna that requires a tuner to operate at its design
> frequnency with less than 1.5:1 to be a compromise at best.

Most rigs will accept swr of 2:1 without reducing the power appreciably if
at all. And even if you are using coax, you are probably not going to notice
any loss in signal strength betwen 1:1 and 2:1. With this kind of swr you
are not likely to need an antenna tuner unless you are a purist, fiddler, or
have a very finicky rig. Also if you only operate cw near the qrp frequency
than the simple solution to this non problem is to adjust reasonance to
14.08 or so and then the entire cw portion of the band will be at what you
characterize as an acceptable swr. This obviously wont work if you also want
to operate SSB on 14.313 (but why would anyone).

BTW, an antenna can be resonant and have an swr of 1.5:1 or 2:1.  This has
to do with impedance matching, not reasonant frequency. For example, the
directions for my Butternut HF-2V vertical point out that the swr at
resonance may be 1.5:1 or higher because the radiation resistance of the
antenna is very low relative to the impedance of the coax cable. The
vertical uses a length of 72 ohm coax and in some configurations a small
coil across the coax connection at the antenna to better match the antenna
to the feedline.

73 de Dave, N0IT