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PA2RHB > WANTED 17.09.04 12:01l 30 Lines 1085 Bytes #999 (0) @ WW
BID : E70040PA2RHB
Read: GUEST
Subj: Re: 70 Mhz horizontal antenna info
Path: DB0FHN<DB0RGB<OK0PPL<DB0RES<ON0AR<PI8WFL
Sent: 040917/1058Z @:PI8WFL.#NH1.NLD.EU #:46812 [Enkhuizen] $:E70040PA2RHB
From: PA2RHB@PI8WFL.#NH1.NLD.EU
To : WANTED@WW
X-Info: uploaded with password authentication at PI8WFL.#NH1.NLD.EU
Eldred, ZS1DJ, wrote:
> I am looking for ideas / sketches for a HORIZONTAL MOBILE antenna for
> 70 Mhz (4m). I would like to fit across the WIDTH of my car and LDV.
I think the only reasonable thing would be a Halo antenna. That would keep
the dimensions within the car's perimeter. A shortened-element turnstile
would be very critical to set up for omnidirectionality, and the four
horizontal end points are not considered safe in traffic.
A halo antenna is a little like a half-wave dipole bent round until the
ends almost touch. The space between the ends should be kept fixed, as the
tuning varies with it. In some designs there is a variable capacitor
between the ends, making the halo tuneable.
Matching is often done with a gamma match, but one design from the ARRL
"Mobile Manual" used a vertical whip as a "single wire feeder".
Let us know what you made, mobile antennas always make for interesting
reading.
Rudolf, PA2RHB @ PI8WFL
Heemskerk, JO22im
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