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ZS1DJ > WANTED 25.09.04 11:14l 78 Lines 2844 Bytes #999 (0) @ WW
BID : FE1463ZS1DJ
Read: GUEST
Subj: Re: 70MHz Horizontal Mobile Ant?
Path: DB0FHN<DB0MRW<DB0WUE<DK0WUE<HA3PG<7M3TJZ<F6CDD<F6KBI<F4CEP<F3KT<
ZS6FB<ZS0DLD<ZS6RO<ZS0BEL<ZS0STB
Sent: 040923/0626Z @:ZS0STB.TBG.WCP.ZAF.AF #:59941 [Satgat] FBB7.00g25
From: ZS1DJ@ZS0STB.TBG.WCP.ZAF.AF
To : WANTED@WW
Hi fellas
Thank you for your ideas.
I notice there is some question on my requirements.
Herewith a repeat of of my initial request ...
> Hi Readers
> I am looking for ideas / sketches for a HORIZONTAL MOBILE antenna
> for 70 Mhz (4m). I would like to fit it across the WIDTH of my car and
> LDV.
> I have a few ideas up my sleeve already, but looking for more.
> Your thoughts etc. will be much appreciated.
The ideas I had up my sleeve was ...
1) A trapped dipole held on to one of the two plastic insulated "struts"
that run across the car roof (there's two of them). I don't use this
"roof carrier" (it came with the LDV when I purchased it), so I could
support the anntenna securely on this, with the help of two plastic/nylon
ties.
2) Then I thought of a quad, using thin Alluminium rod or 3mm stiffish
wire. Again making use of, and held firmly on both "roof carrier" struts.
These struts are pretty securely fitted to the vehicle roof.
I've just been out to check on it, and found that these supports are
28mm thick, are made of metal which is covered with a plastic insulation.
This, I am quite sure, will throw the cat amongst the pigeions !
What's to say you, that I make use of one or both as a radiator ?
(Please can someone loan me an MFJ antenna analyzer) ?
Sheesh, this is getting more complicated than I thought !
More ideas welcome !
Cheers and thanks again
Eldred
ZS1DJ
PS The law in our country states that use of the 70Mhz / 4m band, requires
a HORIZONTAL ANTENNA !
> From: PA2RHB@PI8WFL.#NH1.NLD.EU
> To : WANTED@WW
>
> X-Info: uploaded with password authentication at PI8WFL.#NH1.NLD.EU
>
> VK3ABK, Dick, wrote:-
>
>> A 'Halo' for 4 Metre is a bit big and may get
>> caught up in garage, car-port, or low flying objects! We used them on
>> 2 metre AM mobile, but that would be about the limit for convenience.
>
> It was the smallest I could think of. The diameter would be under 70 cms,
> much less than the width of the car roof. You could mount it lower (in
> terms of wavelength) than you ordinarily would a 2 meter version.
> For any horizontal 70 MHz antenna over a ground plane, 30cm seems to be a
> practical minimum, otherwise you would get too little lower angle
> radiation.
>
> Of course you could build an even smaller one and use an end capacitor to
> tune it.
>
>> The DDRR antenna ( short for 'Directional Discontinuity Ring Radiator')
>> is mounted close to a conducting ground plane ( maybe a car roof ) and
>> is much less in diameter than a corresponding Halo.
>
> Yes, but the trouble with the DDRR is that it is a vertically polarized
> radiator. ZS1DJ would like a horizontally polarized antenna on his car.
>
> Ruud, PA2RHB @ PI8WFL
> Heemskerk, JO22im
73 - Eldred, ZS1DJ @ ZS0STB
Message timed: 08:22 on 2004-Sep-23
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