[OZAPRS] Need a hand - mobile antenna

Bob VK6KW rlockley at bigpond.net.au
Sun Dec 10 11:45:15 AEDT 2017

Springs  made for mobile antenna use usually* have a braid internally making electrical connection end-to-end so the electrical length does not change as the spring flexes. however Capacitance changes as the whip (whatever the make)  moves in relation to the vehicle so tuning will inevitably vary in motion.


*The braid can be seen inside either through the threaded hole or by bending to open up the spring coil but if not, or you are concerned about it, simply add one externally – form it into a spiral around 180 degrees to allow flexion.


Bob VK6KW                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        

From: OZAPRS [mailto:ozaprs-bounces at aprs.net.au] On Behalf Of Matthew Cook
Sent: Saturday, December 09, 2017 8:45 PM
To: Australian APRS Users
Subject: Re: [OZAPRS] Need a hand - mobile antenna


The base should have a wire that electrically shorts the spring, otherwise bad things happen to your tuning point as the antenna moves.







On 9 December 2017 at 15:03, <vk4tec at tech-software.net> wrote:

Does a spring base affect the length ?




From: OZAPRS [mailto:ozaprs-bounces at aprs.net.au] On Behalf Of Bob VK6KW
Sent: Saturday, 9 December 2017 1:37 PM
To: 'Australian APRS Users' <ozaprs at aprs.net.au>
Subject: Re: [OZAPRS] Need a hand - mobile antenna


Hi Folks,

One day I’ll actually get to ‘play radios’ again and be able to join you on air; but in the meantime have to console myself with reading the mail and storing up the good ideas; however in earlier times as Net control for the 14.116 Traveller’s Net, and even travelling o’seas (VK7 & ZL) I found the centre loaded Hustler system to work well on my 80 Series (bull bar) and borrowed/hire cars (tow bar). Simple, convenient, effective – and no I don’t own any shares.

Main components are HD spring loaded base, a common folding articulated ‘mast’ section  (1/4 wave on 6m) onto which fits coil loaded ‘resonator’ for whichever band – available for 80m – 10m including WARC.

My subjective observations were that it out performed the Codan 9350+ 1.8m SS whip on any given band.  


I presume they are still available – have not had to look as I have several sets including the suitcase-ready one. Just don’t try taking it onto a cruise liner or they will lock it in the hold!!! Rotten spoil sports!




From: OZAPRS [mailto:ozaprs-bounces at aprs.net.au] On Behalf Of vk2tv
Sent: Saturday, December 09, 2017 5:08 AM
To: ozaprs at aprs.net.au
Subject: Re: [OZAPRS] Need a hand


The more I look at the vehicle, the more I read and the more I hear, the less I want to install something I'll hardly use!

I did consider a nudge bar but not at $800.

I'll build up a tilt-over mast for at home and populate it before I spend too much time on the X-Trail.

Ray vk2tv


On 08/12/17 20:40, Liz wrote:

QTR Mon, 4 Dec 2017 09:19:27 +1100 vk2tv QTC

I've just looked at my X-Trail and I think I've lost any enthusiasm I 
had for installing radios, hi. I think the engine block was poured in
The main frame of the vehicle - subframe, floor pan, roof, firewall
and door frames - seems to be a welded mass of metal to which
mudguards, bonnet, doors, etc are bolted, so any bolts attaching
components to the sub-frame could be a possibility. A "Z" bracket
coming out from under the bonnet could possibly utilise one of the
mudguard mounting bolts. A magbase on the edge of the bonnet could be
earthed via a short lead to a mudguard mount or the bonnet hinge
mount. Most bonnets are not purposely earthed so heavy(ish) straps
(RG213 braid, e.g.) around the hinges could be beneficial. A couple
of possibilities there, but this is just one specific vehicle.
My days of crawling over and under vehicles to install radios ended a 
long time ago; these days I'm the wrong shape for crawling under, and 
multi-focal spectacles don't work well upside down under a dash.

I've got a 32 series Xtrail.
You forgot to mention the 8cm of insulating foam as well....
My OM took out the passenger seat and got a base plate fitted to the
base of the seat, on which the radios sit, with one head on the dash
and the other on a stalk attached to the passenger seat bolt.
Antenna for 2m is in the middle of the roof and HF antenna on the
bullbar. As indicated previously, motorising the antenna support cost
about $45K.
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