[SMCARA] RE: Mobile HF Antenna Advice??

[Clarke, Tom T (Veridian)]

Hi Dan,

I have had great  luck with the "hamstick" type antenna on a triple mag
mount on the roof of the van.  You whack an occasional tree, but as long as
it does not exceed 13 1/2 feet you are good to go on the highway.  13.5 is
the min clearance for bridges, etc and most are in the 15-16 foot range
observed on my recent trip to AZ.  The Hustlers work OK also, but are a bit
heavier and are not happy with the roof mount without guys (kinda kludgy
looking, but then again we are hams right?)

I also use the quick disconnects on the hamsticks, which makes changing
bands a lot easier.  If you go with the hamstick be sure to get a base
matching coil from the "BUM" at Lakeview Antennas in SC.  It allows you to
tweak the VSWR down to next to nothing.  MFJ also sells a capacitor matching
device, but I have found that the inducto-match is better and more
broadbanded.  I have found that one tap setting works for 20, 17, 15 and 10.
I need a different tap setting for 40.  When you tune the hamstick, trim the
excess whip, so that it does not extend down into the top of the fibreglass
antenna.  It will detune the antenna and actually arc, spark and smoke with
high power ( 100watts or so) and destroy the antenna.

The Lakeview guy is at  most of the hamfests around here and probably will
be at Timonium on the 27th.  I basically got all my stuff from Lakeview and
it is good quality (he is really not a bum, his call sign is WD4BUM!).
Hamsticks, mounts and accessories are available from several vendors, so you
should have no problem.

A 4 magnet mount is available and would be even more secure than the 3 mag.
It also has a larger footprint, which is necessary to provide capacitive
coupling to the ground plane (i.e., the roof of the van).  I have found that
the 3 mag mount works well down to 40 Meters, but any lower there is not
enough capacitance to the roof for a good VSWR.  Of course you could throw
all caution to the wind and drill a hole in the roof and put a strap from
the base of the antenna to the roof!

Bumper mounts are poor performers compared to the roof mount.  Getting the
loading coil above the roof line will help.  This is true for all antennas
including the screwdriver type.  The new mini Tarheel looks interesting and
I think is short enough to roof mount with mag mount.

The best antenna in all the "shootouts" that I have seen is the Texas
Bugcatcher with the coil above the roof line and capacity hat on the lower
bands (especially if you want to use 75 Meters.  Big and ugly, but works
well.

Some folks use a good old boy CB type 108" stainless whip with an auto tuner
such as an Icom AH-4 or one of Dwayne's (LDG Electronics) tuners.  Some
swear by them and others say they are no good at all.  Obviously a resonant
antenna such as the hamstick or the Hustlers will be better performers.
Trying to trick a 108" whip to work on 75 meters is futile.  It might work,
but the efficiency will be in off the charts, low!

Back in the glory days of 10 meters (2-3 years ago during the solar peak), I
used a Larsen mag mount with a Larsen NMO commercial antenna for 33 Mhz,
that I brought down to 10 meters by substituting the whip from a Larsen 2
meter 5.8 wave antenna that was about 8 inches longer than the 33 mhz whip.
Looked like a 5.8 wave 2 M antenna on steroids, but worked like a bomb!
Usually ran the Icom 706 at 45-50 watts and had great fun when I was
commuting up to Maine every other weekend, back in 1999-2000.

Points to remember:

	1.  Ground everything with heavy strap or braid (rig, antenna,
tuner).  A big strap from the mount to the chassis if you use bumper mount.
	2.  Go directly to the battery for your power, unless you are QRP.
	3.  Keep radiating portion of antenna above roof line.
	4.  Quick disconnects make life tolerable.
	5.  Resonant antennas are better.
	6.  Try anything! Experiment!  As they say on the internet groups
YMMV!
	7.  Remember Clarke's First Rule of electronics . . . "If it sounds
stupid but it works, it isn't stupid"
	8.  Have the max fun permitted by law.

73 de Tom/W4OKW

>  -----Original Message-----
> From: 	Hatcher, Dan (Eagle)  
> Sent:	Friday, July 18, 2003 9:05
> To:	PAX MARS
> Subject:	Mobile HF Antenna Advice?? 
> Importance:	High
> 
> Folks:
> 
> Does anyone have any experience with HF mobile antennas ?  I'd be
> interested in which products/models are worthwhile & which are ones to
> avoid.  I'll probably limit my selection to those that require a manual
> band change rather than the remote motorized units.
> 
> Appreciate any info you can provide - also, any practical suggestions for
> installation on  vans that have non-metal bumpers (my old Chevy has a
> metal bumper & I've got a set of Hustler antennas + bumper mount that I'll
> try on it - the van is another story, so please comment).
> 
> Appreciate any help or insights provided.
> 
> 73
> 
> Dan Hatcher KD3CQ