Greetings from So.Cal.

I'm at wits end, now having gone through 4 antenna mounts on my vehicle.
This is the situation: I have a Jeep Wrangler, on the rear of which I
have a trail rack (for cargo, and mounting Gerry cans). Over the last
few years, the trail rack has become my mobile antenna farm, hosting a
Diamond NR770 NMO dual band whip, a 1/2 wave Larsen base loaded NMO
220MHz whip, a 1/2 wave Larsen base loaded NMO 144MHz whip (for APRS),
and a Larsen VHF-UHF-800/900MHz NMO center loaded monitor antenna. For
HF, I mounted a K400 mount with 3/8" stud for a Lil' Tarheel II compact
screwdriver (16" body, plus 5' whip), on the left rear corner of the
trail rack (about 6' off of the ground). This location puts the antenna
at a high point at the rearmost location on my Jeep. Being a short
wheelbase vehicle with a 3" lift and 32" tires, the ride is inherently
bouncy. The daily commute on the I-405 in the South Bay of the L.A.
basin injects speeds of 5 to 70MPH during the commute. To date, I have
cracked the base plate of the trunk lip K400 mount around the front edge
of the round protrusion where the adjustable head of the mount supports
the antenna. Twice, on separate new K400 mounts. The K400 is too
flimsy (the fact that it is being made in China from metal not of the
same original stainless grade as the original article is a separate
issue) to support the stiff antenna, which is bounced and rocks front to
back and side to side on every bump, dip, and pothole. Complicating
matters is that the mount is at the rearmost and highest point on the
rear of the vehicle, and the momentum of flexation is greatest at this
spot. However, it is the absolute best spot to mount the antenna for
performance and loading (perfectly flat on all bands 10 through 75M).

My Alinco DX-70T only delivers 100W, and when mobile in motion, doesn't
always have enough punch, so I enlisted an amp that would provide me
with about 200W PEP, the max. rating of the Tarheel II. The amp
exceeded this a few times, and after replacing the coil once, Tarheel
informed me that a new compact version was under development, with a
max. rating of 500W PEP. Armed with this knowledge, I installed an
Ameritron ALS-500M with remote and soon abandoned the K400 and smaller
Tarheel II for the heavier duty Tarheel "Stubby" (16" body with 5' whip)
and a new Hustler stainless ball mount. Worked great, but within two
weeks, upon arriving at my office one day, a co-worker asked me if my
antenna had broken. When I went out to check, the antenna had rotated
down at a 45° angle into a big 6.5' curb feeler mode into the left
parking space next to me. I removed the antenna, and found that the
outer ball half had cracked at the 3/8" stud that protrudes from it,
causing the ball to loosen and slip. The candy store was nice enough to
replace the part under warranty, and that night I was back on the air.

A couple of weeks later, I noticed (during my daily mount checks
provoked by the paranoia of losing a $350+ antenna on the freeway, and
causing an accident, to boot) that some "wiggle" had developed between
the 3/8" stud exiting the outer ball half, and the outer ball half
itself. Enough movement to make me fear that another 30 or 40 miles
would be enough to snap off the antenna cleanly from the replacement
ball mount, unexpectedly. I removed the antenna, and searched for a
stronger mount. I remember the old Motorola stainless ball mounts from
the Broderick Crawford 2150 days, and that they were nearly
bullet-proof. I also remembered that Antenna Specialists made them for
Motorola (ASP-3, or something like that). These are as rare as $3 bills
nowadays, since A/S abandoned making them. However, I collected an
ancient Batwing ball mount with a cracked gray phenolic base (too bad,
as that's where the Moto branding was) years ago at the swapmeet, so I
tore my garage apart and finally located the old gem. I retired the
Hustler stainless hardware, and installed the Moto / A/S stainless
hardware into the black phenolic Hustler baseplate. Perfect fit, and
very tight mount (no slop at all). About three and a half weeks have
passed, and I have just discovered the same "wiggle" that caused me to
scrap the Hustler ball mount. Needless to say, my screwdriver is again
off the air.

Sorry for the preceding "diary" - but a good understanding of my dilemma
couldn't hurt. Now, does anyone out there know of a strong 3/8" stud
mount that will support my screwdriver (which probably weighs about 8 to
10 pounds, with a 16" body, 2" dia. coil, and 5' whip) now and forever?


I am able to bolt into the 1" square tubes of the trail rack - that's
how I affixed the fabricated steel mounting plate that I put on the side
of the rack to host the ball mount. The top and bottom tubes are about
4" apart. Can anyone offer a practical solution? My HF capability is
important to me (ARES emergency comms and stuff, you know...). Thanks
in advance.

73 de Doug, N6XQY