Diamond Dual Band Antennas
J. Burklin
I'm looking to purchase a dual band mobil antenna, a minimum of 5/8
wave on the 2m side. Diamond manufactures several of significant size(i.e.
57 inches or larger) with UHF mounts(SO-239 & PL259). Given the size of the
antenna and anticipated wind load can I expect to see problems with the
mount cracking or breaking off? In addition, Diamond's SG & NR series dual
band mobile antennas reportedly need no grounding. Is this possible or
even suggested with a 5/8 wave. I'm looking specifically at the SG7900 or
the NR-790A. Any recommendations pertaining to these antennas would be
appreciated.
BTW.... What size ground plane does a 5/8 normally need?
Bill Macpherson
I can't make any specific recommendations with regard to the ground plane
requirements. What I can tell you is this. I have a Super Gainer Dual Band
Antenna on the minivan. This antenna is now on a huge magmount, it blew of
the Accord one time and was run over at freeway speed, I lost the static
ball off the end of the antenna, and there is a residual kink in the end
of the antenna, when it was put back on the car it still worked. This
antenna has travelled 1000's of miles on two-lane highway at speeds of up
to 140 - 150 Kph. It hasn't blown off with the new magmount. It still
works great. From in the city, and with 20 watts ( Kenwood 702 ) it will
work repeaters some 60 miles line of sight with no great elevation
advantage, and others in the hilly, bushy environments out to about 40
miles line of sight steadily. With picketing and occasional fading I can
work these same areas from the aforementioned 60 miles. Given the
advantage of altitude I can work Plattsburgh New york from Ottawa, on a
regular basis. Distance ... only a guess 100 miles. The higher the better.
Requires ground plane ... can't tell you, but a friend uses one on his
Sport Bike with a handheld.
Hope this helps.
--
Bill VE3NJW Advanced Amateur
Packet Address : VE3NJW@VE3KYT.#EON.ON.CAN
Freenet Address: aj...@Freenet.Carleton.ca
Karl Beckman
rule for the amount of ground plane required for mobile antennas:
The ground plane SHOULD extend at least the length of the antenna in
all directions from the mounting base. In the real world, at least 1/4
wavelength is OK for "gain" antennas, but the H=R idea gets better field
strength and signal reports. Remember that the elevation of the main lob
generally will increase when the ground plane size decreases. 73-Karl
------------------------- Original Article -------------------------
From: chri...@merle.acns.nwu.edu (J. Burklin)
Subject: Diamond Dual Band Antennas
Followup-To: rec.radio.amateur.antenna
Date: Tue, 09 Nov 1993 00:40:54 -0600
NNTP-Posting-Host: elvex7.acns.nwu.edu
David Josephson
>I can't comment on the first part of your query, but there is a simple
>rule for the amount of ground plane required for mobile antennas:
>The ground plane SHOULD extend at least the length of the antenna in
>all directions from the mounting base. In the real world, at least 1/4
>wavelength is OK for "gain" antennas, but the H=R idea gets better field
>strength and signal reports. Remember that the elevation of the main lob
A longer ground plane than 1/4 wave might bring the radiation angle
down a bit.
And the original poster asked:
>I'm looking to purchase a dual band mobil antenna, a minimum of 5/8
>wave on the 2m side. Diamond manufactures several of significant size(i.e.
>57 inches or larger) with UHF mounts(SO-239 & PL259). Given the size of the
>antenna and anticipated wind load can I expect to see problems with the
>mount cracking or breaking off? In addition, Diamond's SG & NR series dual
Well, I have a 23 foot antenna up on a hilltop where we get 50+ mph winds
all the time. The only real problem (that reportedly has caused Motorola
to stop using these and go back to the 9-12 foot version) is that during
earthquakes they tend to oscillate, and they have lost a few.
73 David WA6NMF
--
David Josephson <da...@josephson.com>