Best 2M ground plane?
wse...@megsinet.net
full,..???
I'm going to build one for my moblie/base 2M radio and will be installing it
on the roof. I cause it matters the rig puts out 5w/10w/50w of power. And it
would be used for reapter work and some local simplex.
Also, is it worth spending the time and effort building a ground plane when I
can just order MFJ's 5/8 wave ground plane for $19.95? Thanks in advance! 73!
--
-\/\/ard--KB9TFF
wse...@megsinet.net
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Mark Keith
> What is the best wave length for a 2M vertical ground plane? 5/8, 1/2, 1/4,
> full,..???
>
> I'm going to build one for my moblie/base 2M radio and will be installing it
> on the roof. I cause it matters the rig puts out 5w/10w/50w of power. And it
> would be used for reapter work and some local simplex.
>
> Also, is it worth spending the time and effort building a ground plane when I
> can just order MFJ's 5/8 wave ground plane for $19.95? Thanks in advance! 73!
If it's going to be an elevated ground plane with radials, I'd go with
the 1/4 wave.
If it's on a car, I'd use a 5/8 wave. I WOULD NOT use a 5/8 as an
elevated gp. And the half wave can easily have problems with feedline
radiation. The good part is the 1/4 is the easiest to make and generally
will work the best elevated and up in the clear. If you need gain, I'd
use a isopole or something like that. Dual 5/8 elements. MK
mun...@ibm.net
Dan Starkenburg wrote in message <3681D1E0...@mci2000.com>...
>> If it's going to be an elevated ground plane with radials, I'd go with
>> the 1/4 wave.
>> If it's on a car, I'd use a 5/8 wave. I WOULD NOT use a 5/8 as an
>> elevated gp. And the half wave can easily have problems with feedline
>> radiation. The good part is the 1/4 is the easiest to make and generally
>> will work the best elevated and up in the clear. If you need gain, I'd
>> use a isopole or something like that. Dual 5/8 elements. MK
>
provide
>the maximum amount of gain of any element, but was
>not aware they can be problematic if elevated.
>
>DS
>
>
I would be curious to hear the answer to that also. I used a 5/8 wave for a
base antenna at my old QTH for 25 years with no complaints, and it also
loaded up as a 1/4 wave on 6 meters. I had two sets of radials, one set 20
inch for 2M, and one 60 inches for 6M. Maybe I was just lucky.
The primary problem with inexpensive commercial antennas is thin wall tubing
and rust-prone hardware. If the tubing is heavy and you use stainless
hardware and Locktite or shakeproof nuts, then go for it.
73, Crazy George
Dan Starkenburg
marc schneider
>What is the best wave length for a 2M vertical ground plane? 5/8, 1/2, 1/4,
>full,..???
>
>I'm going to build one for my moblie/base 2M radio and will be installing it
>on the roof. I cause it matters the rig puts out 5w/10w/50w of power. And it
>would be used for reapter work and some local simplex.
>
>Also, is it worth spending the time and effort building a ground plane when I
>can just order MFJ's 5/8 wave ground plane for $19.95? Thanks in advance! 73!
>
------------- I've read the other responses so far and have this to offer.
I made my own 1/4 wave according to the "Now Your Talking" book - with
modifications of my own as my first ham project. It works fine and is in my
attic up one story. I live in northern suburb of Chicago and hit the home
radio on simplex while on the interstate south of the airport. I hit a
machine some 40 miles away using 2.5 watts with this antenna setup. No need
to expect the need for big, expensive or otherwise great antennas if you live
in a general metropolitan area. I used scrap wire from wiring project for the
house and a SO239. Small brass screws to connect the radials to the SO239 and
then this was put on an angle piece of aluminum which I then screwed to a
stick of wood as a mast. I was sure to have the very top of the antenna touch
the inside peak of the rook to maximize radiating rather than reflecting
inside the attic.
You can put this together for $2. and if it does not meet your needs - then
worry about your other questions.
Marc Schneider, Psy.D.
e-mail to: <drm...@wwa.com>
(call sign: W4NVY)
John Mock
with modifications of my own as my first ham project. It works
fine and is in my attic up one story. I live in northern suburb
of Chicago and hit the home radio on simplex while on the
interstate south of the airport. I hit a machine some 40 miles
away using 2.5 watts with this antenna setup. No need to expect
the need for big, expensive or otherwise great antennas if you
live in a general metropolitan area. I used scrap wire from
wiring project for the house and a SO239. Small brass screws to
connect the radials to the SO239 and then this was put on an angle
piece of aluminum which I then screwed to a stick of wood as a
mast. I was sure to have the very top of the antenna touch the
inside peak of the rook to maximize radiating rather than
reflecting inside the attic.
You can put this together for $2. and if it does not meet your
needs - then worry about your other questions.
Yep, they work great if you understand their limitations. They're also
decent for listening to satellites, if you're interested in getting into
that someday. You can tune on to have decent SWR at 70cm, but don't
expect decent performance out of it, as negative gain (in dBd) for
terrestrial use (e.g. it works a couple of dB worse than a dipole or
quarterwave groundplane), because most of the energy goes skywards:
http://www.qsl.net/kd6pag/nec/2mModGndP.html
But if you tune it right, at least it won't make your dual-bander
unhappy due to bad SWR, and it's not a bad omni for satellite purposes
at 70cm (you might even hear AO-27 with it if you have a sensitive
receiver and there's not too much out-of-band QRM in your area). But
don't expect to hear well at 70cm if you use alot of RG58 feedline.
To tune it, get a 2m/440 SWR meter from Radio Shack; they're cheap and
are fine for qualitative purposes. (e.g. Is this better or worse?
Later you can get an antenna analyzer or a better meter if you want to
know what's really going on or make claims about SWR to other people.)
Make the main element a little longer than specified. Then trim off
small amount (1/8" or a few mm) and then make four or five measurements
across the band(s) of interest. Repeat until the minimum SWR gets
close to being in the middle of the band (or in this case, where you
have a good compromise between the two bands). Put a plastic bead of
the sharp end for eye protection if it's not going to be permanently
mounted outside. (Or tune it with a 1/4" loop at the end, and then you
can use a rubber band to hang if from the ceiling for indoor use. Nice
thing about this antenna is that the materials are cheap enough that if
you go too far, you can just get another 20" or so of wire and start
over.
You can find instructions on building one of these things in any recent
ARRL Handbook. If you build it to their specifications, it'll work
well enough; here, tuning is for perfectionists (or dual-banders). But
do check the SWR before using it for more than brief tests at high power
just to make sure you don't make a measurement or construction error.
You can also build it with an N connector was well as a SO-239, which
are more water-resistant and have better impedance characteristics at
UHF and above. And i find the connectors easier to attach to coax than
PL-239 -- but that's personal taste.
So, for the money, if you have simple tools (and aren't visually impaired),
the best 2M ground-plane is one you make yourself.
-- KD6PAG
Dan Starkenburg
> the best 2M ground-plane is one you make yourself.
I, too, have made a 1/4 wave groundplane. I used single-strand #12 THHN
wire, available from almost any hardware store. It worked quite well.
I used tiny nuts and bolts to fasten the wires, although the plans I viewed
recommended soldering the radials. My problem was that I could not get
my 100W solder gun hot enough to get the solder to "stick" to the SO239.
The nuts and bolts eventually wiggled loose, but I am looking for an
alternative
method to fastening the radials (besides nuts/bolts and solder).
My only complaint was the antenna's inability to stand up to "the elements".
The antenna
works great hanging from my wife's plant hook inside, but I don't dare stick it
outdoors, as the wind and snow would probably get the best of it. I think that
is why
people are willing to spend few bucks and just buy the antenna -- because it
will probably
withstand the outdoors better than a homemade antenna.
DS
Dave Martindale
>I used tiny nuts and bolts to fasten the wires, although the plans I viewed
>recommended soldering the radials. My problem was that I could not get
>my 100W solder gun hot enough to get the solder to "stick" to the SO239.
>The nuts and bolts eventually wiggled loose, but I am looking for an
>alternative
>method to fastening the radials (besides nuts/bolts and solder).
You might try using solder with a small butane soldering iron/torch as the
heat source. A little torch like the Weller Pyropen puts out an amazing
amount of heat into one of its soldering tips, considerably more than a
100 W iron by my estimation. And if *that* still isn't enough heat, you
can use the bare flame from the torch - but then you've got to avoid
getting things too hot, rather than not having enough heat.
You also need a SO-239 with a real Teflon insulator for this. Teflon will
withstand soldering temperatures, even if the whole body of the connector
is heated to soldering temperature. Most other insulating materials won't.
Dave
Mark Keith
It has the maximum gain of a single element.(.64 wave to be exact) but
with an elevated 5/8 gp it's usually not on the horizon where you want
it. On 2 m , this is very critical. The reason for this is most 5/8 gp's
use 1/4 wave radials. This is the first problem. It's an incomplete
image return for a 5/8 wave. Which means you end up with rf on your
feedline.(common mode currents). This rf skews the pattern up off the
horizon.
Now if you use a set of 3/4 radials and make sure that you have no rf on
the feedline, then you may see an increase over the 1/4 gp. This can be
modeled using Roys elnec demo and it confirmed what I've been saying. I
tried it a while back during the last 5/8 gp controversy. A 1/4 gp with
sloping radials has the maximum angle at about 4 degrees. This is very
good and even though the antenna has no theoretical gain it will almost
always outperform the 5/8 gp for 2 meters. Now on say 10 meters , it's a
whole new story, with the takeoff much less critical and the 5/8 will
almost always beat a 1/4 gp.
Also the same on a car. The car has the metal to make a decent return
for a 5/8. If you want a gain vertical you are better off using multiple
5/8 elements in a collineer type setup. Like the isopole or RR or
whatever. The isopole is a very good 2 m vertical. Probably one of the
best for the size, except it's so dang ugly. Looks like a ballistic
missile on the house. I recommend a small yagi for serious use. Light
years better than any vertical. I remember when I got my first 2 meter
rig , years ago. I made a 1/4 gp and then decided HEY!!! I'll take my
larson 5/8 car whip and make a gp out of it. That should be better for
sure. Boy, was I wrong....The 1/4 gp mangled it. And the larson is one
of the best coils and whips you can buy for a 2 m 5/8. MK
Ken Bickel
quarter wave groundplane. So does a properly designed j-pole which does not
require radials.
What is your time worth? Buy the 5/8 wave MFJ, which works well (I had
one!) and avoid the hassle of making one. OR - make an antenna and write
off your time as a learning experience.
LOL
Dan Starkenburg wrote in message <3681D1E0...@mci2000.com>...
>> If it's going to be an elevated ground plane with radials, I'd go with
>> the 1/4 wave.
>> If it's on a car, I'd use a 5/8 wave. I WOULD NOT use a 5/8 as an
>> elevated gp. And the half wave can easily have problems with feedline
>> radiation. The good part is the 1/4 is the easiest to make and generally
>> will work the best elevated and up in the clear. If you need gain, I'd
>> use a isopole or something like that. Dual 5/8 elements. MK
>
>Why would you not recommend a 5/8 wave groundplane??? I've readthat they
provide
>the maximum amount of gain of any element, but was
>not aware they can be problematic if elevated.
>
>DS
>
>
Gary Coffman
>I used tiny nuts and bolts to fasten the wires, although the plans I viewed
>recommended soldering the radials. My problem was that I could not get
>my 100W solder gun hot enough to get the solder to "stick" to the SO239.
>The nuts and bolts eventually wiggled loose, but I am looking for an
>alternative method to fastening the radials (besides nuts/bolts and solder).
File the plating off the connector flange before trying to solder it. You'll
find it "takes" solder much better. Also, the low mass tip of a gun can be
a problem. A big iron is better. I use a 300 watt American Beauty when
I have AC power handy, or the big Weller Pyropen if I'm away from power.
You can also use a traditional soldering iron, IE a real chunk of tinned
copper with a wooden handle, heated over a gas stove. I used one of
those for years. (Actually I used two, one heating on the stove while
the other was in use, then swap as the one in use cools.)
Gary
Gary Coffman KE4ZV | You make it |mail to ke...@bellsouth.net
534 Shannon Way | We break it |
Lawrenceville, GA | Guaranteed |
Mark Keith
>
> A 5/8 wave ground plane, such as the MFJ, have about 3 db gain over a
> quarter wave groundplane. So does a properly designed j-pole which does not
> require radials.
less gain. Properly decoupled it would be appx 1.8 db over a 1/4 gp. But
no one ever makes them properly decoupled so they probably show a loss.
>
> What is your time worth? Buy the 5/8 wave MFJ, which works well (I had
> one!) and avoid the hassle of making one. OR - make an antenna and write
> off your time as a learning experience.
> LOL
compared your mfj 5/8 to a 1/4 gp? Also a j pole MUST have some sort of
decoupling or it's not properly designed. Very few do/are. MK