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Author Topic: Best portable antenna  (Read 1145 times)

KB1GMX

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Re: Best portable antenna
« Reply #15 on: October 25, 2021, 10:03:03 AM »

RE: Grasswire

Most people that are not aware of ti use a 2M ht with a 5" rubber duck
and think its great.

The Grasswire is the HF version of rubber duck..  Longer but not all that much
ado about deployment.   I started using it as at that time I was an antenna
development engineer and the 75M net was what I wanted to hit on my break
time during the week.  Problem is tress near buildings while useful suffered
from very high RFI (S9+++).   The parking lot maybe 500 yds away was far
quieter but the tallest thing was maybe 5ft.  The mobile 8ft whip for 75M
was plain terrible even at 100W as the efficiency due to loading was maybe
1-2%.  So The Grasswire was tried and the bushes and short trees used to
support it mostly just off the ground by a few feet it proved effective in that
people 100 miles away hear me , some for the first time.  Two spools and
the funny transformer and a good match was easy and spools made wind
up and deploy a trivial thing.

That said, its not a all powerful antenna, but I was able to setup, do the
net and collect it in under 45 minutes.  I keep it in a large surplus magazine
pouch for transport and it weighs total 11oz with the spools.  That worked
well in that environment with its limitations.  It was also quiet, I could hear
with it.  I would later use it to get on 160M as on the ground it tuned up fine
and is shorter by a factor of 2 than in the air.

Its how I developed rule three for antennas, anything is better than a
bucket of wire in the shed.  Sometime optimal is just being on the air.

An aside and as WB6BYU suggested that same antenna could be
repurposed as dipole in the  are, inverted L, end fed random wire
using 1:9 transformer... so being able to adapt is a feature to consider.

Allison
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WB6BYU

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Re: Best portable antenna
« Reply #16 on: October 25, 2021, 12:29:19 PM »

Quote from: K2WPM

1.  Open up the pole - I put painter's tape on each junction.  Install a carabiner at the top to act as a pulley so I can raise and lower the antenna to change bands.  Unsnarl the string and raise the pole, lash it.  15 - 20 minutes.



A lot here depends on the specific pole, of course.

With my MFJ "fishing pole" I don't tape the joints - I just pull them
snug.  That seems to work as long as I don't put a lot of tension
on the pole:  light rope and antenna help that, along with light
tension on the wires of the inverted vee.

My other telescoping mast is a Max-Gain fiberglass with 4' sections:
it is considerably heavier, and not quite as tall, but has latches
that hold pretty well (once I get them adjusted).  Yes, I could go
taller and/or lighter using 6' sections, but with a full stack that
was a bit too far of a reach to push up the top ones without
standing on a stool or ladder.

I also found a telescoping squeegee handle at Home Depot with
flip latches rather than twist-locks on the sections, and it is
also easier to use.

Install a carabiner:  I use one of the little "not for climbing" ones
with a short loop of string.  Takes me a moment to wrap the
string around the pole and cinch it tight.

Untangling the string:  that's why I went to the figure-of-eight
method.  Saves a lot of time.  (I got sunburned one day trying
to untangle a rope.)

You can also roll up the string with it already tied into a halyard,
possibly with the carabiner / pulley / eye ring already on it.

Bungee cords, Velcro® straps, tie wraps, or nylon webbing
help to lash the mast to a support in a hurry.





Quote

2.  I don't use the pole anymore, I shoot a string over a high branch ... hopefully 50 feet or more -- using Long John pole-sling shot.  Tie it off and hoist the antenna.  still 15 - 20 minutes.



My throwing bucket is good to 50 - 60 feet.  Next version will
be a more portable one in a 3 pound peanut butter jar or similar,
that will also hold the ball, with a screw-on lid.

For a simple trip with a single antenna, I'd use the braided throwing
rope to raise the antenna, but otherwise I use it to pull up a second
rope for the antenna. 



Quote

3.  Assemble the linked dipole.  I store each band's elements in plastic baggies labelled for the band.  Center feedpoint and 20 meters is one bag.  40 meters is next bag.  75 meters is a bag.  Finally, I've never seen this done, but I also have bag for 80 meters ... short five-foot segments that allow me to do CW band.  Since I usually operate 20-40-75 meters (in that order). I connect those segments, using insulated carabiners pre-attached to the respective segments in the baggies.  15 - 20 minutes.



If you regularly put up all the sections, then you might try
winding up the antenna with all the sections connected
together, and possibly with the strings already on the ends.
(You can always add more if it isn't long enough, but at
least have enough that you can reach it from ground level
once the antenna has been hoisted up in the air.)

I carry separate wire elements for each band, which allows
me to pick and choose which ones I want to use each time
I set up the antenna.  But for specific purposes, I sometimes
leave a particular set of wires attached to the feedpoint (like
40m + 20m).

At one time I could get electric fence insulators that were like
plastic carabiners, and that made a good linked dipole, as all
the wire segments were normally left connected, but could be
removed if needed.  Unfortunately they appear to be discontinued.
Otherwise a short piece of rope is all that is needed to join
the wires mechanically.

While having separate 75m and 80m sections on a linked
dipole isn't uncommon, my approach is to attach the end
rope several feet back from the end of the wire, put a
plastic clothespin on the end, and use that to fold back
the end of the wire to tune the antenna across the band.


Quote

4.  Pull out 75 feet of coax, unsnarl it and attach to feedpoint, hoist antenna.  10 minutes.




The coax in my dipole kits is permanently attached to the
center insulators, saving some weight at the feedpoint.
Generally it is 30 - 50 feet, and I can extend it if needed.

Again, learning to avoid the untangling time will help.
Actually, the figure-8 approach doesn't work as well with
RG-58 coax, as it is stiffer and tends to take a set when
left rolled up that way.  You might get one of the spools
for rolling up power cable and wind the coax on that.



Quote

5.  Take string, unsnarl it (have to try that figure-of-eight trick) and and attach 25 - 50 foot on each end of the antenna, find a suitable tree to tie it off so vee ends are well above ground level.  15 - 20 minutes.



My guideline is that antenna wire + end rope should be at least
twice the height of the mast, to maintain a 120 degree minimum
angle on the inverted vee.  That assumes it tie it off at ground
level using the full length.  My target is to get the wire ends up
half the height of the mast, which means the rope would need
to be at least as long as the antenna wire (generally only an
issue on 80m).




Quote

6.  Check antenna with my Rig Expert AA-170.  One advantage of the linked vee is being able to get under 1.5 SWR, and therefore not need external tuner on various bands, connect coax to rig and power up the rig.  5 minutes



Have you ever had a case when you checked the antenna
and found you needed to make adjustments?  How do you
do that if the dipole lengths are set?

One of my objectives was NOT to need an analyzer or a
tuner when operating portable.  There have only been
rare instances when I haven't been able to use a pre-cut
dipole with out adjustment:  the SWR curve might not
be perfectly centered, or as low as I might like, but it
still was capable of making contacts.

So, yes, it is good to know that the antenna is working,
but if my rig has an SWR meter, that is good enough.


Not that there aren't other ways to speed things up,
but those are the ones that I have found worked for me.

AK4YH

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    • Radio Prepper
Re: Best portable antenna
« Reply #17 on: October 26, 2021, 03:17:33 PM »

For portable operations I have found nothing more practical than the end-fed half-wave wire with a 49:1 or 64:1 transformer. It is very fast to set-up with a 7, 10 or 12m telescopic mast. You can even make an inverted V, sloper, or horizontal antenna for NVIS. It's very fast to set-up. I've had great results with toroids as small as the FT-82-43. Size does not seem to change performance much, only max useable power. It remains my favorite portable antenna, and I have been at it for more than nine years.

Gil.
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AE0Q

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Re: Best portable antenna
« Reply #18 on: October 26, 2021, 08:20:09 PM »

I see a number of suggestions for getting antenna wires in trees, the higher the better.  It should be noted that many State and National Parks so not want wires in trees.  Many don't even want stakes in the ground for mast supports unless in a campground.  Techniques that many of us have been using for years in the National Forests are frowned upon in the Parks.

With POTA and SOTA becoming very popular, Parks On The Air activators probably could use more practical suggestions for antennas and/or supports that do NOT use trees.  SOTA activators face some different challenges but many are also in places with no trees.

Glenn AE0Q
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WB6BYU

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Re: Best portable antenna
« Reply #19 on: October 26, 2021, 10:36:01 PM »

We had an ARES exercise in a local city park.  They didn't
permit us to attach to any tree or infrastructure in the
park, and we couldn't pound stakes in the ground for fear
we might hit a sprinkler pipe.

So the challenge was where to tie off the ends of the
80m dipole.  It couldn't have any portion sloping down
where someone might bump into it.

The first end was tied to the luggage rack on another
vehicle across the parking lot.  That kept the rope above
head height.

But the other end went out into a grassy field.  I solved the
problem with a pair of bamboo garden stakes - probably the
8' ones, although sectional tent poles would also work.

We lashed the poles together close to one end to make a "bipod",
and the rope from the antenna ran over that (about 7' off
the ground), then straight down to a bucket of water sitting
on the ground that served as an anchor.

I've used this approach when experimenting in the back field,
and the bipod makes it easy to lower the ends of the wire for
adjustment without needing to untie the end or lower the
center insulator.  I generally use it with a stake, but the bucket
of water comes in handy when a vertical pull is needed.
(Another time I used a bucket of railroad spikes, but the
water has the advantage that you can dump it out when you
are done with it.)


In another case we set up Field Day at a BLM parking lot
where we were not allowed to pound stakes into (what was
left of the) asphalt.  One side of the parking area was close
to the edge of a steep embankment, with a line of boulders
as a divider so cars wouldn't accidentally drive off the edge. 
Of course, we wanted our antennas as close to the edge as
we could manage for best low angle propagation.

In that case, I cut several lengths of webbing and tied them
in big loops around 2 of the boulders, with a ring or carabiner
to secure the guy ropes to it.  The third rope went to an
anchor over the edge - either a tree or a stake of some sort.
We put up the triband yagi at 32 feet and it stayed up through
a severe microburst overnight.


For a while I used cinder blocks with ropes tied to them to use
as anchors for a canopy at a Farmer's Market.

Generally, weights such as a sand bag, bucket of rocks, bricks,
etc. can be used for anchors as long as there is enough weight
and friction that it won't slide under the applied load.  One of my
future projects is a piece of heavy fabric with a rope stitched
around the edge and a point to tie a rope to.  That can then
be weighted down with rocks, bricks, sand, a picnic table, or one
wheel of a car as an anchor point without needing to drive a stake
in the ground.   You probably could do something similar by sewing
a grommet in the corner of a sandbag.  I've also seen concrete
poured in a plastic washtub with an eyebolt or other tie point
to make a (relatively) easily movable anchor.

Similarly, many tripods can be modified to take weights on the
bottoms of the legs to hold them in place, in place of guy ropes,
although they probably won't survive as much wind as a good
set of guys would.

Some parks have strict prohibitions on "weapons", which may
be interpreted to include sling shots and pneumatic antenna
launchers.  A throwing bucket with a (weighted) tennis ball
and a Chuckit looks a lot more innocuous, especially if you
have a dog helping you.

My general approach is to use as thin of a rope / antenna / coax
as I can, and keep to the less populated portions of a park.  But
that doesn't always work as well for operating from a vehicle.


What this does point out, however, is that, just as there is no
"one best" antenna, there isn't a single "best" way to set up the
antenna in every situation, either.  It makes a big difference
what sorts of parks you frequent, whether you plan to operate
from inside your vehicle, a picnic table, or sitting on the ground
in a less-developed part of the park.  Your vehicle will place some
sort of limits on what you can carry with you (my 8' bamboo
poles are inconvenient on a bicycle), and the condition of the
operator and the number of helpers may also affect what one
can attempt for antennas.

This comes back to the idea that there isn't just one type of
"portable operating":  there are many different types, with
varying needs and capabilities, and lots of trade-offs to be made.
For example, I might make totally different choices if I am
operating a 100W radio from a vehicle vs. a QRP radio
from a picnic table, even in the same park, because in the
latter case I can move the station to a convenient support,
and antenna performance may be a more important criteria.
That's not to say that either mode is better than the other,
just to point out that they have different requirements and
trade-offs to make, depending on the circumstances, so it is
quite likely that different antennas (and supports) may be
preferable in each case.

KL7CW

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Re: Best portable antenna
« Reply #20 on: October 27, 2021, 03:32:24 PM »

Several times decades ago I got long lasting nylon or other lines stuck high up in a tree.  Probably some still there decades later.  I felt really bad about the pollution. Now I often use just ordinary (cotton ?) string if there is any possibility of getting an antenna stuck in a tree.  I can easily jerk on the antenna, coax, or the line and break it. Usually everything comes down fine.  If it gets broken or tangled, I can just throw it out.  Some of my line has lasted decades.
     Finding degradable line is probably not easy these days.  For trips into the hills, often I just make sure I have a full water bottle, it makes a good throwing weight and you will drink all the water at the top and carry down the empty.  A good pliable water bottle will survive MANY throws.  Disposable plastic bottles may break. 
                        Rick  KL7CW
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KB1GMX

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Re: Best portable antenna
« Reply #21 on: October 31, 2021, 10:35:22 AM »

A handy item is a 3 gallon or larger paint pail.  At the site it can
be filled with water, rocks dirt for weight.
 
It can be used as a end stop, or as a point to anchor a mast/pole.

Since its plastic it can even be base and support for a vertical.

I ahve one filled with concrete and a fixed tube in it for fast
setup in the yard for antenna testing be it wires or V/UHF
yagis.

However a sage once told be a site inspection at a prior date
will be great preparation for what may be needed.

Allison
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