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Author Topic: Looking for help with a portable HF setup  (Read 2322 times)
FREEMA22
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Posts: 23




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« on: January 27, 2013, 01:15:10 PM »

Hi Team,
I am a member of a support organization for the Illinois Terrorism Task Force. Apparently I am the only ham on the team, so I have been given a task. A couple of years ago, the team purchased a Yaseu FT-450 (not the D) and a PTCIIPro pactor controller. Everything is mounted in a Gator Case rack case. The guy that started the project left the team years ago.

The Pactor controller has never been connected, and is a whole separate project. I want to get the FT-450 on the air.

The antenna that the team selected was a Perth Plus from Outbacker. The mount they chose was a Tram 3 magnet mobile mount like this:
http://cdn2.bigcommerce.com/server1600/d4c67/products/831/images/1324/gm300t__74268.1342377279.1280.1280.jpg

I tossed the antenna and mount out in the front yard yesterday, and was able to hear people a couple hundred miles away (conversation between Ohio and St. Louis, and I am in northern Illinois). I didn't key up out of fear that the SWR and grounding was inadequate.

Is this setup adequate? Do I need to create any type of radial plate, or counterpoise? The instructions for the Outbacker are really focused on mobile mounting, and not so much base station mounting.

Secondly, should the station itself be grounded somehow? I just feel like the setup that they handed me to evaluate looks good in theory, but in practice, it needs a lot of attention. Sorry for the litany of questions. I got my General ticket this summer, but have never actually used my new privileged.

Thanks for your assistance,
Mike
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N9AOP
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Posts: 159




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« Reply #1 on: January 27, 2013, 01:58:04 PM »

Hi Mike,
I am a team leader with ITECS#3 in Will county.  This is one of the state's comm units on a trailer.  Since short vertical antennas are generally not that efficient, I prefer a wire which is cheap.  For NVIS I use either a 124 foot or a 52.5 foot length.  This is set up as a short inverted L and fed at the base thru a remote tuner.  Attach end of the wire to the antenna feed on the tuner.  Run it up on a support about 12 to 16 feet and then out as far as it goes.  This way you only need two supports.  I use the surplus 4ft military fiberglass masts stacked together.  Attach another wire of the same length to the ground connection on the tuner and run it out on the ground under the elevated wire.  If you don't have a remote tuner you can use a 9:1 UNUN and it will perform just about as well.  I have used this setup on MARS nets and have had good comms with Ohio, Indiana, Wisconsin, Minnesota, Michigan and Iowa.  As I said, this doesn't cost much and any kind of wire that you have will work.  I was once on a field operation and used electric fence wire and it worked OK.  That vertical will work but you will have to have a good ground plane or use some radials.  Don't forget to adjust the stinger everytime you change frequency in addition to the wander lead.  Where do you need the signal to go to--Springfield or Langly?
Art
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WB6BYU
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Posts: 13571




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« Reply #2 on: January 27, 2013, 07:22:28 PM »

What distance do you want to cover? 

What bands are you using?

Oregon has a statewide ARES digital network with a station in each County.  In our case,
we probably would choose a different antenna depending in whether we were trying
to reach (1) the state OEM, (2) counties on the other side of the state, or (3) an Airmail
gateway elsewhere in the country.

It also depends what sort of station you are setting up:  in a vehicle?  in a building?
in an open field?

In most cases I'll agree with Art that wire often gives better results over commercial
whips, etc.  For relatively local work (out to a few hundred miles) then a low dipole
is hard to beat for performance and simplicity:  it can be hung between two supports
or from a flagpole as an inverted vee.  You're limited to 40, 60, 80 and 160m for
NVIS operation, so a trap antenna is a reasonable option, or separate dipoles for each
band on a common feedpoint, or even a dipole with switches to choose the band.
(We use an 80m dipole with a junction in the middle of each side:  when disconnected
there it is a 40m dipole, or we can connect a loading coil there for 160m.)

A vertical antenna has a null overhead, so isn't as good for NVIS.  I've seen some
operators stick a such an antenna horizontally of the back of a truck, and I've had
reasonably good luck sticking one out a second story window, using the aluminum
window frame as a ground.  But, when erected vertically it isn't a good choice for
NVIS.  For some other paths it might work better.


If you can be more specific about bands and the range of distances to be covered,
then it is easier to recommend antenna that will work best for that application.


Even the largest 3-magnet mobile mounts don't provide enough capacitance to
ground to be efficient on HF, especially on the lower bands.  A wide strap to ground
will help a lot.  The grounding will also affect the tuning.  A ground system is
absolutely needed for good efficiency and repeatable tuning:  it could be a set
of radial wires laying on the ground, or a large chunk of metal (such as a car or
truck.)
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KQ6Q
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Posts: 993




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« Reply #3 on: January 27, 2013, 09:03:13 PM »

for NVIS, the antenna has to be horizontal. for EmComm HF, as long as you're not QRP, go with a Buddipole in dipole configuration, or the equivalent model in the Superantenna line. either setup can work 40 through 10m, and mast and tripod mounts are available from the same manufacturers.
I run a bunch of mag-mounted Hustler verticals on my big metal mobilehome roof, but to get some closer in contacts on 40, I put a hamstick dipole on a mast on the side of the house. It's nice to be able to select horizontal vs vertical from the operating position!
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K5LXP
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Posts: 4536


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« Reply #4 on: January 28, 2013, 06:25:05 AM »

I think the first thing you need to do is understand who you'll be communicating with and when, which will answer WB6BYU's question of how far and when.

What is this outfits' mission?  Does this communication even take place in the ham bands?  Given the size and scope of this organization I'm wondering just what one guy with a mobile HF rig can be expected to do.


Mark K5LXP
Albuquerque, NM
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W5WSS
Member

Posts: 1782




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« Reply #5 on: January 28, 2013, 08:03:55 AM »

And IF you want to utilize the Perth Outbacker you can connect some radials to the shield driven base mount and have an option for longer communications.

Elevate the base a little or ground mounted adding either tuned 1/4 wave radials or on the ground radials will work. non tuned and longer like 1/2 long.

For ecomm use one can place alligator jaws on the radials and use for quick attachment at the base mount

Elevated a little like 5ft and adding sets of tuned radials sloped downwards towards the surface and insulated at the ends with non conductive anchors can be effective with as little as two per set that travel away from the feed point of the Perth vertical.

If you want all the bands offered by the Perth choose with the jumper ed plug and add 1/4 wave tuned radials in sets traveling as described earlier and use a few inches of separation between the sets of tuned and elevated radials. 73
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FREEMA22
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Posts: 23




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« Reply #6 on: January 29, 2013, 06:02:32 PM »

This has been a great learning experience so far.  I think what I will end up doing is getting a mast of some kind, around 20' in length. From it, I will suspend one of the multitude of NVIS antennas for 40 & 80 meters that can be found online, from it.  With a tuner, I should be able to work some of the other bands, right? Since most, if not all communications would occur within 200 miles, I think this might fill our requirements nicely.

What do you think?
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WB6BYU
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Posts: 13571




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« Reply #7 on: January 29, 2013, 08:28:56 PM »

The 4' military mast sections are pretty common.  7 of them make a nice bundle, with
a couple bungee cords holding it together, giving you 28'.  (You can then use the bungees
to secure the mast to a fence post or a street sign.)  You don't have to put it all up, but
that is a convenient height for one person to assemble.  (All of our ARES members practice
doing it when we have a field antenna training.)  Yes, you can find lighter masts, but these
are versatile:  I have several bundles ready to go out for field teams.  This method does
require guy ropes, so we practice tying knots as well.

20' is a reasonable height for 40m and 80m, though going to 28' will give you about
1dB of improvement on 80m (depending on ground conditions.)  But the biggest
improvement will be on 160m.  Wait...  why that?  Well, this is why...

Start your journey at the Australian Ionospheric Propagation Service here:

http://www.ips.gov.au/HF_Systems/7/1

Click on "Combined HF Prediction".

Click the dot for the the Local Area Mobile Prediction (LAMP) tool.  Eventually a tab
will open in the top bar - click it.

Click the "Base Location" tab and enter your coordinates, or simply click your
location on the world map.

Select the "Frequencies" tab and choose "Amateur".

On the "Date and T-Index" tab, click "Real Time T-Index" and select "Northern
Hemisphere" in the pull-down menu.

Then hit the "Predict" button.

What you get is a chart of time-of-day vs. distance (up to 1000km), color-coded
to show what frequency band is open for that distance at that time.  If you look
at you'll see that (as of today when I ran it with your approximate location) that
40m is open for about 3 hours of the day.  80m is open for short length paths from
about 1500Z to 0300Z each day.  The rest of the time - from 0300Z to 1500Z,
80m won't cover paths less than about 400 miles, and you'll need to use 160m
to contact Auburn or Sacramento.


We've had this problem for several years here in Oregon:  while more distant
stations come through OK on 80m, it won't support local work around the
state during much of the night.  We're still in the "80m during the day, 160m at
night" mode, as we usually are during the winter, and/or during times of low
sunspot activity.  That doesn't mean you always have to put up an antenna
for 160m, but it is important to have one as a backup if you are planning to
utilize HF
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FREEMA22
Member

Posts: 23




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« Reply #8 on: January 30, 2013, 06:35:28 AM »

WB6BYU - This is great information. Thanks for pointing this out.

Mike
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WB6BYU
Member

Posts: 13571




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« Reply #9 on: January 30, 2013, 09:11:37 AM »

A couple suggestions for antennas:

This is AE5JU's adaption of my original 160m / 80m / 40m dipole kit (he built it for
80 / 40 / 20m) with a single 40m / 160m element the same length as the 80m wire.
(I used the same wire lengths on both sides of the antenna, however.)  This allows
all three bands on a single feedline with no manual bandswitching.

http://www.hamuniverse.com/ae5jufielddayantenna.html


When you expect to be on a single band for a while, a simpler method is to start with
a 40m dipole, tune it to resonance, then put an Anderson connector on the end.
Tie an extension wire on the other end of the insulator and cut it so the antenna
resonates on 80m when the wires are connected together.  That gives you 80 / 40m
with a quick disconnect to switch between them.  Then I wound loading coils for
160m with Anderson connectors on each end, with the coils hanging down from
the same middle insulator on each side.  By using color-coded Anderson connectors
I can write a simple set of instructions like "For 80m, connect GREEN to YELLOW."


You can browse the "Antennas" downloads on the YCARES web site for other ideas:

http://www.ycares.org/index.php?option=com_phocadownload&view=category&id=15:antennas
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FREEMA22
Member

Posts: 23




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« Reply #10 on: February 04, 2013, 07:20:19 PM »

I took the suggestions offered here, and recommended the "modified" AS2259 crossed dipole. The problem now is that the team thinks that the antenna footprint is HUGE. I tried explaining to them how HF radio worked, and all I got was "that footprint is the size of our field hospital".

So back to the drawing board. Is there a way to make a vertical work for what we are trying to do? They talked about being able to mount a whip to the Mobile Command Center, which is similar to a FEMA trailer. There should be plenty of steel to ground to, but I don't know how effective a whip would be for communicating over only a couple of hundred miles (ie NVIS). I have already explained what will be lost by not using a proper antenna, and now they are talking about ditching the ham equipment all together if I can't make it work in a small foot print.

What other ideas do you guys have?

Thanks so much for all of the assistance.

Mike
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K5LXP
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Posts: 4536


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« Reply #11 on: February 05, 2013, 06:15:21 AM »

now they are talking about ditching the ham equipment all together if I can't make it work in a small foot print.

I would use that opportunity to gracefully bow out.  What you are proposing to do with what you have in the scope of this organization is way out of your (and ham radio's) league.


Quote
What other ideas do you guys have?

A satellite phone.


Mark K5LXP
Albuquerque, NM
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WB6BYU
Member

Posts: 13571




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« Reply #12 on: February 05, 2013, 10:02:42 AM »

Quote from: FREEMA22
I took the suggestions offered here, and recommended the "modified" AS2259 crossed dipole. The problem now is that the team thinks that the antenna footprint is HUGE. I tried explaining to them how HF radio worked, and all I got was "that footprint is the size of our field hospital".

So back to the drawing board. Is there a way to make a vertical work for what we are trying to do? They talked about being able to mount a whip to the Mobile Command Center, which is similar to a FEMA trailer. There should be plenty of steel to ground to, but I don't know how effective a whip would be for communicating over only a couple of hundred miles (ie NVIS). I have already explained what will be lost by not using a proper antenna, and now they are talking about ditching the ham equipment all together if I can't make it work in a small foot print.

What other ideas do you guys have?

Thanks so much for all of the assistance.

Mike



There are other options at the expense of efficiency.  In the end it all comes down
to how often and in what circumstances you expect to need to use HF.  (And that
applies to the rest of the ham gear as well.)  If you have adequate VHF/UHF coverage
in most areas, you might not need it at all.  Our Search and Rescue team often set
up a base camp in the bottom of a canyon because that was the trailhead into the
wilderness area:  sometimes we could hit a Fire repeater from there, other times we
had to put a manual relay station up on a ridge - especially to communicate with
the field units, who were out of radio contact by the time they got a few miles down
the trail.

Generally HF wouldn't be used for mobile communications because VHF is more
convenient over relatively short distances.  In difficult terrain you probably can
get 10+ miles on 80m with vertical antennas using ground wave, though antenna
efficiency becomes more of a limiting factor (attenuation is relatively high, so
radiated power has a direct effect on usable distance.)  Otherwise it is more suited
to communications from a base camp or command post.  Whether that meets the
needs of your team will depend on how they organize a search:  if the command
post is expected to be mobile, it might not be useful at all.  That's a decision you
need to make based on your team.


But there other antenna options.  For NVIS propagation you need a horizontal
antenna.  One common approach is to make a dipole using two mobile antennas
and stick it on top of a mast.  This gives you a dipole 16' long that doesn't need
to be guyed off to external points, commonly referred to as a "Hamstick Dipole",
even if it uses mobile antennas that don't carry the "Hamstick" label.  Our ARES
unit and several individual members bought commercial systems of this type:  they
are usable on 40m (though noticeably worse than a wire dipole), but we've never
been able to get any sort of reliable results on 80m.  Bandwidth is very narrow - we
could watch the SWR varying due to a tree branch waving in the wind 5' away from
the antenna.  Tuning is touchy, and efficiency is perhaps a few percent.  I have the
team kit in my barn right now to see if I can make it usable by extending the elements
with some aluminum tubing.

The "Buddipole" ( http://www.buddipole.com/ ) is similar, but uses larger diameter
coils which can improve efficiency over mobile antennas using a fiberglass tube with
a top whip, and includes a lot of other accessories.  But even at that, efficiency
will still be rather low and the operating bandwidth narrow.

Another option would be a loop of some type:  for example, hanging a wire loop off
the top of a mast and making something like this: 

http://www.ycares.org/index.php?option=com_phocadownload&view=category&download=29:medium-tuned-loop-for-160-meters&id=15:antennas

likely with an autotuner at the feedpoint (if it will handle the high voltage.)  It
should work reasonably well on 80m and 40m with a smaller loop.

Since you have a large metal mass available for a ground plane, you can use
various sorts of mobile or similar vertical antennas from it if you mount them
horizontally off one side.  I've seen mobile setups where the mobile whip
is mounted on the back of the roof angle angled 15 to 30 degrees from horizontal
sticking off the back of the vehicle.  A conventional ball mount should provide
the necessary range of adjustment.  The longer you can make the antenna,
especially between the feedpoint and the loading coil, the higher the efficiency.
Wire antennas will also work fed against the metal frame, either a full quarter
wave, using a loading coil or trap, or a random length fed with an autotuner.


If you really want to use a vertical whip for 100-mile communications, then
the digital WinLINK system might be the best choice:  it allows you to connect
to a digital station at a longer distance using any of a number of different bands
and send email messages via the internet from there.


In my experience, HF is an option that might be useful under particular
circumstances depending on terrain and the communications needs of your
group.  Or it might not.  It takes a lot more work to set up antennas and maintain
contacts than on VHF/UHF.  Unless you have an existing HF network using
commercial equipment, generally I'd leave the HF link to the "Communications
Auxiliary" (radio geeks) and let the SAR folks focus on VHF/UHF for more tactical
communications.  But that is a decision that you have to make based on your
specific team, resources, etc.
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