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Author Topic: Single op field day antenna for campsite  (Read 5203 times)
N8TI
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Posts: 115




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« on: February 23, 2012, 10:17:49 PM »

I intend to do Field Day this year at a compsite in Northern Michigan. Just me and the IC706 with a LDG auto tuner doing CW. What do you think the best antenna to work all the bands, except probably 160?  A simple 66 foot long wire?  Or, perhaps a 100 ft dipole fed with ladder line? I may run off the car battery, so may be using 100 watts.

Suggestions?

Joe
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WB6BYU
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« Reply #1 on: February 23, 2012, 11:12:12 PM »

What antenna supports do you have?

What is the ground conductivity in the area?

How serious are you about making lots of contacts?

How much space do you have for antennas?


All of these are important considerations.  I've used lots of antennas over the years, both
for Field Day and other portable operation.  The last couple of years I've used a full wave 80m
horizontal loop and made twice as many QRP contacts as the other three stations combined.
It is a bit of a chore to set up - because of the slope of the hill two of the trees are at 50',
and the antenna crosses a road.  But if you can get it up a reasonable height it should be a
good all-round performer. 

We also set up an old TA-33jr at about 28', though it doesn't really need to be up that high
given that the site has several hundred feet of steep drop on the East side.  This might work
better than the loop on the bands it covers, but I always let the others use it instead.
I wanted to demonstrate that I could set it up all by myself, but one of the other hams insisted
on helping.  I would consider it practical for a single person, however, if you stack the mast
sections vertically rather than trying to tilt them up.

I've tried various sorts of long wires, including a sloping long wire over salt water in Alaska,
and 185' sloping vee beams.  These have the advantage that each wire can be moved
maypole-fashion to change the pattern, but the sloping wires reduce the effective height.

For several years I operated 1E from home using just dipoles - a tri-band rotatable on the
tower (the driven element from a yagi) and a pair of inverted vees for 40m and 80m.  My
goal was to work all 50 states on QRP:  I haven't made it yet, but got up to 47 in less than
8 hours of operating.

Conditions are different in Michigan than out here in Oregon.  Most of the lower 48 States
and Canada are within a single hop distance, while we need double hop propagation to much of
the East Coast.  On the other hand, we can just point our antennas East and work everything
(Hawaii and Alaska still come in fine when the band is open, and California is never a problem,
even off the side.)  So that affects your choice also.

A simple doublet fed with open wire line is still hard to beat.  They will have nulls in some directions
on the higher bands, but you'll still put out a lot of RF.  You'll want to look at the radiation patterns
(both vertical and horizontal) to see how best to align them to the population centers.  Or consider
using two different antennas - one sized for 10 / 15 / 20m with a more predictable pattern, and one
with longer wires for better efficiency on 40/80m.

And I've tried several more exotic antennas:  our standard for many years was a 2-element wire
quad for 40m, which is practical if you can get the top spreader up 40' or more.  I even tried
3-elements once (and nearly got a reflector added to our 80m vertical loop).  But those are better
for those of us who only need to aim in one direction, as they aren't convenient to rotate (but can
be switched between two directions.)  A 40m Bobtail curtain actually worked better on 20m than any
other antenna we had that year, but wasn't as good for the relatively high angle 40m contacts
during the day.

Given you location, I would be hesitant to suggest a vertical, because you'll be working lots of
relatively close stations.  Especially on 80m you'll want horizontal polarization to work the locals.
Generally if you can put a dipole up 1/4 wave or more on the higher bands it will outperform
a vertical of the same height, but there may be times when a vertical is your best choice:
perhaps it is the the best option due to space constraints, or if you are sitting next to salt water.


If you want to take the time to install it, a full wave loop for 80m (or even 40m) will give you a
good all-round antenna with reasonable impedances.  Similarly a small beam works quite well and
can be feasible (though not trivial) to be set up by one person.  For simplicity a center-fed
doublet with twinlead to a tuner is easier to set up and can be used on all bands.  Most of my
portable operating these days uses a set of dipoles on a common feedpoint - it is reasonably
simple to string up the feedpoint and tie each wire off in a different direction, and allows
operation on multiple bands without a tuner and with minimal feedline losses.


In practice, while the antenna helps a lot, getting it up in the air and avoiding antennas with
low efficiency (due to the antenna, ground, or feed system) will make the most difference,
regardless of the specific antenna you choose.
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WX7G
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« Reply #2 on: February 24, 2012, 05:06:12 AM »

Yes there is no real FD activity on 160 meters. So for 80-10 meters a G5RV mounted as an inverted-vee will do a good job.

The reason I suggest a G5RV rather than a simple ladder line fed 100' dipole is the limited tuning rang of the LDG tuner. The G5RV will present a more limited impedance range.

I have used inverted-vees on many field days with great success and much fun at the 5 and 100 watt levels.
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N4OGW
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« Reply #3 on: February 24, 2012, 06:04:53 AM »

As BYU said, the main consideration is what supports you have. If you have trees, it is hard to beat a simple dipole fed with ladder line. If you have room, put up two dipoles oriented in different directions and use a simple coax switch to switch quickly between them.

A car battery will not last very long at 100w. With a trolling battery you can probably go the entire field day at 5W output.

Tor
N4OGW

I intend to do Field Day this year at a compsite in Northern Michigan. Just me and the IC706 with a LDG auto tuner doing CW. What do you think the best antenna to work all the bands, except probably 160?  A simple 66 foot long wire?  Or, perhaps a 100 ft dipole fed with ladder line? I may run off the car battery, so may be using 100 watts.

Suggestions?

Joe
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N8TI
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Posts: 115




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« Reply #4 on: February 24, 2012, 12:00:27 PM »

Well, I will be up in the woods in Michigan.  I imagine I can reserve a campsite that backs up to a woods, so I will have lots of trees for support.

Being up at the top of the lower 48, I could probably put up two dipoles, fed with ladder line, aiming one SW and the other SE and probably cover the whole of the U.S.

The loop idea is one I never thought of.  I imagine the loop would be fed with ladder line? In a way, putting up a loop in the woods would not be that much harder than two dipoles, would it?  You would have to walk one end of the wire through the trees to form a square and then hook it up to the feed line. It looks like I would just use 280 feet of wire plus the ladder line as I will be using it on multiple bands.  Four supports should be pretty easy to find in the woods, Hi. I will test that out next month to see if the tuner can handle it.

As to how serious I am about Field Day, I am probably not as serious as I could be. I usually like to work FD at night when things calm down. Most of the activity is during Saturday afternoon and it is a little too wild then, especially for QRP. I don't like fighting for every QSO.  At night it seems that activity  slows down by at least half. I wonder if anyone has ever made a study of that. With QRP, into the evening and the wee hours of the morning seem to be the time for best hunting. Doing a one man op you can't work the 24 hours (well, you could, but it would be tough), so you have to pick your 14 to 16 hours of operation.  I think that in the middle of the night is when it is the most fun. You get the die hard guys then.

Joe
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WB6BYU
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« Reply #5 on: February 24, 2012, 01:23:48 PM »

Quote from: N8TI
Well, I will be up in the woods in Michigan.  I imagine I can reserve a campsite that backs up to a woods, so I will have lots of trees for support.

Height of the trees, spacing between them, and shape the upper branches are all important.


Quote

Being up at the top of the lower 48, I could probably put up two dipoles, fed with ladder line, aiming one SW and the other SE and probably cover the whole of the U.S.


Remember that such an antenna only fires broadside up to the point where it is 1.3 wavelengths
long.  For an 80m dipole or G5RV, the pattern has multiple lobes on 20m and higher frequencies.
For an 80m dipole on 20m the lobes will be about 45 degrees to the wire, so two such antennas
90 degrees apart will have lobes and nulls in the same directions.  But it still isn't a bad approach.


Quote

...I imagine the loop would be fed with ladder line? In a way, putting up a loop in the woods would not be that much harder than two dipoles, would it?  You would have to walk one end of the wire through the trees to form a square and then hook it up to the feed line. It looks like I would just use 280 feet of wire plus the ladder line as I will be using it on multiple bands.


Open wire line will work, as will a 4 : 1 balun and coax feed.  If the loop is properly dimensioned
for CW you may be able to get SWR below 2 : 1 an all 5 HF bands that way.   I've used either a
Johnson Matchbox or a MFJ 949 manual tuner.  Instead of using the normal jumper from the single
wire output to the balun I ran a wire from the COAX 2 jack, which allows me to run the antenna
through just the 4 : 1 balun and bypass the tuner.  It tunes up easily on all FD bands 80 - 10m.

My Field Day loop terminates at one corner of my tent - I just pull up the slack in the wires (about
5 feet on each end) and use that as the feedline to my tuner.  That's because the operating site
is at the top of a cliff dropping down to a road, and that gives me enough open space to string it
up horizontally with the far end about 50' in the air.  I chose the antenna because it allowed me to
make use of a corner of the operating area that was not otherwise used, so it doesn't get in the
way of all the RVs that park there and the antennas they put up.  It also takes advantage of the
ground slope to the East.

Ideally the trees are spaced far enough apart that you can lay the wire on the ground where you
want it and toss a rope over each of your corner trees to hoist it.  Sometimes I tie loops in the
corners of the wire, other times I put electric fence insulators around the wire (ones that don't
need to be threaded on) and let the wire slip through the insulators to adjust its shape on its own
as I pull up the corners (particularly useful when the trees are not evenly spaced - the exact
shape of the loop isn't particularly critical.)  This is more difficult if the trees are too close
together:  in dense woods the easiest antenna to install might be one running along the edge
of a clearing or over a road or trail where it is relatively clear between the two end supports.

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VE3FMC
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« Reply #6 on: February 26, 2012, 06:47:11 AM »

Joe you could come here, we could operate at my daughter's place in the country. No noise, room for some dipoles. We could put a beam up too!

Nice cozy room in the back of their big utility shed to operate from. Cold beer, BBQ'd burgers  Grin

I think your best bet for FD is KISS. One man show, you need easy to erect antennas.
You could use one of the military masts that are available on Ebay dirt cheap as a center support. Just in case you can not access a tree for the center support. You would need a couple of guy ropes, and then dipole would act as the other two guys.

Depending on how big the campsite is you could use a simple center fed dipole, feed it with ladder line, 1:1 balun and away you go. With your CW skills you will make plenty of contacts.

Remember, the battery won't last long running 100 watts, you might think about operating QRP.

73, Rick VE3FMC
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K5LXP
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Posts: 4448


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« Reply #7 on: February 26, 2012, 01:01:01 PM »

As someone that does a fair amount of operating in the woods, I stay away from non-50 ohm antennas.  Not that a balanced line antenna and tuner wouldn't work well, but especially in a Field Day setting, dorking with a tuner will get very old, very quickly.  An autotuner is an option but it would take some careful forethought to plan antennas that will be easy to deploy, work for the bands you want, and work within the limits of the tuner.

Field Day is a 40 and 20 meter event.    As a single op you will not likely run out either of those bands. My antennas of choice are multiband ("fan") dipoles pre-cut and ready to go. One 40/20 dual dipole covers 40, 20 and 15 and once it's up, you're ready to go.


Mark K5LXP
Albuquerque, NM
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WA9YSD
Member

Posts: 138




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« Reply #8 on: February 27, 2012, 11:13:18 AM »

Look into extended dipoles. Might be worth your while. Get some gain on 40M.

Did many single op Field Days.  160M is not worth it. 80M at the best that I have operated for field day is good for about 150 QSOs.  40M and 20M is your best and needs to be balanced when one slows down the switch to the other. 15M is good for Sunday operation, will be a new band and numbers will pile up. 10M and 6 M will be good for 150 QSOs plus or minus if you have a good opening.

Single mode, use CW only and have the computer auto send CW that way you will have time to eat something or have a sip of your favorite beverage every now and then when given a chance. You will be busy.  For the most part except for 10 and 6M opening.

If your good you will make more contacts with CW. If you do SSB and your good you can keep up with CW but takes more effort and you will tired faster and get slower. Use of auto recordings can help.  All ways get into arguments what is faster CW or SSB, just depends boils down to which one your better at.

Jim K9TF
« Last Edit: February 27, 2012, 11:21:36 AM by WA9YSD » Logged
N8TI
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Posts: 115




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« Reply #9 on: February 27, 2012, 04:18:23 PM »

On your field day dipoles, do you always use a balun (or un-un), at the feed point of the dipole if using a fan dipole?

I agree with the 40/20 band plan. Probably won't run out of contacts on CW.

Joe
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W8JX
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« Reply #10 on: February 27, 2012, 06:29:43 PM »


I agree with the 40/20 band plan. Probably won't run out of contacts on CW.


I would suggest maybe 12m too as there is a surprising about of activity on 12m CW when band is open.
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N4NYY
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« Reply #11 on: February 27, 2012, 06:44:32 PM »

Quote
I would suggest maybe 12m too as there is a surprising about of activity on 12m CW when band is open.

I think the WARC are a no-no in a contest. The 20/40 works for me.
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WB6BYU
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« Reply #12 on: February 27, 2012, 09:04:02 PM »

15m is no good on Sunday out here on the West Coast - it never quite opens before the
11AM end time, at least not enough for the East Coast crowd to hear us very well.  I start
15m (and 10m if it is open) as soon as possible Saturday to get as many stations as I can
before the band starts going out on the East Coast.

Dipoles certainly aren't a bad choice:  that's what I use for most of my portable work.
Usually I don't bother with a balun.

But at this particular site, there are convenient supports for the loop that keep it out
of the way of the rest of the stations, and it seems to take good advantage of the
sloping terrain.

The truth is, it doesn't matter a lot what antenna you use, as long as it is reasonably
efficient.  It also helps to consider the radiation pattern (both horizontal and vertical)
with regards to the major population centers.

Hmmm...  maybe I'll try the 2-element quad for 40m again this year...
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W8JX
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« Reply #13 on: February 28, 2012, 05:38:13 AM »

Quote
I would suggest maybe 12m too as there is a surprising about of activity on 12m CW when band is open.

I think the WARC are a no-no in a contest. The 20/40 works for me.

I think your right but I was surprised the amount of CW i heard on 12 when it was open.
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ONAIR
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« Reply #14 on: February 28, 2012, 11:18:22 AM »

Quote
I would suggest maybe 12m too as there is a surprising about of activity on 12m CW when band is open.

I think the WARC are a no-no in a contest. The 20/40 works for me.

I think your right but I was surprised the amount of CW i heard on 12 when it was open.
    And on 10 as well!
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