02-15-2013, 00:02
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#16
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SF Candidate
Join Date: Mar 2008
Location: JBLM
Posts: 20
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My partner force was shooting only about 600-800 miles to there base. The terrain was high mountain jungle with lots of vegetation but not triple canopy type stuff just lots of green. My partner force at the time was using HF for every thing short of squad communication. Alot of the shots where valley to valley or valley to a ridge line for retrans. I taught them during our class portion that its supposed to be low to the ground for NVIS shots but under real world condition for that region it worked up high. I suspect it had some thing to do with the soil and water tables.
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rocketjok is offline
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02-15-2013, 17:46
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#17
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Quiet Professional
Join Date: Jun 2007
Location: Hope Mills, NC
Posts: 2,759
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yup, sounds likely. Water table is apt to be higher in that environment...
Just remember..."what's the best antenna???"...the one that works...
Get it 1/4 wave up electrically (or possibly a bit lower)...viola...(that's "waalaaa") for the grunts...
Good NVIS that way, higher take off angles..but...freq's, freq's freq's....good prop'll do ya.
69 harley is on to some good stuff...
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glebo is offline
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02-18-2013, 06:55
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#18
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Quiet Professional
Join Date: Oct 2006
Location: MD
Posts: 448
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Yes I 100% agree...hell we always had a water table in the desert...but it was about 1000 feet below ....
glebo... when you go to open a school to tech this shit let me know...
AL
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albeham is offline
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02-18-2013, 12:45
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#19
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Quiet Professional
Join Date: Jun 2007
Location: Hope Mills, NC
Posts: 2,759
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Quote:
Originally Posted by albeham
Yes I 100% agree...hell we always had a water table in the desert...but it was about 1000 feet below ....
glebo... when you go to open a school to tech this shit let me know...
AL
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haa, I'd love to. My best job was on the 18E committee as a green suiter (87-91) and a civilian (03-06), my favorite class to teach was theory and antennas....amongst the others I had..
Shoulda stayed there, and not moved up to DOT-D...oh well...
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glebo is offline
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02-19-2013, 06:52
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#20
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Quiet Professional
Join Date: Oct 2006
Location: MD
Posts: 448
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I feel your pain!!!!!
Maryland sucks...
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albeham is offline
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02-22-2013, 09:51
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#21
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Asset
Join Date: Jan 2013
Location: Colorado
Posts: 2
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Artificial Ground Plane
Have you tried using a second wire staked out in a mirror of your current antenna as an artificial ground plane? I haven't done any HF work in the jungle but it seems to me that if the water table is the issue, take it out of the equation as best you can. I would imagine there are many things that you could try that would work but I didn't see this suggestion anywhere so I thought I would put it up. Good luck.
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MFF18E is offline
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02-28-2013, 16:01
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#22
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Quiet Professional
Join Date: Dec 2008
Location: Arizona
Posts: 91
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Quick update
The elevated fling wire worked great the entire duration of the exercise. For the latter half of the training, a new basestation was brought in and we were only working 40ish km away. I was a little concerned at first because of the close NVIS shot. I ended up using the elevated fling again in lengths of 10-20ft. Again I had no issues sending data.
And just for fun we attempted to shoot back to the states at Norfolk, VA. We set up a Sloping Vee of approx 30ft height and 40ft feet lengths spread at approx 60 degrees. We used a 10 watt radio with no power amplifier. We shot from Thailand to Virginia, a distance of approx 9000 miles and were able to send data with this antenna. I was pretty impressed.
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k-rub is offline
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11-17-2013, 10:20
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#23
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SF Candidate
Join Date: Jun 2010
Location: VA
Posts: 36
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I have few questions,
Can a gauge of a speaker wire used for antenna design prevent RF output, say not enough power?
For sloping "vee" used for ALE on 137/150, you would suggest cutting an antenna to expected freq (time of day, etc) or using a set length (117ft wire)?
Also, would you say it makes any sense to use 100 ft slant wire for the same platforms during the day for a midrange shot?
Questions are in general, not necessary for jungle environment.
Thank you, back to PT.
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Last edited by Dalik; 11-17-2013 at 10:23.
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Dalik is offline
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11-17-2013, 10:43
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#24
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Quiet Professional
Join Date: May 2008
Location: Idaho
Posts: 1,200
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Quote:
Originally Posted by 69harley
An excellent tool for HF is VOACAP. You can download it here, newest version was updated in 2012. VOACAP
This has some very usefull tools to predict propogaton, signal to noise and antenna modeling.
Although the freqs are sort of preset with the 137, this software can be used to predict where the link will be made and the take off-angle required. It also has program to design an dipole antenna to a user spec'd freq and take off angle.
Try inputing the locations for the two stations, transmit power, solar flux, etc and run the prop. then look at the time of day for when you want to communicate. It will give you the muf, luf and fot. Will also give you the take off angle and the number of hops required.
Take the freq and the take off angle and use them in the antenna modeling program. Design and build an antenna on the computer before ever cutting a piece of wire.
I used this software (older version) for many years to successfully plan HF networks that relied on PRC-104s and DMDGs. Had very good success.
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I could have used that site back in '99 while in Vannuatu. Group gave me prop charts and freqs for some Latin American mariachi radio station.
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TOMAHAWK9521 is offline
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12-05-2013, 21:57
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#25
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Guerrilla Chief
Join Date: Sep 2005
Location: Harrisburg PA
Posts: 864
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Quote:
Originally Posted by glebo
Just remember..."what's the best antenna???"...the one that works...
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That sounds familiar.
I took an antenna theory class when I was with Third Herd at Tinker. Seemed we always used a 500 foot long wire and were trying to find some other alternatives to use.
We did just about any HF antenna you could think of; long wire, sloping V, you name it.
Figured out the 500 foot long wire was the best. It was good training, tho.
One thing we always made sure we had plenty of was "bug nuts". Seemed like we were always needing them.
And Ardmore, OK was an RF black hole. We'd get great comms during the day, but at night it was a bear trying to keep the link up and running.
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Monsoon65 is offline
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12-06-2013, 06:02
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#26
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Quiet Professional
Join Date: Oct 2006
Location: MD
Posts: 448
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Quote:
Originally Posted by Dalik
I have few questions,
Questions are in general, not necessary for jungle environment.
Thank you, back to PT.
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Can a gauge of a speaker wire used for antenna design prevent RF output, say not enough power?
..No. I have used 28 ga wire to make my shoots.
For sloping "vee" used for ALE on 137/150, you would suggest cutting an antenna to expected freq (time of day, etc) or using a set length (117ft wire)?..
..Google sloping vee. Learn..Do. When you run an ALE station there is always that lowest freq that is will try to use. So when you have an antenna that has at least several quarter wave cut to that freq, and when you start to go up in freq you now get an antenna that will give you many more quarter wave lengths, this gives you more gain, low angel antenna pattern, etc. This is a good thing. You could, depending on the freqs get a 500 foot sloper. But 117ft wire, is can work, you just need to try it. Let the magic work.
Also, would you say it makes any sense to use 100 ft slant wire for the same platforms during the day for a midrange shot?
Remember a midrange shoot you would like to have a more higher angle antenna pattern, more to the 90 degree as possible. NIVIS google it. So when you shorten a long wire, (the legs of a Vee), you antenna starts to react to the ground and your antenna pattern moves into this NIVIS type pattern. (frequency dependent )
I have use 100ft wire for low band VHF and HF, works.
AL
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albeham is offline
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05-14-2015, 09:29
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#27
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Quiet Professional
Join Date: Apr 2012
Location: north carolina
Posts: 6
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long haul HF
we are looking at trying to talk long hual HF. Command is expecting us to talk back states side. the fling wire will work to hit the local base station at around 700 miles. and retrans over email from that point. like previously stated they cant get away from the G2W of sat com. does anybody have any ideas for around 7800 miles?
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sneakypete314 is offline
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05-14-2015, 11:29
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#28
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Guerrilla
Join Date: Apr 2008
Location: Fayetteville, NC
Posts: 280
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Quote:
Originally Posted by sneakypete314
we are looking at trying to talk long hual HF. Command is expecting us to talk back states side. the fling wire will work to hit the local base station at around 700 miles. and retrans over email from that point. like previously stated they cant get away from the G2W of sat com. does anybody have any ideas for around 7800 miles?
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The prop chart is the key to making this work. Run a prop between the two ends of the HF circuit and look at the predicted take off angle. That angle will drive antenna selection.
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69harley is offline
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05-14-2015, 11:57
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#29
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Quiet Professional
Join Date: Jun 2007
Location: Sneaking back and forth across the Border
Posts: 6,628
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Quote:
Originally Posted by 69harley
The prop chart is the key to making this work. Run a prop between the two ends of the HF circuit and look at the predicted take off angle. That angle will drive antenna selection.
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Do not forget the terrain and climate (jungle vs Desert vs wooded terrain) Those are also factors.
We would use a portable tower, log periodic or other tower mounted antenna for FID missions since we would be static. 7800 miles living out of your ruck is going to be hard. I once did a shot from NE alps in Italy back to Bragg with 3 rolls of foil, 2 long wires and got through but I had a great focused reflector and I was not hiding while setting up.
just my 2cents
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SF_BHT is offline
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05-14-2015, 20:23
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#30
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Asset
Join Date: Oct 2013
Location: Left Coast
Posts: 37
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HF antenna - 1800 mile shot from jungle
I think "it depends". I would not consider 1800 miles on HF to be NVIS - it's more like one or two hop F Layer skip, depending upon the freq/time. If you are confined to one freq, I'd go with a half-wave dipole, one half wave above "ground" to get the low takeoff angle you need for that shot. You might have to cut several dipole legs depending upon your freq plan. As noted above, use insulated wire - and clear away any nearby wet foliage - if you can. String the dipole at right-angles to your target azimuth of course. If you have some "lift" to help with weight, here is the portable kit I use for field expedient antennas. You should find what you would need in a pile like this! VOACAP is really pretty good too, if that's all you can get. Given your path and freq, it will tell you the optimum time, etc.
http://www.n6cc.com/field-antenna-kit
AR
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