Field Expedient Antennas

[genesis98]

This is pretty much a lost art in the reserves, it's not given the attention it deserves I know I am not nearly as strong at antenna building as I should be. Could some of you guys give me an idea of some different types of antennas, aswell as what should be carried in a Field expedient antenna kit.

 

[Spr.Earl]

Yowzer!
I have not heard about this for ages and do forget how to put one up. :
I do remember,you need insulators at either end of your antenna and the line to your radio comes off the middle
Your range is judged by the length of antenna and directiion it's placed?

Am I correct?

Please correct me   if I'm wrong.
Ah another note morse code is no longer used to day.

 

[pronto]

I used to cheat - I bought an Alpha Delta Sloper kit, and carried that around for years! You can get them on line or at a radio store.

I also carried 100 feet of cable, wire, alligator clips, PVC pipes, twine, and pegs.

I also had an ARRL basic anntenna design book. You can probably get its latest incarnation at chapters or amazon or direcctly from ARRL. A great book, explained 1/2 and 1/4 wave antennae, lots of information on standing waves, signal chasing, etc. We used to run expedient exercises regularly to see what we could come up with. I would point out though that we also used ACP 125 CANSup 1A, so I am really really old, and this may be nonsensical to everyone except my fellow farts....

 

[career_radio-checker]

How about a spare antenna ;D

 

[Bert]

Wheres RadOp when you need him?

If I understand the question properly, antennas typically come as part of a field deployable
radio kit.  You can also build/attach suitable antennas to a deployable field radio kit.
There are alot of radio kits for varous applications so the answer to the question
is broad.  For field deployability, the intention is to set up the system including the
antenna (usually supplied with the kit) as quickly as possible.

The 'net offers alot of MF, HF, VHF, UHF, and microwave antenna theory and product
information.  It might be a good idea to start reading up on antenna theory basics,
transmission lines, and radio system block diagrams. 

This is a good starter:

http://www.arrl.org/

http://www.scanshack.com/antcal.htm

After that, various radio kits come with with own antennas.  Sometimes, the antennas are
busted, damaged feed line, or defective connectors, or the radiation pattern isn't suitable
for the application.  Then a best effort custom built punch in the face antenna has to be
constructed for the desired functionality; directional or omni-directional for the band,
frequency, and power output.  Understanding the application, the characteristics of the
frequency band, the possible locations of stations (yours and enemy), output power
levels, and reception limitations lead to figuring out what type of antenna to build. 

Having test equipment to measure the SWR and field strength is nice, but if you have
to eye-ball it, you may wish to have quick antenna design memorized and calculation
in your head.  For instance, a 6.8 MHz HF quarter wave dipole has legs approximately 17.25'. 
A higher frequency will have shorter legs, a lower frequency will be longer.

Radio work is fun.  Enjoy the job.

 

[Pte.M13]

made a couple antenna's last month, overall one of the better classes i had all summer, we made one sorta like a tee pee with 3 radiating elements coming down from the cobra head (lets you connect your wd1 to your coax) at the length appropriate for your freq, and then at the bottom we used three ground plane rods (from a gpa antenna kit) taped together into a triangle, resisters at each corner taped together in a hell of a mess with the rods. then used a pully system to keep it up in a tree.

found that the better your measurements were, the better your comms would be away from the freq you made it for... some could get clear comms across a field for any VHF freq, others got worse because of bad measurements and other errors.  sadly we never really tested actual range.

 

[Sig_Des]

I can tell you that with a field expedient antenna, properly made, and at the right time, you can get clear comms from St-John's to Petawawa.

I've also heard of people getting comms from Canada to the Golan Heights

 

[Jason Bourne]

Maybe not to slight the ongoing REG QL3 courses going on but there isn't enough time spent on field AE anymore. I think I built one on the entire course. It did work too...hooked that bad boy up to a 138 and talked in the sun all day But I've heard crazy stories about guys attempting AE out of C7's etc etc lol. Ahh good time.

Jason

 

[Radop]

Wheres RadOp when you need him?

Did I hear my my name?

What type of frequency range, directional, non-directional, mission, etc are all the things you have to consider when desiding what to bring.  The 522 has an antenna adapter that mounts onto the antenna base but has a push clamp to put in WD1, coax cable or other type of wire you bring to make an antenna.  Most people forget the most basic of techniques which is to place the wire into the broken end of the antenna, attaching the broken ends togeather then taping or tying the wire and antenna together.  You then use a branch (perferably Green to help conduction and for suppleness) to hold the whole thing together.

A basic expediant antenna kit would consist of 100' of wire, a connector of some sort (cobra head being best), insulator and pop can or resistor.  100' of cable will tune to any antenna in the HF, VHF and higher spectrums and can be made directional (long wire), bi-directional (di-pole) or omni in the case above or field expiediant vixam.

Although a fading art, like HF, I feel it is something that we will eventually come back to as we will again see the need for it.  What do you do if you get into loc to find that the B&W is broken and you have to send comms back 200 Km?  The obvious answer for us radops is to build a multi freq antenna because when night hits, the freq you were using during the day will probably not work at night.

If you do the math as well, 234/freq will give you a quarter wave antenna.  As we seldom go below 2 mhz, 100 feet is pretty close to that low a frequency.  That is why the 100' (plus easier to remember than 103' 9 3/8ths".

Well that was a load off of my mind, shut up Cnd Sig!!!!

 

[SigPigs]

Yes go to the ARRL and also to rac.ca which is the Canadian equivalent. Never ever BUY anything, why? You are throwing money to someone for the chore of simply soldering some wire together. Do it yourself and save a bundle. As far as wire antennas go there is NOTHING that can't be made as well or better then ANYTHING you buy.
Grab the formulas on those web sites and use them. Look at NVIS antennas, look at all the types and you will have more ideas of what to build and why you want a particular one. There really aren't a lot of choices though, it's either built for local comms within 400Km and is NVIS, or it's built for long range comms. People don't understand that comms are routinely made around the globe on a few watts, yes a few watts only. So when you have the luxury of 1Kw or 100W then you can normally do what you want with the right antenna.
Also realize the HF antennas are almost always a compromise, you will never get it long enough or high enough as it should be, so it's a trade off that we all have to live with. For example a 7 MHz antenna ideally should be around 64ft off the ground. That almost never happens, that's a long way! So you make do with what you have.
Oh and Radop, you would not use a green branch for an antenna, yes great for suppleness, but bad for reducing efficiency of your antenna. Anything near an RF field that will conduct is bad news for your antenna.
This is a subject that could fill volumes and yet can also be done simply and quickly with a small amount of knowledge.
Email me if anyone would like more in depth info on antennas and HF comms. I can get you some great links etc....

 

[Radop]

I was talking about a veh antenna with the green branch so that if you hit a overhanging branch while on the move, it would be able to flex with the strike.  It is also attached to the tx part of the antenna so it doesn't matter if it will conduct or not.  I agree though for a field expediant antenna such as a multi-freq dipole, wood is used to insulate and should be dry and old.

 

[armyguy62]

I was a Rad Tech with the Infantry, Armour and Artillery and worked hand in hand (so to speak with my Rad Op brothers in arms building a lot of antennas....best resource I found was the (I hope this is right....has been a while) ARRL (Amateur Radio Relay League??) handbook, basically a guidebook for those in the hobby of ham radio. It was a fantastic source of info on expedient antennas, transmission lines and how radio works (particularly HF)

 

[Shilly]

  Hello;
Alot of good information in this thread, and Sig ops have seemed to have gotten away from Antenna construction with the roll out of TCCCS. So i am going to add a few pieces for field expedient antennas.
The information is taken from B-GL-321-006/FT-001 , SIGNALS IN BATTLE Vol 6 , SIGNAL FIELD HANDBOOK , Chapter 7.
Enjoy!

http://www.geocities.com/fallen_angel_2001ca/pg247
http://www.geocities.com/fallen_angel_2001ca/pg248
http://www.geocities.com/fallen_angel_2001ca/pg249
http://www.geocities.com/fallen_angel_2001ca/pg250

 

[G-Fresh]

Good to see that people are becoming more interested in the lost art.

I have been lucky enough to teach at the School and on an Infantry Comms course.  Teaching the construction of field expedient antennas was probably the most enjoyable class I have ever taught.  The students seemed to enjoy it as well.  When the construction was done, the students were pretty impressed that a some WD1, some 88 tape, and some buttons actually came together to create a working antenna.

Having the access to the information is great, but having the knowledge is always better.

"Give a man a fish, feed him for a day.
Show a man to fish, feed him for a week.
Teach a man to fish, feed him for a lifetime."

 

[DG-41]

Now if I can just get one of you Sigs-types to teach us how to build a field-expediant 522 battery, life would be good.

DG

 

[Carbon-14]

They should bring back those hand-crank batteries..  I believe they were for the 515.  Never used one myself tho 

 

[Radop]

They should bring back those hand-crank batteries..  I believe they were for the 515.  Never used one myself tho 

I did, they suck not to mention to make you tired while making a hell of a racket especially with the 15 ft whip.

 

[Weekendsig]

The ANPRC 522 NI CAD battery (the square one) is junk. Get a grip on some of the Lit ones you and you can operate almost 3 days (depending on usage) and still have 60% battery life.

That goes with all NICAD batteries for the radios.

 

[Hawk]

A lot of years ago I lived in a trailer in the mountains and acquired a Model 19 radio. I hooked it up with a field-expedient that was a wire from the back of the radio, out a window and up to the roof. Mid-way we soldered a spark plug. That wire was attached to one that went angle-wise front to back of the roof. I reached out of the Elk Valley to all over the world!

When I was in Reserves we got a bit on field expedient antennas, not much. We had an old short wave radio at home, so, as an experiment at first we hooked it up with an L antenna-back of the radio up to the ceiling then along the ceiling to the other corner. We were living in a condo at the time-virtually a row-house with a metal beam running under 5 units. It made a great ground plane with a wire running down to it and attached with an alligator clip.

I wish we'd learned more. It was the fun part!


Hawk

 

[Weekendsig]

The handcrank was an interesting peice of kit but it took a long time to charge the battery and you could only turn it so fast without screwing up the battery. But the idea was awesome.  Also provided supervisors with some productive corrective training besides serializing mod spikes.