Military VHF Radio Antenna

[codenamegriffin]

I'll start off by saying I'm sorry for falling short on information on this subject matter; so if at any point I seem like I don't have a clue about what I'm talking about, you're right. That is why I'm here.

I'm an Radio Telephone Operator in an infantry recon platoon and I need to know how to get the most out of my radios.

I've been getting very bad range out of my 1523Es. I've been using old long whip antennas, and trying to come up with some solutions on my own. I've tried to make my own field expedient antennas; but the resources available to me are too difficult for me to understand (I've never been trained throughly on the topic). I don't know much about radio wave propagation. I've tried to use different army manuals and people actually in communications jobs; but the manuals are broad and difficult to understand and in MOST cases, I've become as or more knowledgeable than the people assigned as commo.

To get right too it; I want to find a place to buy or a way to make a better antenna with a BNC connector for FM / VHF. When we deploy and often in training we use frequency hopping, and I know that wires have to be specific lengths to get the best reception/transmission possible. It would have to be able to be put up and taken down quickly, and quietly and not stick out like a sore thumb. It would have to be able to work better than a long-whip in crappy terrain, surrounded by woods, and be somewhat rugged. I've been told about dipoles, but I don't know the difference between a half wave, quarter wave....yada yada. And none of the people who I should be able to go for this information know either. I just need something that WORKS!

Am I asking too much? Is this possible. Please, if you are an expert on this subject, I am in dire straight. I need to be able to make comms better. Here's a quick recap...

PRC-119 (or RT 1523E if you prefer)
Better than Longwhip
BNC Connector
Quick, Easy, Rugged (or at least not delicate)
Sometimes getting less than 2000 meters

Thank you

[IdunBenhad]

Hi:
You're getting into a subject that has reams upon reams upon reams of information available.

You are apparently searching for the ultimate antenna that covers all frequencies equally. Sorry to tell you, but that doesn't exist. You and every engineer and ham radio operator and communications experts have been searching for years and haven't found it yet.

Looking at the 1523E on the WIKI, it has about a 50 mhz range and as you said, frequency hopping. Frequency hopping makes an antenna problem, but surely the military thought of this, as well as the designers of the radio, so there should be an effective antenna available for it through the military.

If you want to study the different types of antennas and how to design and build them, look into the ARRL (American Radio Relay League) Antenna Handbook. This book is written for hams, beginners and experienced alike. You will find a wealth of information there at a reasonable cost. Even though it is primarily for the ham radio bands, the design principals cover all frequencies.

Go to www.arrl.org (http://www.arrl.org) for information on how to get the book, or go to a local Ham Radio Store.

Your post doesn't indicate your location, so I can't locate a store for you.

You might try Amazon.Com. They sometimes have these books for good prices.

Also, you didn't say what power you're using. The radio has 1 mw-100mw-5 watts-50 watts. Makes a difference!

[bmcgeeny]

Gotta love it. The military is turning to DIYC to engineer electronics!

[Aurbo99]

We've been here longer than you know... =) muhahahaha!

[Andy.wpg]

To get right too it; I want to find a place to buy or a way to make a better antenna with a BNC connector for FM / VHF. When we deploy and often in training we use frequency hopping, and I know that wires have to be specific lengths to get the best reception/transmission possible. It would have to be able to be put up and taken down quickly, and quietly and not stick out like a sore thumb. It would have to be able to work better than a long-whip in crappy terrain, surrounded by woods, and be somewhat rugged. I've been told about dipoles, but I don't know the difference between a half wave, quarter wave....yada yada. And none of the people who I should be able to go for this information know either. I just need something that WORKS!


What does 'quickly' mean? Are we talking set up for a few hours (or overnight)? Or are we talking 'deploy it for a couple minutes while we take a drink of water' fast?

I have had amazing success with a 'twin lead j-pole' but there are some limitations to it. Power for one. It can't take a whole heck of a lot of power, and your radios can put out 50W (would probably melt the thing), but 5W is easily handled. It could be designed for your frequencies, but, it would work best at ONE frequency. Everything else would be less efficient.

It's easy to put up (throw a fishing line up a tree and haul it up), but that weight crashing through the trees would probably be too much noise for a tactical situation.

Unfortunately, as IdunBenhad said, the engineers who built the radio have probably come up with the best compromise of efficiency, range, and portability that a lot of money could come up with. Unless you are using a SINGLE frequency, EVERY antenna is a bunch of compromises.

While I support your willingness to research antennas and learn about them (learning is a great thing), I have a feeling that you already have the best antenna you are going to get for that radio.

Good luck in your search,

Andy
VE4RDO

[codenamegriffin]

Thanks Andy for being so straightforward...

I would be using my RT dismounted, so I'll be pushing 10W. No power amplifier, since everything that I have I'm carrying on my back. My freq range is 30 to 88 MHz; which I know is a HUGE gap. When talking to my Battalion's so called "experts" on the subject; they say that the only thing I have to take into consideration when using FM / VHF is getting a antenna that is big, and high. I simply know that that can't be right and they're just giving me a quick answer to get me out of their hair. There are plenty of handbooks that talk about dipoles, inverted Vs.....so on so forth....but they don't tell you enough about anything to actually make one. Resistors? Ground wires? I'm sorry that I'm such a numb-skull; but I'm an infantryman. I know how to close distance and destroy the enemy. I'm not an electrician, I'm not an HAM operator. I'm not an idiot... My Battalion recognizes me as the best RTO in the unit... and this is how little I know. I could asked to get sent to Ranger school to become better at operations, or Sniper School to be better at shooting and recon... But there isn't anywhere I can go to TRULY become a better radio operator, or actually understand how my radio works and how I can make it work better. I can't find ANYONE who can actually help me make one, buy one, or do anything it takes to put them into motion. The most effective thing that we use right now is a long-whip. It's about 7 feet tall....just a straight line...up in the air. Omni-directional. Out in the middle of woods and hills. Some times it'll send 4 or 5k. Sometimes I can't get 2k out of it. The manuals state that I can get 10k out of my equipment. I understand that those ratings are for PERFECT conditions; but there simply has to be something that can be done. The Ranger handbook and Sapper handbook both talk about getting better signal out of all these type of user made antennas; but just don't go into the sort of depth it takes to make a completely unexperienced person understand any of it. I strive to do EVERYTHING I can do to be the best, most effective RTO my division has ever known. I'm fairly sure that I already am; even knowing what little I know. I just need some direction to really understand the underlying concepts of waves.

[IdunBenhad]

Hi:
If you want to see how a dipole is made, look in the Forum "Radio Waves" and look at the first entry in the thread "FM02 Transmitter Setup". The dipole can be scaled to match your frequency, but if that frequency is moved very far, say 1-3 mhz, then the antenna will be out of tune and not respond as it would at the design frequency.

Also remember that the antenna on the far end should be a good one too.

I think the biggest problem here is that you can't depend on using one frequency for your excercises and therefore cannot use an antenna that is cut for a certain frequency. It seems your problem is not the equipment but the lack of training by your Battalion. I would think that within the great big military establishment, there is a school you can be sent to and learn the fundamentals.

It is almost impossible on a forum like this for you to learn about antennas, how to make them, design them, etc.

I am not trying to "put you off" as I very much respect what you do and champion your effort to do it better, but I just don't see how any of us can go much beyond what we have said so far. Most of the participants here are not communications oriented. Perhaps you could find another forum more in the field of what you need to do. Try QRZ.com for one.

I was in communications for most of my working life, and this knowledge and "how to do it" just doesn't come overnight. Sorry, my friend.

[BuzzKill]

Should probably start with something more basic. You need to understand the problem before you can come up with a solution. An antenna is not the only part of the equation here. Power, terrain, and the freqs being used all play a roll in how the signal will propagate in a given environment.

Obviously, the whip is omnidirectional. Are you trying to extend your range using something more directional so you are focusing your transmission? You can't have it both ways. You would have to up the power, change your freqs that you operate on, and or get your antenna higher to get more range.

If you want to learn antennas, start chatting with HAMs. We have lots of hams on this board. Some are the right kind of HAM, and some of the others... well, not so much.

[Andy.wpg]

Thanks Andy for being so straightforward...

I would be using my RT dismounted, so I'll be pushing 10W. No power amplifier, since everything that I have I'm carrying on my back.

Twin lead J-Pole would work then - do a google search for that - the only thing is, the designs you see will be for Amateur Radio frequencies. Some of the pages include the formulas for calculating lengths. I wouldn't design for more than 10MHz range for each one, so you would carry several.

They are made from the 300 ohm twin lead antenna wire that EVERYONE had going up to their TV antenna on the roof - before cable and satellite, that is. They roll up into a small package. It would be worth a try.

You can use a fishing weight and fishing line (fired up as high as you want in a tree with a slingshot) and haul up the antenna - low visibility wire, hard to see in the bush.

You are limited in how high you can go by the coax. Thin 50 ohm coax (like RG-58) would work for (probably) 25' and not much more. That would mean the top of your antenna would be 30-32 feet in the air - would help a lot. I certainly wouldn't want to pack several rolls of anything bigger than RG-58 on my back.

If you send me a PM with your personal email, I'll see if I can come up with some measurements for, say, 40-50MHz - it would be worth giving it a try. But I would HIGHLY recommend that you contact an amateur radio operator that has an antenna analyzer to thoroughly check it for SWR and impedence match to your transmitter before you hook it up to goverment-owned equipment.

Any blown finals would be your problem....... :)

73

Andy
VE4RDO

[codenamegriffin]

Thanks for the ideas guys; and keep em coming. I can't explain much more as far as the problems I'm having, but one way or another, this IS making me better. Today I asked our commo guys (radio "experts") for a male to female BNC adapter. 48 hours ago, if you asked me what a BNC end was, (I had to ask 4 of them before finding one who knew what I meant) I wouldn't have had the slightest clue. If you showed me the end and asked me which equipment it went to, I would have been all over it. Right now I'm trying to get my head wrapped around this J-Pole idea. Crawl>Walk>Run...

http://1.bp.blogspot.com/_k07pirzBU34/TA8W0x5E59I/AAAAAAAAE1c/RoUxHlHgUts/s1600/WD-1TT.gif
WD-1 Wire - I have as much of this at my disposal as possible. Is this the same (or similar enough) to the 300 ohm TV wire? If not... If I go to radio shack and ask for 300 ohm TV wire, will I find it. It would be better for me not to have to dip into my own pockets, but it wouldn't be the first time I've payed out of pocket for something I'm doing for this big ol' Army (and even tho I'm a recon grunt; I really like doing this stuff). Last thing on WD-1... Do civilians call it the same thing? WD-1 Wire on Google pointed me right to what I was looking for but would a civilian radio expert know what I meant if said WD-1?... would just like to know... Moving on.

I just this second learned that what we would normally call a W-2 cable is just a coaxial cable with BNC ends. SICK!

The layout for the JPole that you directed me to... will it be omni-directional? I'll always be able to figure out an azimuth for who I need to talk to; so I'm trying to get away from omni-directional antennas because if I understand correctly; directional antennas get more range (in that desired range only). Like I said, before I was thinking about a dipole (bi-directional I think) because anything seems better than sending weak waves in all directions.

The lengths that I would be trying to figure out...would I be looking for the length for half-wave or quarter-wave?

You said something about an antenna analyzer... Have you ever heard that called a Primm? I know that a while back, I thought maybe my antennas weren't getting the power they should have, so they said they could hook them up to a Primm. Maybe the same?

Hopefully I can find time at work to do this. You know; learn how to use radios VERY effectively...MY JOB! We get bogged down with some much administrative CRAP, that working on projects like these never gets followed thru. I love the challenge of figuring tech out; but it's just silly that the biggest challenge is finding time to do the challenge.

[Andy.wpg]

Here is a site with a decent twin lead jpole design for 29MHz and up http://www.wb6nvh.com/jpole.pdf

Here is 300 ohm twin lead at Radio Shack http://www.radioshack.com/product/index.jsp?productId=2049618

WD1 is not the same thing - it appears to be twisted pair telephone cable.

What kind of frequency range are we talking about during frequency hopping? Can it jump across the whole band, is it limited to a couple of MHz, any idea on this one? If its more than 4 or 5 MHZ you are going to run into problems.

Not sure what a Primm is (couldn't find it on Google), but an amateur radio operator in your area will have something like this:

http://www.mfjenterprises.com/Product.php?productid=MFJ-259B

That will allow him to check the SWR (Standing Wave Ratio) on the antenna you build - THIS IS IMPORTANT. Too high an SWR can damage the final amplifiers in the radio.

As you see the design, it will produce an antenna with 50 ohms impedence - most radios require a 50ohm antenna. But your radio (being military) may be different. You need to check that and make sure what your radio wants to 'see' at its antenna terminals.

One thing about this antenna, is, as it is shown, it will have a tendency to induce RF radiation at the radio. This can be stopped by making 3 or 4 turns (about 2-3" diameter) in the coax right at the bottom of the antenna. Tape the coil together. This is called a 'choke balun' and will stop the RF from getting back to the rig.

The reason I mention this antenna so much is because of a few things:

1. Portability - it can be rolled up into a fairly small package
2. Range - pull it up high in a tree and your range is dramatically increased.
3. Visibility - 300 ohm twin lead is dark brown in color - hides nicely in the trees

Build one for ONE frequency and experiment with it on that frequency - then try it our while frequency hopping (with an SWR meter attached) and see what it does for you.

There are MILLIONS of antenna designs out there - this one might not be for you, but its easy to build as a first try.

Good luck, let us know what happens,

73

Andy

[Andy.wpg]

The layout for the JPole that you directed me to... will it be omni-directional? I'll always be able to figure out an azimuth for who I need to talk to; so I'm trying to get away from omni-directional antennas because if I understand correctly; directional antennas get more range (in that desired range only). Like I said, before I was thinking about a dipole (bi-directional I think) because anything seems better than sending weak waves in all directions.

The lengths that I would be trying to figure out...would I be looking for the length for half-wave or quarter-wave?


The problem with a dipole is that it is (generally) hung horizontally. This will make your signal horizontally polarized. Most of the VHF radios you will be talking to will be vertically polarized (vertical whips). This is a poor situation. You want to have your signals polarized the same way, better signal that way.

You can make a vertical dipole - for example, an end-fed 1/4 wave dipole hung vertically in the tree would be a good way to go.

On HF (below 30MHZ) you are using the ionosphere to bounce your signal off of, polarization doesn't matter because the ionosphere randomly changes the polarization of the signal. Your VHF radios are using ground waves and the polarization doesn't change (much).

Hope this helps

Andy

[IdunBenhad]

Hi:
Do a search for Yagi Antennas. This is a directional antenna that is easily made to be portable and by using adjustable length elements, can be made to cover a broad range of frequencies.

Yagis' can increase your effective radiated power from your 10 watts to 80 watts easily. They can be mounted either horizontally or vertically, to match polarization with your field units.

You can make them easy to take apart and put together, so they become easily portable.

Hams use them to take with them packpacking, etc. You can use 5 foot telescoping mast sections, available at Radio Shack for the mast to get the antenna up 20 to 25 feet. Use nylon twine or small rope for guy lines.

A 3 element Yagi can exhibit gains up to about 9 db or so, which is the increase in power I stated earlier.

Good Luck.

[Gebbinn]

frequency hopping as I remember it. the modern military radios break up the signal into numerous small bits and send each bit over a different frequency, the receiving radio reassemble those bits to complete the message. they use a secret key that changes daily or weekly that tells each radio what frequencies to use to transmit and receive the signal. this prevents the enemy from spying on radio communication. it would be nearly if not completely impossible to have 1 antenna cover the entire range of frequency that is needed without losing a great deal of performance on all frequencies. I was always taught and I found that height was the key in getting a good signal. the higher you can get your antenna the better your signal will be and that's the best I can tell you.
good luck I wish you the best trying to come up with something better lord knows I never could.

My credentials

15 years infantry. 3 years in bn s3 as toc rto. 2 yrs in bde s2 as transportation nco and rto. 8 yrs as fdc in bn mortars. All of which are commo intensive positions. I have been medical retired for over 10 years and I know equipment has changed so this might all be for nothing.

[Andy.wpg]

it would be nearly if not completely impossible to have 1 antenna cover the entire range of frequency that is needed without losing a great deal of performance on all frequencies. I was always taught and I found that height was the key in getting a good signal. the higher you can get your antenna the better your signal will be and that's the best I can tell you.
good luck I wish you the best trying to come up with something better lord knows I never could.

That was what I was worried about - I wasn't sure exactly how the hopping worked. The antenna I was was talking about is fairly broadband, but....... is it broadband enough?

That's why I was stressing testing the antenna over and over with an analyzer.

Personally, I would hesitate to hook anything I made up to government owned equipment. But if it works for him - more power to you guy!

Thanks for the info!

Andy

[codenamegriffin]

Hey guys. Went away from my duty station and back home for the weekend to catch my dad's wedding, so I might have seemed to disappear, but not really.

Ok, I went to Radio Shack and turned my pockets inside out for some of this gear for the J-Pole. Used the calculations to figure out all my various lengths and TA-DA! I got the twin-lead J-Pole now. Haven't had a chance to take it out and give it the test I want because of other obligations at work; but I have had a chance to talk to some other people who know more about electricity than I do and all this is starting to make a little bit more sense, but of course; me being me, thought of a bunch more questions on the way. So here are a few of those...

IdunBenhad - (from Yuma; I must say in all the places my military travels have taken me; I loved Yuma and Yuma Proving grounds the most) - You spoke a little about the Yagi antennas and said that it could get up to 9dB of gain. Is that without a power amp? If so, that's a new concept to me. I asked around and none of the commo guys thought it would work like that. But I guess the question is... Can you get gain from just any antenna? Or was the Yagi that you were refering to have some sort of plug in (or built in battery powered) power amp that gives it gains. Will I get any sort of gains from this J-Pole? Maybe I'm not understanding gain as well as I thought, but I just sort of always assumed that's what PAs (Power Amps) are for. Thanks for clearing that up.

I made my J-Pole and it's the first time for alot of things. First time with solder. First time making a field expedient out of anything other than just stripped coaxial cable. It seemed easy enough.

Do my measurement and cuts have to be EXACT? Let's just say that right now, they're pretty DARN close, but not exact. Nothing's feet off, but I'm maybe half an inch off here and there. Does that really matter?

[IdunBenhad]

Hi:
The "gain" of an antenna does not have anything to do with power amplifiers or batteries.

Gain in decibels (DB) is an expression of the apparent increase in power of a radiated signal. If the gain is increased by 3 DB, the apparent transmitter power is doubled. In this case, your 10 watt transmitter would look like a 20 watt transmitter at the receiving end.

The basis of comparison is a theoritical antenna called an "isotropic radiator". An isotropic antenna is a single element radiator placed over an infinite groundplane, which also does not exist in real life.

The J-pole and other antennas exhibit "gain" by concentrating the power of the transmitter in all directions. This concentration of power is even more prononounced when using a beam type antenna, or Yagi. With a beam antenna, most, but not all, of the tranmitter power is pointed in one direction. The receiver at the other end of the path thinks the transmitter is much more powerful than if it had been on the isotropic antenna. Be aware that all the talk about isotropic radiators is theory only. Look up isotropic radiator on Google to get a much better explanation.

A yagi antenna with 9 DB gain will make your 10 watts look like 80 watts at the other end: 3 DB (10 x 2=20) + 3 DB (20 x 2= 40) + 3 DB (40 x 2= 80) watts. 3 + 3 + 3= 9 DB

In your case, the J-pole, which shows about 2 to 2.5 db gain over the isotropic, may be just what you need, as you must be able to get it up and down in a short amount of time.

The only thing that will happen with inexact measurements is that the antenna will be "tuned to" a different frequency than what you designed for. If the measurements are shorter, then the antenna will tune to a higher frequency. If longer, it will tune to a lower frequency. Also, a great many things will affect a perfectly designed antenna. Leaves, branches, trees, masts, people or anything that is close to the antenna will change its characteristics. Unless the antenna is very close to an object, it is not something to be concerned about.

The following is from the Wiki on J-pole antennas:


"The J-pole antenna is an end-fed omnidirectional (http://en.wikipedia.org/wiki/Omnidirectional_antenna) dipole antenna (http://en.wikipedia.org/wiki/Antenna_(radio)) that is matched to the feedline by a quarter wave transmission line (http://en.wikipedia.org/wiki/Transmission_line) stub. Matching to the feed-line is achieved by sliding the connection of the feedline back and forth along the stub until a VSWR (http://en.wikipedia.org/wiki/Voltage_standing_wave_ratio) as close as possible to 1:1 is obtained. Because this is a half-wave antenna, it will exhibit gain over a quarter-wave ground-plane antenna. The J-pole is somewhat sensitive to surrounding metal objects, and should have at least a quarter wavelength (http://en.wikipedia.org/wiki/Wavelength) of free space around it."

If you are going with the J-Pole, just remember that its bandwidth is not very wide. It may be as wide as 3 mhz before the SWR (Standing Wave Ratio) becomes unacceptable. SWR is the power reflected back down the transmission line toward the transmitter and caused by an "unmatched" antenna. This power is dissipated in the transmitter and shows up as heat.

Andy-VE4RDO can tell you much more about the bandwidth, etc. for a J-Pole as he has had much more experience than me. J-Pole antenna can also be looked up on the internet.

Hope I didn't get too heavy into the theory for you, but that is the best I can explain it. The WIKIs do a much better job.

YPG is quite a place. I have a very good friend who works up there, loading the ammunition in the big guns for testing. I wouldn't like his job.

Good Luck.

[Entropy]

Probably a forum dedicated to hams would be better than DIYC - fortunately, as you've discovered, quite a few of us are hams.

I was going to recommend the twinlead J-pole until I read up more on your radio - It appears to use frequencies from 30 to 88 MHz. This is an extremely broad bandwidth (covering almost a 3x frequency range), and broadband antenna design is fairly difficult.

For a directional antenna you might be able to look into a log periodic design. I forget the name, but there is an antenna similar in design concept to a log periodic but is omnidirectional (it has a kind of conical shape), however, this is going to be a very bulky setup.

[Andy.wpg]

Hi:
Andy-VE4RDO can tell you much more about the bandwidth, etc. for a J-Pole as he has had much more experience than me. J-Pole antenna can also be looked up on the internet.



I don't know about that - you seem to have your antenna theory down pat. Heck, I've only had my callsign since last May!

Ok, I was in a communications squadron in the reserves back in the day, but that's not important here :)

I am worried about the bandwith. Another message says its about 3MHz, sounds about right. That's why I was wondering what kind of limits we are talking about for the frequency hopping. Is it limited to a couple of MHZ, or does it 'hop' across the whole frequency range of the radio?

Any gain will help - a couple of db is better than nothing.

73

Andy

[Andy.wpg]

For a directional antenna you might be able to look into a log periodic design. I forget the name, but there is an antenna similar in design concept to a log periodic but is omnidirectional (it has a kind of conical shape), however, this is going to be a very bulky setup.

I was imagining an infantry squad dragging a big log periodic and about 3 tower sections around in the bush. Mighty stealthy! :D

73

Andy