Tuners are important for a couple reasons. Most importantly, they make the most efficient use of an antenna for your set, and second, they protect your set from damage should there be a high SWR. A tuner should most definitely be part of your radio kit, especially if working in less than ideal or field expedient conditions.
That being said, you may not always have the luxury of a tuner. Equipment fails or gets broken, and they also can lull the otherwise unknowing or inexperienced into a false sense of security. Lastly, among the “prepper” crowd, much focus is given to the flashy piece of equipment and usually not to the items supporting it. It’s important to know how your gear works and how to make it work in an improvised setting; only then to you begin to master your trade.
We know from previous posts that if you can remember 936 you can build virtually any antenna; and that’s true. The antenna will be mathematically correct for resonance, but it may not be actually resonant.
Often with the new antenna builder, they’ll measure everything out, check and double check, make the connections, and possibly even model it, and yet, still get a high SWR in actual practice. This can be frustrating, discouraging, and potentially dangerous to your equipment. This can be due to a number of factors- the type of wire(insulated vs. non-insulated), antenna design(horizontal dipole vs. inverted vee, for example), the use of a balun, antenna height, length quality of coax, etc, etc, etc. Luckily there’s a method to remedying this.
Construct your antenna using your standard formula( go back and re-read Jungle Antenna if you need a refresher) and go to your potential antenna site. Get it up in the air to the appropriate height and anchor the ends. Run the coax to your radio. Set it to your resonant frequency and a constant carrier mode(FM or AM) and if it’s equipped with an internal SWR meter, key the mic. If not, get an external SWR meter. See where it’s at; if it’s anywhere below 2:1 you should be good to go for all intents and purposes, if higher, time to make some adjustments.
The end of this wire is terminated with an insulator attached to 550 cord anchoring it on the ground to form an Inverted Vee for NVIS. The other wire at the bottom you see is a counterpoise for tightening my signal for the NVIS effect. You don’t always need this but it helps. What’s important here is that I included extra wire at the ends for adjustments in case I needed it; it easier to make a wire shorter than longer. Shorten it up a little bit at a time on both ends of the antenna equally, and check your SWR again. Rinse and repeat till you get a proper reading below 2:1.
The use of a Balun makes life easier too. In addition to BALancing UNbalanced feedline(which is what coax is, and center-fed antennas are balanced, so there needs to be a match made) it also cleans up your signal. 1:1 baluns have 1 torroid core, 4:1 have two, and 9:1 have three. Your feed point impedance determines which one you need, but from experience 1:1 and 4:1 works just fine as long as you work with your gear to figure it out before you greenlight it for field use.
They’re pretty hard to see, weigh very little, and go up quickly. It keeps a small footprint in the RTO’s ruck and Jetstream’s balun attachment points(screws to attach a ring terminal) are super-simple. You’ll appreciate super simple when you’re cold, tired, and wet.
Another reason for adjusting your antenna sans tuner
Tuners do not make your antenna resonant; they simply create a proper electrical match between all of your components. I’ll state though that no antenna is more efficient than the one properly matched to frequency using the method I described here. It’s truly resonant and will make a big difference in your antenna efficiency. Doing so will protect all of your components, including your tuner, from damage and boost overall efficiency. Very, very important for the QRP Patrol Radio.
All of this does not negate the importance of a tuner by any means, and you should definitely include one in your kit. It’s crucial to understand the ins and outs of your equipment however; because when things turn inconvenient you’re going to need to know why and how to fix it. Somebody’s life might just depend upon it.
Reblogged this on The Dixie Traveler.
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Could you speak to the need (if any) for an antenna analyzer and it’s preferred method of usage? Thanks for all of the good information and the great blog.
Matt
Antenna analyzers are great tools to have for a number of reasons. I consider them in the “great to have, but not always required” category. There’s other ways to get it done, albeit with more work. Antenna modelling programs are great to become familiar with as well, such as EZNEC.
You forgot one simple step – if your swr is high, change freq up 100 kHz and recheck. If better (lower swr), your antenna is too short; if higher, you antenna is too long. This beats randomly guessing which way to adjust.
You’re exactly right. Thanks brother.
Also remember that a lot of the resonance has to do with the ground that you are working with, and the actual ground has a lot to do with the electrical ground. An antenna that performs beautifully with perfect 1.1:1 SWR at a location with a nice alkaline, moist soil, might suddenly turn to crap because you are out in a dry, acidic desert. What happened? Your ground is suddenly much less electrically grounded.
Just because it was fine before doesn’t mean it doesn’t need to adjusted this time. Always check (assuming you have the time, meaning, no one is shooting at your or about to start shooting at you, no one is bleeding out, etc.)
Absolutely! In writing this, I try to keep it as simple as possible for the new or inexperienced operator to learn and keep it simple. Operating environment can have a huge impact on SWR- thus it’s a great idea to run your equipment in that area before staking your life to it.
Right — that’s why it should be, “when you move, check it” rather than trying to explain the difference between the two. People should just know that they might be different and don’t assume something broke in transit because you aren’t getting good SWR anymore.
Hey,
I will carry the batteries en stuff. You guys make my head hurt. I like the acid/alki soil and moisture, never thought that about radio but with home electrical,
Anyway thanks for the info.
I’ll still be a mule, not an operator.
I was too for a while Brother. Different skill sets for different folks, makes a great team in the end. Thanks for reading!
Was wondering if you’ve used the milsurp AS-1743, a reel-type multi-band dipole. As issued, it uses 10m of RG-58 into a simple enclosed feedpoint. I’ve never taken the feedpoint apart to see if there’s torroids inside. Wondering if you know. Or if I’d be better off using a 1:1 current balun as feedpoint instead of it.
I’ve used that, and another antenna built for NVIS around here somewhere(I can’t recall the nomenclature, but it was built for us by I company somewhere out west) that used stranded wire on two reels and is designed for NVIS. It has a 1:1 center balun that attaches both reels for storage. I may dig it out this afternoon just to see what it’s called. Likely there’s a 1:1 inside. If it doesn’t work well, you can build one that works cheaper than buying.
A few of things for newbies:
The first image shows a nice, proper antenna insulator. They are great but not necessary. When I was young and setting up my first few stations I used rings of cheap plastic pipe to insulate between the wires and each othe and between the wires and ground. Take a section of plastic pipe between 3/4 inch and 4″ in diameter and cut a ring off that’s about 3/4″ or an inch thick. Fix the antenna to one side and the support rope to the other. Actually, if you live in an are where it doesn’t rain very often you can use the rope as an insulator. Especially if it’s made of plastic.
Second, you need an SWR meter. Learn to use it as is described above. You can get them cheap at yard sales.
Third, get some wire. It does not make a difference if it is insulated or not.
Fourth, if you are trying to communicate on the low bands like 40M, 75M, or lower and have limited space, consider winding loading coils. If your antenna need to resonate and needs to be smaller than the space you have for it, wind fifty or so coils of wire on a piece of plastic tubing. Put it in the dipole elements and test with your SWR meter. Trim the wires that are not part of your coils to where you have an SWR of 2.00 or less.
Fifth, put your antenna as high as you can. Sometimes you can only put it a few feet from the ground. It may not be ideal but it will work.
I’m working on a post regarding improvised equipment, including insulators. Types of wire absolutely do make an impact on a number of variables, too many to cover in a comment. Loading coils and such add other issues and are compromises, but sometimes they’re needed. The focus of my commo posts are tactical in nature; keep that in mind. As far as antenna height or type, that’s all dependent on what you want to do. From a hobbyist’s perspective, yeah sure, from a guy concerned with regional NVIS and local LOS communications, no, not at all.
This blog is dedicated to teaching a broad spectrum of skills revolving around Scouting and Reconnaissance. Communications is but one leg of the table. I write it as a primer for the average joe to read and understand; a starting point, and that’s hard to do when bombarding the reader with overly-technical info. Every post builds on something. Keep It Simple, Silly.
.Mil manuals show buttons and C-rat spoons as insulators
Found an MFJ tuner at our local DI (Goodwill variant) for $5. Grab it? Hell yes!
Nice snag Brother!
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Field-expedient solutions FTMFW.
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Antenna analyzers are one of those tools where I would like to have one, but I haven’t had the money to get one. I came across this guy, an MFJ-207 ($110). On the MFJ website I see you can use it to dial a tuner in to an antenna WITHOUT transmitting. To me that now makes an analyzer an almost per-requisite for the RTO. Of course if you can tune a dipole in, why would you need the tuner, but you can still use it to check SWR without transmitting. I have always wondered how tactical it is to be sitting there trying to get a tuner dialed in. By the way, I use an MFJ-971 tuner. I know there are also better tuners out there that will tune faster, but to be honest it doesn’t take very long with a resonant antenna to get tuned in to a perfect 1:1. I set to 1W on CW, tune to the loudest setting, and adjust the capacitors while transmitting. Takes about 10 sec. But, I think a 10 second burst of CW would show up pretty good to someone looking for it.
Analyzers are in the “great to have, but not always needed” category. Remember 936 and what it’s for, and 90% of the work is done.
I use an LDG for each of my HF sets. While not needed on resonant antennas, they’re purpose in life is an insulating barrier for a number of variables which can ruin your day.