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.