When do i need an antenna tuner

Here's what you need to keep in mind though, losses due to high SWR on coaxial cable especially inexpensive cable can be very high, while high SWR on a ladder line is really not a concern. Keep the coax from your balun to your tuner as short as possible to avoid losses. Pay particular attention to the graph in Figure 1, which illustrates attenuation losses for various types of coax over a foot run with an SWR of Additionally, Figure 2 shows what happens to line attenuation as SWR goes up!

Note that open wire line attenuation losses for feet of wire only start to appear above 30 Mhz. Normally antennas fed with coax are designed to work on a specific frequency, or a selection of frequencies based on the use of traps and other tricks of the trade. Do you need an antenna tuner for this type of setup? It depends on how broad banded the antenna is on the specific frequency of interest. Antennas have only one point of resonance or near resonance on a single band.

The resonance point is generally designed to fall into the middle of the band with the hopes that the antenna system will be broad banded enough to give the operator a fairly low SWR on the edges of the band. This is most often visible on bands like 80 meters where retuning will most likely be necessary if you want to switch from the phone part of the band to the CW part.

This is where an antenna tuner can come to the rescue. Even very simple tuners inexpensive can be used to tame rising SWR on purpose tuned antennas and most hams have an antenna tuner in their shack for just this reason. The really good news is that most modern solid state rigs come with a built in antenna tuner.

You may be thinking WOW! It's great that our manufactures were generous enough to add an antenna tuner to our radios so that we don't need an external tuner. Well, the truth is a little less generous. One option is to build a resonant antenna to match the frequencies you plan to use.

A resonant antenna is a multiple of a quarter wavelength at a desired frequency. For example, if you wanted to make a dipole resonant at the middle of the 40 meter band 7. Dipoles: The dipole antenna is one of the most effective and inexpensive antennas. Using simple hookup wire and some insulators, you can build single band or multiple-band fan dipoles. Kits for making dipoles are available from DX Engineering from its own brand and other manufacturers such as Bushcomm. Put your antenna in the air and connect some good quality coax.

Under these circumstances, the antenna tuner can be located close to the transmitter, even when coaxial feeder is used to connect the tuner to the antenna. It is a common misconception that a high standing wave ratio itself causes loss. This is not true. When a high standing wave ratio exists, this results from power being reflected back along the feeder as a result of a mismatch.

When it enters the antenna tuner, it is reflected back along the feeder to the antenna where a proportion is radiated and some reflected back along the feeder again. Open wire feeder is often used for antennas where there are high levels of reflected power in the feeder.

As the losses in open wire feeder are very low, this is not a problem. For coaxial cable, losses are higher, but if high quality low loss cable is used, then the overall losses are acceptable. Provided the coaxial cable can operate with the higher voltage and current levels caused by the high SWR, then this is quite acceptable.

The main issue is to prevent the transmitter seeing the high SWR as this might damage the output, or the protection circuitry will reduce the power output. Accordingly it is quite acceptable to use an antenna tuner or antenna tuning unit close to the transmitter and not at the feed point of the antenna. It is worth placing a VSWR meter in the line to monitor the actual level of standing waves seen by the transmitter. Cut your antennas For the longest frequency of the band its for.

Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. How can I safely transmit without an antenna tuner or SWR meter? Ask Question. Asked 8 years ago.

Active 3 years, 3 months ago. Viewed 17k times. Keeping it simple Say, A simple mono-band centre-fed dipole is constructed after calculating the length for that band Say further, neither an AT nor an SWR meter is available Given the above assumptions, what I would like to know How can I transmit without an antenna tuner?

As a corollary What if the antenna is not a simple centre-fed mono-band antenna? How did they tune antennas back when the hobby was still new? I guess Does a tube based HF transmitter need an antenna tuner?

Improve this question. Community Bot 1. Actually, I was probably a naive teenager but I didn't know what an SWR meter was 50 or more years ago. In fact, I don't remember any of my ham radio friends ever even thinking about SWR. Tube amps could redden without any overheating issues due to the high VSWR.

We had plenty of time to adjust the "tuning box" to "reduced power" as a precaution Long live the EL34s and others of the past Current transistor amplifiers have "instantaneous protection" which makes them operate at reduced power as long as the VSWR is not "good"!

Add a comment. Active Oldest Votes. Lower power transmitters also have more leeway for mismatch before damage occurs. Do this at low power though, so you reduce the risk of damaging your transmitter. Improve this answer. VU2NHW 2, 2 2 gold badges 17 17 silver badges 42 42 bronze badges.

Adam Davis Adam Davis By Reciprocity this works just as well, but is much easier to accomplish. I suspect that most enthusiasts will get an S-meter before they get another radio that overlaps in frequency though. Not all, but most. Just listen to anything already on the band -- another station, or even atmospheric noise. Improving SWR reduces your losses on transmit and receive equally. You don't need to transmit anything: you can just receive. I need to think of the correct question to ask about the best location for the antenna tuner, thinking the best location is at the interface from the feedline to the antenna instead of from the transmitter to the feedline which is the mistaken practice today.

With a low-loss feedline, especially at HF where feedline losses can be very low, the losses are usually pretty small, and for many people not enough to justify a more expensive remote tuner, or separate antennas for each band. So I wouldn't call it a "mistaken" practice: it's just important to understand the compromises being made. This is exactly what would happen if the antenna was tuned properly. So there is virtually no difference between an untuned antenna with an antenna tuner in the feed line, and a tuned antenna connected directly to the transmitter.