Amateur Radio Stack Exchange
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Questions tagged [antenna-tuner]

Questions relating to the setup and use of antenna tuners, the virtues and shortcomings of various types of tuners, etc.

An antenna tuner, also known as a transmatch or antenna tuning unit (ATU) is a device connected between a radio and its antenna to improve power transfer between them by matching the impedance of the radio to that of the antenna.

Transmitters transfer maximum power when they are presented with a fully resistive load of a specified value (typically of 50 ohms). Antennas are resonant only at particular frequencies. Operating into an antenna at other frequencies is possible, but at a reduced efficiency.

An antenna tuner contains a matching network of capacitors and inductors designed to cancel out the reactance that occurs when operating an antenna at non-resonant frequencies leaving just the resistive load.

Therefore, an ATU allows the use of one antenna on a broader range of frequencies. An antenna and transmatch are not as efficient as a resonant antenna due to feedline losses and losses in the ATU itself. Note that an ATU does not change the resonant frequency of the antenna, merely changes the impedance.

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Why do I need to tune an antenna?

I've heard that when an antenna is set up, it needs to be tuned to reduce reflective power back into the radio. Is this always necessary, and if so how would I go about tuning it?
berry120
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How can I safely transmit without an antenna tuner or SWR meter?

Just what the title says. An Antenna Tuner, henceforth AT, is almost a de facto piece of equipment in a shack; working the bands without one is tantamount to leaping off the diving board into a swimming pool with tarantula nests in it ... or…
VU2NHW
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What is an antenna tuner? Why bother with resonant antennas in the first place?

There are a lot of antenna tuners on the market that have various capabilities in terms of how they can allow random radiators to work with our transceivers. What exactly do they do? My understanding is that they can neutralize the imbalance…
SDsolar
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What is the actual loss in a feed line with high SWR?

It is well-known that it is unwise to have standing waves on the feed line between one's antenna and one's transmitter, unless it is a very low-loss type (e.g. ladder line), because the transmitted signal is reflected multiple times through the feed…
Kevin Reid AG6YO
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What is the best practice when tuning an antenna on air?

I have a magnetic loop antenna that takes a long time to tune and of course, while tuning it, I need to be transmitting. What is the best procedure for tuning on air? I understand I need to check the frequency and identify myself before…
David VK2VXK
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Why is the risk of damage to a transmitter due to a mismatched antenna at lower frequencies greater?

A quick follow-up to this answer ... If the impedance mismatch is large, you risk damaging your radio, particularly on the lower frequencies ... I'm sorry to be so dense, but uh why is the risk of damage to the Tx due to an antenna mismatch…
VU2NHW
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What types of materials increase the inductance of a coil when inserted inside it?

I'm asking this because of the comments in this answer, that imply that steel (mostly iron) has similar characteristics to ferrite. Specifically, it is implied that inserting solid steel into a single-layer coil (as is commonly used in an antenna…
Mike Waters
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Two Antenna Tuners in Series

My radio has an internal antenna tuner that can be activated to rapidly tune for the frequency in use. My antenna has a disgusting SWR for the band I want to use (as measured with an AA-54 antenna analyzer). When activating the internal antenna…
Steve
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Antenna tuning while receiving

I've built AA5TB's antenna coupler for a 5W 20m transceiver. Tuning was kind of difficult because my transceiver has buttons for sending a dot and a dash, but no tuning mode, so I couldn't have the transmitter on permanently to tune easily. I had to…
user885
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Tuner at antenna side versus transmitter?

I figure the transmitter has a 50-ohm pure resistive output and that the transmission line is 50-ohm as well. I think it's usually the antenna itself that actually needs to be tuned, yet it sounds like everyone places the tuner at the transmitter…
pgibbons
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Does a tube based HF transmitter need an antenna tuner?

With the adjustments on a transmitter such as a Yaesu FT-101E, is there any purpose for an antenna tuner, or can you accomplish the same thing by adjusting the loading and other controls?
K9KRB
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Why does capacitive loose coupling increase selectivity?

There are multiple ways to couple antennas. It is said that an antenna is capacitive loose coupled if a small capacitor is used between the antenna and the parallel resonant circuit (like C2 in the image below). Such a loose coupling will increase…
dudekowsky
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Adapting an antenna coupler

I've built AA5TB's antenna coupler: I left out C2 because I didn't understand why I would need it - why would I? It works fine without. Unfortunately, when I started tuning for a 5W 20m transceiver, the LED was on all the time. I then measured with…
user885
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Does an antenna pick up signals of all frequencies or only its resonant frequency?

I heard that an antenna picks up signals of all frequencies, and then these signals are filtered by a circuit using an inductor and capacitor, and that this is how a radio is tuned. However, I also heard that an antenna has a resonant frequency, and…
Urthona26
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Antenna tuner at the transceiver output confusion

I am a bit confused. Let's take a HF transceiver for example. My understanding is that the output impedance of the transmitter is 50 ohms. The impedance of the coaxial cable feedline is 50 ohms, and if we have a resonant antenna at the operating…
Engineer999
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