Questions about fixed impedance matching networks, the necessity of impedance matching, etc.
See also:
- impedance for questions about the general theory of impedance.
- An adjustable impedance matching network is an antenna-tuner.
Questions tagged [impedance-matching]
138 questions
22
votes
3 answers
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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13
votes
3 answers
UHF FM power amplifier design without expensive software
I'm designing a small UHF data transceiver for the 70cm band, based on a Silicon Labs EZRadioPro Si4463 IC. Modulation is FM, 12.5kHz channel step. The concept is similar to SiLabs' AN656 application note but with a different power amp BJT as the…
philpem
- 131
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11
votes
6 answers
What is a Gamma match in the context of the driven element of a Yagi antenna?
How (and why) does a Gamma match work, when used on the driven element of a Yagi antenna? As shown here:
(source: http://www.iw5edi.com/ham-radio/?2-element-yagi-for-10-meters-band,49)
The article describes a 10 meter Yagi where the driven element…
Ron J. KD2EQS
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11
votes
1 answer
How to combine two 50 Ω antennas such that they appear as one 50 Ω load?
I'm looking for a simple way to impedance match an array of two 50 Ω antennas so that when they are combined they appear as one 50 Ω load.
Assume that both antennas are identically constructed, are in phase with one another, and have the same VSWR…
Ben
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10
votes
1 answer
Does Coax Limit the Maximum SWR a Transmitter 'Sees'?
A recent discussion about SWR led to the assertion that a length of coax cable will ultimately limit the SWR to which the transmitter will be exposed.
By experimenting with an SWR calculation tool like TLDetails, there appears to be a basis for this…
Glenn W9IQ
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10
votes
5 answers
How did hams manage to tune their antennas before VSWR meters?
In the early 20th century --back when the hobby was still new-- before VSWR meters and antenna analyzers were invented, how did radio operators know whether they were tuned for maximum power out?
This is not asking about antenna tuner design or…
Mike Waters
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9
votes
2 answers
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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9
votes
1 answer
How effectively do modern transmitters protect against high SWR?
The following are fairly common knowledge:
Transmitting at full power with too much of an impedance mismatch can damage your finals.
If we do so inadvertently, modern radios drop the power significantly for self-protection.
Yet, it's still very…
Dominick Pastore
- 555
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9
votes
3 answers
Impedance ratio vs. SWR
The specs of the Elecraft T1 tuner say, that it can match a 10:1 SWR.
What does that mean in terms of impedance ratio?
What antenna impedance can it match to 50 Ohm then?
Or is it not that easy?
Dominik Heidler
- 93
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9
votes
3 answers
RigExpert AA-35 - Interpreting The Information
I have a new RigExpert AA-35 antenna analyzer. 1st one I have had & 1st time trying to use an analyzer on an antenna. My questions are very basic and general, but I am having difficulty in Googling for answers. Hope someone can help, or direct me…
B. Varner
- 149
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8
votes
1 answer
SWR Measured at the Transmitter versus SWR at the Antenna
It is fairly well understood that due to transmission line losses, the SWR as measured at the transmitter will be less than the SWR at the antenna.
Some of the new antenna analyzers and some vector network analyzers can 'zero out' or compensate for…
Glenn W9IQ
- 18,498
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7
votes
2 answers
Are "end-fed" antennas really more multi-band than dipoles?
Several "end fed" antenna kits (including the ARRL's for example) include wording suggesting that they are useful as multi-band antennas.
But does feeding a wire antenna highly off-center with a transformer/balun/unun actually allow it to radiate…
hotpaw2
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7
votes
1 answer
Why ferrite-core transformers are wideband while air-core are not?
While experimenting with end-fed antennas I've made two 1:49 transformers.
The first one has an air core, as shown in the article by John, M0UKD. This transformer doesn't even work as a transformer until you add a capacitor in parallel to the load.…
Aleksander Alekseev - R2AUK
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7
votes
2 answers
Why aren't "ghosts" and intersymbol interference due to unmatched impedance (high SWR) a concern for HF receivers?
In amateur radio, we care about impedance matching when we need to keep the load within the equipment's specification (for best performance, or just to avoid damaging a transmitter), when we want to maximize the power delivered into the load, or…
比尔盖子
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7
votes
3 answers
Impedance Matching between RF Amplifier Stages
I'm in the process of building a RF buffer-amplifier chain for a VFO and I'm experiencing a design issue trying to impedance match between the sections.
The issue I'm having is that many (most) of the circuit designs documented are characterized…
Buck8pe
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