Antenna tuner

2009-04-08T11:46:47Z

VK1WJ:

Related wiki pages: [[Apparatus]], [[Antennas]], [[Feedlines]]

An antenna tuner, also known as a transmatch, is a device for correcting an [[impedance]] mismatch between a transmitter or receiver and an [[Antennas|antenna]].

== The Tuner Fallacy ==

It is often believed that a tuner actually "tunes" a non-[[resonant]] antenna, tricking it into behaving as though it were resonant. This is not the case, as a simple experiment will show.

Suppose that we set up a transceiver system like the one below.

[[Image:Tuner_diagram.png]]

Suppose that the tuner is set to ''direct'' or ''bypass'' operation, connecting the two SWR meters directly together. If the transmitter is keyed, both SWR meters will indicate the same level of SWR. Assume that the non-resonant antenna has SWR at both meters of 10:1.

Now if the tuner is taken out of bypass mode and its [[inductors]] and [[capacitors]] adjusted until it produces a perfect match between transceiver and antenna, the SWR meter at left will be indicating 1:1, but the SWR meter at right will ''still be indicating 10:1''. In other words, our "antenna" tuner is actually tuning the transmitter to the antenna, not the antenna to the transmitter. We might better call it a transmitter tuner or transceiver tuner! There will always be feedline losses on the line between the tuner and the antenna. To minimise these keep this connection as short as possible and use the best cable you can afford!

== Tuner Models ==

The most common amateur antenna tuners are the many models made by [[MFJ]]. Other manufacturers also produce tuners. The assembly of a tuner is so simple that many hams build their own from scratch using [[homebrew]] techniques. Simple schematic:

[[Image:ATU.png]]

{{stub}}

Operating procedures

2009-04-08T11:34:38Z

VK1WJ:

Use this page to explain what various functions of a transceiver are and how to use them.

Related wiki pages [[Apparatus]]

==AF gain==

Simply the volume control - like the one at your everyday BC radio.

==Passband Tuning==

Passband tuning manipulates the tuning circuitry of the transceiver, allowing "close together" signals to be separated - one is rejected by the filter, one is allowed to pass through. It is similar to IF shift, where the IF of the transceiver is shifted slightly to tune in slightly off frequency signals.

Passband tuning and IF shift are used because simply narrowing down the passband would produce muffling of any audio signals. Narrowing down the passband is however the best way to pick out narrow band signals (like CW and narrow band digimodes) from a noisy band.

External link [http://www2.arrl.org/qst/2005/04/passband.pdf from QST]

==RF gain==

Controls the amount of pre-amplification in the RX before the first if stage is reached. It is very useful in QRN and other noisy conditions where otherwise SSB stations become unreadable. Take the RF gain back and have a QSO that would be impossible with full gain.
Some rigs have also a switchable additional RF gain button, that sometimes has also an attenuation function. This in effect just widens the margin of the overall RF gain.

==Roofing Filters==

See [http://en.wikipedia.org/wiki/Roofing_filter the regular Wikipedia]

2009-04-04T04:55:15Z

VK1WJ: Basic Antenna tuning unit

Basic Antenna tuning unit

2009-04-02T05:34:09Z

VK1WJ: /* VK1 Australian Capital Territory */

Related wiki pages: [[Personal Ham Radio Websites]]

== VK1 Australian Capital Territory==

[http://www.vk1od.net/ VK1OD Owen]

[http://ilgonis.orgfree.com/ VK1WJ Waldis]

== VK2 New South Wales ==

* [http://vk2fqzl.tooraweenah.com/ VK2FQZL - James] - Linux Hacker in the Bush
* [http://www.vk2bac.teviot.net/ VK2BAC - Adrian] - Amateur Radio Stuff & related Information including some Home Brew
* [http://www.sydneystormcity.com/ VK2TDN - Dave] - With subpages on Stormchasing, Amateur Radio, Seismlogy and Astronomy
* [http://www.electronics-tutorials.com/index.htm VK2TID - Ian] - A wealth of information about all manner of ham radio, electronic theory and other topics of general interest.

== VK3 Victoria ==

* [http://www.roity.com/vk3ldr/ VK3LDR - Dave]

* [http://home.alphalink.com.au/~parkerp/qrp.htm VK3YE - Peter] - QRP Australia

== VK4 Queensland ==

* [http://stuartl.longlandclan.yi.org/blog/category/amateur-radio/ VK4FSJL - Stuart] from Brisbane, Australia. Administrator of the [http://ham.longlandclan.yi.org Amateur Repeater database]
* [http://www.qrz.net.au VK4KTX - Peter] from Brisbane, Australia
* [http://vk4radio.info/ VK4XZ - Bill] - repeater co-ordinator for Queensland
* [http://timroberts-vk4yeh.id.au VK4YEH - Tim] from Brisbane, Australia

== VK5 South Australia ==

[http://homepages.ihug.com.au/~vk5vka/ VK5VKA ] from Stephen Newlyn.

== VK6 Western Australia ==

== VK7 Tasmania ==

* [http://www2.vk7ax.id.au/ VK7AX - Tony] - N/West Tassie's Premier Amateur Radio Station

== VK8 Northern Territory ==

== VK9 Australian Territories ==