ATU: The Magic Box

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Of all the things we talk about when discussing commo, some of the most important gear gets passed over. When we look at setting up a HF station we think…..

  1. Radio
  2. Power source
  3. Antenna

?????? Oh yeah, a tuner? ?????

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My old MFJ-949. A great tuner for the money.

ATU: Antenna Tuning Unit

The lonely tuner……It is not as sexy as a fancy HF rig with lights and cool display, but it’s pretty important. Most of us want our antennas to do things physics will not allow. As we know, the best antenna is one that is cut to be resonant on the frequency in use. If we only wanted to operate on one frequency this would not be a problem but…….we want something for nothing! Give me an antenna that works on all bands and give it to me now!!! Enter the tuner. If you ever mess with old “Green Radios” (AKA military surplus) you will notice a lot of the older units are channelized. This is because they used specific assigned frequencies and stayed within those parameters. This also translates to the tried and true field manuals that show field expedient antennas cut to a specific frequency. So, what does a tuner do for you? A tuner does not fix your crappy antenna, it makes your radio happy and allows it to safely deliver power to the “crappy” antenna.

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MFJ-941 ATU. Old but still serviceable.

Long story short, cut resonant antennas.  This is not always possible. A tuner is your friend, if used properly, you can get good multi band operation from your antenna. As a side note; a tuner does not make up for a lousy ground, use a counterpoise or earth ground, whatever the antenna design calls for.

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A manual tuner can make magic happen…….

There are basically two types of tuners, a manual tuner or an auto tuner. This is a touchy subject. ……I will enter cautiously…..let’s look at pro’s and con’s.

1. Manual antenna tuner

PROS

  • Hands on. You are in control.
  • Most have a meter so you can see what’s going on.
  • You usually have a wider tuning range.  Some guys claim to have tuned bed springs????
  • You can fix them in a grid down situation with available parts.

CONS

  • Some have a big foot print.  Not as good for portable ops.
  • Hands on, you have to know what to do
  • Learning curve. Some people have a hard time “getting it”. You have to be quick and accurate.

2. Auto antenna tuner

PROS

  • Easy to use.  Push a button.
  • Small. They are portable.
  • No meters to read, just tune and go!

CONS

  • Not as wide of a tuning range.
  • Uses batteries (sometimes).
  • No meter, no real time visual.
  • No user control.
  • A lot harder to fix in a grid down situation. Lots of surface mount components and special relays, etc.

With all that said, I prefer a manual tuner for two simple reasons. 1) Tunes anything within reason. 2) It can be repaired in grid down situation. I am not saying I don’t like auto tuners, but if I had to pick…. You have to decide what fits your needs.

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As you can see, not much going on under the hood of a manual tuner. You can fix this thing!

Remember,  your antenna is the most important part of your station, don’t cut corners.  If life where perfect I would not need to write this blog, but life is not perfect and sometimes we have to make things work. With tools like your trusty ATU you can make the best of your operating conditions and get comms up.  You may have to construct “less then perfect” antennas when operating covertly and a tuner makes it work. For around $150 – $170 you can purchase a new unit, but you can find them at a ham fest much cheaper. Stock pile them because you never know. ……

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Just a few in the tool box.

Don’t forget to get to class!! More info on a early September class in southern Pennsylvania coming in the next few days. ….

https://dialtoneblog.wordpress.com/2015/07/12/new-southern-pa-northern-md-grid-down-communications-course/

DIALTONE OUT.

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