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I live in Japan. Japanese houses are very narrow, but I want to try 160 m band.
Is there good antenna for 160 m band?
I want to operate HF (160m~10m) bands. Now I use vertical antenna (40, 30,20,15,10m).

I want a low band (under 40m) antenna. Low band antennas is small in Japan. So I have to make it. Is there the antenna that it is small, and production is easy?

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  • $\begingroup$ My best operating on 160 meters has been in the field with a random length wire thrown into a tree and a single wire counterpoise laying on the ground. Using a 9:1 balun helps plus you need an antenna tuner. Length of wire in most cases that I have done this is about 60 to 70 feet and try to get it up high, even near vertical works. You probably will not be working any DX. Works best late at night. $\endgroup$ – K7PEH Sep 19 '15 at 3:45
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The cheapest solution for the 160m band is probably a magnetic loop antenna, but do be aware that these antennas are optimised for small space and low cost, and NOT for performance.

A magnetic loop is an extremely high-Q antenna with a very tight bandwidth (think ~5kHz on the 160m band), but they are tunable. The gain of such an antenna will be anything from 0dBi to -20dBi (that is to say they are not very efficient).

However, it will allow you to get on the air.

(The usual warnings about the high voltages present on a magnetic loop antenna apply here, especially if you put any power into it! Do not install one where people can get close to it while you are transmitting.)

An example of a magnetic loop antenna is here.

Good luck!

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You can modify your vertical to work on 160m. Small antennas are always a compromise in performance, but they do work.

You might research mobile antennas, intended for operation from a vehicle. These have similar restrictions on size, and so they usually use two methods, or both in combination, to make the antenna appear longer electrically than it is physically.

Capacity or capacitance hats

These come in a lot of styles, but the idea is to put spokes or something similar at the top of the antenna to increase the capacitance to ground at the tip of the antenna.

Here's an example from K0BG:

vertical antenna with capacitance hat

There are all kinds of variations, but anything that makes the antenna thicker accomplishes the same thing. Increasing the thickness at the top has more effect than increasing it at the bottom. See the T-antenna for an antenna where the capacitance hat is most of the antenna.

Loading coils

As you might guess from duality, it's possible to electrically lengthen an antenna (and thus, make it physically smaller), with inductance also. This is accomplished by putting an inductance somewhere along the length of the antenna.

Here's a homemade loading coil by KC7FYS:

loading coil

Putting the coil near the base of the antenna is more effective at electrical lengthening than putting the same coil near the tip. But the current is higher at the base than the tip, so the closer the coil is to the base, the higher the losses, and thus the lower the antenna efficiency. Likewise, a bigger coil will electrically lengthen the antenna more, but losses will be higher.

So as usual, placement and sizing of the loading coil is a compromise between size and performance. A lot of designs end up putting the coil somewhere around the middle of the antenna.

These aren't the only options

There are a lot of ways to make antennas and this is just one. As Scott Earle says, a magnetic loop antenna is an equally valid solution. People do all sorts of things: just about any conductor can be made into an antenna. People have used rain gutters, metal fences, metal roofs, or just random wires strung around wherever they can fit them. If you can match your radio's impedance, and keep losses low, it will work as an antenna!

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