Wednesday, January 4, 2017

Simple Ham Radio Antennas--Ham Radio--How To Make a Frame Aerial for the Medium Wave. Post #1002.

Ham Radio--How to make a Frame Aerial for the Medium Wave
(https://g4ydm.blogspot.com/2017/01/ham-radio-how-to-make-frame-aerial-for.html).
Please click link or insert title URL into your browser to read the full article.
Author:  John Allsop (G4YDM).
Accessed on 05 January 2017, 05:35 hrs, UTC.

Comment:

John Allsop (G4YDM) has a fascinating website, which includes many interesting and simple projects that will enhance your enjoyment of Amateur Radio (see https://g4ydm.blogspot.com).

In this article, John reaches back to a classic antenna design from the early 1920s which still produces amazing results in receiving signals on the standard broadcast band (medium wave) and on the 160 meter Amateur Radio band, a set of frequencies close to the upper reaches of the AM band.  This simple receiving loop can notch out noise and align itself for the best reception of broadcast and ham radio signals.  Radio amateurs who experiment on the often noisy 160 meter band will find John's design a benefit in pulling out those weak, muddy signals.

According to John, construction of this simple receive antenna is well within the technical abilities of most radio amateurs:

"I start off with a wooden frame or roughly one metre per side a piece of flat wood can be nailed to the corners at ninety degrees to help support the windings which form part of the aerial. Wind about 200 turns of wire around your frame spacing the wire a couple of millimetres apart. Aerial wire of about one millimetre in diameter is ideal for this project.
After you have would about 150 turns terminate the each end of the wire by screwing the ends into a chock-block and secure it to the bottom of the frame. The other 50 turns which I suggest you use to make your frame aerial can be added later and attached in series with the other turns; the extra turns are for greater inductance which you will need for the long wave bands.
You will also need a capacitor to bring the frame aerial into resonance on the medium wave band, I use a three gang capacitor each with a maximum capacitance of around 250 P.F. and you can wire the capacitor in series and parallel to alter the ratio for tuning purposes.
Alignment and tuning of the loop is a trial and error exercise you may need a little more capacitance when connecting your 150 turns to the extra 50 when tuning in stations on the long wave. If you place the capacitor in parallel with the turns connect a short length of coaxial cable to the same connectors the other end of the coax requires a plug to connect into your radio. You can place a single loop of wire around the frame aerial and connect this directly via coax to the receiver it works just as well, this is called inductor coupling."
If you want to boost your ability to receive weak signals on 160 meters or on the standard broadcast band, then this antenna may be what you need.
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