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A 35 Mhz mini aerial

Loaded whip

For many years now, I have been using some form of loaded receiver aerial. Back in 27 Mhz days we used to use a 1 amp TV choke at the base of 12 - 15 inches of piano wire. Similar aerials have been available commercially for almost as long. The first I encountered was produced by GMP for use on model helicopters. Theirs was said to work with both 27 and 72 Mhz, which seems most unlikely.

Some 15 years ago, an aerial appeared which was specifically produced for 35 Mhz by ABC Models. The company no longer exists, but I still have a well-used example of the aerial in use. Unfortunately, the base is sealed and I would have to destroy it to find out what was inside. A search of the web will reveal instructions on how to make an example for 72 Mhz. This is the FlyWire by Tony van Roon and basically consists of an RF choke and a piece of piano wire. Obviously, The same idea can be used for 35 Mhz, but what value should the choke be.

More recently, similar aerials have become available for 35 Mhz, but at a price. I bought one and removed the heatshrink covering to find that, as expected, it was just an RF choke and that the markings had been scraped off! By a process of elimination I came up with a value of 10 microhenrys.

I obtained some of these from Maplins and made up some samples to try. The results were far better than I expected. With a standard receiver using a 1 meter aerial, the loaded whip produced about 80 - 90% of the same range. On indoor type receivers using a 50 cm aerial, I obtained 25 - 30% greater range.

The orientation is not too important, but the best results are obtained with the rigid piano wire section mounted vertically. The choke can be glued to the fuselage stick of park flyers like the 'Pico-Stick'. It should be kept away from metal or carbon pushrods.


Loaded whip

You need about 4 inches of hook-up wire (or 4" of your original receiver aerial) to which you solder one 10 microhenry (10 uH) RF choke (Maplins part number WH35). The other end of the choke should then be soldered to 7 inches of piano wire. This should be the thinnest you can find, I used 0.020" diameter. Do remember to put a safety loop in the outer end of the wire, so you don't stab yourself - or, worse still, scratch your model. To be honest, I copied the length of the piano wire from the commercial unit which was said to be 'tuned' to 35 Mhz.

Choke Safety loop

Cover the choke with heatshrink tubing to produce a rigid unit. You will probably need to use two sizes of tubing; small diameter pieces over the piano wire and hook-up wire and a larger diameter piece to enclose the whole unit.

A word of caution

Do a comparative range check against the standard aerial before flying. I would not suggest that you use the unit with large, fast, heavy models for obvious reasons. A suggested limit would be Speed 400 power for electric models and no more an 049 - 09 power for an IC model.

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