Ham Radio-DIY VHF ANTENNA TUNER made from junk


Ham Radio-DIY VHF ANTENNA TUNER made from junk




Ham Radio-DIY VHF ANTENNA TUNER made from junk.  I had a question a few days ago from a reader about an ATU for his scanner, I like to call the device an Aerial Matching Unit. Robert said he had a Discone aerial in his loft and wondered if he could improve reception-he did tell me about his research for an AMU. He likes to listen to aircraft.

The circuit used in the video will work very well, I calculate variable capacitors to match the coil and load using the formulae for XC reactive capacitance  =1 divided by 2 Pi F C

2 Pi is 3.142 x2 = 6.284
F (Frequency) for aircraft band 124 Mhz

Your coil is calculated using 2 x pi x F x L (L is the inductance in uh microhenries) F frequency in megahertz.

Choosing a capacitor, we need 50 ohms at 124 MHZ these will be in the pf range picofarads. They may be difficult to get a hold of, but you can always used fixed values in series or parallel with a variable capacitor, it is an interesting experiment at the end of the day.

When C and L are equal we have the resonant frequency calculated from

1 divided by the square root of  L inductance multiplied by C capacitance.

This equation will give you the resonant frequency where the reactance of L and C are equal, canceling each other, we have only the resistance left of 50 ohms.

This little A.M.U. will improve your reception, but it does add loss to the signal, being a filter it will help block out band breakthrough.

You can also build a dipole CLICK HERE

Enjoy experiment and building radio and electronic projects, knowing comes from doing...73

Ham Radio-DIY VHF ANTENNA TUNER made from junk











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