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I am trying to build an antenna tuner for my 2m (1m + 1m) dipole antenna. It has a 1:1 balun and is connected to a coaxial cable which is connected to my radio with an impedance of 50 ohm. I can't hear all the FM and even short wave station reception is very poor.

After some research I got the idea for an antenna tuner which can be used for both SW and FM.

The LC circuit and the air capacitor I need for impedance matching is not available in my area. Hence, again after research got the idea of capacitance multiplier with variable resistance.

I don't have much idea/knowledge on this circuit. Can anyone help me on this antenna tuner unit? Which chip can I use for the above functionality?

Edit 1: Seems like both SW and FM tuner in a single unit is more complex and will be beyond my reach. I want to focus only on FM 88MHz to 108MHz, what would kind of antenna should I use and what should I do for impedance matching?

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  • \$\begingroup\$ You'll probably find more success if you were to move or re-post this on the amateur radio SE community. \$\endgroup\$
    – SteveSh
    Commented Jun 19, 2023 at 20:56
  • \$\begingroup\$ That's an enormous frequency range. Are you sure? \$\endgroup\$
    – Hearth
    Commented Jun 20, 2023 at 0:54
  • \$\begingroup\$ For a single frequency range yes. But not with switchable bands (channelization). My old Lafayette short wave set covered 140 KHz to 54 MHz in 5 or 6 bands, with each band covering an approximate 3:1 range of frequencies. \$\endgroup\$
    – SteveSh
    Commented Jun 20, 2023 at 1:33
  • \$\begingroup\$ @Hearth , wanted to have a single unit for both SW and FM, now it seems more complex. I think I should focus only on FM as of now, 88MHz to 108Mhz. \$\endgroup\$
    – Remo
    Commented Jun 20, 2023 at 16:26
  • \$\begingroup\$ @SetveSh is that a DIY unit ? \$\endgroup\$
    – Remo
    Commented Jun 20, 2023 at 16:27

1 Answer 1

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It sounds like you have several different things mixed up. An antenna tuner is going to need real inductors and capacitors, capacitance multipliers are mostly used for filtering DC voltages. You don't use chips and transistors for antenna matching.

Also you're specifying a rather large frequency range, to work from 1 MHz to 150 MHz would require large variable capacitors and/or switched fixed capacitors and multi-tapped coils. Look at the design of some amateur radio tuners.

A dipole with 2 meter long elements is going to work best at around 71 MHz, at shortwave frequencies it's not going to perform very well and a tuner isn't going to fix that. You might get a bit of improvement but I wouldn't expect much. If you want better reception on shortwave you might look into a different antenna, either a much longer dipole or a tuned loop should work better.

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  • \$\begingroup\$ Thanks for your reply . If I focus on only for FM tuner, how to achieve that? I have several radio stations between 88MHz to 108MHz. Also, air capacitor is not present in our area. :( \$\endgroup\$
    – Remo
    Commented Jun 20, 2023 at 16:24
  • \$\begingroup\$ What kind of antenna input does the FM radio have? \$\endgroup\$
    – GodJihyo
    Commented Jun 20, 2023 at 17:17
  • \$\begingroup\$ One is having 3.5mm jack like hole another don't have anything. An alligator clip might resolve the problem. \$\endgroup\$
    – Remo
    Commented Jun 20, 2023 at 17:21
  • \$\begingroup\$ Yeah, trying to use a tuner on something like that is probably going to just be a waste of time. If you had a receiver with a 75 or 300 ohm input (coax or screw terminals) you might get some help from a tuner. \$\endgroup\$
    – GodJihyo
    Commented Jun 20, 2023 at 18:05

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