Antenna Tunning Unit for HF Radio

[SU-4]

my radio using antenna with length 1.5 M so it's capacitive for frequency below from frequency resonant of antenna. i have tested Antenna Tunning Unit for HF radio with iron powder toroidal, i want matching all frequencies range from

1 MHz - 30 Mhz with VSWR 2. That's Antenna Tunning Unit using nine iron powder toroidal with different sum of winding, formula of the winding is multiple of 2 for inductance, so it's mean iron powder toroidal first have value 0.5 uH,

second have value 1 uH,.......and last iron powder toroidal have value 64 uH. i hope that's linear for the result, i mean when i want match at 30 MHz, iron powder toroidal which used is only iron powder toroidal with value of inductance

1 uH, and when i want match at 23 Mhz, i need value inductance combination from iron powder toroidal is 1.66 uH. but fact i can't get linear, i don't know why it can be happen, may be all of u guys can help me???

note : i am use iron powder toroidal 50-6 mix (yellow), 94-2 mix (red), and 106-2 mix (red)

 

[flatulent]

You are fighting a losing battle. The antenna is way too short for these frequencies. The radiation resistance is orders of magnitude lower than the loss resistance of your matching components.

 

[SU-4]

thank you for replying, but can u give some reference for this topic :-D

 

[flatulent]

Look at amateur radio handbooks in the chapter on antennas for cars. One thing that will help you is to use a helix instead of a straight conductor. You can make one by winding wire around an insulating rod, such as fiberglass or plastic water pipe.

 

[SU-4]

that book free or not because i can't find it at google may be u can give its reference website so that it's make me easy to download and find it, thanx a lot before

 

[enjunear]

that book free or not because i can't find it at google may be u can give its reference website so that it's make me easy to download and find it, thanx a lot before

If you can, find a copy of the ARRL Handbook, for starters. ARRL also has an "antenna book", but it might be harder to find. Also, try searching on qsl.net for "HF antenna". There are a lot of HAMs that have webpages on that site.

 

[RCinFLA]

If you are transmitting any power you also have the issue of how much power the iron cores can take.

What you describe is similiar to mobile HF antennas for vehicles. The usually use large air wound loading coils.

 

[SU-4]

If you are transmitting any power you also have the issue of how much power the iron cores can take.

What you describe is similiar to mobile HF antennas for vehicles. The usually use large air wound loading coils.

thank you for your reply, i'm consider that i have to use some capacitors, because i belive that although that antenna usualy capacitive for 1-30 MHz, but it's not make me to not use some capacitors, i have looked an automatic antenna tuner for hf manpack radio or for vehicle, both of device use some capacitors too

thank you

 

[enjunear]

thank you for your reply, i'm consider that i have to use some capacitors, because i belive that although that antenna usualy capacitive for 1-30 MHz, but it's not make me to not use some capacitors, i have looked an automatic antenna tuner for hf manpack radio or for vehicle, both of device use some capacitors too

thank you

To design an effective antenna coupler, you absolutely need to know what your load impedance is over your desired range of tune frequencies. Once you know what your load will look at multiple frequencies you can start experimenting with combinations of impedance matching circuit elements to find a set that can be switched in/out in order to tune the system across your entire freq range. At the heart of it, you'll need a big inductor, since a 1/4-wave monopole looks like a capacitor at the low end of the HF band. You can probably start by looking at a switchable PI-style compensation network.... shunt C's, series L, and shunt C's.