The Secret of a Balun

[A71AN]

I bought so far 3 different Baluns and breaded them into piece, to find out the way they been built.

One of them had a coax gray Cable, made into 3 turns with a bead on each turn, checking the continuity the wire to wire is conducted, wire to child is not and the vies versa.

The other is not the same, continuity was given me wire to child and wire to wire and chilled to child, is this right, or may be some thing happened during breaking this balun made the continuity go all the way through.

I understand my English here is real poor, but I hope some one will understand what I mean.


Thank you all and 73 my friends

[VK2TIL]

There are different kinds of balun (some are, strictly speaking, not baluns at all).

The first one you describe sounds like a "choke" or "W2DU" device; just ferrite around the outside of co-axial cable so there is no DC connection between the two.

These are very useful & effective devices if enough ferrite of the correct permeability is used. They do not transform impedances so are "1:1 baluns".

The other one sounds like a "transmission line" balun; you will get DC continuity between all terminals.

These may or may not transform impedances; the transformations are usually (but not always) based on the square of the turns ratio so may be 1:1, 1:4, 1:9 etc.

Here is a basic description of baluns;

http://en.wikipedia.org/wiki/Balun

You should recognise the types you have.

Baluns/transformers are a huge subject on their own; entire books (eg W2FMI's wonderful works) and many scientific papers have been written on them but they are still, I think, the subject of more misconceptions in amateur radio than anything else (with the possible exception of SWR).

Do some Googling; there is a lot of information out there.

[A71AN]

There are different kinds of balun (some are, strictly speaking, not baluns at all).

The first one you describe sounds like a "choke" or "W2DU" device; just ferrite around the outside of co-axial cable so there is no DC connection between the two.

These are very useful & effective devices if enough ferrite of the correct permeability is used. They do not transform impedances so are "1:1 baluns".

The other one sounds like a "transmission line" balun; you will get DC continuity between all terminals.

These may or may not transform impedances; the transformations are usually (but not always) based on the square of the turns ratio so may be 1:1, 1:4, 1:9 etc.

Here is a basic description of baluns;

http://en.wikipedia.org/wiki/Balun

You should recognise the types you have.

Baluns/transformers are a huge subject on their own; entire books (eg W2FMI's wonderful works) and many scientific papers have been written on them but they are still, I think, the subject of more misconceptions in amateur radio than anything else (with the possible exception of SWR).

Do some Googling; there is a lot of information out there.


Thank you my friend, I will look around the net and learn more about them.

The last experiment I did with an antenna for the FT-857 ATAS-120 did not tune.

I mounted it on a base and designed a 14 meter post which driven up and down with a motor, a coax cable from the base to the radio, but this antenna which usually mounted on a car, is earthed using the car body, my design did not have an earth that why may be it did not tune, a friend of mine also brought his high sierra antenna which also did not tune, while on his car do tune without any problem , on portable we thought of having a high post to have better working condition, I am not sure yet weather the earning is necessary or not, and if it is, how to do the earthling for such antennas while they are not mounted on the car ?


Thank you my friend, I try to learn and do things by my own, there will be a lot of try and errors.

I hope my good friends, do not make a joke out of what I have done:)))))

Thank you my friend and 73

[N2RJ]

Any vertical antenna needs a ground plane, not simply an earth.

Normally your car acts as a (very poor) ground plane, but if you are operating fixed you should have radial wires.

These are quarter wave for elevated radials. Four per band will be 90% efficient.

For ground mounted radials, these can be any length, but the longer the better, and you would need about 100-120 radials to be 90% efficient.

What happens when you don't have any radials with a vertical is that your feedline (coax) shield acts as a radial, of random length, with unpredictable results. It may work, but it will work poorly and it will also radiate, which isn't really that good. You want your antenna to radiate, not the feedline.

The 1:1 balun is a choke to block RF current from coming back on your feedline. It helps with feedline radiation, but your antenna is still not efficient if it has no ground plane.

[A71AN]

Any vertical antenna needs a ground plane, not simply an earth.

Normally your car acts as a (very poor) ground plane, but if you are operating fixed you should have radial wires.

These are quarter wave for elevated radials. Four per band will be 90% efficient.

For ground mounted radials, these can be any length, but the longer the better, and you would need about 100-120 radials to be 90% efficient.

What happens when you don't have any radials with a vertical is that your feedline (coax) shield acts as a radial, of random length, with unpredictable results. It may work, but it will work poorly and it will also radiate, which isn't really that good. You want your antenna to radiate, not the feedline.

The 1:1 balun is a choke to block RF current from coming back on your feedline. It helps with feedline radiation, but your antenna is still not efficient if it has no ground plane.


Thank you my friend, the more you do the more you learn, I have already made the redial, 21 meters each, 16 of them, but that I had in mind to cover the 80 meter, nothing worked for us at all, not even the 20 meter although these types of antenna is having auto tuning, like a motorized one.

I have a vertical at home, for the 40 and 80 meters, on the 40 SWR is 1:5 which is great for me and made many qso with it including Japan and the state, but this vertical did not work on 80 meters, yes I made the redial and fitted them, there was still no different gain, that why I removed them all, as they been a great miss on the roof of the house.

Now for our camping I have a better Idea for this system, I will connect and earth to the antenna base and connect it to the car earh, may be this will work, just to see what happen


Thank you my friend and thank you for the wonderful qso again on 20 meter, your qso made my day by all means.

73 my friend

[kd7kcr]

A71AN - I think your "mobile operation" is very similar to what American & Canadian hams do every year for "Field Day" - a very popular event here.

look here for an explanation: http://en.wikipedia.org/wiki/Field_Day

then google for: field day antennas -- to see some of the many, many ideas hams use for simple antennas that are easy to put up and still perform well.

then google for: ugly balun -- to see simple ideas for keeping rf off the feedline,
if you decide not to use a choke balun.

enjoy,

kd7kcr

[A71AN]

A71AN - I think your "mobile operation" is very similar to what American & Canadian hams do every year for "Field Day" - a very popular event here.

look here for an explanation: http://en.wikipedia.org/wiki/Field_Day

then google for: field day antennas -- to see some of the many, many ideas hams use for simple antennas that are easy to put up and still perform well.

then google for: ugly balun -- to see simple ideas for keeping rf off the feedline,
if you decide not to use a choke balun.

enjoy,

kd7kcr


Thank you my friend, for the link and wishing you all of the best

73

[w7lpn]

I built one of these and I feel I understand them a little better now. :cool:

[k6jpd]

from what you have said, it sounds like one is a CURRENT balun and the other is a VOLTAGE balun