Impedance Matching

[jazzsinger]

Change the 5/8 wave as having a higher impedance than the 1/4 wave too. The 5/8 wave antenna has a lower impedance then the 1/2 wave end fed but is still much higher then the 1/4 wave.

what Shockwave says is backed up by the fact it needs a loading coil which is tapped at some point between the top of the coil (1000 or so ohms) and the base of the coil ( 0 ohms), at some point inbetween it must be 50 ohms which is exactly where you tap the center conductor of the coax too, which is why the correctly designed 5/8 wave shows good match to 50 ohm coax.

the end fed halfwave with an end impedance in the couple of thousand ohm range is tapped exactly the same way.


the radiator in both is made slightly shorter than a full 5/8 or 1/2 wave to counteract the reactance introduced by the addition of the impedance matching coil.

 

[Greatvalue1]

Hey check out this video. Nice.

Sorry: Can't figure out how to Hypertext.

Standing Wave Ratio explained - YouTube

 

[The DB]

From the video about 2:15 into it.

Strangely the operators noticed that this did not make much difference to their signal at remote locations.

Just thought it was worth mentioning, mind you the low loss open wire lines used at the time and the coax primarily used today do have different properties. That being said, even with coax, once you get to a certain point the returns gained are pointless.

That being said, there are other things to tune for that will have more of an effect, if you have the right equipment.


The DB

 

[W5LZ]

That is a very good explanation of SWR for a number of reasons. It gives a history of it and shows where a slight misinterpretation/misunderstanding of it has given it's the 'importance' is has today. While SWR is important it is only one of the important things about a good antenna system, not really the most important thing.
Antennas and how they are fed is not a simple thing at all, and requires knowledge to understand. Getting that knowledge is also not a simple thing because there's too much misinformation also available. If it ain't one thing it's another, ain't it??
- 'Doc

 

[jazzsinger]

Antennas and how they are fed is not a simple thing at all, and requires knowledge to understand. Getting that knowledge is also not a simple thing because there's too much misinformation also available.
- 'Doc

Is that a confession ?
<gotproof>

 

[W5LZ]

jazzsinger,
Bless your heart...
- 'Doc