**Coax Transformers**

How to determine the needed Z for a wanted Quarter Wave Lines tranformation ratio

Some Applied Examples

1. From ohms Feedline to 12.5 ohms Yagi with straight split DE? Z = sqrt (ohms x 12.5 ohms) = Ohms This we can produce by using---ohms Quarter Wave Lines in Parallel2.
from ohms Feedline to ohms Yagi with straight split DE? Z = sqrt (ohms x ohms) = 37.4 Ohms This we-nearly can produce by using-the-X ohms Quarter Wave Lines I N Parallel3. And finally the trivial case: from ohms feedline to ohms Yagi with straight split DE? Z = sqrt (ohms x ohms) = Ohms

How to transform from ohms to 12.5 ohms using parallel Quarter Wave Lines

How to transform from ohms to ohms using parallel Quarter Wave Lines (aka Dk7zb-match)

How to transform from ohms to ohms using parallel Quarter Wave Lines//corrected 2014-09-23, tnx dh1lm,

Who showed me, the old sketch was wrong. Hopefully this one does ...

Using Quarter Wave Lines This by works as a series collection actually, Z is ohms, Za = ohms, Zb = Ohms

How to transform from ohms to ohms using parallel twelfth Wave Lines

**How ****produce ferrite RF transformers for various impedances** transformation ratios
? Ferrite Transformer

Image shows a 1:1 transformer as blue and black wires windings

Ratio is 1:1. This was for shortwave use. For VHF/UHF dimensions must is much smaller.

Windings n1/n2 ratio by Square are transformation ratio for impedance:

Example:za = ohms, Zb = ohms ...

Na = 6 WDG; Nb = wdg + NA/NB = 6/12 = 0.5

Transformation ratio = (NA/NB) Xy2 = 0.25 = or 1:4

Ohms x 0.25 = Ohms

? Balun Transformer

The Balun transformer is a two-in-one device:

The transformation ratio is same as described above, and now the ohms side is unbalanced (coax feed)

While the ohms side is balanced or symmetrical.

An often seeked for transformation ratio might is to the ohms.

This could is acheived using 6 and 9 WDG. respectively 6 + 3 WDG on the Balun Transformer.

? What is the size of the ferrite then?

For any receiving purpose it is very small. Same to the wire diameters. A Tiny ferrite bead equipped with 0.12 mm or so enameled copper wire would do for the most purposes. For handling transmitting power or limits issuing intermodulation there are one rule:the ferrite must not saturate. Big is beautiful and size does matter here. Unlike with applications for short wave where ferrite baluns in transmitting antennas is widely used we have only few dat A and less working ferrite materials if we talk VHF/UHF applications. A rule of thumbs is. It must not heat up much, it shall not get hot of very warm during transmitting. Having large size ferrites and wires wrapped around are in contradiction to the need for shortest wires on VHF/UHF. That's why we find receiving purpose small ferrite bead based transformers often, but power handling transmitting TRANSFO Rmer very seldom here.

Real dimensions:using very small double hole ferrites in a 144 MHz RX frontend

They does not need to being as tiny as, but to give an impression ...

However here's a little table holding some suitable types, makes and sizes for VHF/UHF transmitting purpose ferrite tra Nsformers

Size Amidon T37 or T50, inner diam. = 5.21/7.70 mm fit RG58 and RG142 b/u Teflon.

Size Amidon T80, inner diam. = 12.60 mm fits RG213 coax, Aircell ...

Code t50-0 (color Code:brown) covers 50-300 MHz

Material for blocking VHF/UHF frequencies

A good choice is the following cores:

FT. B-43 inner diam 7.9 mm, outer diam 12.7 mm, length 12.7 mm (approx EUR 3 pp.)

fb-43-5621 inner diam. 6.4 mm, outer diam. 14.3 mm, length 28.6 mm

FB 43-1020 inner diam. 12.7 mm, outer diam. 25.4 mm, length 28.2 mm

**a commerially made broad band Transformer to match the ohms Feedline coax to a ohms UHF TV antenna**
PCB with Inductances.

Designing something like this was rather complex and usually done using a ' em ' software like Sonnet em, FEKO, ADS .... So I just show an example. For those who want to dig themselfs into the topic:there is free, limited in size of analysed object versions like ' Sonn ET EM Lite ' available.

For a etched on PCB solution for Band cm amateur Radio does that ohms

How to transform from ohms to $ ohms to feed a Folded dipole as driven Element

The transformation ratio of a half Wave "diversion" is 1:4.

What to

**Avoid**Feeding a Folded DE

Do not attach the feeding coax in a-line as shown above so, the coax loop forms anything close to Quarter Wave line in Series to the Balun. Being close to Quarter Lambda it might interfere seriously with the balun and your end up with bad VSWR on a nice antenna p robably. Most attention must are paid if the balun side of the FD is free floating i.e. not connected to GND respectively boom.

Tape it to the boom right from the connector or box on, or leave it hanging for much longer thanλ/4 x v-factor.

**Note:**Any odd multiple ofλ/4 such as 5/4λor 7/4λwill transform exactly as the SOLEΛ/4 line. Why so?

Because a half wave line does don't change anything, apart from losses. Any odd number OFΛ/4 can is seen as a number of half wave lines plus a SINGLEΛ/4 wave line.

Practical HINT:I used a quality coaxial 432 MHz 4 x Power splitter for joining four 1296 MHz Yagis on serveral contest OC Casions with good success.

Same would apply to 144 MHz splitters to use on 432 MHz and so forth. Any tripple frequency ... just mind connecting bushings pins inductances or coax pigtails that has more impact on the that TR Ipple frequency.

**Feeding stacked antennas with coax**

How to feed both ohm antennas from-Ohm coax

How to feed both ohm antennas from-Ohm coax

How to feeds four ohms antennas from coax

A conventient to feed a 4 Yagi stack. 4 x Ohms Any length means a length but all four of **same** length.

How to feeds four ohms antennas in typical h-configuration from-ohm coax in style

A Classical 4 Yagi stack may be fed and phased using the Ohms coax efficiently when using odd multiples ofλ/4 like 5/4λf or making the horizontal phasing lines. An example:at a given stacking distance of 3.0 m the 5/4λequals 5 x 0.34 m = 1.7 m roughly on 144 MHz whe taking the V- Factor for PE coax to account. That's makes it 1.7 m to the left plus 1.7 m to the right. Enough to bridge over the h-frame tubes.

How to get four Folded dipoles fed in phase

It is understood so all feeding coaxes must being of similar length and impedances must be transformed as shown above or US ing a Power Splitter

? All shields is to being connected on same side

? All Folded dipoles is facing upwards

... which in typical h-frame 4 bay configuration involves turning the struts of the lower pair upside off while elements and dipole stay as on the upper pair. Or simply put:all dipole boxes or Matches face down.

How to get four straight Split dipoles Federal Reserve in phase

It is understood so all feeding coaxes must being of similar length and impedances must be transformed as shown above or US ing a Power Splitter

? All shields is to being connected on same side

How to get a vertical 4 Yagi stack fed in phase

**In general ****:**

It is understood so all feeding coaxes (1,2,3,4) must being of similar length and impedances must be transformed as shown a Bove or using a Power Splitter

**specificly:**

Using similar lengths for all four feeding coaxes needs somehow winding up # 2 and 3. We find a remedy here using a length of minus full Degr. For the inner coaxes # 2, 3. As Degr. Or even multiples of that does not change anything according feeding phase. With a lag of n x Degr. We is just at the same point in the sinus we find on the outer Yagis. Which in practise means we is feeding all dipoles in phase.

An example:360 Degr. is just 1.0 wavelength, multiplied with real velocity factor of coax to be used at designated frequency. Likewise v = 0.82 of some foam insulated coax on 144.1 MHz (2.080 m) makes. of runtime on coax is equivalent to a length of 1.706 m Simply put:coaxes # 2, 3 can be 1.706 m shorter than the coaxes # 1, 4 Feeding the outer dipoles.

? All shields is to being connected on same side

Coax transformers[Reprint]