Hi-Z Antennas HIZ-PC-4A Podręcznik - Strona 17

Przeglądaj online lub pobierz pdf Podręcznik dla Antena Hi-Z Antennas HIZ-PC-4A. Hi-Z Antennas HIZ-PC-4A 19 stron.

The cables as we supply them are listed in the table below. The lengths may change a

small amount if the cable vendor supplies us with a changed Velocity factor for the cable.

4 element 80 feet

100.5 feet/50.25 feet

80 and 40 degrees

It is very important that the short delay cable remains ½ the physical length of the Long

delay cable in the case of use alternate phase delays.

Custom Delay cables

In order to make custom cables one can use our values from the table above. We have

established that 100.5 feet will equal an 80 degree phase shift at 1.840MHz using precision

equipment. Take 100.5 divided by 80 degrees and you get a feet per degree answer which is

the key value. 100.5/80= 1.256 feet of RG-6 per degree of phase shift.

From this key value you can calculate any value of phase delay cable length.

For instance, the MAX RDF delay values needed for an 80 foot 4 element array can be

calculated by referring to the needed phase delay from the 4 element manual.

The values are 50 and 25 degrees are taken from the manual. All we need in this case is to

multiply our key of 1.256 feet per degree times the 50 degrees needed.

1.256 * 50= 62.8 feet of Rg-6 cable. As stated above the short delay would ½ of that value

at 62.8 / 2 or 31.4 feet of cable. The cables would be 62.8 feet and 31.4 feet.

A second example would be the 60 foot per side 4-square which shows in the 4 element

manual a needed 70 and 35 degree set of cables for side maximum front to back.

Again, our key of 1.256 * 70 degrees= 87.9 feet for the long delay and 87.9 / 2 or 44 feet for

the short cable.

Rounding cable length values to the nearest 0.1 foot value is very sufficient when 1.256 feet

equal 1 degree of phase shift. At 1840 KHz one wavelength = 534.55 feet. Dividing this by

360 degrees gives 1.485 feet per degree. Our measurement of 1.256 feet per degree divided

by the 1.485 feet per degree gives a Vp or velocity of propagation in the coax of .846 .

Factory cables can be used with short cables adding to the length by using good quality type

F barrel connectors. This image shows good and bad barrel connector choices.

4 element 60 feet

75 feet/37.5 feet

60 and 30 degrees

8Pro 113 feet

100.5 feet/50.25 feet

80 and 40 degrees

8Pro 85 feet

75feet/37.5 feet

60 and 30 degrees