**Next message:**Craig LaBarge: "WB3GCK Springs to the Field"**Previous message:**KE3FL@delphi.com: "Battery Charger/Eliminator"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]

To ALL at QRP-L:

The J-pole equations I use in my program are a combination of those in

QST September 1994, pg. 61 & 62 in an article by Jim Reynante/KD6GLF

and those in an article by John S. Belrose/VE2CV also published in QST

in April of 1982.

I programmed these equations into the present program which allows for

different wire velocity factors, and for display of the lengths in either

English or Metric. The calculation results can also be sent to a printer

by setting the printer toggle switch to the ON position (Tools Menu).

I have also included a change calculation that computes the expected

change in frequency due to a length change. Remember: cutting the

antenna increases the frequency (decreasing the wavelength) and adding

length to the antenna decreases the frequency increasing the

wavelength). The equations I use are:

factor = 11811 (English, inches) or 30000 for (Metric, cm)

delta = 0.25, .5, 1.0, 10, 20", or .5, 1, 2, 25, or 50 cm

The size of the recommended cut, dependent on frequency.

lambda = (factor/freq)

stub = vf * lambda / 4 (vf = .81 - .85 for twin-lead)

radiator = vf * lambda / 2

tap = lambda * .0155

gap = .25

total = stub + radiator

changes = freq - [(vf * factor/4)/(stub+delta)] MHz per delta cuts

(My program is available from Circle Software, PO Box 74, Mt Airy MD

21771 for $12, + md state tax + $3 shipping.)

One last thought. If you already know the size of the antenna for 52 MHz

simply scale it for 50.125 MHz as in:

(SIZE * 52)/50.125 = New size

Example: SIZE = 141.4 ft then New size = 146.7 ft.

(The info from my program below is no better than this!)

Using a velocity factor of 0.83 my program gives:

Freq Stub Radiator Total Tap Gap

MHz in in in in in

52 47.1 94.3 141.4 3.5 .25

50.1 48.9 97.8 146.7 3.7 .25

I hope this helps. 72 & 73 de KE3FL/Phil

:-)

**Next message:**Craig LaBarge: "WB3GCK Springs to the Field"**Previous message:**KE3FL@delphi.com: "Battery Charger/Eliminator"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]

**[
QRP-L Archive |
] [
1993 |
1994 |
1995 |
1996 |
1997 |
1998 |
1999 |
2000
] **