VHF / UHF Filters and Multicouplers: Application of Air Resonators

Chapter 12

Utilities

In this chapter we will find first a series of small BASIC programs which, coded in a pocket calculator, constitute a very practical support that every HF specialist should always have with them and which the author has used daily himself for the 20 years he has worked in the field. Afterwards come tables of values whose frequent consultation justifies their presence within this work. The programs were developed in 1985 on a pocket calculator, Tandy PC-6, that no longer exists, and they consume no more than 10 kilobytes of memory. They enable the main dimensions of a combline filter to be given instantly according to Dishal’s formula, for example, or the Q0 of a cavity to be obtained as a function of its dimensions, as well as enabling us to solve the little conversions that we have to do dozens of time every day, such as passing from VSWR to adaptation in dB, etc. Anyone can add to them whatever they want according to their habits and needs.

12.1. BASIC programs

Program P0: Return Loss.

Gives the adaptation (or reflected power or return loss), as a function of the VSWR, as well as the reflection coefficient.

10 PRINT “Adaptation”

20 INPUT “VSWR=”,R

30 X=20*LOG(1+R)/(1-R)

40 Y=.01*INT(100*X)

50 PRINT “Return Loss =”;Y

60 Z=(R−1)/(R+1)

70 A=.01*INT(100*Z)

80 PRINT “COEF REFLEXION=”;A

90 GOTO 20

100 END

Test: VSWR = 1.8 return loss = 10.88 reflection coef. = 0.28 ...