Line 112 should calculate diameter based on circumference, not on diameter
var diameter = round( circumference /PI *10) / 10;
The equation of HPBW is displayed incorrectly, line 249 should be
= 52/(C<sub>λ</sub>*√(n*S<sub>λ</sub>))
Similarly, line 257:
= 115/(C<sub>λ</sub>*√(n*S<sub>λ</sub>))
Gain calculation is wrong. You use log, but that is NOT base10, it's the natural log. I traced back the typo to the ARRL antenna book - it uses the somewhat unusual convention (as explained in Appendix 5)
ln — natural logarithm
log — common logarithm
In most engieering texts, lg would be base 10, ln would be the natural and ld the base 2 logarithm.
Due to this, your calcultor uses the wrong logarithm. There exists a Math.log10, and your calculator should use that.
Also, the gain formula is also on the optimistic side. Kraus has 2 formulas for directivity (not the same as gain, but an upper limit)
optimistic: 15Clambda^2*n*Slambda
"more realistic": 12Clambda^2*n*Slambda
The ARRL book formula takes the first, converts to dB, splits the multiplication and thus 10*log10(15) becomes 11.760+... rounded to 11.8. The "more realistic" version would have 10.7912...
Thank you for the calculator, this and your videos and site helped me getting started on designing helicals.
Line 112 should calculate diameter based on circumference, not on diameter
The equation of HPBW is displayed incorrectly, line 249 should be
Similarly, line 257:
Gain calculation is wrong. You use
log, but that is NOT base10, it's the natural log. I traced back the typo to the ARRL antenna book - it uses the somewhat unusual convention (as explained in Appendix 5)lgwould be base 10,lnwould be the natural andldthe base 2 logarithm. Due to this, your calcultor uses the wrong logarithm. There exists aMath.log10, and your calculator should use that.Also, the gain formula is also on the optimistic side. Kraus has 2 formulas for directivity (not the same as gain, but an upper limit)
15Clambda^2*n*Slambda12Clambda^2*n*SlambdaThe ARRL book formula takes the first, converts to dB, splits the multiplication and thus 10*log10(15) becomes 11.760+... rounded to 11.8. The "more realistic" version would have 10.7912...Thank you for the calculator, this and your videos and site helped me getting started on designing helicals.