[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

*Subject*: [amsat-bb] re: modeling qha*From*: John Mock <kd6pag@xxxxxxx>*Date*: Mon, 19 Apr 2004 12:44:19 -0700

I tried for a long time to model a Quatrifial Helical Antenna using NEC2 without much success. Sure, i got one which had a pattern and impedance that looked somewhat plausible at the design frequency: http://www.qsl.net/kd6pag/nec/apt1g.html But it did not appear to be very numerically stable to me (i.e. small changes in parameters yielded large changes in the model; see also the variation of impedence vs. frequency in the above example). Hence, i never trusted the results and pursued other antenna. Perhaps someone else has come up with a better NEC2 model for this antenna (which i would be interested in seeing). I suspect the problem with simulating these with NEC2 is that this antenna may involve cancelling fields and that's probably what impairs the numerical stability of the model i tried to use. The difficulty most likely involves the subtracting two floating point numbers which are nearly equal, results of which are rather approximate at best... Perhaps someone familiar with computational analysis and numerical modeling can explain this better than i can. -- KD6PAG Note: If you receive something purportedly from <kd6pag@qsl.net> that isn't signed with my callsign, then it probably isn't from me. ---- Sent via amsat-bb@amsat.org. Opinions expressed are those of the author. Not an AMSAT member? Join now to support the amateur satellite program! To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

**Follow-Ups**:**Re: re: modeling qha***From:*Dave Guimont

**Re: re: modeling qha***From:*Gary \"Joe\" Mayfield

**re: re: modeling qha***From:*John Mock

- Prev by Date:
**Soyuz Kep's** - Next by Date:
**FO29 on today:-19/4/04** - Prev by thread:
**SV: modeling qha** - Next by thread:
**Re: re: modeling qha** - Index(es):