On my web page at: http://www.w5dxp.com/G5RV.HTM
I show how to install a 1000 pf capacitor across
the G5RV transmission line at the twinlead/coax
junction to improve the 75m SWR and move the
resonant point into the 75m phone band.

I have never been able to model the shunt capacitor
with EZNEC. Anyone know of a way to do that?
--
73, Cecil http://www.w5dxp.com

On Oct 15, 2:55?pm, Cecil Moore wrote:
On my web page at:http://www.w5dxp.com/G5RV.HTM
I show how to install a 1000 pf capacitor across
the G5RV transmission line at the twinlead/coax
junction to improve the 75m SWR and move the
resonant point into the 75m phone band.

I have never been able to model the shunt capacitor
with EZNEC. Anyone know of a way to do that?
--
73, Cecil http://www.w5dxp.com

Hi Cecil, Looking at your webpage, looks to me like a 103' dipole
with 36-j324 impedance at 3.8 Mhz needs 28' of 450 ohm line instead of
300 ohm. 28' of 450 ohm line put you at 24+j25 with an swr of 2.7:1.
1000pf shunt cap. puts you near 1:1.

As for modeling the Shunt Capacitor, I have never done it, but you
might try a stub to simulate the Xc. Don't have time at the moment,
or I would give it a try.

73 Gary N4AST

wrote:
Hi Cecil, Looking at your webpage, looks to me like a 103' dipole
with 36-j324 impedance at 3.8 Mhz needs 28' of 450 ohm line instead of
300 ohm. 28' of 450 ohm line put you at 24+j25 with an swr of 2.7:1.
1000pf shunt cap. puts you near 1:1.

I wasn't trying for perfection, just improvement. I actually
tried it on my G5RV and got considerable improvement in reality.

As for modeling the Shunt Capacitor, I have never done it, but you
might try a stub to simulate the Xc. Don't have time at the moment,
or I would give it a try.

That's a good idea, Gary, thanks for the suggestion.
--
73, Cecil http://www.w5dxp.com

wrote:

As for modeling the Shunt Capacitor, I have never done it, but you
might try a stub to simulate the Xc. Don't have time at the moment,
or I would give it a try.

With EZNEC v. 4.0 and earlier, the only way to model a shunt load other
than a short stub was to make a small triangular or square loop and put
the load on one leg and the parallel object on another leg. If the loop
is too small, NEC will have trouble with it; if too large, its reactance
will affect the result. Sometimes there's no suitable size.

Which is why I added the new parallel connected load feature to EZNEC v.
5.0. In that version, it's simple. The rightmost column in the Loads
menu grid is "Ext Conn". Enter "P" or "Par" in that column, and the load
will be connected in parallel with any other object on the same segment.
See "Load, Parallel Connected" in the EZNEC v. 5.0 manual for more
information.

Roy Lewallen, W7EL