On Apr 9, 2:08 am, Owen Duffy wrote:
K7ITM wrote :

...

Yes, EZNEC has some nice features. I exercised a couple of them
tonight, doing frequency sweeps with inductive and capacitive
matching. I did cheat: since I do not know the dimensions of the
hairpin match, I elected to just use a pure lumped inductance. I
suppose the error compared with a transmission line stub (hairpin)
won't be great. I also used for the first time ASCII file import for

It probably isn't.

However, you could get an idea from my Two Wire Line Loss Calculator
(http://www.vk1od.net/tl/twllc.htm). It looks like a hairpin made of 4mm
dia aluminium 50mm spacing and 150mm in length give an impedance of 0.02
+j61... so the Q is probably mainly determined by the end connections.

a o/c stub made of 4mm dia aluminium 50mm spacing and 1300mm in length
give an impedance of 0.07-j80... so, it is not quite as good
electrically, it is unweildly and end connection resistance will probably
still be significant. This is no doubt why people use a hairpin in
preference to an o/c stub!

Owen

Thanks, Owen. Actually, the error I was thinking of was not the Q,
since both a good hairpin and a good helical coil will have Qu's very
much higher than the loaded Q of the matching network -- but rather of
the slope of reactance versus frequency, since the hairpin is a
transmission line and will presumably show a sharp resonance at a
different frequency from the coil's self resonance. But that error
should also be small--negligible as Wim notes.

Cheers,
Tom