"Wes" wrote in message
oups.com...
On Feb 5, 7:59 am, "Yuri Blanarovich" wrote:
"Wes" wrote in message

ups.com...

On Feb 4, 2:35 pm, "Yuri Blanarovich" wrote:
[snip]

Tony,
by using hairpin matching, you take out portion of the highest current
on
the element and fold it into the hairpin where it is taken out of
antenna
"participation" for the price of match.

You're kidding right?

Disclosu I use a hairpin (beta) match on my HB Yagi.

In that case I must be :-)

Can you elaborate why would I be kidding?

As far as I know:

If you use hair pin inserted in the middle of the element, you get the
shorter physical length of the element - smaller high current carrying
length.

I believe that your first problem is that you are considering the
hairpin (Beta) to be part of the radiator instead of considering the
actual case; it's part of the matching network.


Do you have to shorten the (driven) element if you insert the hairpin in the
middle or not (to maintain the resonant frequency)? Telrex 40m Yagis did use
hairpins at the center of the element as a loading and shortening the
element length. To me that is the matching network too, but at the expenses
of shortening the element length - center loading, similar to base loading
the resonant quarter wave vertical.


Half wave resonant element has maximum current in the center, by folding
portion of that element into a hair pin we take that portion "out of the
picture". Just like a loading coil at the base of the vertical - current
drop along the coil.

op cit. I'm not "folding a portion of the element." If you subscribe
to the idea that part of the antenna can be "folded into" the feeder
and that by selecting the right feeder length you can "lengthen the
antenna" (as shown in a lot of old ARRL literature) then I have a new
limited space antenna for you. It's a one foot long radiator with a
variable length feeder (a la Cecil) that "makes up" the missing
antenna length.


You fold the portion of the element, it's called loading, at the base, in
the middle or anywhere along the element length. The folded hairpin has
inductance, just like a coil, and can be replaced with the coil of similar
inductance. The loading element is not the limited space antenna, look at
the currents at its ends and see the difference in curent distribution along
it and how it participates in the overall radiator current distribution and
corresponding area under the cosine curve representative of the efficiency.
We are back to the loading coil "problem" and that's why we pointed out the
efect and its impact on the antenna performance.


Hairpin is usually folded back on the boom, 90 deg. to radiator, with any
current left, not participating in the plane of the elements.

If I placed a discrete (lumped element) L-network at the feedpoint the
current in it would not be "participating" either.


Not much, but help with cleaner pattern.


Hairpin loading stubs were proven to be worse loading elements than good
quality coils.

When, where, by whom, etc? Oh, BTW, did I mention "THE HAIRPIN IS NOT
A LOADING ELEMENT. It's the inductance in an LC L-network.


Here we go again? We are talking about standing wave circuit - antenna
radiator or element. So inductance is not a loading element? As far as I
know inductance (coil, hairpin) or capacitance (top hat, L, T loading) are
used as a loading elements to shorten the physical length of the antenna
element, while maintaining electrical length.
There was an article by W6?? in CQ and other examples when they replaced
hairpin loading on Yagi elements with coils and got significant improvement
in the performance of KLM 3 el 80 Yagi, better gain, much better pattern due
to less interference of the folded back hairpin with the element.
Measurements and modeling before and after showed that.


pointas
mentioned before.

Why? The hairpin will handle all the power an amateur can supply, it
can (does in my case) form an integral balun and it DC grounds the
element.


No argument here, you can do that with coil and gain some edge.

We might be splitting hairs here, but I hate to lose even fraction of dB
if
there is a better way.

No gain is lost. I can model my Yagi with and without the Beta,
resonating the antenna without it by lengthening the element and the
gain remains the same within 0.01 dB.


No gain lost would be 0.0000 dB :-)


I know Beta match works, I used it in some antennas (don't like Gamma
matches), even made a QSO with a ligthbulb as an antenna. It's all
relative.
Contesters like to chase every fraction of a dB lost, soon they can add
up
to some noticeable real dBs.

I've been a moonbouncer, I know all about fractions of a dB.

Then you should appreciate the above.

73 Yuri, K3BU