[Towertalk] IS Boom length the HOLY GRAIL ?> More thoughts

[k0sd@juno.com]

   It is very evident from the notes below that someone has never had a
good working quad up.   I've only built about  a dozen or so, from 2
element boomless quads to 6 elements using a tri-gamma match on one
feedline.   The quad is a dream for working RTTY, especially when the
signal level is very low, and reads S0 (doesn't move the receiver S
meter).   The beam will be almost useless from the band or atmospheric
noise, the quad would give nearly a q5 copy.    It's like comparing a
dipole or vertical to a 4 square on 80 meters (yes, I totally built mine,
including phasing box), it's nothing unusual for the 4 square to be 20 db
quieter.  I still remember working my first 20m cw qso with a VU2 station
in about 1968 with a 3 el/band quad.   He wasn't moving the S meter, but
we had a nice 10 minute qso.
    If you've lived in South Dakota (and other states where horizontal
snow at 60 mph goes on for days at a time sometimes), the yagi will be
about S9 to S9+ 20 with snow static, the quad S0.    Same way with rain. 
 Don't ask me to give you the physics of it, I just know it from 35 years
of antenna experience.   For a simple antenna on a roof mount or in
restricted space, a 2 el boomless quad does wonders.   The big drawback
is the amount of maintaince to keep them going.   That's why I have a
TH11 up now, but am thinking of putting another 2 el boomless quad up low
for high angle close-in stuff and low noise for rtty.
   My gut feeling is that the manufactures site mentioned that started
this all off is starting myth's themselves about quads and the yagi's
they sell.   I've had 2 100 ft sticks of 25g up for many years, and have
played with many antennas.   The TH7 vs TH11 gain on the low end of 10
meters is very evident when you have them both up like this.   I hadn't
heard about the low-end roll-off on 10m on the TH7 when I had them on the
two tower for comparison with the A/B switch, but it was very  noticeable
on 10 cw (I mostly operate below 28025 on cw).  
   Yes, I've experimented with and built lot of yagi's also, 20 m 6
element, 15m, 10m, 40m KLM with 30m loaded elements from Cushcraft 40m
beam interlaced, 12/17 5 element yagi before the first commercial ones
were out, and the list could go on.   Still have lot of pieces of
aluminum and wire, want to do more experimenting when time allows.   I
may even get another tower up on the mountain top now at the new qth.   A
hundred ft of 25g gives me a 500 ft HAAT, run 7/8ths Heliax to most
everything..   It's nice working simplex FM and repeaters with 25 watts
on 2m at 100-125 miles at will.

73's de Stephen, K0SD in NC

*************************************

On Sat, 16 Nov 2002 18:06:14 -0600 n4kg@juno.com writes:
> On Sat, 16 Nov 2002 "Bill Wall" <billwall@eyecon-solutions.com> 
> writes:
> > Hi Jon;
> > Consider the full wave Quad has about 1.8 db more gain than a 1/2 
> > wave Yagi.
> 
> 	HUH?  The stacking gain for two *straight* half wave 
> elements
> 	spaced 1/4 WL (the spacing of a square loop) is 1.0 dB
> 	as shown in the ARRL Antenna Book.  Turn the ends towards
> 	each other and the gain drops a little ( to 0.84 dB per W2PV 
> ).   
> 
> 	The old studies by W7?? comparing Quads and Yagi's
> 	were performed at 440 MHz where Yagi DE matching
> 	is pretty lossy, accounting for most if not all of the 
> measured
> 	difference.  Quagi's are very popular and effective on VHF,
> 	utilizing a Quad DE and Reflector with multiple Yagi 
> Directors.
> 	VE3BMV made them famous on HF with his Razor Beams.
> 	N4KG
> 
> > The Quad is quieter on receive and does not hear rain static. 
> 
> 	HOW does a Quad receive less radiated atmospheric
> 	noise than a Yagi (especially if it has *higher?* gain?
> 	The rain static argument 'seems' to be true.   N4KG
> 
> > The efficiency  of the average 3 el Quad is in the 90% + category. 
> 
> 
> 	Maybe.  What is your SOURCE for this information?
> 
> The 3 el Yagi is  about 50%. Put 1000 watts on the Quad and you have
> apprx. 900 watts. Put 1000 watts on the same Yagi and you have aprrx 
> 500
> watts out. The power  is lost  in resistive heat.
> 
> 	Where did you find this falacy?  
> 	Can you QUANTIFY the element resistance of a Yagi?
> 	...and for a Quad?
> 	N4KG
> 
> > A few years ago Lew Mccoy W1ICP published an article in CQ 
> magazine 
> > about this. 
> 
> 	With all due respect, what are Lew's relevant 
> qualifications,
> 	and educational background?  N4KG
> 
> Boom length is gain, but there are other things that are more
> > important like, takeoff angle, frontal lobe pattern and so forth.
> 
> 	Take off angles below 30 degrees are SOLELY a function 
> 	of antenna height for Horizontally Polarized Antennas and 
> 	has NOTHING to do with TYPE of antenna.  Pattern and Gain 
> 	are closely related.  Gain *is* a (non-linear) function of 
> boom
> 	length as stated.   N4KG
> 
> 	That said, I believe the 2L Quad is a VERY GOOD
> 	antenna that is fairly easy to tune. My 2L 40M Delta Loop '
> 	was a KILLER antenna.
> 
> 	More than 2 Quad elements gets very tricky to tune properly
> 	and *early* modeling software was not very accurate. Multi-
> 	element multi-band Quads get REALLY tricky to tune (IMHO).
> 	N4KG
> 
> >         Bill Wall KC4UZ  Antenna Mart 
> 	(Manufacturer of STURDY Quad Antennas)
> 
> 
> 
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