[Towertalk] IS Boom length the HOLY GRAIL ?

[n4kg@juno.com]

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)



________________________________________________________________
Sign Up for Juno Platinum Internet Access Today
Only $9.95 per month!
Visit www.juno.com