[NLRS] (LONG) yagi newbie questions

Wed Feb 28 14:26:13 EST 2024

'Afternoon, Aaron.

The "Cheap Yagis" are a good place to start for building antennas for UHF.  The only
"warning" I can give (and I do it for everyone) is 'Follow the directions !"  Don't try to
"improve" the design by, say, using metal booms, a 2X4 as a boom to make it stronger, 1/2"
Al tubing for elements, or a driven element OTHER than the one shown.  None of those will
work.  Build it to specs and it will work very well.

There are two "issues" with the .pdf you were referred to:  1) it is implied, but not
stated, that the elements go THRU the (center-line) of the boom with the exception of the
driven element.  Take look at the drawings for any of the antennas' driven element.  Also
the photo "Driven Element Detail."  2) Most of the tables for spacing and lengths of the
elements have "spacing" problem:  One or more of the rows are "off-set by one position.
In an row, the '0' should be in the 'Ref' column.

ALL of the rows in all of the tables should look like this:  (1296 antenna shown)
                           Ref      DE     D1  - - - -
Length              4.3                  3.9  - - - -
Position             0          1.7    2.8  - - - -

ONLY the 144 and 900 antennas have tables with the connect alignment.

As to your questions:  1) gluing the elements, etc.  See comment above.  Also, see the
4th paragraph of the introduction.  (The 1/2 x 3/4" wood referenced is called "parting
stop" - used in double-hung windows, and available in good hardware stores.  3/4 x 3/4 is
also called 1 x 1" best found at places like Home Depot (or a real lumber yard).
2) Zip ties.  They are used to provide stress-relief for the feedline coming off the
driven element.  In the picture, the coax is at the BACK END of the boom... all of the
elements (except the reflector) are to left of the driven element.  3) Yes, you need some
sort of cable connector at the end of the pig-tail.  Uptown 1296 you can get away with
SO-238/PL-259 connectors.  'N' connectors are certainly acceptable also.  (Don't use crimp
UNLESS you have the correct dies for your crimp tool... you cannot make good crimp
connections with pliers !

Also:
a) The  boom needs to be long enough BEHIND the Reflector to provide space to mount the
antenna to a mast, etc.  Do not attempt to run a mast, etc., up "into" the antenna.  If
you will be using the antenna (any frequency) for FM, you would be best off using the 3/4
x 3/4 boom, which will give you a larger flat area to put on a plate for "U-bolts" when
mounting the antenna for vertical polarization.
b) For mostly outdoor usage (actually, its just good practice in any case) mark and drill
all the holes needed and then put at least one coat of good spar varnish (outdoor varnish)
on the boom, including IN the mounting holes. Two coats is better.  Don't forget the flat
"U-bolt" plate.
c) I would NOT RECOMMEND using RG-58... period.  RG-8X is a better choice.
d) One last comment:  The length of the pig-tail (and the feed line in general) depends on
long they need to be to get from the radio to the antenna.  I would recommend that
anything over 15' or so use something like LMR-400, especially at 900 and 1296.
Actually, I would recommend LMR-400 for ANY length and use the RG-8 only for a 2-3'
pigtail.  And add more strain relief to pig-tail; support the LMR-400 on the mounting
plate or mast near the antenna.

Be more than happy to discuss with you here or at the next Breakfast (either in Maplewood
or Maple Grove).  Good luck.

73 Donn
WA2VOI/0

----- Original Message ----- 
From: "Aaron David Lewis" <W0ADL at outlook.com>
To: <nlrs at mailman.qth.net>
Sent: Wednesday, February 28, 2024 5:32 PM
Subject: [NLRS] yagi newbie questions

> Greetings.  I'm looking to get on the air from my QTH on 440, 900, and 1200.  I've been
> pointed to https://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf to make my own.  I'm a total
> newbie and I understand about 90% of this but I wish it were more explicit.  It says to
> glue the elements to the boom.  This sounds flimsy.  There's no mention of drilling
> holes into the boom which would seem better, but I don't know.  At the bottom I'm not
> really understanding the zip ties. I do have scrap RG-58.  should I keep this pigtail
> short and crimp/solder it to an n socket? Does anyone have photos? I admit I could do
> more googling.  Does anyone have surplus antennas they might want to sell?  Thank you.
>
> Aaron David Lewis
> W0ADL ◊ EN35hc
>
>

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