Compact DIY UHF Antenna Cheap and easy to build 9-10dbi - Canadian TV, Computing and Home Theatre Forums

 1Likes
  • 1 Post By ljhavener
 
LinkBack Thread Tools Search this Thread Display Modes

post #1 of 1 (permalink) Old 2018-05-18, 01:27 AM Thread Starter
Rookie
 
Join Date: Jan 2018
Location: Salida, CO
Posts: 27
Compact DIY UHF Antenna Cheap and easy to build 9-10dbi

The idea behind this antenna is to be cheap and easy to build. It is well within the ability of most DIYers. Made from readily available parts. Element is 1/2" copper tubing and 4-90 degree elbows, soldered together with 1/4" brass rod. Reflector can be 2x4" welded wire fencing. Another great reflector is the 16x20" metal rack from an oven. I realize that 1/2"(actually 5/8" outside diameter) tubing is overkill, but it is what you are going to find at your local home depot or Lowe's. Smaller diameter tubing can be used, but is harder to find, and usually more expensive. Element is mounted 5 1/4" from the reflector(measurements are center of the tubing to center of the reflector rods. You can use PVC, wood, or other insulating material to build the offset. The antenna has a null point in the center of the outermost horizontal tubing, that allows you to put a 1/4" bolt through this point straight down to the reflector. This provides a simple and very solid method of mounting the element at the proper offset. First picture is a version using a dog crate door as reflector and 1/4" bolts for the offset. Second picture is of a PVC offset from an oven rack. Both antennas use earlier designs of the element. They work, but are not as easy to build.







Element is made by cutting 1/2" copper tubing to form the outer rectangle. Measurements in diagram are to the center of the tubing. lengths of the tubing will depend on the brand of the elbows, that you purchase. Cut the tubing for the outer rectangle, but do not solder it, until you have all parts dry fit. Drill the three 1/4" holes, for the brass rods, through the copper tubing. Getting the holes all parallel is the hardest part of the build. If the holes are not lines up, the brass rods will not go through properly, and the element will not lay flat. I used a drill press and built a jig to hold the tubing in the proper place. Cut the two 1/4" brass rods, that form the upper and lower cross and wings, to a total length of 7 3/4". Slide them through the holes in the tubing, and adjust any holes that need it, to allow your element to lay flat. The gap between the two threaded rods, in the center is marked as 1 1/4". This is the actual location of the wires, for the 300/75ohm transformer(balun). Since you will need room for the inner brass nut, the actual gap between rods is 3/4". This makes the length of the two center rods/wings 4". I cut a rod at least 8" long, and dry fit it across both tubes. Once everything is dry fit and working, you can solder all of the joints, except the 8" center rod. Once everything else is soldered, you can slide the 8" rod out and thread 1/2" of each end of this rod. Then cut it into two 4" rods. Slide these rods in place, so that the wing is 1 3/4" from the end of the rod to the center of the copper tubing. The center rods can be made of pre-threaded rod, if you don't have the tools to thread the rod end. Then you can mount your element 5 1/4" back from the center of the element tubing. This can be done with a pvc or wood frame, or with two 1/4" bolts centered in the upper and lower tubing. Attach the transformer/balun, and you are done. Mounting the antenna can be done as part of the pvc offset frame, or by mounting to a mast mounted along the back of the reflector.

Antenna is a compact, easy and cheap build. Gain is between 9 and 10db across the UHF range. SWR and impedance is pretty good. Gain can be improved a bit if a larger reflector is used. Folding the top and bottom of the reflector, at a 45 degree, also helps. I've also modeled a slightly larger element, with only one wing, on each side, that gives great results for the repack. Let me know if you need anything explained more clearly.

Code:
CM QuadQuad antenna made from 1/2" copper tubing and 1/4" brass rod
CM Easy, cheap build using readily available parts
CM Reflector can be 2x4" welded wire fence.  Another option, that is cheaper, is the 16x20" rack out of an oven.
CM 
CE
SY Eradius=0.3125
SY E2radius=0.125
SY Wradius=0.125
SY Gradius1=0.0625
SY Gradius2=0.125
SY Sradius=0.0975	'AGT=1  non auto seg =0.0975
SY Dist_back=-5.25	'5.125
SY db=Dist_back
SY feed_gap=1.25
SY feed=feed_gap/2
SY rect_width=5.25	'5.125
SY rs=rect_width/2
SY z1=5.75	'5.75
SY z2delta=3.75
SY z2=z1+z2delta
SY wing_length=1.75	'1.75
SY wl=wing_length
SY wing_length2=1.25
SY wl2=wing_length2
SY grid_height=1.0
SY gz=grid_height
SY grid_width=8.0
SY gy=grid_width
SY scale=1.0
GW	1	1	0	-feed	0	0	feed	0	Sradius
GW	2	1	0	-feed	0	0	-rs*scale	0	Wradius
GW	3	1	0	feed	0	0	rs*scale	0	Wradius
GW	2	1	0	(-rs-wl)*scale	0	0	-rs*scale	0	Wradius
GW	3	1	0	(rs+wl)*scale	0	0	rs*scale	0	Wradius
GW	2	1	0	(-rs-wl2)*scale	z1*scale	0	-rs*scale	z1*scale	Wradius
GW	3	1	0	(rs+wl2)*scale	z1*scale	0	rs*scale	z1*scale	Wradius
GW	2	1	0	(-rs-wl2)*scale	-z1*scale	0	-rs*scale	-z1*scale	Wradius
GW	3	1	0	(rs+wl2)*scale	-z1*scale	0	rs*scale	-z1*scale	Wradius
GW	4	2	0	-rs*scale	0	0	-rs*scale	z1*scale	Eradius
GW	5	2	0	rs*scale	0	0	rs*scale	z1*scale	Eradius
GW	6	3	0	-rs*scale	z1*scale	0	rs*scale	z1*scale	E2radius
GW	7	2	0	-rs*scale	z1*scale	0	-rs*scale	z2*scale	Eradius
GW	8	2	0	rs*scale	z1*scale	0	rs*scale	z2*scale	Eradius
GW	9	3	0	-rs*scale	z2*scale	0	0	z2*scale	Eradius
GW	9	3	0	0	z2*scale	0	rs*scale	z2*scale	Eradius
GW	10	2	0	-rs*scale	0	0	-rs*scale	-z1*scale	Eradius
GW	11	2	0	rs*scale	0	0	rs*scale	-z1*scale	Eradius
GW	12	3	0	-rs*scale	-z1*scale	0	rs*scale	-z1*scale	E2radius
GW	13	2	0	-rs*scale	-z1*scale	0	-rs*scale	-z2*scale	Eradius
GW	14	2	0	rs*scale	-z1*scale	0	rs*scale	-z2*scale	Eradius
GW	151	3	0	-rs*scale	-z2*scale	0	0	-z2*scale	Eradius
GW	151	3	0	0	-z2*scale	0	rs*scale	-z2*scale	Eradius
GW	111	1	db	0*gy	0.5*gz	db	0*gy	-0.5*gz	Gradius2
GW	112	1	db	1*gy	0.5*gz	db	1*gy	-0.5*gz	Gradius2
GW	115	1	db	-1*gy	0.5*gz	db	-1*gy	-0.5*gz	Gradius2
GW	101	9	db	0*gy	0.5*gz	db	1*gy	0.5*gz	Gradius1
GW	105	9	db	0*gy	0.5*gz	db	-1*gy	0.5*gz	Gradius1
GW	111	1	db	0*gy	0.5*gz	db	0*gy	1.5*gz	Gradius2
GW	112	1	db	1*gy	0.5*gz	db	1*gy	1.5*gz	Gradius2
GW	115	1	db	-1*gy	0.5*gz	db	-1*gy	1.5*gz	Gradius2
GW	101	9	db	0*gy	1.5*gz	db	1*gy	1.5*gz	Gradius1
GW	105	9	db	0*gy	1.5*gz	db	-1*gy	1.5*gz	Gradius1
GW	111	1	db	0*gy	1.5*gz	db	0*gy	2.5*gz	Gradius2
GW	112	1	db	1*gy	1.5*gz	db	1*gy	2.5*gz	Gradius2
GW	115	1	db	-1*gy	1.5*gz	db	-1*gy	2.5*gz	Gradius2
GW	101	9	db	0*gy	2.5*gz	db	1*gy	2.5*gz	Gradius1
GW	105	9	db	0*gy	2.5*gz	db	-1*gy	2.5*gz	Gradius1
GW	111	1	db	0*gy	2.5*gz	db	0*gy	3.5*gz	Gradius2
GW	112	1	db	1*gy	2.5*gz	db	1*gy	3.5*gz	Gradius2
GW	115	1	db	-1*gy	2.5*gz	db	-1*gy	3.5*gz	Gradius2
GW	101	9	db	0*gy	3.5*gz	db	1*gy	3.5*gz	Gradius1
GW	105	9	db	0*gy	3.5*gz	db	-1*gy	3.5*gz	Gradius1
GW	111	1	db	0*gy	3.5*gz	db	0*gy	4.5*gz	Gradius2
GW	112	1	db	1*gy	3.5*gz	db	1*gy	4.5*gz	Gradius2
GW	115	1	db	-1*gy	3.5*gz	db	-1*gy	4.5*gz	Gradius2
GW	101	9	db	0*gy	4.5*gz	db	1*gy	4.5*gz	Gradius1
GW	105	9	db	0*gy	4.5*gz	db	-1*gy	4.5*gz	Gradius1
GW	111	1	db	0*gy	4.5*gz	db	0*gy	5.5*gz	Gradius2
GW	112	1	db	1*gy	4.5*gz	db	1*gy	5.5*gz	Gradius2
GW	115	1	db	-1*gy	4.5*gz	db	-1*gy	5.5*gz	Gradius2
GW	101	9	db	0*gy	5.5*gz	db	1*gy	5.5*gz	Gradius1
GW	105	9	db	0*gy	5.5*gz	db	-1*gy	5.5*gz	Gradius1
GW	111	1	db	0*gy	5.5*gz	db	0*gy	6.5*gz	Gradius2
GW	112	1	db	1*gy	5.5*gz	db	1*gy	6.5*gz	Gradius2
GW	115	1	db	-1*gy	5.5*gz	db	-1*gy	6.5*gz	Gradius2
GW	101	9	db	0*gy	6.5*gz	db	1*gy	6.5*gz	Gradius1
GW	105	9	db	0*gy	6.5*gz	db	-1*gy	6.5*gz	Gradius1
GW	111	1	db	0*gy	6.5*gz	db	0*gy	7.5*gz	Gradius2
GW	112	1	db	1*gy	6.5*gz	db	1*gy	7.5*gz	Gradius2
GW	115	1	db	-1*gy	6.5*gz	db	-1*gy	7.5*gz	Gradius2
GW	101	9	db	0*gy	7.5*gz	db	1*gy	7.5*gz	Gradius1
GW	105	9	db	0*gy	7.5*gz	db	-1*gy	7.5*gz	Gradius1
GW	111	1	db	0*gy	7.5*gz	db	0*gy	8.5*gz	Gradius2
GW	112	1	db	1*gy	7.5*gz	db	1*gy	8.5*gz	Gradius2
GW	115	1	db	-1*gy	7.5*gz	db	-1*gy	8.5*gz	Gradius2
GW	101	9	db	0*gy	8.5*gz	db	1*gy	8.5*gz	Gradius1
GW	105	9	db	0*gy	8.5*gz	db	-1*gy	8.5*gz	Gradius1
GW	111	1	db	0*gy	8.5*gz	db	0*gy	9.5*gz	Gradius2
GW	112	1	db	1*gy	8.5*gz	db	1*gy	9.5*gz	Gradius2
GW	115	1	db	-1*gy	8.5*gz	db	-1*gy	9.5*gz	Gradius2
GW	101	9	db	0*gy	9.5*gz	db	1*gy	9.5*gz	Gradius1
GW	105	9	db	0*gy	9.5*gz	db	-1*gy	9.5*gz	Gradius1
GW	111	1	db	0*gy	9.5*gz	db	0*gy	10.5*gz	Gradius2
GW	112	1	db	1*gy	9.5*gz	db	1*gy	10.5*gz	Gradius2
GW	115	1	db	-1*gy	9.5*gz	db	-1*gy	10.5*gz	Gradius2
GW	101	9	db	0*gy	10.5*gz	db	1*gy	10.5*gz	Gradius1
GW	105	9	db	0*gy	10.5*gz	db	-1*gy	10.5*gz	Gradius1
GW	111	1	db	0*gy	10.5*gz	db	0*gy	11*gz	Gradius2
GW	112	1	db	1*gy	10.5*gz	db	1*gy	11*gz	Gradius2
GW	115	1	db	-1*gy	10.5*gz	db	-1*gy	11*gz	Gradius2
GW	101	9	db	0*gy	11*gz	db	1*gy	11*gz	Gradius2
GW	105	9	db	0*gy	11*gz	db	-1*gy	11*gz	Gradius2
GW	101	9	db	0*gy	-0.5*gz	db	1*gy	-0.5*gz	Gradius1
GW	105	9	db	0*gy	-0.5*gz	db	-1*gy	-0.5*gz	Gradius1
GW	111	1	db	0*gy	-0.5*gz	db	0*gy	-1.5*gz	Gradius2
GW	112	1	db	1*gy	-0.5*gz	db	1*gy	-1.5*gz	Gradius2
GW	115	1	db	-1*gy	-0.5*gz	db	-1*gy	-1.5*gz	Gradius2
GW	101	9	db	0*gy	-1.5*gz	db	1*gy	-1.5*gz	Gradius1
GW	105	9	db	0*gy	-1.5*gz	db	-1*gy	-1.5*gz	Gradius1
GW	111	1	db	0*gy	-1.5*gz	db	0*gy	-2.5*gz	Gradius2
GW	112	1	db	1*gy	-1.5*gz	db	1*gy	-2.5*gz	Gradius2
GW	115	1	db	-1*gy	-1.5*gz	db	-1*gy	-2.5*gz	Gradius2
GW	101	9	db	0*gy	-2.5*gz	db	1*gy	-2.5*gz	Gradius1
GW	105	9	db	0*gy	-2.5*gz	db	-1*gy	-2.5*gz	Gradius1
GW	111	1	db	0*gy	-2.5*gz	db	0*gy	-3.5*gz	Gradius2
GW	112	1	db	1*gy	-2.5*gz	db	1*gy	-3.5*gz	Gradius2
GW	115	1	db	-1*gy	-2.5*gz	db	-1*gy	-3.5*gz	Gradius2
GW	101	9	db	0*gy	-3.5*gz	db	1*gy	-3.5*gz	Gradius1
GW	105	9	db	0*gy	-3.5*gz	db	-1*gy	-3.5*gz	Gradius1
GW	111	1	db	0*gy	-3.5*gz	db	0*gy	-4.5*gz	Gradius2
GW	112	1	db	1*gy	-3.5*gz	db	1*gy	-4.5*gz	Gradius2
GW	115	1	db	-1*gy	-3.5*gz	db	-1*gy	-4.5*gz	Gradius2
GW	101	9	db	0*gy	-4.5*gz	db	1*gy	-4.5*gz	Gradius1
GW	105	9	db	0*gy	-4.5*gz	db	-1*gy	-4.5*gz	Gradius1
GW	111	1	db	0*gy	-4.5*gz	db	0*gy	-5.5*gz	Gradius2
GW	112	1	db	1*gy	-4.5*gz	db	1*gy	-5.5*gz	Gradius2
GW	115	1	db	-1*gy	-4.5*gz	db	-1*gy	-5.5*gz	Gradius2
GW	101	9	db	0*gy	-5.5*gz	db	1*gy	-5.5*gz	Gradius1
GW	105	9	db	0*gy	-5.5*gz	db	-1*gy	-5.5*gz	Gradius1
GW	111	1	db	0*gy	-5.5*gz	db	0*gy	-6.5*gz	Gradius2
GW	112	1	db	1*gy	-5.5*gz	db	1*gy	-6.5*gz	Gradius2
GW	115	1	db	-1*gy	-5.5*gz	db	-1*gy	-6.5*gz	Gradius2
GW	101	9	db	0*gy	-6.5*gz	db	1*gy	-6.5*gz	Gradius1
GW	105	9	db	0*gy	-6.5*gz	db	-1*gy	-6.5*gz	Gradius1
GW	111	1	db	0*gy	-6.5*gz	db	0*gy	-7.5*gz	Gradius2
GW	112	1	db	1*gy	-6.5*gz	db	1*gy	-7.5*gz	Gradius2
GW	115	1	db	-1*gy	-6.5*gz	db	-1*gy	-7.5*gz	Gradius2
GW	101	9	db	0*gy	-7.5*gz	db	1*gy	-7.5*gz	Gradius1
GW	105	9	db	0*gy	-7.5*gz	db	-1*gy	-7.5*gz	Gradius1
GW	111	1	db	0*gy	-7.5*gz	db	0*gy	-8.5*gz	Gradius2
GW	112	1	db	1*gy	-7.5*gz	db	1*gy	-8.5*gz	Gradius2
GW	115	1	db	-1*gy	-7.5*gz	db	-1*gy	-8.5*gz	Gradius2
GW	101	9	db	0*gy	-8.5*gz	db	1*gy	-8.5*gz	Gradius1
GW	105	9	db	0*gy	-8.5*gz	db	-1*gy	-8.5*gz	Gradius1
GW	111	1	db	0*gy	-8.5*gz	db	0*gy	-9.5*gz	Gradius2
GW	112	1	db	1*gy	-8.5*gz	db	1*gy	-9.5*gz	Gradius2
GW	115	1	db	-1*gy	-8.5*gz	db	-1*gy	-9.5*gz	Gradius2
GW	101	9	db	0*gy	-9.5*gz	db	1*gy	-9.5*gz	Gradius1
GW	105	9	db	0*gy	-9.5*gz	db	-1*gy	-9.5*gz	Gradius1
GW	111	1	db	0*gy	-9.5*gz	db	0*gy	-10.5*gz	Gradius2
GW	112	1	db	1*gy	-9.5*gz	db	1*gy	-10.5*gz	Gradius2
GW	115	1	db	-1*gy	-9.5*gz	db	-1*gy	-10.5*gz	Gradius2
GW	101	9	db	0*gy	-10.5*gz	db	1*gy	-10.5*gz	Gradius1
GW	105	9	db	0*gy	-10.5*gz	db	-1*gy	-10.5*gz	Gradius1
GW	111	1	db	0*gy	-10.5*gz	db	0*gy	-11*gz	Gradius2
GW	112	1	db	1*gy	-10.5*gz	db	1*gy	-11*gz	Gradius2
GW	115	1	db	-1*gy	-10.5*gz	db	-1*gy	-11*gz	Gradius2
GW	101	9	db	0*gy	-11*gz	db	1*gy	-11*gz	Gradius2
GW	105	9	db	0*gy	-11*gz	db	-1*gy	-11*gz	Gradius2
GS	0	0	0.0254
GE	0
LD	5	0	0	0	58000000
GN	-1
EK
EX	0	1	1	0	1	0	0
FR	0	25	0	0	470	10
RP	0	1	73	1510	90	0	1	5	0	0
EN
Yurii Pylypenko likes this.
ljhavener is online now  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Canadian TV, Computing and Home Theatre Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome