When building a yagi...

[Erik71]

How do you know whether or not to make the boom conductive or non-conductive? Would like to build one for 800-900MHz. This Yagi Calculator is great, BTW. Thanks for any help.

 

[k9wkj]

make it conductive
its alot easier to build that way
may have to make the elements a bit shorter

 

[prcguy]

The boom can be conductive or non conductive. The elements can attach and ground to the conductive boom or not. In each case the element lengths will be a little different.

 

[Ubbe]

The middle of the reflecting and directing elements are "cold" and doesn't really matter to the function of the antenna, but the extra metal added from a metal boom will make a slight difference and will be bigger the thicker the boom are as it will begin to interfere more with the active part of the elements.

/Ubbe

 

[Erik71]

I was going to use copper TIG welding rods and maybe 1/2" pvc for the boom. Coax loop balun (?) I've used the rods a few times to make ground planes with SO-239s.

 

[prcguy]

You might use a coax loop balun (50-200) ohm if you were going to tap each element of a grounded dipole driven element up some ways from center, or to feed a folded dipole. For an insulated center fed dipole you could just feed the elements at the center then use a choke balun made of ferrite.

I was going to use copper TIG welding rods and maybe 1/2" pvc for the boom. Coax loop balun (?) I've used the rods a few times to make ground planes with SO-239s.

 

[Erik71]

Thanks for the input, everyone. Much appreciated

 

[iMONITOR]

How do you know whether or not to make the boom conductive or non-conductive? Would like to build one for 800-900MHz. This Yagi Calculator is great, BTW. Thanks for any help.

Please update us how it performs and post some pics when completed!

 

[Erik71]

Sorry BTW. I should've looked a little closer at where to post this.

 

[KB4MSZ]

I have built a number of Yagi antennas for the VHF/UHF bands, including air traffic control, FM broadcast and military bands. Welding rods make great elements, especially brass or stainless in the 1/16" to 1/8" range. The stainless rods can be a bear to cut but they make a very stout antenna. They are inexpensive and easy to solder if you decide to go with small diameter rigid copper tubing for a boom. This allows soldering the elements to the boom once everything is in place. To solder stainless, first tin the center area of the element (wide enough to extend beyond the boom on each side) by rolling it in a bath of soldering iron tip cleaner while applying heat and solder with the iron. Be sure to wear eye protection as the cleaner can spit at you when it boils. Because stainless holds heat for a long time (and also takes a month of Sundays to cool off), wipe off any excess from the rod as soon as it is tinned. This will keep it's outside diameter close to it's original size and allow inserting it into close fitting holes in the boom. Now the stainless can be soldered to copper easily by simply reheating the pre-tinned area. The driven element can be insulated as it passes through the boom (allowing direct feed) or it can be soldered in one piece as the other elements are. One piece, or "plumber's delight" construction will require a gamma match feed system to tap the driver on one side. An advantage of this is a fully 100% DC grounded antenna.

I also have a collection of SO-239 connector ground plane antennas. One of them has 2mm bullet connectors on 4 places around the flange and one soldered vertical to the center conductor. This allows a selection of different sized "sets" of elements (with male connectors) to be attached as required, and then allows the assembly to be taken apart and packaged in a PVC tube which I keep behind the seat of my truck.

If you enjoy experimenting in VHF frequencies using Yagi antennas, I have a design I use that allows me to change frequency bands, driver arrangements, spacing and tuning very quickly. It takes some time and effort to build a set of driver assemblies but once they exist the sky is the limit for experimentation. Here is the link:

https://forums.radioreference.com/threads/multi-use-driver-assembly.382607/

 

[Erik71]

Very cool! I also use the bullet connectors. Makes construction so much easier (--when I started I tried to solder everything lol)
For as long as I've been in the monitoring hobby (late 80s ) I've always loved building/experimenting with antennas. Kinda like making fishing lures lol. Thanks for the info. Much appreciated!

 

[Erik71]

Threw this little guy together today. Until I get the yagi done... A wee ground-plane egg... (S0-239, copper TIG welding rods, crimp-on wire connectors, and 1" PVC end caps) Weather's just too nice here today to not spend the day hanging off a ladder lol

 

[WB9YBM]

How do you know whether or not to make the boom conductive or non-conductive? Would like to build one for 800-900MHz. This Yagi Calculator is great, BTW. Thanks for any help.

I remember hearing that the dimensions do change a bit, but unfortunately I haven't been able to find any formula that would help with figuring out those changes...

 

[jhooten]

For an easy to build, cheap yagi with non-conductive boom:
http://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf

 

[Erik71]

Okay, so trying to get holes STRAIGHT through a piece of 1/2" round PVC (so all the elements are on the same plane) without a drill press is a pain lol. Gonna start over with some square aluminum tubing of some sort and just mount everything to one nice, flat side lol. Antenna Engineer I aint!

 

[Ubbe]

You could use this online calculator to see the difference between isolated and non-isolated boom.
Yagi Uda Antenna (Rothammel)

/Ubbe

 

[WB9YBM]

Okay, so trying to get holes STRAIGHT through a piece of 1/2" round PVC (so all the elements are on the same plane) without a drill press is a pain lol. Gonna start over with some square aluminum tubing of some sort and just mount everything to one nice, flat side lol. Antenna Engineer I aint!

About the PVC---if memory serves I think I might have heard someone say that PVC doesn't do well outdoors 'cause of UV from sunlight...just a heads-up...

 

[mancow]

Okay, so trying to get holes STRAIGHT through a piece of 1/2" round PVC (so all the elements are on the same plane) without a drill press is a pain lol. Gonna start over with some square aluminum tubing of some sort and just mount everything to one nice, flat side lol. Antenna Engineer I aint!

Go to harbor freight and look for a doweling jig.

 

[SDRPlayer]

Go to harbor freight and look for a doweling jig.

Great advice! Saved me a heap of trouble and i use it around the house too. Only about $20 here.

 

[Erik71]

Go to harbor freight and look for a doweling jig.

Went right on the list. Thanks.