Quarter Wave Dual Band VHF/UHF Ham Radio Antenna by Asni Nor Rizwan

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Introduction: Quarter Wave Dual Band VHF/UHF Ham Radio Antenna by Asni Nor Rizwan

A Simple & Cheap Dual band antenna will save you having two different antennas for UHF and VHF

Step 1: Step 1

You will need copper or brass welding rod cut to
3 X 19.5"  length, a bit longer, eg 20" is OK if you have a SWR meter and want to cut it to tune it
3 X 6.5"    length, a bit longer eg  7" is OK if you have a SWR meter and want to cut it to tune it

-You Will Also need
-Normal SO-239  4 holes chassis mount connector
-Solder & Soldering Iron
-6 X Electrical Eyelets
-4 sets of screws, nuts and washers
-2 X  6 inch black nylon cable ties
-Silicon Sealant
-RG-8 cable with PL-259 plug. For lightweight RG-58 cable, you need an appropriate adapter, eg.  PL-259 to BNC female
-SWR meter for testing

Step 2:

Adjust the electrical eyelets wire grip so that it can fit the end of the copper rod

Step 3:

Fit snugly the end of the copper rod to the adjusted electrical eyelet.
Solder it to improve the contact but make sure you sandpapered it until shining  and swab the copper and metal eyelet with methyl spirit by to clean it from grease.

Step 4:

-Repeat until the 6 rods have been fitted with eyelets.
-Then, solder all the eyelets to the copper rods.
-See the SO-239 socket on the right

Step 5:

-Take the SO-239 chassis mount connector and clamp it to a vice.
-Test fit one 6.5 " and 19.5" copper rod, putting it at the center contact of the SO-239 and bend  it  at the eyelets to form and angle of    
 approximately 60 degrees apart forming a V.
-By any means, hold the two 60 degrees angled rod so the V shape stay in place temporarily.
-Carefully solder generously the two angled rod and do not move the solder point while the solder hardened. A good soldering work
 will shine like silver and not dull.

Step 6:

We have  2 X 19.5"  and 2 X 6.5" radial rods not yet attached. 
Arrange the radial rods, making sure the 19.5" VHF rod  is in between the 2 X 19.5"  radial rods and the 6.5"  UHF rod  is in between the 2 X 6" radial rods
Attach the 4 radial rods with screws and nuts, putting in washers in between. Before tightening the screws, align the 4 radial rods so that they are 45 degrees of each other horizontally

Step 7:

-Attach the antenna assembly in a 1" diameter heavy duty  PVC pipe. The length depends on your planned setup.
-The SO-239 will not be  tight fit but you can think of a way to do it. One option is holding it using a thick, black cable tie and threading  
 it through 2 holes drilled at opposite sides of the PVC pipe.
-Carefully angled the 4 radial rods 45 degree vertically
-Connect a RG8 cable  with a PL-259 connector. Use an adapter if you want to connect to a RG59 cable.
-Test using a SWR meter, making sure the SWR readings is between 1  to 1.5 . Testing procedure will be in the next step.
-You can cut the rod end little by little, about 1/8" at a time to adjust the SWR but too much it will be unadjustable

Step 8: SWR Testing Procedures

VHF Tuning
-To tune the antenna to my country, Malaysia amateur VHF band 144-148 Mhz, I set the radio frequency to the center frequency of 146  
  Mhz so it can generally covers the whole VHF amateur band.
-Connect a SWR meter to the antenna and to the radio, making sure  you attached it to the right connector posts
-Take a SWR reading, and if it is beyond 1.5, cut the 19.5" VHF element rod 1/8" at a time until the readings is in between 1-1.5. -
-Theoretically , a reading of 1 is the best but rarely achieved. If you try to achieve it, you may cut a bit too much until the antenna is
 unadjustable and you have to replace the elements to a longer one, back to square one :-)

UHF Tuning
- The amateur UHF band of Malaysia  (ITU Region 3) is 430-440 Mhz set the radio frequency to the center frequency of 435 Mhz 
  so it can generally covers the whole VHF amateur band.
- Repeat the VHF tuning procedures but this time you must cut the 6.5" UHF element rod 1/8" at a time.

Step 9: Weatherproofing

-Tie the rods with black cable ties and cover the soldering point with silicone sealant for weatherproofing.
-Happy transmitting !
-73 from 9W2WDX  Asni  ( QTH: Bandar Baru Bangi,Malaysia)
-View my other activities at think2bgood.blogspot.com and kakipedal.blogspot.com

Step 10: My Other Project

Dont miss the opportunity to see my other exciting video on hardware coding for small kids at https://youtu.be/yCF2LiYm1WA

Epilog Challenge V

Participated in the
Epilog Challenge V

3 People Made This Project!

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19 Comments

0
vu2eaf
vu2eaf

Tip 3 months ago

VERY NICE IDEA

0
willisaefudin1960
willisaefudin1960

5 months ago

best job for 2 meter antena , must be tray

0
TomC257
TomC257

5 years ago

There is no need for the 6.5" elements, unless you have a UHF SWR
meter and want to spend a lot of time installing the antenna, measuring
SWR, taking it down, trimming the elements, re-installing the antenna,
measuring SWR, taking it back down, trimming the elements again, etc.,
etc. until you get it set for one precise frequency.

The
common version of this antenna uses all 19.5" elements -- ONE up and
four down -- is easier to build, gives dual band performance at least as
good as this more complicated version, and a significantly smoother
omnidirectional radiation pattern.

Hams should know that a quarter-wave element for 2m VHF will also work as a three-quarter-wave element on 70cm UHF.

0
aboy.
aboy.

Reply 2 years ago

LOL.
no need to spend alot of time for tuning, i just can do that not more than 5mnt,
just place the antenna around 2meter from ground and it will be good for tuning.
swr meter is mandatory for every HAM radio, without that u cant homebrew or do antenna installation.

0
TomC257
TomC257

Reply 1 year ago

And how many hams do you suppose have an SWR meter that works at UHF?

0
eflester
eflester

Reply 1 year ago

Of course... the same way that a 40m dipole works on 15m. Sheesh....

0
eflester
eflester

1 year ago

I made this antenna but decided to go cheap and not buy any welding rod. I had some 12 gauge solid wire, which stays fairly rigid in these lengths. It works OK, and takes power well with no adjustment to length on both 2m and 70cm. The resulting antenna is a little fragile, though, and I'm sure it would be better the way you did it, but it was fun to make it out of stuff I already had. Thinking about coat hanger wire...

0
RichardE51
RichardE51

5 years ago

This is the antenna I built as a Novice, (KA9WXT), back in 1983 and I placed the antenna in the attic. I am proud to say it is still in the attic and performing quite well. I also have one in my 'GO BOX' along with my two SLINKIES.

0
asni73
asni73

Reply 5 years ago

3/32 inch, but Neo commented below he used a larger diameter, maybe 1/4 inch and hammered the end flat and drill holes for the screws

0
idefix01
idefix01

5 years ago

someone mentioned that silicon becomes conductive at high frquencies

did your swr change after you added the silicon?

may i suggest hot glue?

0
asni73
asni73

Reply 5 years ago

Tqvm for the suggestion

0
pmcquain
pmcquain

8 years ago

Great write-up! Would this antenna work well in a "stealth" installation, about 18 feet up in my attic? Thanks! Pete

0
asni73
asni73

Reply 8 years ago on Introduction

Yes you can, that is what I did, but make it as far as possible from electrical runs and any metal pieces at the roof. I actually hanged it from a rope thrown over a roof beam ! Attic installation can also protect from lighting strike.

0
neo71665
neo71665

8 years ago

I hammered the ends of the copper rod flat and drilled holes when I made mine. One less connection point to worry about.

0
asni73
asni73

Reply 8 years ago on Introduction

Tq Neo, is the hammered end has enough space for the screw holes and does it weakened the hammered part or the rod ? Or maybe you use a larger diameter rods because the one I use is only 3/32 inch diameter

0
neo71665
neo71665

Reply 8 years ago on Introduction

Cold working metals actually work harden them. It can make it more brittle but being copper and pretty soft it doesn't hurt it. I think I used 1/4 inch but don't remember.

0
asni73
asni73

Reply 8 years ago on Introduction

Tq neo, I have updated the instructions to be more helpful.