My Arrow-Style VHF/UHF Portable Satellite Antenna
By: Bertrand Zauhar, VE2ZAZ / VA2IW
Last update: 16/02/2024

One of the pleasure of working the amateur radio satellites is making contacts in a portable application and with QRP power. This requires a VHF/UHF handheld FM radio and a handheld 2-band antenna.

After browsing the various Internet antenna construction sites in search for the best portable satellite antenna for the V/U and U/V modes, I figured I could build something good. So I decided to combine the best ideas of a few existing designs and add my own twist to it. This gave my own "Arrow-Style" VHF/UHF antenna. My sources of inspiration were:

• Homebrew Satellite Antenna, G6LVB
• Cheap Yagi Antennas for VHF/UHF, WA5VJB
• The Microduplexer, KI0AG

• I use a 3/4-inch CPVC plastic pipe as the boom, as opposed to wood,
• I use 1/8-inch brass rods for the elements; they are commonly available in hardware stores and are stiffer than aluminium rods or copper wiring of the same diameter,
  
• I feed the driven elements with the "semi-folded dipole" approach, which simplify mechanical construction and impedance matching,
  
• I fit a Microduplexer inside the boom,
• I use RG-174 coaxial cable,
• I conceal the coaxial cable inside the boom,
• I make the VHF elements easily disassembled, which makes the antenna much smaller for travelling or storage purposes.

Boom Drilling Technique
Care must be used when drilling element holes on a circular boom. I found it almost impossible to drill element holes that would yield elements that are parallel and in the same plane, without using some form of guidance and reference. My trick for getting parallel elements is to first screw down the boom at both ends against a narrow wooden plank or board, and to use a vertical drill press to make the holes.

VHF Driven Element Fastening
Since the boom has only a 7/8-inch outside diameter, I added another short piece of pipe to support the folded portion of the VHF Driven element. I used 2 self-tapping screws to fasted the piece of pipe to the boom. (see picture below).

UHF Driven Element Fastening
The UHF Driven element has a gap of only 1/2-inch, so bending the feedpoint end of the folded section to create a 1/4 inch gap is manageable and allows to support the element without adding another short piece of pipe like for the VHF Driven element.

Element lengthening
If, like me, the only length of brass rod available to you is 36 inches, you will need to lengthen each of the VHF elements by splicing two brass rods together. A good way to do this is by filing off half of the rod thickness for about 1/2 of an inch long at each end with a grinder. Then, position the two ends one against the other and solder the two rods together using a gas torch or a powerful soldering gun. The end result is illustrated below.

VHF Feedpoint Connection
The feedpoint connection to the VHF Driven element is done in such a way that it can be disconnected if the antenna is to be disassembled for travelling, which will be the case for most situations. I use DIP integrated circuit socket pins for the mating. You need a DIP socket of the machined type, the kind that has barrel contacts. Using a sharp knife, cut the plastic to detatch 4 pins from their socket. Solder two pins with their barrel end facing the coaxial cable. Solder two pins to the coaxial cable with the pin ends facing the driven element. This is a temporary but effective connection.Connect the coaxial center conductor to the folded section end and the shield to the long section.See the picture below. Other means of connecting can be used.

UHF Feedpoint Connection
Since I don't intend to disassemble the UHF section, the feedpoint connection for the UHF Driven element is more straightforward. I simply split the coaxial center conductor and shield. Again, I solder the coaxial center conductor to the folded section end and the shield to the long section.

 
Microduplexer
Since most handheld dual-band radios have a single antenna connector (VHF and UHF signals are combined), you will need an antenna duplexer. A commercial duplexer will work fine, but is quite heavy. Remember that you will have to point this antenna by hand for 15-minute satellite passes. Because of this, I elected to build the Microduplexer. I have the capability to make my own PCBs, so I tried to obtain the original layout from the author. It appears that the final layout in a ready-to-make form is no longer available. So I re-imported the Autocad DXF file, re-worked the proposed layout, filled the islands, etc. The final Microduplexer board layout is available below. Printing the PDF file with 100% scaling will give accurate results. I also provide a Gerber file for those who would like to have the PCB professionally made. Note that in order to fit the Microduplexer PCB inside the CPVC boom, I had to file off a bit of both long edges of the PCB. I did this before installing the components.

Microduplexer_Board_Layout

Microduplexer_Board_Gerber

Coaxial Cable Runs
I run the coaxial cables inside the boom. I drill holes at an angle, close to the feedpoints, where I bring out the coax (see pictures). The Microduplexer is located inside the boom, within the handle portion. this is where the three coaxial cables converge. I bring out the transceiver feedline at the back of the handle.

• I installed plastic caps on the element tips to save my eyes and my furniture...
• I Installed 7/8-inch vinyl endcaps on the boom. Looks neat... I punctured a hole through the rear endcap to bring out the transceiver feedline.
• I do not fasten the elements to the boom in any way. The elements fit quite tightly when drilling the boom with a 1/8-inch drill bit. Some hot melt glue, choc nut, set screw or clips could be used if you are worried about exact positioning...