Building Prototype Arrow Antenna – Part I

While searching on the internet for good plans to build this type of antenna, thete were problems with finding the correc element lengths and spacing. Most sites are using cm and mm measurments which may or may not come out correctly. A ham known as Kent Britian (WA5VJB), came up eith tables containing element lengths and spacing in inches. I used the 144 MHz and the 435 MHz AMSAT measurements. The antenna that I build is an 8 element UHF and 4 element VHF arrow.

http://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf

http://www.wa5vjb.com/references/Cheap%20Antennas-LEOs.pdf

Below is an approximate list of materials. You can use what materials you need to make this light weight.

Materials:

Approximately 30′ – 3/16″ diameter coated steel rods or aluminum tubing or aluminum rods – will be cut into sections.

Approximately 10′ – 3/4″ diameter PVC pipe – will be cut shorter in size

2x – 3/4″ diameter end caps for PVC pipe

A microdiplexer from combining antennas to one coax

Tools:

Phillips Screwdriver
Drill Press
Dremel
Hacksaw
Drill
Drill bits

In order to build this antenna it is best to start off with building the UHF section first. The driver element is the most critical and will need to be as close to 13″ in length.

Length for elements:

Reflector = 13.40″
Driver =13.0″
Director 1 = 12.40″
Director 2 = 12.0″
Director 3 = 12.0″
Director 4 = 12.0″
Director 5 = 12.0″
Director 6 = 11.10″

Spacing for elements:

Reflector = 0.0″
Driver = 2.5″
Director 1 = 5.5″
Director 2 = 11.25″
Director 3 = 17.5″
Director 4 = 24″
Director 5 = 30.5″
Director 6 = 37.75″

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Attempt to Arrow type Satellite Antenna

I decided that since I have not worked ham radio satellites in quite some time and have never used a real satellite antenna, that I would build a prototype Arrow antenna. I want to thank Dave (KE5HBB) and Jason (N4JTC) for the help and encouragement in building this project. Below is what the antenna looks like after the build. I will be posting the instructions that I used in the next post.

I used a hair pin / JPole style director section which seemed to be the easiest to build, so far. Below are the tuning sections that will be used to tune the frequencies. I want to try gamma matched next time. In the picture you will see a little board, which I need to mount, this is a home made diplexer to take both 2M and 440 antennas and bring them together into one coax for use with a radio with one coax connector.

UHF Tuning Section:

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VHF tuning section:

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Below you can see the bright pink tape on the tips. This is for protection from people getting hurt or furniture getting poked. I did have wire nuts in place but I was told that the ones I used may have been throwing the SWR off on both bands.

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I need to tune both 2M and 440 for the satellite sub bands in order to transmit to and receive the satellite signals as they come over the horizon. With the help of Dave, we did some testing on 2M simplex to his home QTH (about 30 miles), at ground level and I did hear him. Also I tested with the 147.380 repeater in medical area of town and had it loud. The 440 side did not go as well as I could not hear Dave on simplex but I did key up his 440 repeater.

***In the next section, make sure you slow down and check your connections as I found with my prototype that I had the VHF and UHF coaxes switched on the board. ***

In order to bring both antennas together to a single coax, I built this prototype diplexer to make it happen. This will allow you a listen on one band and transmit out on another. For example if a satellite is using a downlink in the 440 band and an uplink in the 2M band, this board will allow me to transmit on 2M and listen to the response on 440 without needing two radios.

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The inbound coax will be from a single dualband radio (HT) which will be split into two bands, 145 (VHF) and 437 (UHF).

– The UHF side of the diplexer has 2 x 4.7 pf Capacitors and 1 x 1 1/2 turn coil. Both caps come together and connect in the middle along with one end the coil. The other end of the coil will go to ground.

– The VHF side of the diplexer has 1 x 10pf Capacitor and 2 x 3 turns coils. Both coils come together in the middle along with one end of the cap. The other end of the cap with go to ground.

– The open end of the last 4.7pf capacitor and the 3 turn coil will connect to the center of their respective band coax. The 4.7pf capacitor will connect to the 435MHz coax while the 3 turn coil will connect to the center of the 145MHz Coax.

– Make sure that each coax is connected to the proper driver element of the antenna as there are two different bands.

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