Do It Yerself Firestik

So, I went to Walmart the other day. They sell fiberglass sticks for about tree fitty ($3.50). I also have a tub full of copper wire bits. If you know what to look for, it's not that expensive in case you don't have a butt ton of wires. So, I've made a homemade firestik, a four foot rod with 20g bell wire wound at one turn per 1-1/2 inch. Looks decent.

Next, I'm going to take an L match coupler and use it to find out what the input impedance of this rod is. Chances are, it won't be 50 +/- 0j ohms. That will let me know what kind of loading coil (resonator) to make. I imagine that I'll still need a match network to match the shortened antenna to 50 ohms.

If all of this works well, I can make a mount on my wood lathe, then use some scrap pieces to make a mount for my truck rail. The only other thing I might need to buy is some coax cable for running it to the radio. I say that like I won't need cable anyway. So, I'm going to use this and see how it works as compared to commercial antennas.

All of this is still less efficient than a 102 inch whip (I figure a 104 inch whip would be slightly better) but we all have to work in some restraints.

The Ed

 

I have some on one of these devices. Give me a minute and I'll see what I can do.

 

You can see it before and after I wrapped it with tape. I am going to make a base insulator out of hardwood on a lathe and attach it with some marine epoxy.

It may need a base loading coil. The first thing I'll likely do is use an L match tuner to figure out what the radiation resistance looks like.

The Ed

 

A straight wire 48 inches long is a quarter wavelength at roughly 59 MHz. The spiraled wire will lower that a little but not enough for 27.2 MHz. I'm going to have to work on finding a feed point impedance and then I'll make a loading coil for the base.

The Ed

 

Here's what I plan to do for this.

I assume you know what an L match network is. Hams use it to tune antennas on frequencies they're not resonant to make them more effective. I'm going to finish mine and then tune the whip antenna to match 50 ohms.

Since there is only one setting on this type of tuner for a given load, I can use the settings to find what the resistance and capacitance of the antenna is. Let's say, for argument's sake, I have 30 ohms - j200 ohms.

First, I need to make a loading coil for the base that is +j200 ohms. At frequency, I get 1.17 microhenries. That's not a lot of inductance and can be made with wire or tubing.

Now, I have an antenna with a base impedance of 30 ohms. The next step is to make another l match for matching 30 ohms to 50 ohms. That will be as easy as duplicating what I get on the l matcher with permanent components.