antenna

How To DIY A Cantenna For Your WiFi Network

If you are interested in extending the range of your wifi network, and don’t mind a little construction, here are plans for building a 2.4 gHz high gain antenna for wireless networks. (A.K.A. Cantenna). With the use of one of these cantennas, I have been able to connect to my wireless access point a half a mile away! (they were pretty ideal conditions, but more on that later..) And I probably could have gone farther, but I wasn’t too keen on hiking through the woods with tall weeds, and uneven terrain balancing my laptop with one hand, and pointing one of these cantennas with the other hand. In this post I will show you how to DIY a Cantenna for your Wifi network.

Here is a photo of the finished wifi cantenna:

Typically my approach to projects is that they need to be inexpensive, but they also need to use readily available materials. this project is no different. Please excuse me while I slip into “geek mode” for a minute.

This type of antenna is what is called a waveguide. There are several parameters. The two most significant ones are called the cut off frequency of the TM 01 mode and the cutoff frequency of the TE 11 mode. Basically these two parameters define the highest and lowest frequency that the cantenna can operate.

My problem was that I was having a hard time finding some sort of tube that was readily available. The closest thing I could find was a 4 inch aluminum dryer vent tube. This, according to waveguide calculations, was too big in diameter, and causes the upper cut off frequency to be too low. However, in messing around with many antennas through the years, I have realized that although antenna theories help us design antennas, sometimes it is an inexact science.

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How To Build A 2 Meter Antenna For Bicycle Mobile

Perhaps the biggest problem with taking your HT bicycling is coming up with a decent antenna on your bicycle. This is because the bike doesn’t provide much of a ground plane. I found an article in the ARRL’s Hints and Kinks written by Charlie Lofgren , W6JJZ, titled “The Bike ‘n Hike Special”. Below are the plans for the antenna for bicycle mobile he described in the article.

This antenna is a 1/2 wave vertical dipole made out of RG-58/U coax. The beauty of this design is that it is cheap, simple, and easy to make with readily available materials. The radiator should be 39 inches long for 2 meter operation. What I use for the radiator, is the center conductor of the RG-58/U coax. I start out with a 12 foot piece of coax. Then there is enough left so it can be run up to the radio. I keep my radio in my handlebar bag.

First measure how long the radiator is to be, then trim off the outer sheath, and shield. Next, on the other end of the coax, I cut off a piece of coax that is going to be the shorting stub. The proper length is dependent on the velocity factor of the coax used (see table below). In all cases, I always make the lengths to the long side. This way the antenna can be trimmed in to the desired frequency with a SWR bridge.

Short the center conductor to the shield of the coax at point C

The dimensions for the matching section are dependent on the velocity factor of the coax used.

Dimension	Vel. Factor 0.66	Vel. Factor 0.80
A to B	11.25 in	13.5 in.
B to C	1.63 in.	2.0 in.

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How To Build a HDTV Antenna With These Plans

Since my TV antenna was damaged by an ice storm, I needed to build an HDTV antenna. While searching, I found some HDTV antenna builds that used coat hangers. Being 70 miles away from the HDTV stations, I definitely need my HDTV antenna to be outdoors. Coat hangers rust, and end up with bad connections which makes your HDTV antenna useless over time. In this post, I will show you how to build a HDTV antenna.

Additionally, the HDTV antenna builds I have seen don’t seem to have the long range that I need, such as the DB4. So I have come up with a modified version that works well in HDTV fringe areas. The photo on the left is my HDTV antenna that I built. I have also seen where people will take two HDTV DB4 antennas and gang them and then use a splitter / combiner to feed the HDTV antennas. Although this seems to work, my thinking is that adding a second antenna typically yields 3 db of gain. However a splitter / combiner has a 3 db insertion loss. Which is spelled out on the splitter’s package. It seems to me that you are losing what you have gained in ganging two DB4 antennas. My HDTV antenna build eliminates the need to use a splitter / combiner.

Its surprising the number of people that think that in order to get HDTV stations, you have to have cable. This is not true, as TV stations still transmit their signal in what is called Over the air – OTA. So if you live within say, 70 miles of a TV station, you might be able to receive HDTV over the air too, and eliminate your cable bill.

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Build An Indoor FM Antenna With These Plans

The easiest way to improve your FM reception is to build an indoor FM antenna, instead of using your FM stereo’s internal FM antenna. This indoor FM antenna is easy to build, and cheap. It works every bit as good as other FM antennas that you can buy for as much as $100.

In order to build this indoor FM antenna, all you need is two 3/8” dowel rods 48” long, 10 ft. of 20 ga. wire, and some 75 ohm RG-59 or RG-6 coax (for TV’s). All of this can be picked up at your local hardware store. However sometimes hardware stores don’t have dowel rods 48”. If you can’t find any that long, you can always take two 36” dowel rods and tie them together with cable ties to the correct length.

This FM antenna is what is called a Full Wave Loop antenna. The diagram below shows the design of this indoor FM antenna:

The red is the wire, which is to be 30” on each side. The brown represents the 3/8 inch dowel rods. Also notice that the coax is fed from the side. This is not necessary, as typically full wave loops are fed from the bottom. I was interested in receiving one particular station that transmits a vertically polarized signal. Almost all FM stations transmit circularly polarized, which is both vertical, and horizontal polarization. Also feeding the Fm antenna from the side seemed to be a stronger, more reliable means of connecting the coax to the FM antenna.

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How To Construct a J-Pole Antenna for the 70cm Ham Band

Here is an inexpensive J-pole antenna that is easy to construct. In about an hours time, and about $10 worth of materials, you can have a great performing omnidirectional j-pole antenna. This antenna is based on the same ideas as my 2 Meter J-Pole construction plans. The j-pole antenna is basically an end fed half wave dipole that uses a 1/4 wave shorted matching stub as an impedance transformer. The j-pole antenna will yield slightly less than 3 DB of gain omnidirectionally.

The material I chose to build the j-pole antenna was 1/2 inch copper pipe used for plumbing. Here are the plans:

The above dimensions for the J-pole are in inches, and aren’t typical for a 440 mHz. J-pole antenna. This is what it took for me to get the SWR low. Measurements on overall length, and stub length are from the centerline of the separation pipe (horizontal) to the top of the antenna. The Connect at measurement is 1 1/2 inches from the top of the horizontal member to the point of connection. The distance between the main element of the j-pole centerline and the tuning stub centerline is 0.75″.

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Programming Your Radio For The ISS Crossband Repeater With Chirp

As of September 2, 2020, the new FM ISS Crossband repeater on board the International Space Station is activated. This is great news as it has been quite a while since anything significant has happened with Ham radio on board the ISS. Early reports indicate that the receiver is quite sensitive and can be used with just an handheld such as a Baofeng.

If you have never done any space communications via ham radio, there are some things to get acquainted with. The most important one is Doppler Shift. This can be a bit tricky. What is happening is that as ISS is moving and transmitting, you have to have to adjust your receive/downlink frequency. It is the same phenomenon as a passing train blowing its whistle, and you hear the tone of the whistle drop as it passes by you. In the case of the ISS, what you have to do is to listen a little bit higher when it is coming at you. As it is more overhead, you will hear it become noisy in your receiver. Just tune down 5 kHz, and you wil hear it. As the ISS moves away from you, you will have to tune down another 5 kHz.

The new crossband repeater on the ISS has an uplink frequency of 145.990 mHz and a downlink frequency of 437.800 mHz. In order to access the crossband repeater, it requires a 67 Hz tone on your radio. Also this is an FM repeater.

The best way to handle doppler is to pre-program the frequencies into your radio. I use the Chirp program. Its free and open source. This is what I use for my Yaesu FT-857D as well as my various handhelds like my Baofeng radios. You can download Chirp here if you don’t already have it.

Below is a screenshot of a portion of my chirp file for my FT-857. I have programmed 5 channels for the ISS Crossband Repeater. This allows me to easily adjust for doppler as things get quite busy when working the ISS Crossband repeater.

Programming your radio for the ISS crossband repeater with Chirp

Some items to note, I gave each channel a specific name. Obviously it starts with ISS so I know what satellite I am dealing with. In addition I also added RP for Repeater. The reason for this is that there are other ham radio rigs on board the ISS such as APRS and I didn’t want to get confused. Additionally I added a lower case letter at the end.

So at the beginning of the ISS pass, I start out on the channel labeled ISS RPa and listen. Sometimes on a low pass I will toggle between ISS RPa and ISS RPb since the affect of Doppler isn’t as pronounced on a low pass as it is on a more overhead pass.

Speaking of listening, its best to run your radio unsquelched. In the past I have missed passes of other satellites because I had my radio squelched. Even though unsquelched can be annoying, it does give you the best chance for success in working the ISS crossband repeater.

Once your radio is programmed, the next problem is knowing when the ISS is visible. There are several satellite tracking programs available for download. Being a Linux guy, I use gpredict. Its free and open source. There are other windows and MAC based satellite tracking programs as well. Doing a google search and you will find several for whatever computer you are using.

Another option if you don’t want to download and install software is to use N2YO’s Satellite page for the ISS. There are also apps for android and iPhone to tracking satellites as well.

One thing I do when working the ISS crossband repeater is record the pass. This helps with logging as it is very fast paced and its quite easy to mis-write a call.

Hope to catch you on the ISS repeater someday!

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