Silver Ink Antenna Part 2
We discovered we could make a working antenna with our Circuit Scribe conductive ink and were curious to see how it stacked up against other designs. So, we tested it against a few DIY and commercially available antennas.
We compared five different antennas: two using conductive ink, one with copper tape, an RCA Amplified Flat Indoor , and the Mohu Releaf. To make your own antenna, check out our article from last week.
Each antenna was placed in the same spot and facing the same direction for ten minutes. We ran the channel scan, recorded the number of channels, and looked through them to roughly determine the quality of the received signal. We also tested the durability of each antenna and the resistance of the traces for the DIY fractal designs.
Ideally, we would be testing the S11 and the SNR, but that would require more equipment. The S11 is the amount of loss across a range of frequencies measured in decibels. When using an antenna as a transmitter you send a signal through the antenna and it radiates out of the antenna at different frequencies. If your antenna has high loss at a specific frequency the antenna is radiating the signal out of the antenna, for a more in depth explanation you can check out Antenna Theory. Since different channels are on different frequencies this would show the best channels that the antenna could receive. S11 is very useful when comparing antennas over wide ranges of frequencies.
(Picture of network analyzer data)
We could also use a signal analyzer to directly measure the signal to noise ratio, or SNR, at each channel. The SNR measures the strength of a signal at specific frequencies so we could directly compare the signal strength of channels received by each antenna.
Conductive Silver Ink
First, is Circuit Scribe’s conductive ink fractal antenna design on paper. The total cost for this antenna is 15 dollars and takes just under ten minutes to draw. To make the antenna more durable, we put ours in a toaster oven at 180 degrees Fahrenheit for 15 minutes. This lowered the resistance and kept the tape from peeling off the ink. The traces had 0.5 – 0.8 ohms of resistance.
The second antenna we tested was the copper tape version of the fractal design. This antenna was made using the same pdf as the conductive ink antenna. First, we cut copper tape into quarter inch strips and placed them along the black lines so that they were covered completely and made sure to overlapped each corner to ensure a good connection. Resistance values were relatively high compared to the conductive ink antenna, measuring between 5 and 12 ohms. The higher resistance is due to the glue on the bottom of the copper tape pieces. When making corners you have to overlap the copper tape which increases the resistance. A week later we tested the resistances again and found that they had drastically increased.
During long term projects the glue can dry out causing the resistance to jump. The type of tape is very important if you want projects that last. HEZE makes a good version that has lasted for two weeks with only one issue. For a work around you could put a bit of solder over the joints to reduce the resistance.
We ended up making two of these to double check the resistance. The first was tricky to put together and took about 45 minutes. It was easier the second time and only took about 30 minutes. It takes patience to making sure the copper tape is lined up exactly verses filling in the lines with a pen.
The third antenna was made with Circuit Scribe’s CS Pro conductive pen on Plexiglas. It has the same fractal pattern but is twice the size of the original design. We measured the dimensions of the original fractal pattern and doubled them. Then using painters’ tape and a star shaped stencil we drew the traces with a CS Pro pen. This is one of our new products that lets you control how much ink you can use at one time. By squeezing the pen, we were able to draw on the Plexiglas. Each CS Pro pen comes with 3 times the ink of a normal Circuit Scribe pen. After finishing the design, we used a heat gun, a hair dryer works just as well, to dry the ink and lower the resistance of the traces. Since Plexiglas melts at 160 degrees Fahrenheit we DO NOT recommend putting this in the oven. Another safe way to lower the resistance of the traces is to put the antenna in a hot car and leave it in direct sunlight for a few hours. This was the most expensive DIY antenna coming in at 30 dollars. It took 30 minutes to make and another 30 minutes to seal. The traces had a resistance of between 3 and 5 ohms.
RCA Amplified Flat Indoor
The fourth antenna we tested was the RCA amplified flat indoor antenna, a 35-dollar antenna from Home Depot. The antenna is made of copper plated ridged fiberglass with some components soldered to the board.
It originally had a black plastic housing, but we removed it to get a look at the inside. It also came with a signal booster that plugs into a wall outlet. We tested it with and without the booster.
The fifth and final antenna we tested was the Mohu Releaf. It comes fully assembled for a price of 38 dollars. It’s made of one sheet of cardboard and one sheet of recycled plastic with a thin metal antenna sandwiched between them. It also has a circular plastic housing to hold coaxial connector in place and has a TV matching transformer inside. Since it’s cardboard it is not completely rigid, but much more durable than the single sheets of paper we used for the conductive ink and copper tape antennas.
Each of the antennas were simple to place on the window and worked right away. Starting with the least number of channels received was the RCA antenna. We were only able to pick up 38 channels with it. Even with the signal booster it received the fewest number of channels. The antenna that received the second fewest number of channels was the larger plexiglass antenna. We received 47 channels with this one. The greatest number of channels received was a three way tie at 52. The Circuit Scribe conductive ink on paper, copper tape on paper, and the Releaf antennas. The reception on the received channels was similar as well. After two weeks the antennas were tested again and we found that the copper tape antenna had poorer reception quality in the high VHF band, most likely caused by the larger uneven resistance across the traces. The only other difference in performance came when we jostled the antennas to see how the signal was affected. The Releaf was slightly more stable than the conductive ink antenna while the copper tape antenna’s signal was affected the most when touched.
Since we were able to receive the same number of channels for each of the paper antennas and the Releaf, the differences come down to cost, aesthetics and durability. The two paper antennas are cheaper to make and have less impact on the environment since they use the fewest materials. While the Releaf is more durable, it is less noticeable with its cardboard design.
Purchasing the Mohu Releaf is a fine product and suited for someone looking for a quick antenna solution without a DIY experience. Overall, the Circuit Scribe conductive ink antenna is the superior DIY HDTV antenna. It is cheap, a unique paper design, and you get to build yourself!