Can you measure again with the cover on? I was doing some reading, and the length of the antenna may need to be shortened by 5% to account for the cover effect.
Not that the original antenna had the correct length to begin with. This is for the modified version I’m working on.
OK, I will do that and post results.
Currently the antenna is tuned at 1615 Mhz instead of 1090 Mhz, a deviation of 148%. Even if placing cap brings it down by 5%, it will still be far off the desired 1090 MHz
Just curious to see how much difference, if any, the cap makes.
So i’ve tested the linked the antenna this thread was originally about for a couple of days and i have the impression it’s worse than my cantenna.
@aigochamaloh Do you have a cantenna or similar to compare the antenna?
I really can’t believe it’s better than the FA one.
Also if you don’t mind could you post a picture of both antennas to see how you mounted them?
Pictures showing the ‘new ground plane’ of the antenna being modified. Note the use of the SMA to MCX jumper that was included with the unmodified antenna.
More tomorrow, showing the antenna itself.
Pictures of the antenna and the complete assembly, henceforth referred to as the ‘contraption’.
After about 4 hours of work, and countless up and down a step ladder, plus up and down the stairs to the computer room, a brief report follows:
I built two antennas, one had a problem. This was good as I could see right away what a bad assembly looked like reception wise.
The antenna worked, but it took a lot of trimming. It does seem to be impacted by the cap/cover, since the best results were with a length shorter than the calculated one.
Performance differences were obvious right away. The ‘contraption’ is worse than the QuickSpider. It’s even worse than the little mag mount, trimmed to the correct length, when on top of the can/ground plane.
The FA antenna is still king. The QuickSpider is the next best. The ‘contraption’ has been ‘round filed’.
To paraphrase the great philosopher Homer Simpson in his Dialogues with Bart: “Son, you tried hard and you failed miserably. The moral of the story is: never try.”
I kept the ground plane in place, as it can be used in future experiments. Worst case scenario, as described above, it worked fine with the little mag mount.
P.S. FA robot, back off.
Try this
.
I’ll, but not today. Now that the blood and muscles cooled off, the only joint that does not hurt is the one between the skull and the ears.
I ‘ain’t’ a kid anymore.
Well, I have decided to open my “978MHz” antenna too…
The cylindrical tube is connected to the ground providing ground plane. It is 2-3/4" (70 mm) long.
Exposed part of the mini coax cable is 2-1/2" (64 mm) long, the other piece of wire is 6-3/4" (171.5 mm) long. I think that in between is just a solder joint.
Total length 235.5 mm. The 978MHz wave length is 306.5 mm, in 0.8 medium would be 245.3 mm.
Hmm, I thought that it needed to be lambda/2?
Here is inside of a conventional rubber-ducky.
1/4 WL long tube, 1/4 WL long whip.
It is actually a Coaxial Dipole
NOTE: Part of tube was cut and removed to show interior of the tube.
The Coaxial Dipole (Die Koaxialantenne)
Source: Antennenbuch by Karl Rothammel
Note: in this image, the translation in English in red was added by me.
If I cut the top whip, the remaining piece is as long as the ground tube - 2-3/4" (some 70 mm).
That might be actually good for 1/4 wave.
978MHz in air = 78 mm
1090MHz in air = 69 mm
Don’t know what’s that plastic speed factor. Assuming 0.8, means 62.5mm and 55.2mm.
Dont worry about plastic’s velocity factor, and use lengths for air. First try without plastic cover, then next with plastic cover. I dont think plastic cover is going to make much difference. General talk is only 5%, i.e. velocity factor 95%.
The “tuna fish can bottom” antenna
An excellent example of cutting edge technology. 
Seems the can was not opened by a tin-cutter / can-opener, rather hacked.
He/she likely used this:
Once you use one of those, you’ll never again waste money with an electric can-opener.
And it opens beer bottles as well.
Had a laptop die so been out of antenna testing for some time. 
But based on some of the stuff I’m seeing here it seems very few of these Ebay designs are suitable out of the box for the frequencies claimed. This, is my shocked face.
I do have a question about the printed board designs- are they directional ? Can’t imagine the reception pattern being very good edge-on.
If you use a smooth can opener, it won’t look like it wants to kill you:
https://www.amazon.com/Safe-Opener-GoodCook-11834-Rust-Resistant/dp/B000AX13US
I have a similar contraption, not that exact one, it is awesome for projects.
I had the first one. Did not last very long, and it leaves a dangerous edge on the can.
The second one looks promising, but at $22.50, I’ll pass.
The one I use, see picture above, has more than 50 years of history. It costs a buck or two, but it’s generally available only in third world countries. I can actually open a can faster with it than with the electrical contraptions.
This is one of those things where modern technology has no place. It’s like the anecdote about the million dollar pen prototype that worked in zero gravity. The Soviets used a pencil in space, problem solved.
Too much money and technology is bad for one’s IQ.
I got the second one for free, more than 15 years ago, when we hosted a Pamperedchef party. Doesn’t leave any edges… and still works.
Hey, I have one of those pens that write in space. And upside-down here on Earth gravity. Having flammable Carbon specs (graphite, wood) flying around in pure O atmosphere? Hard-core…
NASA never asked Paul C. Fisher to produce a pen. When the astronauts began to fly, like the Russians, they used pencils, but the leads sometimes broke and became a hazard by floating in the [capsule’s] atmosphere where there was no gravity. They could float into an eye or nose or cause a short in an electrical device. In addition, both the lead and the wood of the pencil could burn rapidly in the pure oxygen atmosphere. Paul Fisher realized the astronauts needed a safer and more dependable writing instrument, so in July 1965 he developed the pressurized ball pen, with its ink enclosed in a sealed, pressurized ink cartridge.
Fisher sent the first samples to Dr. Robert Gilruth, Director of the Houston Space Center. The pens were all metal except for the ink, which had a flash point above 200°C. The sample Space Pens were thoroughly tested by NASA. They passed all the tests and have been used ever since on all manned space flights, American and Russian. All research and development costs were paid by Paul Fisher. No development costs have ever been charged to the government. Because of the fire in Apollo 1, in which three Astronauts died, NASA required a writing instrument that would not burn in a 100% oxygen atmosphere.
This is my late Mom’s 3-in-1 opener: tin / cork / bottle … I remember using it during my childhood and teens
