7
An antenna can't "amplify" a signal, it can only concentrate it in certain directions. If you want a peak gain of 15 dB (about 30x the power density of an isotropic radiator), you can only get it over a very small portion of the sphere (about 3% or less).
When we talk about "omnidirectional" antennas, usually we mean that the antenna ...
4
There are a couple of options.
If your phone supports WiFi calling and your provider allows it, I strongly recommend getting WiFi in the shack if you don’t have it already. If you don’t have it, and that’s because you’re remote, get a LTE<->WiFi router with SMA connectors and an appropriate antenna.
If you can’t use this solution you can buy cell phone ...
4
A quick simulation with NEC2 indicates that scaling the wire lengths and the inductance by a factor of 0.5 will give the results you seek.
As for why a smaller, loaded monopole gives better results than a full-sized monopole, that is a mystery.
4
Similar to optics or a water tank, waves passing through a finite aperture will produce a diffraction pattern.
To over-simplify: In the far field, the difference between the distance to the left and right side of a dipole's aperture will depend on the angle from the main beam. That difference can produce a constructive or a destructive interference, again ...
2
Both an end-fed and a small loop antenna might couple into the house wiring on transmit. You might be able to orient a mag loop to minimize RF noise pickup from the house environment on receive.
As an alternative, I might consider testing a balanced fan dipole for Tx. For a receive antenna, another possibility might be a large loop around the entire attic, ...
1
F connectors are stupid simple to install, the ones I've seen are screw on and you're done. SMA is not going to be that easy.
I've seen solder on SMA, and crimp on SMA might exist, but both require some skill and tools. I've seen screw on BNC, but they require specific cable with a solid center conductor. Very likely your existing coax has a multi-strand ...
1
Here is an easy way to visualize what's going on with those pesky side lobes.
We take the case of a centerfed resonant dipole with a wire a little longer than the dipole mounted behind it by some fraction of a wavelength. That wire is intended to reflect the output of the dipole in the "back" direction (by absorbing and immediately re-radiating it) ...
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