I'm just starter.
I bought MFJ-1622 40-2M APARTMENT ANTENNA (I don't have access to the roof)
I only have RTL-SDR with Upconverter (I'm on budget).
I living on 10th floor and I will use it from my balcony.
Can I listen something with dongle without tuning this antenna?
Yes. Tuners can help with receiving with an antenna of an otherwise unsuitable length, but it is absolutely worth trying without them.
Here's a useful rule: Watch the spectrum and unplug the antenna. If this causes the visible signal level all across the spectrum to go down, then you had plenty of signal from the antenna and there is no need to improve it.
If it did not go down very much, then you'll get better reception by improving your antenna system — whether by an antenna of a different length, a tuner, a LNA, or another means.
Maybe RTL-SDR run from battery. Because of computer PSU ? Any suggestion for battery ? I need 5 V ? Any suggestion for accumulator (I will buy it later)
DO NOT wire a separate 5 V supply, whether battery or otherwise, into your USB connection unless you are willing to risk damaging the USB port/motherboard you plug it into by back-feeding power to it.
The minimum safe way to do this is to use a USB hub which accepts external power. The more-isolating way is to use a USB isolator to separate the power connections completely. USB isolators are unusual and therefore expensive equipment, however.
Another option is to get a computer that does not produce significant noise. Different models can vary widely.
You can power your Rtl-Sdr from a battery in addition to the power supplied by the computer. In some case it is even necessary: I have a Rtl-Sdr with an E4000 tuner that doesn't work when only powered by my Raspberry Pi 1. It needs more power than what the raspberry can supply.
For this, I use a Y-USB-cable, like the one you find on some external hard drives. On one side you put your Rtl-Sdr, on the other side there are 2 USB connectors, one for the data that you connect to the PC and an additional power-only connector you can connect to a USB power source. In my case a 12V lead battery with a 5V linear regulator when I power my raspberry from a battery, a simple phone charger otherwise.
In this setup, it will still take some power from the computer. I don't know if you can remove the +5V line from the data connector to only power from the other source. For the regulator, a dc-dc regulator might give longer battery life (nice for solar powered stuff like my Rtl-Sdr project), but a linear one will be less noisy as this is your main concern.
Maybe just use a good quality USB cable with good shielding and a ferrite core. I effectively get USB noise on my Rtl-Sdr, but it seems to come mainly from the data transfer, not the power supply.
