Hello @zegor_mjol,
With both the information from @Joey_van_der_Gaag and myself, see if you can work through the antenna selection guide from Telco Antennas at https://www.telcoantennas.com.au/site/what-antenna-do-i-need, although it is primarily written for Australia, the fundamentals are the same for anywhere in the world.
You will need to run at least two additional antenna cables (Minimum LMR400 or LCU400 cable).
Use with s suitable high gain antenna setup using antennas like these:
or
or two(2) of
(These antennas can be found here at https://www.telcoantennas.com.au/site/catalog/all-antennas/list-frequency/700mhz
As you have a MAX Transit DUO, you will then need to feed the two antenna feeds into a suitably frequency match RF splitter, this is immediately going to halve your RF signal strength.
Connect your MX Transit DUO using short RF 50Ohm patch leads.
Only use 50Ohm RF Cable and 50Ohm RF splitters, not TV or Consumer Satellite cable or splitters which are 75 Ohm.
I would also highly recommend that you add lightening protection to the antenna feeds, lightening at over 400 meters (1/4 of a mile) can still produces enough energy to damage equipment connected to external antennas. https://www.telcoantennas.com.au/site/catalog/surge-protection
There are partners here (including myself) that can put together all of this as a kit for you to self install if you like. Shipping from Australia can be expensive and take some time, so best to source locally where you are.
Happy to Help,
Marcus 