user37403: I searched for very long range wireless communications between two Arduinos, but can't find solutions. I don't live in USA, In my country there are regions, where GSM does not work.
I want wireless communication approximately 500-1 000 KMs.
What are options without GSM for that distance wireless communication(500-1000 KM)?

user30005: 
What are options without GSM for that distance wireless communication(500-1000 KM)?

1) use the internet;
2) use narrow band transmission, like qrp;
3) use relays;
4) use satellite phones;
5) use a high-powered lw transceivers.
6) ...

user-1: Back in the old days, we used things called modems to connect computers across POTS. 

Your country may not have GMS, but I bet you still have old land lines. In that case, you can use a land line + modem to connect the arduinos directly , no Internet involved, no ISP needed, no overhead, no lag, nothing. It's just one Arduino at each end of a very long cable. No TCP/IP needed, but you need your own protocol to keep data in sync and filter out errors. There is lot of well proven ones from the golden era of BBS.
I search Aliexpress, I didn't find any modem suitable for direct conection with Arduino, but there is a lot of USB modem like this:

I don't know if they can work with Arduino. I'm afraid that they are win-modem only.
What it really works with anything is a traditional modem, like this model from Multitech (not an endorsing):

You will need a RS-232 level converter however, because RS-232's voltages can go up to 25V. The converter avoids you to deal with the peculiarities of the RS-232 standard and DB-9 connector.

And a cable, of course. 
You can develop and test your project using a null modem cable, to connect both Arduinos, a few meters apart, without need of a land line.

37403: <p>I searched for very long range wireless communications between two Arduinos, but can't find solutions. I don't live in USA, In my country there are regions, where GSM does not work.
I want wireless communication approximately 500-1 000 KMs.
What are options without GSM for that distance wireless communication(500-1000 KM)?</p>
 30005: <blockquote>
  <p>What are options without GSM for that distance wireless communication(500-1000 KM)?</p>
</blockquote>

<p>1) use the internet;</p>

<p>2) use narrow band transmission, like qrp;</p>

<p>3) use relays;</p>

<p>4) use satellite phones;</p>

<p>5) use a high-powered lw transceivers.</p>

<p>6) ...</p>
 -1: <p>Back in the old days, we used things called modems to connect computers across POTS. </p>

<p><a href="https://i.stack.imgur.com/HILmV.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/HILmV.jpg" alt="old modems"></a></p>

<p>Your country may not have GMS, but I bet you still have old land lines. In that case, you can use a land line + modem to connect the arduinos directly , no Internet involved, no ISP needed, no overhead, no lag, nothing. It's just one Arduino at each end of a very long cable. No TCP/IP needed, but you need your own protocol to keep data in sync and filter out errors. There is lot of well proven ones from the golden era of BBS.</p>

<p>I search Aliexpress, I didn't find any modem suitable for direct conection with Arduino, but there is a lot of USB modem like this:</p>

<p><a href="https://i.stack.imgur.com/Q5LtI.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Q5LtI.jpg" alt="USB Modem"></a></p>

<p>I don't know if they can work with Arduino. I'm afraid that they are <em>win-modem</em> only.</p>

<p>What it really works with anything is a traditional modem, like this <a href="https://www.multitech.com/brands/multimodem-zba" rel="nofollow noreferrer">model</a> from Multitech (not an endorsing):</p>

<p><a href="https://i.stack.imgur.com/twd2u.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/twd2u.png" alt="Multitech modem"></a></p>

<p>You will need a RS-232 level converter however, because RS-232's voltages can go up to 25V. The converter avoids you to deal with the peculiarities of the RS-232 standard and DB-9 connector.</p>

<p><a href="https://i.stack.imgur.com/0ZDHQ.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/0ZDHQ.jpg" alt="RS232-TTL level converter"></a></p>

<p>And a cable, of course. </p>

<p>You can develop and test your project using a <em>null modem</em> cable, to connect both Arduinos, a few meters apart, without need of a land line.</p>
