I did a quick 2-4 MHz band scan on one of the Russian remote SDRs and the band was pretty quiet except for the very active frequency of 2130. At first I thought it was distorted AM but flipped over to FM (narrow FM, NBFM, NFM, narrowband FM...roughly 9.5 kHz bandwidth) and the voices came in nearly full quieting. I know secretsquirrel mentioned use of NBFM in addition to regular old AM and SSB for village radio...but this is the first time I've come across it.
Roundtable "net" like communications style, hearing lots of different voices chattering with each other, both OMs and YLs. Seems like pretty informal two-way communications. Some of the transmissions have a 1000Hz / 1kHz tone transmitted with the audio. I'm not sure if this is part of some weird selective calling system or simply an malfunction. Some of the transmitters have the tone, others don't. Several times, there was no voice traffic on the channel, but the tone was there. Almost like its serving as a "channel marker" (we know the Russians are fond of those...).
Never seen FM used in the 2 MHz band before. There's got to be at least 8-10 different stations chatting right now, some of them are weak and others are nearly full scale and full quieting. Anybody speak Russian? This is the SDR I'm listening to these stations on:
http://nsk.swl.su:8073/---
Also,
Does anybody know the history of Russian / Soviet military radio design development? I've stumbled upon some bits and pieces of information. For example, discussions of the Red Army using British and US gear in WWII under Lend-Lease, including the famous English W.S. 19 Wireless Set No. 19 with Cyrillic labels and the American BC-348 series of HF receivers with Cyrillic labelling (called the US-9 or YC-9 in Russia) but information on Russian made radios is a little harder to find (doesn't help that I don't speak Russian). There are some obvious nods to US, British, Australian and Italian tactical radio design in several Russian/Soviet bloc radios I've seen...for example the use of switches for 10 MHz, 1 MHz, 100 kHz, 10 kHz and 1 kHz steps for HF radios, and the use of 1 MHz steps, 100 kHz steps, and a 00/25/50/75 kHz switch for 30-76 MHz (or 20-70 MHz) FM tactical radios.
I know about their tank and mobile command radio equipment, mirroring the WWII and Korea-era US military frequency plan of 20-59 MHz, FM mode, often adding AM, USB and CW to FM capability. Of course, there's provision for MF/HF portable and mobile radios, and I found a Russian defense contractor's website advertising an aircraft radio that covers 30-174 MHz and 200-400 MHz AM/FM with various encryption and frequency hopping ECCM capabilities. Doesn't explain the use of FM on the 2-3 MHz band though!
There are lots of articles talking about Soviet-era
receivers covering the frequency range in question...but I can't find much of anything on transmitters and/or transceivers.