Engineering Radio – Page 70 – One Hundred percent Human Generated Content for your Reading Enjoyment

Troposcatter communication system

I found this interesting article on the inter-tubes the other day and thought that I would share it. It is about a disused site from the Soviet era Troposcatter communication system called “SEVER.” There are many more pictures of equipment including MUX, transmitters, antennas, buildings, etc, at that link.

Soviet SEVER troposcatter communications antenna, courtesy ralphmirebs.livejournal.com

Like many of its counterparts in the US, this system has quite a bit of information available, including an interesting blog and associated web site which has lots of interesting information. Some of it is in Russian, which mine is a little bit rusty, but here is what I could find out:

This is site 6/60, call sign Poloska and is located in Amderma, Nenets Autonomous okrug. That is way up north along the Barents Sea. This site was in use from about 1965 until 2001 when it was closed down. It communicated with site 5/60, which was 264 km away.

Amderma map with SEVER 6/60 location, courtesy of trrlsever.org

Troposcatter was used widely before satellites came into availability. It used decimeter wavelengths (approximately 2 GHz) and lots of power with very high gain antennas. Basically, the earth and the troposphere were used as reflectors, creating a type of duct. It is noted the SEVER and the GOREEZONT (HORIZONT) systems used both space and frequency diversity as a part of their system. Frequency diversity means that there were as many as five identical signals transmitted on different frequencies at the same time. Space diversity means that two or more transmit and receive antennas were used, as can be seen in the picture. This site was run by the military but would have likely carried civilian communications as well.

Basically, it was a way to maintain communications across vast distances when wired or microwave systems were not practical or possible. The US used such systems on the DEW line and across the Pacific Ocean between Hawaii and Okinawa. I remember the big Troposcatter dishes up on the hill behind the Navy housing area above Agana.

US Pacific Troposcatter communications system, courtesy of Wikipedia

These systems were massive and expensive to build, operate and maintain. From the looks of the pictures, site 6/60 generated all of its electricity with diesel generator sets. Fiber optic cable is an improvement of several orders of magnitude over this technology.

It is always interesting to see how things used to be done and give thanks to those that went along before us. Last night I was grumbling about the network latency when watching a youtube video. It was terrible, but in retrospect, not really that bad.

This is interesting

Another trove of surveillance documents reveals some interesting technical aspects of spying in the modern age:

What we have here is a copper wiretap. This allows some telco or ISP to split an ethernet feed, and send one output on its merry way, while the other output goes to? If not interception and collection, I don’t rightly know what else this device is designed for.

There are many many more like this on the WikiLeaks website. Have any doubts about how deep the internet surveillance goes? Spend a few minutes poking around, it is an eye-opening experience.

Graphical Network Simulator

I have been working with GNS3 (Graphical Network Simulator) in some of my classes. It is a fine tool with which one can build simulated computer networks using various routers and switches. The software program itself is free, however, the Cisco IOS images are not included and must be found elsewhere due to copyright issues. This detail is a bit of a pain, but not too bad. Once the program is set up and the appropriate IOS images are loaded, the console functions exactly like whatever router is being simulated. This includes running whichever terminal program is preferred, e.g. hyperthermia, putty, or if using the Linux version, x-term, etc.

GNS3 screen shot, topology and router console — GNS3 screenshot, topology, and router console

The advantages to this over something like Cisco’s Packet Tracer program are many. In Packet Tracer, certain functions are locked out and generally there is only one acceptable way to complete any given task. With GNS3, the IOS is fully functional, which means that experimentation and failure are available to play with. Failure is a great way to learn things in any hands-on environment. The advantage of virtual failure is that only you know about it.

For real-world applications, this means that router and switch configurations can be created, tested, and tuned ahead of time and then loaded into working devices, saving downtime and potentially handfuls of hair.

A few things about using GNS3, the PC idle tuning is required. Each instance of IOS assumes that the entire processor is available to use, thus starting several routers can work a PC’s processor to 100% and windows will never fully recover. Secondly, when starting each router, wait 10 to 20 seconds before starting another one. Again, this has to do with the way IOS uses processors. Also, to save time, store the IOS image as a decompressed file. This saves quite a bit of time on startup. Finally, do not forget to copy the running config to startup-config. Even though GNS3 says it is saving the router configs, it does not save the running config unless you issue the copy run start command, just like a real router.

The Raytheon RL10 Limiting Amplifier

Update: Apparently this is quite interesting to a number of people. I have rescanned the manual, properly compressed it and which you may find it here.

Found this manual at one of the older transmitter sites:

Raytheon RL10 limiting amplifier manual cover

The entire manual is available for your reading pleasure here: Raytheon RL10 limiting amplifier

As this is an older design than either the Gates Sta level or the Collins 26U, it may not be as useful to tube audio enthusiasts.

The main issue with the Gates and Collins unit is the GE 6386 remote cutoff triode used, which were great tubes, but very difficult to come by these days. This design calls for a 1612 or 6L7, which is a pentagrid amplifier. Feedback is provided by the screen of the following stage, a 6SJ7GT. Anyway, perhaps it will give somebody some idea of how to make a good tube compressor limiter.