Fraser has bought another toy.... a nice microwave dish and receiver  :) - Page 1
Forum section: electronics / general

author: Fraser
author_rank: Super Contributor
timestamp: July 01, 2016, 12:50:53 pm
content: You know when you are not actually looking for something and then you see it and decide that it is too nice to ignore ? Well that just happened to me.I stumbled upon a microwave dish and receiver on ebay that is painted a nice satin black and it immediately caught my eyeThe Dish/Receiver combination is a microwave video link receiving station. I know its operating frequency but for good reason I am not going to provide that here. The video receiving station was used as part of a remote single channel video feed from a POI. The 6" LCD video monitor that accompanies it is also on its way to me. This is all VERY high quality and expensive kit. Even the LCD monitor is built inside an aircraft aluminium case. Milspec throughout. The dish is fed with a waveguide and measures 18" in diameter.Sadly I do not have the associated transmitter for the video link but I know how to build one so that is not a problem for me.I will be dismantling the unit so thought other forum members might be interested to see what £45K buys you in video link receiving stationsIt is nice quality though.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: July 01, 2016, 12:53:22 pm
content: More pictures.I will post pictures of the receivers internal parts shortlyFraser

author: Nuno_pt
author_rank: Frequent Contributor
timestamp: July 01, 2016, 01:03:40 pm
content: For the looks of the feed and the back of the Waveguide transition, I would say ~24GHz or maybe ~47GHz.

author: Fraser
author_rank: Super Contributor
timestamp: July 01, 2016, 02:04:20 pm
content: Internal picures start here.Quality casingThe 5p piece is my addition and just to cover the operating frequency.

author: Fraser
author_rank: Super Contributor
timestamp: July 01, 2016, 02:16:16 pm
content: More internal pictures

author: Fraser
author_rank: Super Contributor
timestamp: July 01, 2016, 02:20:29 pm
content: Under the PCB, the modular RF deck......

author: Fraser
author_rank: Super Contributor
timestamp: July 01, 2016, 03:19:55 pm
content: Herewith a listing of the signal path and key components along itDish waveguide feed to RF pick-up mounted on rear of dish.Signal enters an RF pre-amplifierSignal enters the Microwave Down-Converter that produces the 1st IF at its outputThe 1st IF is fed to the 2nd Mixer module to be mixed down to the 2nd IFThe 2nd IF is fed to the Video Baseband IF & Demodulator stageVideo Output from system.No decryption is employed in this particular Video receiver.Further details.....2nd Local Oscillator and Mixer Module:Signal Path through moduleA06 MMIC MAR6 DC-2GHzFilterMD12008 M/A-Com 5GHz active mixer (LO2 from MAR7 oscillator on the same PCB))A07 MMIC MAR7 DC-2GHzOutput to Video Baseband IF & Demodulator IC on main PCB.The module contains the 2nd Local Oscillator comprising a MAR7 and associated oscillator components.The module uses an LP2951 LDO Regulator to provide a stable supply voltage to the 2nd Local Oscillator.Main PCBSignal related componentsVideo signal path2nd IF from 2nd Miver module.A01 MMIC MAR1 DC-1GHzFilterA01 MMIC MAR1 DC-1GHzFilterA01 MMIC MAR1 DC-1GHzFilterMC13155 IF and Baseband Video (capable of 300mhz IF input)NE592 Video AmlifierLM359 Norton OP-AMPVideo Output to monitorWell that is all there is to it really. Pretty simple but made to be reliable and perform well.Fraser

author: lukier
author_rank: Unknown
timestamp: July 01, 2016, 04:53:20 pm
content: Forgive my ignorance, but what's the purpose of this thing? Live TV? Satellite trucks, as the name suggests, use satellite relays nowadays. I don't see much point.I'm a RF noob, but I suspect this is similar to microwave telecom links. These things are line of sight, quite directional. Why not then set up a typical off the shelf telecom microwave link and transmit the video as well as any other kind of data.

author: mathsquid
author_rank: Frequent Contributor
timestamp: July 01, 2016, 05:11:47 pm
content: Quote from: lukier on July 01, 2016, 04:53:20 pmSomeone correct me if I'm wrong, but I believe that this sort of equipment is used for relatively short-distance point-to-point communications, like a remote news van, towercam, or helicopter sending a video feed to a tower at a TV station.

author: SeanB
author_rank: Super Contributor
timestamp: July 01, 2016, 05:42:45 pm
content: Your typical microwave link will not survive being carried in a backpack, through mud, swamp, sand, dropped out of a truck onto hard earth, go with a paratrooper in a HALO drop or any of ther assorted things this was designed to endure and still function. About the only thing that might disable it would be a lead overdose, or a terminal case of C4 poisoning.

author: lukier
author_rank: Unknown
timestamp: July 01, 2016, 06:20:11 pm
content: Quote from: SeanB on July 01, 2016, 05:42:45 pmI see. Milspec ruggedness comes at a cost. However this doesn't explain why limit this to video instead of having more versatile data link. Either this is something very old before the days of digital transmission or even techniques like frequency division/multiplexing to pack e.g. multiple channels with various comms or rather a sign of military's conservative approaches to hardware (rugged, old school proven tech, fixed function etc).So this is an old fashion military/spy gadget to get live video from a remote location. Still quite bulky for James Bond to carry and conceal somewhereI wonder how this is done nowadays. Doing IP video over existing telecom/internet infrastructure is risky and easily detectable on the intermediate routers (may be encrypted, but packets flow nonetheless). On the other hand some modern variant of this RF microwave link can also be not only detected but even localized (CRFS in Cambridgeshire makes such equipment, but I don't think they reach 24 GHz and beyond).

author: Fraser
author_rank: Super Contributor
timestamp: July 01, 2016, 06:50:33 pm
content: It is a quick deployment video receiving station. The transmitter is smaller and low power consumption, so clever digital techniques were not used.Audio was not included as it was not required. This was visual observation only.Fraser

author: rfeecs
author_rank: Frequent Contributor
timestamp: July 01, 2016, 07:08:34 pm
content: To me this doesn't look MIL-SPEC. All commercial grade plastic packaged parts. Nothing hermetic. Not even a conformal coating.Not to say it wouldn't be used by the military / paramilitary.

author: lukier
author_rank: Unknown
timestamp: July 01, 2016, 07:08:47 pm
content: Quote from: Fraser on July 01, 2016, 06:50:33 pmOh yes, I forgot that's the receiver and I assumed the transmitted is similar.

author: Fraser
author_rank: Super Contributor
timestamp: July 01, 2016, 07:25:31 pm
content: The build date is post 1993 according to the '93 date codes on the IC'sFraser

author: 1design
author_rank: Regular Contributor
timestamp: July 02, 2016, 12:58:23 am
content: The waveguide looks like a WR-90, so the unit operates inside the 8-12GHz range, pretty standard for point to point links. The dish looks to be around 1 ft in diameter, so we should be looking at roughly 30dB of gain. Noise figure with that long feed cable is probably around or above 10dB.Transmit power I would make a wild guess around 20dBm, this would yield around 50dBm of EIRP and since the device on the other side was pretty low power I would guess around 0dBm of transmit power and no gain on the antenna, noise figure again around 10dB. This would give us a link budget of 164dB-BW integration noise and SNR requirements. Lets assume 60dB of BW correction for a 1MHz channel and an additional required SNR of 20dB, so we are left with roughly 80dB of link budget. Not a lot to play with!

author: Fraser
author_rank: Super Contributor
timestamp: July 02, 2016, 09:17:06 am
content: The dish is 18" diameter.Fraser

author: Refrigerator
author_rank: Super Contributor
timestamp: July 02, 2016, 11:23:40 am
content: Quote from: lukier on July 01, 2016, 04:53:20 pmI don't know but the pizza van outside my house has one on top.

author: Fraser
author_rank: Super Contributor
timestamp: July 02, 2016, 01:14:15 pm
content: OK, time for an evaluation of the receiving stations design and build quality.This is just my opinion based on having worked with Military and specialist Gov't equipment over the years.The Dish section1. The parabolic prime focus dish is a quality item made from spun aluminium. Good enough to be from Andrews Communications stable IMHO.2. The dish to receiver chassis coupling is a quality solid aluminium ring with castellation.3. The feed horn matches into waveguide. A rugged and quality design but with associated losses.4. The feed horn has a Mylar window to seal it and the whole horn/waveguide assembly is protected inside a plastic radome. Good design.5. A quality waveguide adapter sits at the end of the waveguide on the rear of the dish chassis coupling. Its output is via an SMA socket.6. The connection between the waveguide adapter and the receiver module uses rigid coax with SMA plugs at each end. This small diameter coax is a lossy link but is reasonably short. Direct connection to the receiver module input without the rigid coax would have been lower loss.The Receiver Section1. Quality aluminium housing employed. Milled out of solid Aluminium block. This is expensive to make but offers custom internal and external shapes and/or cavities. This is especially good for small production runs.2. Professional connectors. TNC and Amphenol used for cable connects. Always a good sign on a piece of equipment. The Amphenol is a high quality and expensive connector type.3. The Signal strength meter is more often found on Military equipment and is of good quality.4. The case lid is held in place by 20 socket head recessed machine screws. These apply even pressure to the gasket below.5. A quality silver wire impregnated EMC gasket sits between the lid and the lower part of the case. Such screening gaskets are often used to reduce the vulnerability to outside RF interference or to reduce emissions from a unit.6. The interior of the case is milled out into two sections. The main Receiver, and a separate I/O section accessed via an aluminium lid plate.7. The Receiver is split into two tiers. A lower RF input and down converter deck on its own aluminium chassis, and the upper deck that is formed by the main Receiver PCB.8. Stainless steel machine screws with anti vibration washers are used throughout the unit.9. The lower RF deck contains what appear to be high quality modular components. Namely the RF pre-amplifier and RF frequency down-converter. A pre-amplifier can be used to provide low noise amplification and/or to isolate the down converters Local Oscillator from the aerial feed. So preventing radiation of the Local oscillator via the dish. Important in some situations. These modules are likely adapted items from one of the major Microwave module manufacturers, rather than truly custom designs.10. The down-converter does not appear to contain a VCO as no control line is present. There is a Local Oscillator adjustment screw only. This could be a DRO or LC oscillator. Frequency stability will NOT be that good in such a design.11. The 1st IF output from the Down converter will be below 2GHz as that is the upper limit of the MAR6 MMIC amplifier. The connection between the down converter and next stage is via quality silver plated wire/Teflon coaxial cable.12. The next stage sits on the Main PCB within its own metal housing. It contains MMIC amplification of the 1st IF and an active 5GHz capable mixer from M/A Com. The 2nd Local Oscillator that feeds the M/A Com mixer is a VCO design and is also within the same module. It comprises an MAR7 MMIC with Varicap tuning and LP2951 LDO Regulator. The VCO can provide AFC tracking of the signal to offset drift in the Down-Converter Local Oscillator. This is a common design for video receivers that are quite tolerant of frequency drift.13. The 2nd Mixer module is very obviously adapted from a design that usually has its own phase locked loop controlling the 2nd LO frequency. All the PLL parts have been deleted from the BoM for this application. Another case of using proven modules and adapting them for this low production run product.14. The output of the 2nd Mixer (2nd IF) is fed into a MAR1 MMIC using just hook up wire so the frequency is likely to be relatively low. Very high frequencies would normally dictate a more elegant inter stage coupling than simple hook up wire. The 2nd IF is below 300MHz as that is the maximum frequency capability of the Baseband Video IF/Demodulator that receives it.15.The MAR1 amplifies the 2nd IF prior to it passing through a chain of MMIC amplification and filtering before being presented to the MC13155 IF input.16. There appear to be two MC13155 IF/Demodulator IC's connected in cascade (or parallel?) in this design. I have yet to trace out the circuit. This could be in order to use some parts of the IC for other purposes, such as the IF gain stages, RSSI meter or AFC drive to the 2nd Local Oscillator.17. The MC13155 provides the demodulation of the FM 2nd IF signal and provides Baseband Video output. This output is then fed to an NE592 Video amp and LM359 Norton Op-Amp.18. There are two IC's that I failed to identify when the lid was off. They appear to be OP-AMPs, one driving the 2nd Local Oscillator frequency control pin and the other driving the signal strength meter. The MC13155's appear to be driving these two IC's. One for each.PCB construction comment1. The PCB material used is FR4 This is acceptable for the frequencies involved.2. The PCB layouts are relatively old fashioned and functional rather than pretty.3. The re-purposing of the 2nd Mixer/IF module involves the use of hook-up wire. These wires are not secured to the PCB as I would normally expect. This part of the design could be better as loose wiring is not good for reliability.4. The 2nd Mixer/IF module has bare copper PCB tracks which is a surprise to me. The tracks should really be plated. The PCB is lacquered to avoid corrosion though.5. The main PCB has plated tracks but it has not been lacquered. Again this is a surprise to me. Lacquer helps to prevent moisture ingress or corrosion.6. The main PCB contains several wire bridges. Some appear part of the design, whilst others may be error corrections. Not great to see but at lest they are of adequate quality.So what do I think of the design ?It uses basic technology and well proven RF and IF stages. There is not much to go wrong with such a design. The build is old school and the various stages are easily discriminated along the signal path. This is the sort of kit that I used to design and build. It is very much about making an equipment that serves a specific need rather than trying to get clever or adventurous and risk operational problems. It very much employs the KISS principle and so for that I applaud it. There are areas that I do not like but as they do not effect the operation of the unit I suppose the designer was satisfied that it was 'good enough'.It may surprise some people, but it is a fact that some very specialist equipment that has very small production runs, sometimes only a single unit, appears more like something a skilled hobbyist put together. This is because people like me were tasked with providing Product 'X' to achieve Objective 'Y' in Timescale 'Z'. It is not unusual to approach manufacturers of complete RF modules and adapt a current proven design. Why re-invent the wheel with the associated cost and development time. I often used Mini-Circuits modules as they did what I needed and at reasonable cost, with fast delivery.The challenge is often in designing the custom PCB's that control, or interface with, the modules. For very limited production numbers in very tight time frames, it is not unusual to design a prototype PCB run that becomes the production board after a few corrections. If it meets the spec and time is tight, it goes out the door on time and within budget. That is the world of very specialist and sensitive electronics design and build.I hope this has proved interesting to other forum members.Now to decide what to do with this unit. I know ATV fans would love it but I may yet find a use for it myself ? I love parabolic dish based designsFraser

author: lukier
author_rank: Unknown
timestamp: July 02, 2016, 02:07:05 pm
content: Quote from: Fraser on July 02, 2016, 01:14:15 pmThis is quite similar to what you have to do in research environment. When I have to prototype something to perform experiments or take measurements I usually need literally single quantities of components. Ordering 10 pcs PCB from Itead/Seedstudio seems like a wasteThis also explains the cost of the fun stuff in the NSA ANT catalog, COTS components miniaturized, integrated and manufactured in low quantities, often for very specific purpose (e.g. for a particular BIOS or hard disk etc). Some things I suspect aren't even made by the NSA, but with some help from the industry. For example, I don't believe that NSA, even with their resources, can make 3G/4G BTS, especially the full software stack. I know from my previous industrial experience (major telecom infrastructure provider) how many people worked on the 4G BTS project and how obscene amounts of money it costs over the years of development.Quote from: Fraser on July 02, 2016, 01:14:15 pmSure. I find niche equipment very interesting. Maybe I'll do a teardown one day here of a 3G BTS, the hardware is top notch. I got for 10 quid on eBay, with the intention to have a souvenir (obviously I couldn't have any when I left my job) and very very heavy paperweight. I just need to check the NDA I signed years ago so I know how much I can say about how it works

author: Fraser
author_rank: Super Contributor
timestamp: July 02, 2016, 02:49:59 pm
content: The LCD monitor for the video receiver has just arrivedAs expected, it is built like a tank ! All Aluminium milled from a solid block.The LCD screen sits behind a glass window to protect it and a neoprene gasket is installed between the case halves.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: July 02, 2016, 03:14:47 pm
content: Inside the LCD monitor.......Access to all internal parts of the monitor is via the removal of the front panel/faceplate.The LCD monitor contains a single custom PCB and a COTS SHARP Colour LCD monitor.Interestingly, the LCD monitor is pressed against the glass faceplate by four springs. The whole LCD monitor module can float up and down on these springs. interesting design.The rear mounted custom PCB carries power supply related components and the analogue monitor control inputs from the three potentiometers.Not much more to say about it really, except that it is designed to withstand abuse and a life of hard knocks ! It came protected within a heavy duty black fabric carry case with opening front panel and shade blinkers.Considering the use these things got, the unit is actually in very good conditionThe cost new ?It was included in teh £45K system cost. Bargain ehFraser

author: Fraser
author_rank: Super Contributor
timestamp: July 02, 2016, 03:18:02 pm
content: More.....

author: Fraser
author_rank: Super Contributor
timestamp: July 02, 2016, 03:35:07 pm
content: The Sharp 6" TFT monitor module is an LQ6MC02 that provides 240x720 pixels.Pinout data found but not a datasheet.Fraser

author: bktemp
author_rank: Super Contributor
timestamp: July 02, 2016, 03:54:08 pm
content: Quote from: Fraser on July 02, 2016, 03:35:07 pm240x720 sounds a bit odd.Most analogue video displays support only 240 or 272 lines because that's the number of lines in each field of a NTSC/PAL frame. So my guess would be it is 720x240.The horizontal resolution can be arbitrary because it is an analogue source. Sharp counted each RGB subpixel as a full pixel, so 720x240 would result in 240x240xRGB pixels. But they did not sample RGB at the same time, but used 3 phase shifted sampling pulses matching its arrangement on the display. That's why Sharp counts each subpixel as a full pixel when specifying the resolution, because each subpixel gets data from a different sampling point.

author: Fraser
author_rank: Super Contributor
timestamp: July 02, 2016, 03:58:34 pm
content: This units Product ID is MRD300LE.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: July 02, 2016, 04:06:46 pm
content: @bktemp,Thanks for the comment. I regret I can find little detail on the Sharp Monitor. Only the pin outs and a spec from a supplier found here:http://www.lcdsolar.com/products/ProductDetail.aspx/SHARP/LQ6MC02/7051#.V3flXvkrLIUGeneral Information of SHARP LQ6MC02Part Number LQ6MC02Manufacturer SHARPPanel Size 6 inchesPanel Resolution 240 x 720Michanical Information of SHARP LQ6MC02Panel Dimension 149.4 x 117.0 x 23.0Weight in gram 320Active Area 113.8 x 87.6Optical Information of SHARP LQ6MC02Viewing Angle 12:00Optical Information of SHARP LQ6MC02Backlight(Lamp) Information of SHARP LQ6MC02Backlight Type CCFT/Built InSignal Information of SHARP LQ6MC02Input Signal-1 PALInterface Type Composite/Analog RGB

author: Fraser
author_rank: Super Contributor
timestamp: July 02, 2016, 04:28:48 pm
content: For those wondering what the camera options were at the transmitter end of the link......here is the HedgeCam !It is a CCTV Zoom equipped camera with Camouflage jacket for use in a hedge !

author: TheSteve
author_rank: Unknown
timestamp: July 02, 2016, 05:20:51 pm
content: 10 GHz gunnplexer?

author: electr_peter
author_rank: Unknown
timestamp: July 02, 2016, 05:45:53 pm
content: Thanks for interesting teardown and explanations. Equipment looks of very high quality to me. Modern version would have better PCB solder mask and more SMT parts, but for 1993 it looks fine.Case looks really unusual. The first time I saw it the case looked a lot like a big cat house

author: Fraser
author_rank: Super Contributor
timestamp: July 02, 2016, 08:50:41 pm
content: For anyone wondering what resides inside the down-converter module. I attach a picture of a similar module.The oscillator in these units is a DRO type. It drives the lo port of a microwave mixer, such as a Magnum MO64 as in the picture.Sorry it is not a better picture. This was the only one I could find and it formed part of an ATV project PDF document.Fraser