3G, 1.5G, SD   + Analogue  Generation & Analysis “Which-Wire?” Auto IP detect TDR Testing Awakes < 1Sec “EYE~POD”           accessory Emb’d, AES & Analog Audio
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© Murraypro 2017 Iss:7  June 2016  Frequently Asked Questions:-     General Issues. The Test Chest is shipped with a partially charged Lithium Polymer Battery, and Murraypro recommend that your new Unit is given an initial charge prior to use. Thereafter, you may expect the charge period to be around 2~3 hours for a discharged battery. Q: Is Test Chest waterproof? A: NO. Whilst we have attempted to protect the Unit from day to day hazards such as shock, dust and an occasional moisture drip, the Unit is not sealed and operation in wet/damp conditions, or a determined attack with coffee or tea are not permissible. Consequently damage caused by such activities would not be covered by Warranty.  Q: Can I damage the LCD's touch screen? A: YES. Damage is possible, so please use ONLY a 'soft touch' on the touch screen. Use of any sort of stylus or probe is strongly discouraged by the Manufacturer of the 'touch screen'. Damage to the panel's front surface, caused by inappropriate operation of this type, is specifically excluded from Warranty cover. Use of a screw driver, or any ball point pen, is highly likely to cause rapid and permanent damage to the front surface.  Q: Is Test Chest vulnerable to viruses such as the Stuxnet? A: No, certainly not. The Test Chest 3G uses FPGA logic that is configured from high speed look up tables, not by an on-board computer that can be accessed via USB, or similar Ports. This not only eliminates the possibility of external contamination via a User access port, but vastly speeds internal configuration, making the Test Chest impressively fast to operate.  Q: What is the secret of Test Chest’s amazing speed of operation? A: Our intuitive touch screen configuration eliminates 'configurable/soft keys', and the pre-programmed configuration tables enable the FPGAs to spring to life without the requirement for any “PC like” interface, with it's inevitably turgid response. When the legend changes on the bar at the top of the picture....that's it, the Test Chest’s mode HAS changed, and normally this response is essentially instantaneous!   Power Issues. The Test Chest 3G is shipped with a partially charged Lithium Polymer Battery, and Murraypro recommend that the Unit is given an initial charge prior to use. You may expect the charge period to be up to 2 or 3 hours or so for a discharged battery; anticipate this to be somewhat longer when 'running in' a new battery pack. To promote maximum service life, new batteries should be fully charged and discharged 2 or 3 times before serious use.  Q: Can I use Test Chest under external mains power whilst the battery is being charged? A: Yes. Using the supplied PSU, Test Chest may be used indefinitely under external mains power and without regard to battery charge condition. Intelligent battery charging and sophisticated power management ensure that the Battery can not be over-charged, even if external dc power is left permanently connected. Battery over-voltage/current and deep discharge protection are provided, whilst an on-screen bar icon provides an indication of remaining battery capacity. IF Test Chest is to be mains powered for protracted periods (ie: weeks at a time), Murraypro strongly recommend that the battery is periodically permitted to discharge completely, and then recharged. This will help to prolong it’s service life.   Q: Test Chest appears to have no direct power switch, how do I switch it on? A: The Unit is controlled via the touch screen interface. Awakening upon just a single touch, the LCD will display a Switch icon in the bottom-right of the panel. This icon must be touched within 4 seconds of it's initial appearance to confirm the validity of the 'Wake Up' command; if not, the Test Chest will automatically resume it's hibernation mode and power-down to preserve battery power. This double selection requirement confirms that the power-up request was valid, and not the consequence of a 'nuisance' contact with the LCD panel. This feature is particularly valuable in preventing accidental discharge whilst in storage. Q: Test Chest 3G does not appear to have a ‘Battery’ switch? A: Yes, Test Chest-HDVI does have a ‘battery enable’ switch which will be set to “OFF” when originally dispatched.  Whilst this switch does control the main battery power for the logic, it does NOT interupt the micro-power supply to the Logger’s Real Time Clock.   Q: How do I get Test Chest to stay switched on? A: There are a number of separate, and different, power-down conditions to consider:- 1.	The Test Chest is in “Which-Wire?” mode (read more on this below), and the input video signal has been removed. A moment or two after the removal of the input signal, Test Chest will automatically resume hibernation mode, ready for it's next mystery video stimulus. This automatic power-on and power-off feature is one of the major features of our Murraypro “Which-Wire?” logic. 	 2.	Approximately 10 minutes after the last touch-screen command, Test Chest will power itself down automatically, as a battery power conservation measure. This automatic shut down may be over-ridden by selecting “Alway ON”, rather than the default “Auto OFF” on the main Menu's power option.  Be aware however, that you will now need to manually select “OFF” on the main Menu at the completion of a period of operation or the Test Chest will continue to operate until the battery has completely discharged! (Take care to ensure that you do not store the Test Chest for any period with it's battery in a discharged state, as this will seriously jeopardise the battery life.) 	 3.	During battery powered operation the battery voltage is continuously monitored, and when the low voltage cut-off point is reached Test Chest will shut down automatically, to prevent deep discharge of the battery. Prior to this cut off point, the on-screen 'battery bar' icon will have been warning of impending cut off.   Q: Will I damage the battery if Test Chest battery runs 'flat'? A: NO, there is low voltage cut off protection to protect the battery from 'deep discharge', but read on about storage.   Q: Can I store Test Chest with a 'flat' battery? A: NO, this would be most unwise, and will adversely affect subsequent battery life. A discharged Lithium Polymer battery should always be recharged as soon as practical. Remember that the Test Chest's intelligent battery charger circuitry will prevent serious overcharging, however we do not recommend that low voltage power is left permanently connected.   Generation. Q: How do I set Test Chest to operate on a particular video standard? A: This is always at least a 2 command sequence, and one which may extend to several more menu selections. The current selection will always be displayed on the banner at the top of the LCD panel, and guided by this, progress through the set up process is highly intuitive.  1.	On the main menu select, with a single tap, one from the following.... 'SD~270MB/1080I/P~720P~1.5G/1080P~3G' as appropriate. This defines the clock frequency for the selected TV Standard. 	 2.	On the main menu select 'Field/Frame Rate'. Multiple screen-taps of this icon will toggle through the available choices for the Standard selected @ step1. The banner at the top of the screen always shows the standard currently being generated.  3.	If appropriate to the chosen Standard, toggle through 'Interlace' or 'Progressive'. 	 4.	For 60Hz related standards, toggle through 1.000 or 1.001 as required. 	 5.	Confirm that the Banner display matches your requirements. 	 During our Test Chest demonstrations, we always emphasise the impressively short reaction time between the intuitive touch-screen's command entry, and the execution of an instruction. When the legend changes on the banner at the top of the picture....that's it, the Test Chest mode really HAS changed!  Q: How do I select the required video test signal? A: Using the main menu navigate to, and select, the “Generate Video” icon; next, select the “Video TSG” icon. Select the required waveform from the available options presented.  You may subsequently wish to return to the main menu page to continue with other selections, setting Audio for example......   Q: How do I configure the audio? A: Using the main menu, navigate to the 'Generate Audio' option. There are 3 options for the 'Source' of the Audio:-  1.	Internal Oscillator, which is the default mode, and can be menu configured for Frequency and Amplitude. This generates a common signal that may be independently disabled (or not) on Channels 1, 2, 3 & 4. 	 2.	AES: Unbalanced AES presented to BNC #2 (BNC #3 on TC3G) will be processed and available for insertion as a stereo audio source.  	There is no facility for adjusting this level, which is set for 'Unity' dBFS~in/dBFS~out; ie -18dBFS~in =  -18dBFS~out. 	It is necessary for the external AES Word Clock to be synchronous with the Test Chest’s video OP. 	 3.	External embedded audio presented to BNC #1 	There is no facility for adjusting this level, which is set for 'Unity' dBFS~in/dBFS~out; ie -18dBFS~in =  -18dBFS~out. 	It is necessary for the external embedded audio Word Clock to be synchronous with the Test Chest’s video OP.   Q: How do I set which group the embedded Audio is inserted on? A: On the Audio sub-menu select 'Group', and toggle through to the required Group on the touch-key, which will be displayed on the Banner at the top of the LCD. Note that when the selected Group is NOT “Gp1” the Group text will be highlighted in YELLOW.   Q: How can I tell if an AES input signal is synchronous with Video Clock, and consequently suitable for inserting on to Test Chest 3G's audio output? A: Select the Audio Monitor page via the Home Menu, then the “AES-Video Lock” icon; apply the 'Video Reference' signal to BNC1  and the unbalanced AES input signal to BNC#2 (BNC #3 on TC3G). Remember that the Utility AES Transformer in the Audio~POD will convert between Balanced and Unbalanced AES signals if required).  The difference in frequency (if any) between the AES 48KHz Word Clock & TV Vertical  Clock will be presented as a GREEN/RED flashing  icon at the difference frequency. A 1Hz 'Beat' rate indicates an error of approximately 20ppm. Of course, this Utility may be used to check whether ANY particular AES input applied via BNC#2 (BNC #3 on TC3G), is synchronous with the Reference input that you apply via BNC1.   Q: I've been told that Test Chest 3G really can operate on two different TV Standards simultaneously; can this really be true? A: Yes, most certainly; simultaneous Dual-Standard operation is entirely practical. The Generation (Output) and Monitoring (Input) sections of the Test Chest ARE entirely completely independent, and share only the internal power supply rails and control logic. Generating 3G Colour Bars with embedded audio, whilst watching Composite Video and listening to balanced analogue stereo audio, for example, really is entirely practical!   Q: Can you explain, what is, and how to use, "Clapper Board"? A: 	Clapper Board is a Test tool designed to check for, and evaluate, Programme Audio wrt Programme Video delay issues. In visual terms it consists of a simple horizontal Graticule with a Reference point @ time 'zero' (screen centre) and a travelling Puck that repeatedly traverses from right to left; and in audio terms, a tone pulse is generated @ time 'zero', on each of the Embedded, AES and the Analogue OPs. This signal is then offered on to a remote location, where it may have experienced a number of Video processing operations en-route, any of which may have involved Frame Storage; if the associated audio signal has not experienced an identical delay too, lip-sync problems are inevitable. At the final receive point, the Clapper Board signal may be evaluated for V/A delay errors with nothing more sophisticated than a picture monitor and a loudspeaker. Because of the repetitive nature of the signal, it is very easy to assess delay errors visually, and (possibly) a finger slid across the viewing screen to act as a local cursor. Small timing errors will be immediately apparent to the Observer. Naturally, neither Test Chest or the Clapper Board signal are able to correct such errors directly; but the need for correction becomes immediately apparent, and steps can be iniated to adjust existing equipment appropriately.   Q: I've set up the Generator as I want it, but now there appears to be no Output?  Note that all Test Chests, and the late model Test Chest 3Gs, have a ‘grey-look’ menu which automatically flags up ‘unusual’ settings with YELLOW TEXT.  Difficulties with producing an output are usually due to 'finger trouble'…….  A1:  Ensure that you have not inadvertently selected Test Chest’s output to "LOOP". This would set Test Chest to  'Equalise & Reclock' a signal on the input BNC, and then "LOOP" it on to the OP BNC, thereby effectively bypassing Test Chest’s internal Generator.  ‘Looping’ of course, can only function when there is an input signal on BNC#1 to actually process!   A2: Ensure that you do not have "CLAPPER Bd" selected. This is inserted  just before the OP BNC, at the end of the Generation chain, so it totally bypasses the Test Chest's internal TSG.  A:3 The example on the right shows how the TC3G ‘highlights’ the condition of ‘luminance OFF’.   Q: Just how good are the output signals?  A1: All the SDI output signals are generated with 10 bit precision  A2: The Composite video signals (which will only be present when generating the 'SD'  Standards 525 or 625) are generated with 8 bit precision, so Differential Gain and Phase are in the region of 0.5% DG and 0.5' DP.   Q: Just how 'fine' are the Horizontal and Vertical lines on the Grill pattern?  A1: 'Horizontal' lines will be '1 line thick' on progressive Standards, and 2 lines thick (1 on each Field)  with Interlaced Standards.  A2: 'Vertical' lines will have the finest possible width, consistent with the bandwidth  limitations for the Standard being used.        So, does this 'A2' answer mean that I can't have a 1 pixel wide vertical line?  Yes, I'm afraid so; whilst electronically the digital output circuitry might indeed permit such a signal to be generated, the implied bandwidth requirements would be far outside the practical response of a conventional display device, and the viewed image would be masked with unpleasant ringing artefacts caused by these ultra-fast edges.   Monitoring.  Q: I have heard a lot about your “Which-Wire?”, what is it? A: “Which-Wire?” mode is the powerful hands free utility exclusive to Murraypro (and first presented on an earlier Murraypro Product), which enables you to automatically determine vital information about an input signal, such as whether it is actually present (or not!) together with it's TV format and Standard, without you having to make any configuration adjustments what-so-ever......totally ‘hands free’ in fact!  Q: OK, sounds great! So how do I initiate, and use, this “Which-wire?” Mode? A: Simple; first turn the Test Chest OFF, using the main menu's 'Power' icon! Next, apply your mystery video source to Test Chest's “WW?” input. This is will be BNC #1, situated on the bottom-right corner of the front panel. When a TV input signal IS PRESENT, the Test Chest automatically awakens from hibernation, and displays the input signal on the LCD panel. It matters not what standard the input signal is, 3G-SDI, HD-SDI, SD-SDI or even CVBS, the image will be displayed in less than one second, together with a banner declaring the detected input Format and Standard. Pretty cool, eh? A moment or two after the input signal is removed, the Test Chest will automatically power-down and resume hibernation mode; ready for your next mystery source.   Q: If I leave Test Chest monitoring in “WW?” mode, will it detect a change of input? A: Yes, most certainly. The Test Chest is continuously monitoring the input standard, and any change will be instantly detected and displayed on the LCD's Banner display. In fact whilst the Unit is powered and in 'TV Monitor' or WFM mode, the detection is even faster than it is in normal “WW?” mode, as Test Chest has already completed it's “detection of an input” test, so this initialisation is already complete; subsequent Standards detection of an IP source is effectively instantaneous, virtually with no delay at all!   Q: Termination of video lines is always important, do I need to terminate the “WW?” input? A: NO! The Test Chest BNC #1 is ALWAYS terminated in 75 ohms, and no external termination will be required. The BNC #1 has been configured by careful design to present a 75 ohm resistive port, with low return loss up to 3G clock frequencies. In fact, ONLY a precision BNC connector correctly fitted to an appropriate high grade coaxial cable such as Belden 1694A, or a direct equivalent, will return adequate performance at 3G frequencies; lower performance connectors/cable are very unlikely to remain acceptable and return satisfactory performance with the passage of time.   Q: I need ‘Hi Z’, does Test Chest have any “unterminated video inputs? A: No, there is little requirement these days for un-equalised/unbuffered video ‘looping’.   Q: How do I align the trace with a graticule point for measurement, as Test Chest does not appear to have any 'Shift' controls? A: Simple really, just use the touch screen and your finger to 'drag' the trace to the desired screen location!   Q: Can I use the WFM as a simple oscilloscope? A: A qualified yes, but it must be in the ‘analogue’ mode. Be aware that BNC 1, the input connector for the WFM has a non-removable 75 ohm termination. The WFM Utility has a frequency response suitable for baseband audio & video extending to a high of about 10MHz (-1dB); SDI signals @ 270MHz and higher, are not suitable therefore for direct examination, but the LF content of the signal will produce a useful indication of their presence, due to the ADC's high speed sampling of the source. Most of the input signals to be examined are likely to be audio or video related, so it is practical to use the Test Chest's WFM 2V, V, 2H & H timebase ranges to cover low and higher sweep speeds, but the input attenuator present on conventional ‘scopes, is not present.   Q: Could I use the oscilloscope as an 'Audio Signal tracer'? A: Yes, this is entirely practical using the Test Chest's internal loudspeakers, or headphone socket. After setting the Test Chest to 'WFM', navigate away to the main menu and select the “Audio Mon” icon.  Using the 'loudspeaker source selector' icon in the lower-left of the screen, toggle this icon until the LCD's top Banner declares "BNC IP”. This has forced the audio monitoring to monitor the WFM display, and the audio component of any waveform shown on the 'Scope display will now also be audible via the internal audio monitoring speakers (subject to their intrinsic audio response), but use of the 3.5mm jack enables use of Hi-Fi headphones. Navigate back to the 'SCOPE' mode on the main menu, and use the Oscilloscope Utility as described previously. The main menu's increase/decrease icons may be used to control volume.   Q: How do I mute the front speakers, when I am using the external headphone socket? A: Simple, Test Chest detects the use of low resistance external headphones (30R – 600R), and automatically mutes the stereo speaker drive stage when you jack in. Be aware that this muting does not occur as a direct result of the insertion of a 3.5mm Jack, and a disconnected 3.5mm jack, or very high impedance headphones, will not initiate muting if they are inserted alone.   Q: How do I use the TDR/Cable test? A: The 'Cable Test' feature employs Time Domain Reflectometry, which launches a short duration pulse from a 75 ohm source impedance into the cable to be tested, and detects reflections caused by impedance matching errors along the coaxial cable. Ideally, with perfectly matched and terminated cable on the TDR port BNC #2 (BNC #3 on TC3G), there should be no reflected energy at all to view.  The 16nS TDR pulse contains high frequency components, and reflected energy from ‘line impedance’ errors will be visible as a perturbation of the steady state value of the trace following the launch of the TDR pulse, which is always displayed on the left side of the trace at time-value 'zero'. A subsequent positive going excursion indicates the presence of a reflection from an  impedance higher than 75ohms, whilst a negative going excursion indicates reflection from a lower impedance. The timebase of this display is calibrated in metres for Belden 1694A cable, so the distance down the cable to any impedance error may be determined by direct examination of the glitch's position on the X trace.   With very short cables, reflected energy will to some extent be masked by the tail of the TDR pulse, which limits minimum practical cable investigations to about 5M.   Q: How can I use the TDR on long cables? A: The TDR generates a 16nS pulse allowing maximum resolution and is ideal for use with shorter cables. The TDR feature detects and displays energy reflected from impedance mismatches, and in most case the amplitude of a reflection will be rather small. Any reflection(s) result from energy that has travelled along the cable twice, ie there and back, so it will always become increasingly attenuated as the cable length increases.  For use on longer cables, or where reflections are small, we offer an increased option, but use of this will be a compromise between fault detection and the ability to detect errors at all, due to increased noise clutter. The wide pulse option launches significantly more energy into the coaxial cable, but at the expense of the ability to resolve fine detail. Consider the fact that for any artefact shown at 180 metres on the Test Chest’s TDR display, the reflected energy will have travelled 360M, and will have suffered significant attenuation!   Q: Fine picture detail seems 'missing' when I look at  Grill Test Signal? A: Essentially the Test Chest's native LCD display is 800 x 480 pixels, and all the input signals to be displayed must be 'processed' to fit this format. If this were not done, a very significant amount of a 1280 x 768 picture would be outside the scanned area, and most of a 1920 x 1080 Format picture would be lost! Design balances have been made consistent with low power consumption, low image latency and which produce acceptable SD, HD-720, HD-1080 & 3G images with the minimum processing overhead, and without the power hungry overhead of digital multipliers; and inevitably this results in a degree of interpolation compromise.   Q: How do I monitor an AES input'? A: The TDR, External sync input and AES input signals share BNC #2 (BNC #3 on TC3G), which is always terminated in 75 ohms.   Navigate via the main menu's 'Audio Monitor' icon to that page, and then select the  'AES' icon which presets Test Chest to expect an AES audio source for monitoring. Note that the AES input port is optimised for use with a 1V pp signal  (nominal) on coaxial cable with a 75 ohm impedance; see below for use with 110 ohm balanced sources on XLR3.   Q: Can I monitor an SPDIF input'? A: Yes, there is a high degree of similarity between SPDIF and (unbalanced) AES signals; both use 75 ohm impedance ports, although the SPDIF amplitude is only 500m, half that of the  AES. They share very similar coding protocol too, and AES systems for Professional use may have settings that can ignore the SPDIF’s “Consumer” and “Copy Protection” Bits.        There is sufficient sensitivity on the Test Chest’s AES input port for the amplitude differences to be ignored, and Users are unlikely to experience difficulty monitoring SPDIF sources.    Q: I’m getting ‘Audio Clicks’: Can I check whether the AES Word Clock of that signal is synchronous with Station Reference? A: Yes, this is an extension of the AES monitoring described above. With your AES input signal monitored using the ‘AES’ menu option, apply a feed of your Reference signal to the ‘Which-Wire?’ IP (BNC1), then peruse the “AES-VIDEO” icon on the right hand side of the LCD panel. A small panel within this icon will illuminate GREEN when the Reference is detected and the AES Word Clock/Station Reference signals are synchronous. However, if they are not synchronous, the illumination will flash GREEN/RED at the 48KHz’s difference rate; where 1Hz equates to approximately 20 part/million error.    Q: How do connect a 'Balanced 110 ohm AES input’ to the 75 ohm Port? A: Simple! The Test Chest's Audio-POD contains a Utility AES matching transformer which is designed for this application. Connect the Audio-POD to the Test Chest 3G, and lock it firmly in position using the 'over centre' toggle latch to securely clamp on to Test Chest’s BNC clip. Feed the Balanced AES into the XLR3-F of the matching transformer, and loop it’s BNC output to Test Chest's BNC #2 (BNC #3 on TC3G). This transformer is reversible, and can also be used to match the TC3G's balanced 110R OP for 75R unbalanced operation.   Q: Do Test Chest’s balanced audio inputs and outputs terminate in 600 ohms? A: NO, most certainly not! The audio inputs on Test Chest are always high impedance. Terminating audio equipment with 600 ohms is not current audio practice, and is very seldom required these days. The output impedance of the Test Chest audio ports are low, about 30 ohms, and these should NOT be terminated in 600 ohms either, or subsequent amplitude loading errors will occur. This 'low impedance out' & 'high impedance in' concept is used on all Murraypro Equipment, enabling several high impedance loads to be satisfactorily fed from a single output port without any amplitude issues occurring due to loading. Termination loading errors in a 600 ohm environment can easily result in a line amplitude being either 6dB high, or 3dB low, an amplitude swing of 9dB!   Q: Can I automatically identify individual audio channels in a Group? A1: Yes easily, via the ‘Generate Audio’ page, by pre-selecting the required Group, and then by using the individual channel ‘MUTE’ controls. Two further modes are available, both furnishing endlessly repeating sequences A2: Each channel in any selected Group may be sequentially identified by tapping the “Ch Ident’ icon once, which will then be  highlighted with a rectangular box.  A3: EACH channel within EVERY Group, 16 Channels in total, may be sequentially identified by tapping the “Ch Ident’ icon a second time, the “Ch Ident” legend will then be highlighted in Yellow, within the rectangular box.   So, select the		“Generate Audio” icon, then                                   “Ch Ident” icon on the Audio page will then step the Audio Generator through:- “Steady state-on”, to...  “Group Ident”,  to.... “Ch Ident”  = 16 Channel embedded identification, and further on to... “Embed Mute” = ‘Embedded Audio’, ALL Channels MUTE”.           Q: Why doesn't Test Chest offer a native “Eye” display? A: Test Chest’s main video input (BNC1) offers low return loss, whilst handling signals that embrace 3G through to CVBS and unbalanced AES, as well as Which-Wire?’s auto detect logic, so it’s not practical offer an “Eye” feature that uses Port 1, because it’s performance would be compromised. We offer the EYE~POD accessory with no-compromise signal performance, to catch all the nuiances of an input signal, even up to 3GHz.   During the summer of 2016 Murraypro will release “TV Eye” a small self contained video tester that incorporates WFM, Vector, TV Monitor, Audio metering and an Eye feature.     An ‘Eye display’ will clearly demonstrate HF loss/distance on a coax cable; indeed it is necessary to use only the shortest and lowest loss input cables, as anything longer than a few centimetres will produce an erroneous display due to the significant HF losses down the cable. In order to function practically, ALL SDI systems must, and will, incorporate 'input equalision'; this is vital to automatically compensate for all losses, even with modest cable lengths. Therefore in practical equipment, the input signal is always used post-equalisation, and ONLY correctly equalised signals are ever processed in TV's 'real world'.     The ONLY thing that matters with practical equipment is the quality of the signal after equalisation, not before; and this will be a direct function of the performance of the input equaliser stage used in any particular SDI equipment, ...so why attempt to examine such a soggy, tatty and unequalised signal?     It is by no means certain that the equaliser performance in the measuring instrument would be identical with that used in Proprietary Broadcast equipment such as that from JVC, Panasonic or Sony for example, in fact it is highly probable that they are NOT identical. It is no use the Measuring Device using very latest IC which equalises (perhaps) 250M cable, if the Equipment in general use on the Station uses earlier generation devices which might only compensate for perhaps 120M of your chosen Reference Coax!     To be useful when evaluating “RAW Eye” performance, the PCB layout and Analogue Digital Convertor need to have an exceptionally wide bandwidth with high phase linearity if the display is to be accurate; and figures of 10GHz have been suggested for realistic fidelity. How much of a perceived ringing problem may actually due to the (mis)performance of the input stages of the measurement device? At Murraypro we are well aware of the technical difficulties involved with producing an acceptably low return loss at 'only' 2.8GHz; and even this can only be achieved through the use of the very highest quality BNC connectors. The compromised performance of the Bayonet-Neill-Concelman connector (BNC) is a serious issue at 2GHz, and specially so at higher frequencies, which is why modern high frequency Spectrum Analysers shun this 60 year old design in favour of 'N' Series connectors; and that the performance of the optional "Eye" feature offered by at least one of  Test Chest's competitors is highly dubious.     Test Chest's own TDR cable test feature is complementary, and is included in the standard Unit. It also has the  fundamental advantage of using the Installation's destination equipment and it's associated input coax cable, together with it’s own BNC connectors as the actual terminating load, rather than the temporary imposition of the input of a separate ‘EYE’ measurement device, which is quite alien to the normal configuration of circuit under test. In all cases, any practical display down even a meter or two of coaxial cable MUST use an equaliser to restore the signal, which rather defeats the purpose of an Eye display per sec      Consider the 'Real World' case reported to us where investigation of a problem, using the TC3G’s TDR pulse, instantly revealed the imperfect mating of  a  BNC connection at the end of a 100M run of high quality coaxial cable. It is most unlikely that any "Eye" display could have localised this problem in this way, or indeed even being capable of showing it at all; let alone, as the Test Chest 3G did, localising the fault precisely, and in a matter of seconds!   Q: Can I measure SDI jitter using Test Chest? A: Not directly, however using the EYE~POD accessory Timing and Alignment Jitter measurements to SMPTE 292M may be made. Our Jitter histogram display provides immediate confirmation of System Conformance.   Q: Can I use Test Chest to show proximity to the 'digital cliff'? A: Yes, this is simply done using the “SDI CAL” feature on the Set Up sub-menu page, which is accessed via the 'Set-Up' icon of the main menu. Different TV Standards will have differing Clock frequencies, 270MB/S, 1.4GB/S or 2.8GB/S, and different Installations will have been installed with differing types of coaxial cable. Cable losses at System Clock Rate may therefore vary considerably from Installation to Installation in absolute terms, whilst remaining entirely satisfactory in their own right for that particular Installation.  i) Set the Test Chest to Generate a Colour Bar signal on the TV Standard appropriate to the Installation under evaluation.  ii) Select coaxial cable of the type in use on that Installation being tested, and of a length that your local tests have shown are approaching the “Cliff”. Conventionally this is usually determined by evaluating performance of a piece of equipment down a nominal length of the cable selected, and then experimentally extending the cable, in increments of perhaps 10Metres (using a BNC Barrel), and then evaluating for deteriorated performance, as an increased 'Bit Error Rate' (BER).  iii) This process is repeated until the system fails to operate normally. This is the so-called digital “Cliff” and, at this point, performance deterioration will be very rapid with only small increases of total cable length. i v) Ensure that this test is always performed with samples of the Equipment in use in the Installation under test, rather than the Test Chest 3G's own Which-Wire? SDI input, for reasons explained earlier.  v) Murraypro recommend that the 'SDI Cal' length is set conservatively, rather than at maximum length achievable, so that it acts as an “EARLY WARNING” rather than an “UNDER ATTACK” alarm! Be aware that the Test Chest's own Equaliser uses a high performance '3G' device, which offers significantly enhanced performance over earlier devices, and consequently could suggest unrealistically optimistic cable lengths, compared with your own existing equipment's performance.    Knowing the maximum cable length, before compromised performance is likely to occur, enables the User to pre-load and calibrate the Test Chest's “SDI CAL” feature realistically to warn Users of cable lengths that are likely to be approaching this critical length.    To align the “SDI CAL” feature for your particular Reference Cable as selected in paragraph 3, simply loop the Colour Bar SDI OP  back to the Which-Wire? Input using the Reference length of your chosen coaxial cable and tap the “SDI CAL” icon on the setup sub-menu. This will memorise the current SDI Input Equaliser's AGC voltage, enabling direct comparison with other cable lengths in the future. These comparisons are indicated as “Low Eq” when shorter than your Reference Cable; and “Hi Eq” when the local input cable exceeds that of your Reference Length.    As supplied, Test Chest is calibrated for 100M of Belden’s 1694A @ 1.5GHz, and this setting will automatically be restored if the “Factory Reset is used.   Q: Do you have a list of the TV Standards covered? TX & RX Standards available:- 3G 1920x1080: 50Hz Progressive (A & B format) 3G 1920x1080: 59.94Hz Progressive (A & B format) 3G 1920x1080: 60Hz Progressive (A & B format) HD 1920x1080: 23.97Hz Progressive 24Hz Progressive 25Hz Progressive 29.97Hz Progressive 30Hz Progressive 47.95Hz Interlace 50Hz Interlace 59.94Hz Interlace 60Hz Interlace HD 1280x768: 50Hz Progressive 59.94Hz Progressive 60Hz Progressive SD 625: 50Hz Interlace SDI 50Hz Interlace CVBS SD 525: 59.94Hz Interlace SDI 59.94Hz Interlace CVBS   Q: What is HDVI, and what standards are supported? A1:  Test Chest provides twin “High Definition Video Interface” Graphics Ports using industry-standard connectors, enabling PC Display, Graphic cabling, and associated interfaces to be swiftly checked out. This feature should be regarded as an additional Test Chest feature, which facilitates viewing, testing and monitoring remote Display sources,  rather than a substitute for a dedicated Graphics Test Set.    A choice of local HDVI Test signals may be applied to a Display system under test, an arrangement that enables virtually any multi-sync PC or Graphics monitor to be used. If required, Test Chest can also generate separate SPDIF compatible audio output too from the AES OP stream, via the Audio-POD’s integral BAL/UN transformer.    External Graphics signals generated by remote equipment are fed, using commercially available HDMI# cable, to the Test Chest’s Graphics IP port for evaluation and monitoring. The signal may be presented either as a picture on the LCD panel, examined conventionally in ‘scope mode on the WFM as a ‘Colour Parade’, or even in vector format. If required the Test Chest can accept SPDIF compatible audio output direct from external equipment via BNC 2.       Test Chest is primarily intended for use in Television based Engineering applications, rather than ‘Multi-Media’ entertainment environments. So although industry standard connectors are used for convenience, the generation and display capability is firmly pitched towards confirmation of function with SD and HD  Professional TV related display standards, and a non-exhaustive list of the generally TV related Graphics standards that can be coherently displayed is tabulated in the Specification section. Hence we refer to this interface as our ‘High Definition Video Interface’ (HDVI).   Users should be aware that Test Chest does not embrace the High Definition Multimedia Interface# specification, and some features are not supported, although there is a degree of compatibility with elements of ‘681.    The HDMI# specification is continuously developing, and it’s scope is constantly being widened and so it can, we believe, only be investigated comprehensively with the use of the latest highly sophisticated and dedicated HDMI Test equipment.    A2: HDVI IPs: Non-exhaustive list of coherent images include~ 480i	@60Hz 	H:720			420p	@60Hz	H:720 720p	@60Hz	H:1280		720p	@50Hz	H:1280 1080i	@60Hz	H:1920		1080p	@60Hz	H:1920 576i	@50Hz	H:720			576p	@50Hz	H:720 1080i	@50Hz	H:1920		1080p	@50Hz	H:1920 1080p	@24Hz	H:1920		720p	@50Hz	H:1280 3D TB 1080p	@24Hz	H:1920 3D SH	1080p	@24Hz	H:1920 3D TB 720p	@60Hz	H:1280 3D SH	720p	@60Hz	H:1280 3D FP 720p	@50Hz	H:1280 3D SH	720p	@50Hz	H:1280 3D TB	     	(SH = Side/Side Half	TB = Top & Bottom		FP = Frame Packing)  	HDCP# EDID# or CEC# are not specifically supported.   Q: Do you have a list of the Signals Test Chest can generate? A: The Test Chest is intended for use in the Field, rather than use for Product Development in a Lab, and consequently it offers a range of popular Test Signals. All the signals are available virtually instantly on all supported TV Standards, and  either the 'Y',  'Ch', or both components may be independently disabled. Colour Bars Red patch Colour Bars Colour Bars Red Field White Field Grill Multi-burst Augmented Pulse and Bar Bow-Tie Stair Case, 5 step. Limit Ramp Limit Ramp + modulation. Pathological Test Signal. Pluge SMPTE Colour Test field  It must be appreciated that Multiburst (etc) envelope specification will vary appropriately with the set Standard. When set for operation on "SD" Standards, a CVBS OP is ALSO available in parallel with the SDI OP. All Signals may have either 16:9 or 4:3 circle added and a moving Puck to check for frozen processing elsewhere (particularly useful with MPEG sources). A Clapper Board signal is generated to check for downstream video/audio processing delay inequality.   Q: What HDVI signals are generated? A1: Test Chest generates a number of signals that are suitable for quickly checking Graphics displays and their interfaces. Currently Test Chest only outputs on the 800x600 standard, but we envisage future expansion in the standards supported. A2:  Users should be aware that unlike some other Graphics test equipment which often produce signals that are “Out of Gamut”, Test Chest ONLY produces ‘legal’ signals that fully conform to the amplitude requirements of the  Colour Bars Chequer Board 6 Step Staircase Linear sawtooth Red field Green field Blue field White field  Please feel free to ask further questions, if the above response is insufficient for your requirement.     E: tech@murraypro.com  The Test Chest is a developing Product and we are anxious to enhance it in line with User's requirements, therefore we are always pleased to receive feedback regarding 'Requirements' or 'Wish List'. Whilst we can not undertake to incorporate specific requests, we always consider Client feedback very carefully. All constructive feedback is extremely valuable, whether it is favourable to us, or otherwise.  June 2016 Home Page  Home Page Home Page  Home Page
Frequently Asked Questions Note that most of these FAQs apply equally to ‘Test Chest’ and our earlier ‘Test Chest 3G’ high speed  A + V  Testers
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