The test that path of PF721 microwave horizontal stroke disturbs and eliminate -

From;  Author:Stand originally

As the development of science and technology, microwave TV transmits equipment, on one hand more and more develop to muti_function, digitlization, miniaturization, its function and security are higher and higher also. On the other hand, as a result of the limitation of environment and other condition, in use is faced with more and more interference inevitably, horizontal path interference is. The face transmits equipment to PF721 microwave TV below, in use process, the test that the horizontal path of generation disturbs and eliminate, do a few abecedarians to discuss.

One, the generation of interference and the test to interference

PF721 is the replacement product of PF701S of the company on the pool, however this microwave equipment is in just purchased before long when game of direct seeding football, path of first time occurrence horizontal stroke is disturbed. On the picture expression is: Form if leek leaf, black and white alternate with, accident is differ, most time is 9, have 35 now and then, companion twinkles as mobbish and beat, serious when lose image. We go up to microwave machine ark above all each block one by one of the directive that express a head to examine: Include to send end and value of voltage of sink alternating current source, send and receive two end ark of high frequency machine volts d.c. value, send and receive power, inspect frequency extent, each condition is indicated all normal; Check cable of power supply cord, intermediate frequency respectively next, inspect frequency jumper and its interface, yi Zhengchang, commutation channel, breakdown phenomenon still exists; In the input end increases power source isolator, inspect, frequency isolator, the effect not beautiful, have slight improvement only.

When checking afresh the following day, equipment job is regular, breakdown did not appear; In a few subsequently tests normal also, appear without interference. Thinking by accident consequently is power source ground connection bad to wait, the interference that introduces accidentally.

Two week hind, use this microwave device when us again when direct seeding, generated horizontal path interference again, return be mingled with to wear other interference, than last more serious. Expression is not only have the horizontal path interference that appears last, and on whole weaveform overlay has an oscillation signal. When breathed sound is inputted, not only image has interference, frequency passageway also has very big " Zhi " noise; After inputting sound, image interference all the more is serious. Through Tektronix1731 oscillograph can see: No matter signal is be expert at,go up or on field, all overlay has signal of oscillation of a subcarrier, expression is opposite in sound image each rank the extent modulation of n, namely sound modulation arrives in the picture, make travel synchronism and white n, disappear concealed n all are in oscillation, black noise n beats in fluctuation; The oscillation on field is more apparent, whole field signal beats often. After be being looked carefully at carefully, discovered a small error, it is to be in ado so, involved the frequency filter switch of equipment not carefully by accident, make frequency subcarrier is mixed in video signal to be outputted together thereby, caused interference. After correcting an error, sound is normal, image also regains former interference position. Subsequently, we have observation and test again to this equipment, and be below the circumstance that afore-mentioned interference phenomena appear every time still discover at the same time: Switch on the mobile phone for some time, after about 35 hours, interference is met drop off, horizontal line is thinner and thinner, down to disappears, final image returns to normal. We divide a pace to have a test to equipment: If continueing to deliver upright equipment, put out sink equipment only, 5 hour hind restore to switch on the mobile phone again, image, sound is normal still, appear without interference; Conversely, put out only deliver upright equipment, and continue to wear sink equipment, 5 hour hind switch on the mobile phone again, interference arises again, properties still is now form if leek leaf, black and white alternate with, have long have short, accompanying twinkle often jumpy, serious when whole picture is missing, about 3, after 5 hours, interference disappears slowly, image returns to normal, can disturb a source to be in certainly thereby deliver upright equipment.
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