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#1
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Dave,
What happens when you ping your antenna? Clearly the spectrum of the pulse is wider than the bandwidth of a typical antenna, but is there any useful information? Tam/WB2TT "Dave" wrote in message ... "Mike Coslo" wrote in message ... * wrote: They make an instrument called a Time Domain Reflectometer, you hook it up to transmission lines and it sends out a pulse and times how long it takes to get back. The time it takes, reflected pulse polarity, and height says a lot about the line. Used for finding faults on telco/cable lines. Does the same thing with RF lines. Matched well, no pulse, but you can even see connectors on some of these TDR's Googleit, too Fascinating stuff! Why don't we use them more for ham radio? this page: http://www.epanorama.net/circuits/tdr.html even has a diagram for a homebrew pulse source and diagrams for hooking up same to an oscilloscope. While not giving SWR, it would show up any connector faults and crimps in the cable. - Mike KB3EIA - i use one regularly in my station here. most people don't use them because a simple swr meter is adequate for testing most antenna./feedline combinations in use by amateurs. |
#2
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on yagi's and other antennas with matching networks you usually just see the
matching network. i use it the most on my beverage antennas which kind of look like long transmission lines and also to find faults in transmission lines themselves. with 25 lines or so ranging from about 50' to 500' or so it makes for a quick check... especially in winter. "Tam/WB2TT" wrote in message ... Dave, What happens when you ping your antenna? Clearly the spectrum of the pulse is wider than the bandwidth of a typical antenna, but is there any useful information? Tam/WB2TT "Dave" wrote in message ... "Mike Coslo" wrote in message ... * wrote: They make an instrument called a Time Domain Reflectometer, you hook it up to transmission lines and it sends out a pulse and times how long it takes to get back. The time it takes, reflected pulse polarity, and height says a lot about the line. Used for finding faults on telco/cable lines. Does the same thing with RF lines. Matched well, no pulse, but you can even see connectors on some of these TDR's Googleit, too Fascinating stuff! Why don't we use them more for ham radio? this page: http://www.epanorama.net/circuits/tdr.html even has a diagram for a homebrew pulse source and diagrams for hooking up same to an oscilloscope. While not giving SWR, it would show up any connector faults and crimps in the cable. - Mike KB3EIA - i use one regularly in my station here. most people don't use them because a simple swr meter is adequate for testing most antenna./feedline combinations in use by amateurs. |
#3
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but is there any useful
information? most people don't use them because a simple swr meter is adequate for testing most antenna./feedline combinations in use by amateurs. =============================== Following a query, Guru's feel an urgent desire to display their knowledge about S-parameters, Time domain reflectometers, Circulators, and High power UHF TV transmitters. As a consequence, the unfortunate original questioner, with his solitary 1.8 to 30 MHz SWR meter, is entirely forgotten about and remains suspended in mid-air. ---- Reg, G4FGQ |
#4
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Quote below.
The on-channel TDR pulse performance of a narrowband antenna can be seen by controlling the RF bandwidth and spectrum span of the test process to fit the application. The pulse (ping) itself is modulated onto an RF carrier set at the operating frequency. Not practical for most hams, but very useful in evaluating and optimising TV transmit antenna systems. If anyone is interested in seeing a jpg of such a measurement, pls e-mail me directly. - RF _____________ "Tam/WB2TT" wrote in message What happens when you ping your antenna? Clearly the spectrum of the pulse is wider than the bandwidth of a typical antenna, but is there any useful information? |
#5
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"Richard Fry" wrote in message ... Quote below. The on-channel TDR pulse performance of a narrowband antenna can be seen by controlling the RF bandwidth and spectrum span of the test process to fit the application. The pulse (ping) itself is modulated onto an RF carrier set at the operating frequency. - RF Duh! I should have known. Pulse it within the BW of the load. Steve N. |
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