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#1
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Hey Jack! When checking the coax with the ohm meter as you described,
what sort of a reading shoud you get, and I suppose you should set it to DC, but at what voltage? I know these are basic questions, but I am sure I am not the only one who is unsure. Thanks for the reply in advance! Have a great week! Jon. |
#2
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Jon,
When checking a coax with an ohm meter. With the coax disconnected on both ends, measure from shield to ground. This must be an infinity reading. Now measure the center conductor end to end. This shouldn't be over a couple ohms at the most. The same for the shield measurement. If you have a dummy load, connect it to one end and you should read around 52 ohms with the meter. It's best to do that from both ends to ensure the connectors are good. The only way better to test is with either a megger or a TDR time Domain Reflectometer. If you have you atenna connected, you'll find that with most fiberglass base antennas, you'll have a reading from 40 - 150 ohms do to the tuning curcuit inside the antenna. I hope this helps a little..... 73 de Dungeon Master |
#3
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On a sunny day (17 Oct 2005 10:51:15 -0700) it happened "Dungeon Master"
wrote in .com: Jon, When checking a coax with an ohm meter. With the coax disconnected on both ends, measure from shield to ground. This must be an infinity reading. Now measure the center conductor end to end. This shouldn't be over a couple ohms at the most. The same for the shield measurement. If you have a dummy load, connect it to one end and you should read around 52 ohms with the meter. It's best to do that from both ends to ensure the connectors are good. The only way better to test is with either a megger or a TDR time Domain Reflectometer. If you have you atenna connected, you'll find that with most fiberglass base antennas, you'll have a reading from 40 - 150 ohms do to the tuning curcuit inside the antenna. I hope this helps a little..... 73 de Dungeon Master Small correction: There is a difference between 'rsistance' and 'impedance'. For example when I measure the 'resistance' (with the Ohm meter) from my 1/2 wave GPA, I measure a dead short. This is because there is a little transformer in it, you measure the Ohms of the wire in the primary. the *impedance* however is around 50 Ohms (I would hope). There is a simple way to measure impedance too, in a bridge: http://web.telia.com/~u85920178/antennas/bridge.htm The reason is that for DC a transformer is almost dead short.... |
#4
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"Jon L" wrote in message
oups.com... Hey Jack! When checking the coax with the ohm meter as you described, what sort of a reading shoud you get, and I suppose you should set it to DC, but at what voltage? I know these are basic questions, but I am sure I am not the only one who is unsure. Thanks for the reply in advance! Have a great week! Jon. Set the meter on ohms. You should get infinity between the center conductor and ground. You should get a reading very close to zero when checking ground to ground or center to center. On your previous post on swr meter use, place in line close to radio. Place switch to for, key mic and adjust to where it says cal, the switch it to ref. That will give you your swr reading. |
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