Barrel connectors
Are there any potential pitfalls using barrel connectors? Can they cause signal loss in any circumstance? Will they pass through current to a preamp?
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I have bought some miserable F81s. Some don't grab the center conductor very well; others don't even allow the center conductor to enter!
I test every one before I use it by inserting a short length of 18 gauge solid copper wire to see how well it grabs it. That's the same gauge as the center conductor of RG6. Here I'm measuring the output voltage of the CM0747 power supply/inserter under load. It is necessary to have access to the center conductor to measure the voltage and current, hence the 18 gauge hookup wire: http://forum.tvfool.com/attachment.p...1&d=1416169141 The photo is from this post: http://www.avsforum.com/forum/25-hdt...l#post20502719 from this thread: CM7777 preamp failure question http://www.avsforum.com/forum/25-hdt...-question.html Quote:
The better ones are rated to 3 GHz: http://www.mjsales.net/itemsearch.asp?FamilyID=854 These are rated by pin holding force: http://www.3starinc.com/manuals/Holland-F-Splices.pdf These have a current rating of 8 amps, which is probably more than you need for a TV preamp in the 100 to 300 mA range: http://picodigital.com/product-details.php?PID=156 Using the Right F-81 Connector http://www.tselectronic.com/tech_notes/right_f81.php Barrel connectors for satellite discussion: http://www.dbstalk.com/topic/189731-barrel-connectors/ The current carrying ability is determined by the contact resistance, as it is in switches. You can measure the contact resistance by using what is called a 4-terminal resistance measurement which uses a constant current and a measurement of the voltage drop. Ohm's law then gives you the contact resistance. The simple way is to measure the voltage delivered to the preamp to see if it is sufficient for proper operation. This becomes more important with long runs of coax. RG6 with a solid copper center conductor has less DC voltage drop than RG6 with a copper coated steel center conductor. The TV signals use just the surface of the center conductor; this is called the "skin effect." The DC current for the preamp power uses the whole cross-section of the center conductor. |
Very informative!!!
Thank you very much. |
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