[SOLVED] What would be the best coax to use for passing a metal wall ?

[mad_scientist53]

Hi all my 1st post here
I have a small cheap 1.2ghz video/audio R/X T/X unit. that I need to put the T/X in a small metal box with the antenna on the outside from the fac. the ant. screws on the unit which has what I think is sma but has a bushing to convert to I think is called "F" (it's the same size as a standard TV connector)and the ant. screws on it.
right now (because it's all I had) I have a 12"(really only need about 8") piece of 59 running between the T/X and a male to male adapter mounted threw the wall of the box with the ant. screwed on to it. It works but not sure if it will hurt any thing.
What would be the best coax to use and because it has to bend sharply most flexible
thanks
mad

 

[jiripolivka]

Re: coax help

Hello there:
If you need to pass through a metal wall, simply use a good connector: at 1.2 GHz, BNC, N, F and SMA are good. If you need to use a 8"-12" long coaxial cable run inside of the box, use any good flexible or semirigid coax. Only keep in mind that F connectors are specified for 75 Ohm cable (some BNCs, too). I would recommend reading ARRL Radio Amateur's Handbook on how to connect coaxial cable to a connector through a wall for details. At 1.2 GHz, details are important.
One minor problem may be that you may not know the real impedance of your TX inside of the box, and/or antenna impedance connected outside. Impedance mismatch may cause some loss. If you meet some problems in real signal transmission, it may help to tune the antenna, or the transmitter output for the best results.

 

[mad_scientist53]

Re: coax help

Thanks
I'm testing now and the range is is all I need so I guess any mismatch is OK
if I"m not hurting anything.
thanks for the heads up on the handbook. That could be useful in the future
thanks again

 

[jiripolivka]

Re: coax help

Dear cmpter: F connectors are specified for frequency up to 2.5 GHz, and for 75 Ohms. So they are in fact better than BNC, 50 or 75 Ohms, also very easy to use and install.
For a single-frequency application like the above at 1.2 GHz, there would be not much difference between all mentioned connectors except of cost and installation ease.