TV sockets - isolated / non-isolated

[endecotp]

Does anyone know about this? TV aerial sockets are available as "isolated" and "non-isolated". I presume that the isolated ones have a capacitor or inductor - I don't think I've ever seen one of those. What's the rationale behind this? Which should I fit?

Thanks.

 

[pete01]

Didn't know that was a thing....

I'd fit either and if it doesnt work fit the other one

 

[ericmark]

If you have a mast head amplifier, then it needs a DC supply up the coax, so non-isolating is used, but otherwise you can get atmospheric voltages in the aerial which can give one a nasty belt, so isolated used, it will not protect from a lighting strike, but may protect from near misses.

 

[endecotp]

Ah yes, DC for satellite amplifiers etc. We do have an aerial amplifier but it's powered locally.

Thanks.

 

[ericmark]

This was the design given

This combined braid-breaker and high-pass filter prevents HF signal currents from flowing down the inner or outer of the co-axial cable. L 1 has a low reactance to HF or VHF signals. there by by-passing the interfering current. where as C 1 and C2 have high reactance to HF/VHF. Effectively blocking signals to the receiver. L2 provides a further 'short circuit' across the connections on the Rx side of the filter.

At UHF the conditions are reversed. C 1 [4p7]and C2 [4p7]presenting a low impedance path to signals to the receiver and the impedance of L 1 and L2 is so high as to be ignored. R 1 [1M5] is for static discharge of the outer screen.

L1 = L2 = 4 Turns of 20 SWG 6mm I/D 6mm Long
Single sided PC Board 2" x 1" Scrape Grooves - approx. 1.5mmwide in copper to leave four areas as shown.

It was a free instruction set from the government before we went digital on how to stop interference.

 

[mattylad]

It was a free instruction set from the government before we went digital on how to stop interference.

I bet no one in the government would have the faintest knowledge how to build one of those!
Let alone most of the population being governed.