TV Aerial Cable- Thickness?

Richard10002

Richard10002

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Hi,

Just bought the Triax UFO TV Aerial on ebay, (should be delivered tomorrow).

Is aerial cable merely coax cable?

Just wondering if it is possible to get TV aerial cable which has a smaller diameter than the household variety?

I think it is goint to be a tight squeeze to get the normal stuff down the conduits in the mast.

Also, is it worth considering a better quality cable... I think Maplins do the usual at about 50p per meter, and a better quality for about £1.50 per meter. They say the better quality one is typically used for connecting audio units via coax, but offers better performance than regular 75ohn coax.

I dont pretend to understand any of this, and wil be guided by advice.

(BTW did a search, but couldnt find anything specific)

Many Thanks

Richard
 
TV coax is 75 ohm, VHF/AIS coax is 50 ohm. I know nothing else about TV coax. You need RG8X coax for a VHF cable run of under 20 meters. This has a diameter of 6.5mm. It should have a 100% tinned centre conductor and braid. Obviously it should be marine grade.
 
The standard brown 75 ohm coax is fine for the job, the most important consideration is the core, it needs to be solid (copper). This is because it uses F type connectors (the type used on satellite cables into the back of your decoder.

Hope this helps a little.

p.s. If you look for a narrower cable you may have problems as the F types screw down onto the outer insulation, too narrow and you will not get it to screw down tightly. Plus, surprisingly it may be cheaper to source the cable from outlets like B&Q as it is really common stuff.
 
I used satellite coax, solid core, high density braiding with foil wrap. Correct diameter for the "F" connectors and thinner than standard household TV coax. This seems to work well - don't know how the 50ohm cable would affect the signal though. I previously had the standard household coax (thicker stuff) and it was not so good - too much signal loss/interference.
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"Artificial intelligence is no match for natural stupidity"
 
[ QUOTE ]
Used tinned cable. standard domestic aerial cable is usually made to a price, the cores are thin, the screen sparse. It is also not intender to flex or move.

Ask VDC http://www.vdctrading.com/ they are a specialist cable and connector supplier.

[/ QUOTE ]

Thanks you,

email sent
 
I am a little concerned about tinned RF cable. With RF you get skin effect on the wires, does tinning them have an effect on the signal?

Are there any physics experts who can tell me if this could be a problem?
 
Hi Woofie

I don't think it does have any or much effect, not as to be noticable anyway.

But like you, I am not that fussed about using coaxial cable with tinned conductors cos if it is wet enuff inside to corrode then the cable will be lossy and should be replaced tinned or not. My own RG213 to the masthead, for example, is not tinned.

The secret, as I realise you have plenty of experience to know, is just to use good sealed joints to keep the water out in the first place.

John
 
TV antenna systems use 75 ohm coax while radios use 50 ohm coax. It probably does not make much difference in practice however. Yes there are good quiality (low loss) cables and cheap cables however for true low loss cables the size must increase. Unfortunately the loss increases with frequency and so is bad at UHF.
Some examples @ 500mhz UHF TV are economy TV cable 75 ohm 23db loss in 100 metres. Expensive 75 ohm 16 db/100 metres, RG 58 40db per 100 metres The best 10mm dia RG 213 about 16db per 100 metres. Interesting TV cable seems better than 50 ohm for loss at TV frequencies. Db of course are a log ratio such that 6db is half power loss 10db is 90% loss and 20 db is 99% loss. that sounds horrible but of course the signal you receive is like 10 to the minus 10 power of the transmitted power so a large loss only matters if you are in the fringe area of reception.

The impedance of a cable is a balance of the inductance of the centre versus the capacitance from centre to shield. So using audio cable which is not really coax but rather described as shielded cable can leave you with unknown impedance. Even so if you are pressed for space in the conduit you could try it. Try is first using the 12 metres or so you will need before you put it up the conduit. Bearing in mind that antenna height improves signal. A wrong cable impedance won't hurt the TV just lose signal strength which may or may not matter.
good luck and try it olewill
 
As Cliff has said use satalite coax. It is 75 ohm which is correct for TV use. Unfortunately the impedance of it means that it is not compatable with marine VHF use.

Satalite cable is one of those things which has been developed because of the large consumer market. This market demanded a high performance coax at a very competative price.

It is extremely low loss at TV frequencies as it is designed to work at the even higher satalite frequencies.

Use type F connectors as they give a better match then UHF of TV type connectors.

Iain
 
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