Can I use 75ohm cable to extend an antenna that already has a 50ohm cable attached to it?

 

Not if you want the best signal. The impedance mismatch causes signal reflection in the cable and degrades the signal.

 

But it will likely work OK.

Try it.

Just be advised as cruts says there is some mismatch which can increase reflections and loss. If you have enough signal, some loss may be tolerable and reflections may not be severe enough to be noticeable.

 

I would add a foot or less to the existing 5 feet of cable already existing. Worth the try I guess!!!

 

A cable that short should never be spliced, just replace the whole thing.

 

Is the receiver tuned for a single frequency as a two way radio or for a wide range of frequencies as a television ?

Or is it for transmitting ? Or both ?

 

A cable that short should never be spliced, just replace the whole thing.

Are you using the term "spliced" literally,or do you mean using a "bullet" adaptor between two coaxial fittings?

If the former-No you shouldn't do it!

If the latter,proper coax adaptors contribute very little to losses,& in themselves,cause hardly any discernible mismatch.

To the OP--try it!
The mismatch between 50Ω & 75Ω is quite small.

If it causes a problem,you will have to get a 50Ω extension.

 

Are you using the term "spliced" literally,or do you mean using a "bullet" adaptor between two coaxial fittings?

If the former-No you shouldn't do it!

If the latter,proper coax adaptors contribute very little to losses,& in themselves,cause hardly any discernible mismatch.

To the OP--try it!
The mismatch between 50Ω & 75Ω is quite small.

If it causes a problem,you will have to get a 50Ω extension.

The total cable length is going to be less than 6'.There's no reason to splice something that short. The cost of the proper connectors/coupling would be more than the the cost of the cable. Plus, a splice always introduces a weak point into the cable. And looks totally unprofessional.

 

The total cable length is going to be less than 6'.There's no reason to splice something that short. The cost of the proper connectors/coupling would be more than the the cost of the cable. Plus, a splice always introduces a weak point into the cable. And looks totally unprofessional.

Out in the real world inline connections are often used to go from fairly inflexible cable to flexible coax "tails" of similar length to that proposed.

Cost?------- The OP may already have the adaptors & the short piece of cable..
.
I have seen this term "spliced" used a lot recently for cables which were properly joined with an adaptor.

In around 40years in TV & Radio Broadcasting I have never ran across this usage amongst people who (like myself) worked with coax cables.

I have seen coax cables that some newbie or lazy person really has spliced,& they are a mess!

 

By the time the OP makes up a 1 foot piece of cable with connectors on both ends, he/she could have made a 6 foot piece of cable with connectors on both ends, and avoided the "splice" altogether.

 

I have some TNC connectors but I need the female adapter but I could go TNC to BNC to TNC but I think that would create a major loss

 

I have some TNC connectors but I need the female adapter but I could go TNC to BNC to TNC but I think that would create a major loss

I assumed that you had the correct connectors available.

You can probably get TNC adaptors,but if you can't,it is getting a bit messy mechanically, so now, I agree with gerty & tracecom.

You may as well replace the whole cable!

By the way,you never told us what the application & operating frequency were.