Outer Limits 4x4 Board

Hey there!

Excuse my ignorance, but my zook has an antenna mount, with the base and cable attached. I was wanting to put in a UHF radio, would this cable be ok? Or do UHF and old CB's have different requirements?

It was on the vehicle when I got it, so I dont know what used to be in there!

Any advice??

yes the cable and base will be fine, there is no difference between UHF and AM cable.

its only the antenna itself thats different. u will also have to get it swared in cause u wont have massive range until thats done.

screwy

Swared in??

Thanks for that though, antenna shopping I go! Guessing a 6db one should be fine (live in brissy, and radio is mainly for club runs)

P_Byrne wrote:Swared in??

Thanks for that though, antenna shopping I go! Guessing a 6db one should be fine (live in brissy, and radio is mainly for club runs)

swarred in basically means....

take it to the radio place, and they will adjust the length of the areal to suit the radio. either take some off or need to get a longer one......
its the way u get max range out of a particular radio.
If u get a radio with an areal and it gets swarred in then the radio shits it self and u get a new one, unless its the same model radio u will need to get it done again or you will lose some of your range.

screwy

The base for a UHF and a CB have different threads - I was caught out with this recently. The thread on a UHF is finer. Cable is the same. If you are changing the base, you may as well rewire, then you can loom it neatly (away from things that cause interference like ignitions!) with gentle radius bends (knots in the cable DO lose power! Seriously!) and then you know it isn't perforated (little pin holes or nicks, etc) that can let in moisture and destroy performance due to internal corrosion (and damn hard to trace the fault without a TDR - Time Domain Reflexometer).

What he's talking about is SWR'd. (commonly pronounced "swer'd") Standing Wave Ratio. It is to do with transmitted power versus reflected power relating to the total length of your antenna and cable and the wavelength of your carrier signal. If the length is wrong, it tends to reflect power back down the cable to your transmitter. Generally just messes up performance, in worst case will burn out your transmitter output amplifier, hence why you don't run them without an antenna!

You can often buy SWR meters from markets, the trading post, borrow one from a radio nutter (or find someone who'll help you) for about the $20 mark for a CB unit (included instructions for total novices!) as they are not popular these days. Visit an enthusiast or a 'radio shop' to get it tuned otherwise for UHF, though you could be lucky and find one for sale at a sensible price.

Just because I have five antennas on my 720, it isn't fair to call it a Russian Trawler! (CB, AM/FM, UHF, Cellular, fake cellular <- $2 Shop).

Scrapper wrote:The base for a UHF and a CB have different threads - I was caught out with this recently. The thread on a UHF is finer. Cable is the same. If you are changing the base, you may as well rewire, then you can loom it neatly (away from things that cause interference like ignitions!) with gentle radius bends (knots in the cable DO lose power! Seriously!) and then you know it isn't perforated (little pin holes or nicks, etc) that can let in moisture and destroy performance due to internal corrosion (and damn hard to trace the fault without a TDR - Time Domain Reflexometer).

What he's talking about is SWR'd. (commonly pronounced "swer'd") Standing Wave Ratio. It is to do with transmitted power versus reflected power relating to the total length of your antenna and cable and the wavelength of your carrier signal. If the length is wrong, it tends to reflect power back down the cable to your transmitter. Generally just messes up performance, in worst case will burn out your transmitter output amplifier, hence why you don't run them without an antenna!

You can often buy SWR meters from markets, the trading post, borrow one from a radio nutter (or find someone who'll help you) for about the $20 mark for a CB unit (included instructions for total novices!) as they are not popular these days. Visit an enthusiast or a 'radio shop' to get it tuned otherwise for UHF, though you could be lucky and find one for sale at a sensible price.

Just because I have five antennas on my 720, it isn't fair to call it a Russian Trawler! (CB, AM/FM, UHF, Cellular, fake cellular <- $2 Shop).

SWR meters for cb generally won't do UHF. The higher frequency blows the diodes etc up! Not many people have an SWR meter that will handle UHF, and if you borrow a mate's SWR meter and blow it up it's a fair guess that he won't be happy.
People generally don't bother to get the SWR adjusted on UHF's, as it does not make very much difference as the antenna's are pre-tuned, and at the frequency the cable length makes very little difference.

Cheers, Dean

Scrapper wrote:......(and damn hard to trace the fault without a TDR - Time Domain Reflexometer)....

Sure you didn't mean "Time Domain Reflectometer"?

I also thought SWR problems were caused by impedance mismatches between the cable and antenna?

Yes, Reflectometer. That is what you get for trying to post and answer the phone at the same time...

Impedance mismatch does cause reflection, but joins (even expertly joined ones) will cause reflection (poorer quality, more reflection, impedance mismatch looks like a poor connection) and the length of the wire, to do with the carrier wave, needs to be tuned to ensure the 'end of the wave' (without getting into technical description) reaches the end of the antenna and not some other point on the wave. The reflection is proportional to this offset. A SWR meter measures this Forward Vs Reverse energy then you adjust your antenna length to compensate and achieve a ratio as close to 1 as possible.

woohoo... SWR... TDR's... reflections...
at least a few guys here know their RF theory..