HI ALL THIS IS MY FIRST POST SO PLEASE BE GENTLE..
I HAVE RECENTLY BOUGHT A COBRA AND AM STRUGGLING TO KEEP MY SWR DOWN LOW ON ALL FREEQUENCIES THE RADIO GOES DOWN TO LOW LOW UP TO HIGH HIGH AND HAS A UK BOARD FITTED TO IT.
WHEN I USE MY AMPLIFIER(FOR TESTING PURPOSES ONLY..HONEST)IT IS EVEN MORE OF A PROBLEM THE AMP IS ONLY 100WATT..
ANY IDEAS?DO I NEED AN ANTENNA WITH BETTER COVERAGE??
THANKS...
USING AN ANTRON99 WITH A COBRA 148 GTL DX
You will struggle to keep the SWR down across five or six banks of forty channels - the antenna will only be resonant on a particular frequency(say 27.555 for example) dependant on its length & the SWR will get higher the further you move away from this resonant frequency (called antenna bandwidth)
You should adjust the SWR to its lowest point on the frequency you use most (use the tuning rings on the Antron) & you should be able to maintain a SWR below 2:1 across two or three banks.
Using the amp will just highlight the poor SWR even more, so I'd suggest using an antenna matcher/tuner if you intend to use the amp away from the resonant frequency (Note: These matchers only make your rig 'see' a perfectly tuned antenna - and so enable full power from the output stage of your rig to reach the antenna)
How much power is actually radiated by the antenna depends on the SWR at the antenna:
1.5:1 is 96% efficient (or 100W into the coax and 96W out of the antenna)
2:1 is 89% efficient (or 100W into the coax and 89W out of the antenna)
3:1 is 75% effiecient (or 100W into the coax and 75W out of the antenna)
Obviously there will be a bit more loss depending upon the length of the coax cable which rapidly increases with high SWR.
Good luck!
You should adjust the SWR to its lowest point on the frequency you use most (use the tuning rings on the Antron) & you should be able to maintain a SWR below 2:1 across two or three banks.Using the amp will just highlight the poor SWR even more, so I'd suggest using an antenna matcher/tuner if you intend to use the amp away from the resonant frequency (Note: These matchers only make your rig 'see' a perfectly tuned antenna - and so enable full power from the output stage of your rig to reach the antenna)
How much power is actually radiated by the antenna depends on the SWR at the antenna:
1.5:1 is 96% efficient (or 100W into the coax and 96W out of the antenna)
2:1 is 89% efficient (or 100W into the coax and 89W out of the antenna)
3:1 is 75% effiecient (or 100W into the coax and 75W out of the antenna)
Obviously there will be a bit more loss depending upon the length of the coax cable which rapidly increases with high SWR.
Good luck!
You're 5 & 9 - what's your QRZ again???