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SWR Help
- Thread starter LckNLoad
- Start date
Going only by what you've posted here, it sounds like your amplifier's output impedance isn't close to 50 ohms. With only an SWR meter, I think you're stuck with what you've got.
Does that SWR with the amplifier on ever change, get lower if you change channels?
- 'Doc
Does that SWR with the amplifier on ever change, get lower if you change channels?
- 'Doc
I'd like to see what the output of the amplifier looks like on a spectrum analyzer. I'd bet there's a lot of harmonics and spurs far removed from the frequency L&L thinks he's on.
The output impedance of the amplifier doesn't mean much; the SWR meter can't see it. All it sees is what's downstream (toward the antenna) from it, normalized to 50 ohms.
The output impedance of the amplifier doesn't mean much; the SWR meter can't see it. All it sees is what's downstream (toward the antenna) from it, normalized to 50 ohms.
Did you get your swr issue figured out? Mine does the same with the amp on.
Cobra 29 lx/le with rfx75, texas star 500v, dosy 4001 meter, and a 54" open coil antenna.
Radio @ 2w dead key is 1.2 all 40 channels. Turn amp on, over 3 but swings back when modulating. Everyone says "sounds good"!
Still makes me worry though.
2w DK maybe too much for that TS500...If your seeing a backward swing thats usually a sign of too high a DK...Try turning down the DK to just 1w...And if possible try getting your SWR closer to 1.1
Here is what your dealing with.
With the amplifier in standby, the radio is seeing some SWR upset through the total amplifier transmitt/receive relay through circuit to the antenna.
When you put the amp on for transmitt, the radio is seeing an impedence change again when transfered to the amplifier input circuit by the T/R relay.
When the output with the amp on in transmitt, the amp presents yet another impedence difference looking into the coax and it's swr value.
Unless this is all custom tuned for lowest swr at both the input and output of the amplifier with the existing antenna, you have to live with the combination.
None of this is any different than we have to deal with in Ham radio.
At the moment I am building a system for 432 and it's a 100% more touchy and requires special tuning at each point to get the overall SWR down due to the losses in the feedline and equipment requirements.
Good luck.
With the amplifier in standby, the radio is seeing some SWR upset through the total amplifier transmitt/receive relay through circuit to the antenna.
When you put the amp on for transmitt, the radio is seeing an impedence change again when transfered to the amplifier input circuit by the T/R relay.
When the output with the amp on in transmitt, the amp presents yet another impedence difference looking into the coax and it's swr value.
Unless this is all custom tuned for lowest swr at both the input and output of the amplifier with the existing antenna, you have to live with the combination.
None of this is any different than we have to deal with in Ham radio.
At the moment I am building a system for 432 and it's a 100% more touchy and requires special tuning at each point to get the overall SWR down due to the losses in the feedline and equipment requirements.
Good luck.