Good morning, I bought some day ago a new RCI-2970N4 but an issue about high swr when I connected to a perfect tuned antenna, that used with other radios in the shack without problems. If I check the 2970 with dummy load is perfect with no modulation, with modulation the swr jump to high. Other person like me have same problem?! Suggestion to solve? Thank You all. Federico
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RCI-2970N4 High Swr with perfect tuned antenna.
- Thread starter ALANFede
- Start date
Dears,
The dummy load is in tolerance. I'm thinking a not good tuning between the output of the final transistor and the input of amplifier section. I'm thinking that the radio section don't see a 50 ohm from input amplifier stage. I've other radios in the shack and no problem with the same antenna and same dummy load with high power. Probably a component or a coax issue in the radio. I hope to be clearer. Thanks
The dummy load is in tolerance. I'm thinking a not good tuning between the output of the final transistor and the input of amplifier section. I'm thinking that the radio section don't see a 50 ohm from input amplifier stage. I've other radios in the shack and no problem with the same antenna and same dummy load with high power. Probably a component or a coax issue in the radio. I hope to be clearer. Thanks
And just to be clear you check SWR with a carrier only. This is why you don't check SWR in SSB mode.
You're overthinking it. This is simply a limitation of the "automatic calibrate" type SWR meter.
Have you inserted an external SWR meter in line with the radio to compare?
73
Have you inserted an external SWR meter in line with the radio to compare?
73
I'm using only an external swr meter with crossed needles. If I check the swr in SSB the swr value skip to the stars. I'm used to compare an RCI-2995 DX CF in the same conditions with no problem. Same pcb board, same RF transistors PA type, obviously fewer in number, the 2995 is less powerful.
Whups, thought you were using the radio's internal SWR indicator.
The cross-needle meter is harder to fool. This suggests the amplifier has become unstable, producing spurious frequencies not on the actual channel. A wattmeter or SWR meter that is presented with too many frequencies at once can do this.
First thing I would look for is loose ground screws on the circuit board, or for the tiny coax connectors inside the radio to have come partway loose.
Chasing down the cause of an unstable linear can be like a trip down Alice's rabbit hole.
73
The cross-needle meter is harder to fool. This suggests the amplifier has become unstable, producing spurious frequencies not on the actual channel. A wattmeter or SWR meter that is presented with too many frequencies at once can do this.
First thing I would look for is loose ground screws on the circuit board, or for the tiny coax connectors inside the radio to have come partway loose.
Chasing down the cause of an unstable linear can be like a trip down Alice's rabbit hole.
73
can you check the SWR in AM mode with no modulation and tell us the results?
LC
LC
Most probably radio is spitting out harmonics. That's the reason why you see SWR increased.
yep i agree with Mike.
the dummy load doesn't care what frequencies your radio is spitting out, the antenna does.
if someone has been inside that radio turning cans and spreading coils then you're going to need a spectrum analyzer to get it back to normal.
LC
the dummy load doesn't care what frequencies your radio is spitting out, the antenna does.
if someone has been inside that radio turning cans and spreading coils then you're going to need a spectrum analyzer to get it back to normal.
LC