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Rci 2970n2 swr to hi

Charliepr

Member
Nov 14, 2019
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Hello greetings to all I bought the radio rci 2970n2 in the bells store and I can't raise more than 15whatts because the swr rises to 2.9 with two different antennas and meters.
 

What band are you operating on? 10M, 11M, or 12M? Antenna must be tuned for band. My 2970N2 will go from 20w to 260w. Turn down to lowest pwr setting set tune swr on antenna.

When running linears I tune with barefoot radio, no power on amp (or take linear out of system), tune swr at antenna.
 
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Since he's already tried two different antennas and meters, I suggest you try a different radio to see if the final stage is oscillating on a frequency outside of the antennas bandwidth.

Bingo! I'll bet it appears to work just fine on a dummy load. A spectrum analyzer and scope would shed some light on the situation.
 
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I've had them oscillate right out the box.
Darn, got a new one still in box. Haven't hooked it up yet. Shopped around and noticed some reviews of shops tuning. Went with one from Clay's, even called before ordering. They took time to "talk with me" and explain their tuning. They wont crank it up just to be loud......best sound, best modulation to pwr. Every radio is different. Spec sheet values are : low pwr, 20w dk swing to 100w, high per, 100w dk swing 260w.

Finally broke dwn and bought it, and now reading recent failures is not settling well.o_O
 
Darn, got a new one still in box. Haven't hooked it up yet. Shopped around and noticed some reviews of shops tuning. Went with one from Clay's, even called before ordering. They took time to "talk with me" and explain their tuning. They wont crank it up just to be loud......best sound, best modulation to pwr. Every radio is different. Spec sheet values are : low pwr, 20w dk swing to 100w, high per, 100w dk swing 260w.

Finally broke dwn and bought it, and now reading recent failures is not settling well.o_O

This crowd a little picky, huh?

(Have The Backup Radio ready to drop in place).

.
 
I've had them oscillate right out the box.
When the high power final stage uses transistors in a 3 terminal package, the chances of instability resulting from internal oscillations increases a lot. No matter what you place inside the package, you still can't get around those high inductance leads. The very nature of RF oscillations can be so unpredictable that it can be difficult to replicate all of the situations that can cause one to start. Testing on a dummy load just about eliminates your chance of detecting one without a spectrum analyzer. Even then, it may behave well with a purely resistive load.

This is why we see such different reports on the same piece of equipment. Variables within each installation can determine if the amplifier is in a condition where it can run stable or not, when it should be stable under all operating conditions. Anything from coax length to slight changes in load reactance can cause an oscillation. Even changes in drive level can do this, making some amplifiers appear to have a carrier on SSB or holding the RF relay of an external amplifier closed after the mic is unkeyed.

When changes like this cause noticeable differences in VSWR or output stability, do not suspect equipment other than the RF amplifier first. If you do not have the test equipment to confirm a problem here, use process of elimination to see if the amp is the problem first.

One other thing I've noticed is that manufacturers don't like putting short jumper wires on PC boards anymore. They would rather cut into the ground plane surface area of the board to install traces, which also promotes oscillations. The immediate area around the PA stage should be double sided PC board with as much of the conductive surface area as possible, uninterrupted and well grounded. Don't compromise the entire ground plane of the PC board in order to bring a bias trace trough the middle of it or mount some other trough hole part!
 
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Try taking the covers off. I had a stryker 955 that had a very similar issue right out of the box. It would only misbehave with the bottom cover installed....I'm curious. :D
 
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