IM distortion on 6 meters

George Moranian

Tim - W4TME

Steve G1XOW

Steve G1XOW

George Moranian

Tim power level on both screens is at 100 watts, tried at lower power level and same results seems to peak at about 20 watts but just as bad at 100 watts

George Moranian

Bill -VA3WTB

The panadapter is not a very good representation of our TX signals. Can you show the TX on the water fall?

Steve G1XOW

Bill, it's a TUNE carrier at 10w o/p, see below.

KD0RC

If you want to see what your signal looks like, NM9P has a great video on the subject on YouTube. Basically, you put the rig in full duplex mode, transmit on the xverter port, while listening on a different port. With the few mW produced by the xverter port, you will not be overdriving the reciever. I think you will see a very clean sig. If not, then it is time to ask Flex for help. 73, Len, KD0RC

Chris DL5NAM

George, forget what YOU see at your PAN or Water if you transmit.
Search for a Ham who is close to you to check your signal on a SDR with his Pan - if you not have a own Spec Analyzer.
And not forget: if you TX your TRX create also local noise, you will see on your Pan but you not transmit this noise too over air.

Bob KC9RF

Steve G1XOW

Bob, almost exactly the same as I saw. Am pretty sure the real RF output IMD is fine as I checked on another RX with dummy load, but the display software is nasty and needs fixing PDQ.

George Moranian

Good to know, Thanks

Thanks everyone for their reply's. Hope the display gets cleaned up.

Bill -VA3WTB

This is why I suggested to look at the water fall while on TX. It shows much better what is going on. The panadapter is working as designed. What your seeing is everything going on inside the transmitter. Your also seeing the TX signal coming back into the receiver and being mixed with the TX signal. Most companies take steps to hide this, so everything looks clean. Flex decided to leave everything as is so we can see everything being mixed. Also this way if there was something going wrong with the transmitter it would show up,,you won't miss that, it is really messy. On other radios the TX could run into trouble but the operator would never know because their radio will not display the TX problems. Bottom line, the panadapter does not represent what is actually going out over the air.

Steve G1XOW

Bill -VA3WTB

I took my comments from Eric at Flex where he explained what we see. It is a combination of internal noise and the return of the TX signal re entering the radio and mixing with the TX signal. This signal is usually coming back through the other ant input. All radios do this. But most companies design their radios to block this signal so the user can't see it. What you see on the panadapter is not being transmitted. 

Bill -VA3WTB

When I have time I will post Eric's article then you can argue with him..

Bill -VA3WTB

Steve G1XOW

Hi Bill, thanks for the text. Gland to see it is like I said a display handing aberration, not RF IMD. Interesting info from Eric, and I feel this information should be communicated far and wide, is it even in the Radio manual?

As I am also an engineer of some 34 years experience (20 as a low-level comms programmer), I generally concur with the design principle of seeing an unadulterated signal "warts and all". However, where I cannot agree is presenting the user with a screen that is so far out from on-air reality. Misleading or false feedback instrumentation that suggests problems that are not real is not a wise move for any product, and moreover is of no value if the foreground imagery is so wildly distorted that you simply cannot see any "real" underlying RF issues that may be there. Flights tend to crash with a big **** if the pilot gets presenting with misleading information! I saw beyond the problem, less experienced users such as the original poster may not.

George Moranian

I am the original poster of this thread and I was unaware of what was going on with the panadapter on 6 meters when all the other bands are relatively clean, but I am fully aware of IM, harmonics, spurious, birdies and their possible detrimental effect on the transmitted signal.
How is one supposed to tell how well the transmitted signal is with all the other artifacts present? Real or not!

Bill -VA3WTB

As Eric points out, it can be a useful diagnostics tool to see if something is going wrong in the radio. If there were problems in the radio it would show big time. There have been times Flex would ask for a screen shot of the radio in TX mode to help determine what is wrong. After most people understand what they are seeing, most people just ignore it and move on.

Conny

Steve G1XOW

Bill -VA3WTB

Depends on what their working conditions were, how strong were you? It is possible if you were over driving the PA.