I was on 40m when OH8STN sent Heartbeat message from few kilometers away. It was overwhelming my RX and I managed to catch a screenshot.

His message was sent on frequency 889Hz, but we can also see signal harmonic on 1778Hz (2 * 889Hz) and 2667Hz (3 * 889Hz).

Also notice how the width doubles on 2nd harmonic (1778Hz) and triples on 3rd harmonic (2667Hz).

Maybe this doesn't have any other point, but to show how harmonics look like on waterfall.

@oh8hub that's really interesting! I've never seen the spread so clearly shown too.

@M0YNG Indeed! It took me a while to understand what's happening. What I don't know if why is it happening.

From these little things we can learn and build our knowledge.


@oh8hub @M0YNG What once was a great weak signal mode is being destroyed by people running way too much power and improper drive levels. I cringe when I see Eb/N0 numbers like +25dB while stations copy my -25 dB QRPp. My best was Japan on 15 meters with 100mW

@W8HF @oh8hub well it is weak signal, not low power...

I have to admit that I may have been running ft8 at 100w. I thought the tx audio level on my signalink would reduce the output power, but it doesn't seem to make any difference.

@M0YNG @oh8hub My advise. If you routinely get reports over 0dB, you are running too much. At my old QTH I never ran over 5W but I had a nice antenna system. It is more important that the signal is clean.

@W8HF I don't seem to get many reports over 0, but you are welcome to look at my log and make suggestions :)


@M0YNG That looks fine. A better metric for too much power would be seeing very lopsided reports like sent -23 received +10 😂. Sometimes band conditions are great and even a tin whistle signal gets a great report.

@M0YNG @W8HF @oh8hub

How does the signalink not reduce the tx power? Of course it does. I always have a power meter running btwn transceiver and antenna when I am in digi mode. And I really hate fiddeling with the tiny nobs of the signalink. But I always reduce the output power to 10-35W, depending on the mode. I never touch the radio.

As you all know, digi doesn't feel like the 'real thing' to me when being on the radio but being a witness of the arms race of power increase feels ridiculous. To get a rare DXpedition station, people are ready to run 1KW in FT8.

@es0mhi @W8HF @oh8hub so I thought it did, and it probably does. But I offer these two observations

1 changing the tx knob doesn't impact the power draw from my PSU (I don't have an rf power meter)

2 turning up the tx knob doesn't mean stations can hear me 😭

@M0YNG @es0mhi @oh8hub You really need watch the ALC and make sure you are not driving it into limiting. Also research your specific rig. Elecraft had a different approach to the ALC metering than most with their K3. A cross-needle SWR bridge between rig and antenna could serve the dual purpose of keeping an eye on your SWR as well as showing the forward power.

@M0YNG @W8HF @oh8hub

Concerning observation 2: of course you know this very well but the general naivity in these matters may make it worth repeating: doubling the power will result in a signal increase of 3dB. If your antenna is poor or the propagation is problematic that will make no real difference. (And the reason ur not heard doesn't have to be ur signal at all: I get the impression, that digi modes are often run by people with horrible antennas and a terrible noise floor ;-)

obs. 1: sounds as if you can see how much amps it is drawing - now there should be noticeable difference there.

@W8HF Yeah, I'm using a cross needle SWR/PWR meter.

@es0mhi @M0YNG @oh8hub The Cross Needle recommendation was for @M0YNG as he said he didn’t have a power meter. Those are handy since they show everything at a glance.

@W8HF @M0YNG This case of OH8STN signal showing harmonics on my waterfall was my fault!

I had my rig's RF gain up. Lowering gain down removed the harmonics. So this phenomenon was purely on my RX side.

This is a screenshot of me lowering the RF gain in middle of heartbeat transmission. See how the harmonics just disappear while original signal still continues on it's frequency.

@oh8hub @M0YNG Awesome. I meant to follow up and ask about your audio level into your interface. You can also get harmonics like that if you start to overload your audio interface.

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