New Ham Tips - Splatter. What is is it? Why is it bad? How to avoid it.

And about those "599" reports that everyone gives all the time, I give honest reports. I'm not afraid to give someone a 467 because there's QSB, their signal is 3 dB over the noise, and they're overdriving a bit. Those reports really help --- they're reports!

 

I agree that many experienced hams that should know better are blasting a hole in the band 10KHz wide. And then there are some foreign stations with such bad distortion and splatter that they are difficult to understand. I guess some people just look at a power meter and conclude more is better. Whatever keeps that power needle near the top of the range is all that matters. On the FTdx-101 you can clearly see a 3KHz bandwidth and you can see the audio spectrum of the signal in it. Far too many stations have WAY to much bass. A good signal just barely fills the 3KHz bandwidth and has well balanced audio with a minimum of low frequencies. At least half of the stations I see (and I do mean see) have poor audio balance. Some are just as bad in the other direction with screechy, over driven high frequencies. What can you do? Modern rigs almost all have the ability to balance out your audio so it sounds downright pleasant on SB. Kudos to the guys who understand audio enough to get it right. Within 3KHz it's possible to produce beautiful, clean, well-balanced audio that is an absolute pleasure to listen to. Unfortunately we have to put up with folks that just don't get it.

 

599 for voice? whats the extra digit represent?

https://www.acsu.buffalo.edu/~maxwell/RSTInfo.html

 

Woah.... So many things wrong here. While there are a couple good tips provided, using SDRs is just this side of useless for this. They aren't calibrated, there is no way to know what those levels actually are, if the scale is even remotely close to accurate, or if the receiver isn't driven in to a non-linear or clipping state somewhere. Even the example he shows in the beginning, the "splattering" signal is quite a bit stronger than the "non-splattering" signal. Why is this important? Because you can have transmitter IMD products 40 or more dB down and still look like that on an SDR. And how do you know the components in that particular receiver aren't being over-driven in the presence of a strong signal? If I'm 30 or 40 over S-9 at that receiver, my LEGAL IMD3 products could still be S8 or more. IMD5 could be S4-S5, well above the noise floor. And it would look very much like his examples. I know because I have a spectrum analyzer in my shack and I can see what my IMD products are (they are below the legal limits), and I still look like that when signals are strong into SDRs. And no, you CANNOT hear IMD in-channel. A perfectly clean sounding signal in your receiver could have very poor IMD products. Now, while an obviously over-modulated signal CAN cause splatter, that is generally from clipping in the audio or other stages of the transmitter (or receiver). IMD is caused by non-linearity somewhere in the system (which could be in the receiver, as mentioned). I've actually had people complain to me about my signal when they had their noise-blankers engaged. Those can cause massive distortion on strong signals as well.

All we need now are a bunch of band cops going around p**sing & moaning to others about something they don't have a clue about. Please, be very, very careful when using an SDR for any kind of "splatter" evaluation. You might be able to make an educated guess, but even that's best case. I suggest you all (including the podcaster) read up on the subject in a real engineering text.

 

I guess I was talking about digital. But also, what's the problem with keeping the extra digit for tone on a SSB signal? What if, like K0DXV said, there's a foreign station that's extremely overdriven but you can still read them fine and their signal is strong? In the RS system in SSB, it would still be a 59, but then you would need to elaborate more.

 

Agreed. I think that waterfalls should be more linear instead of logarithmic. This would also give a better understanding to people why they can still hear a signal fine even if they can barely see it on a waterfall.
While this would mean that some signals would tower over others to the extent of not being able to see them period, there would theoretically be an option to control the scale of the waterfall.

 

I don't even own an SDR, or use a waterfall. Although I do now have the fancy meter for my FT-5000, it has no waterfall to evaluate anything on. I don't even rely on the fancy little waves on it to evaluate anything, maybe help search for signals to chase.

I know people overdrive because I can hear them. When some screaming moron can be heard, heavily distorted, 60 kHz away from Channel 6 US CB AM, yet there are stronger operators on Channel 6 coming in clear and legible, I don't need an electrical engineering degree to know he is overdriving. When I hear distorted Spanish chatter on the same service, yet you can hear their music playing in the background with beautiful AM broadcast quality when they shut up for a few seconds, you know they are over driving.

When anybody on any AM/SSB phone anywhere sounds like Charlie Brown's teachers, you know they are over driving. When it sounds like someone is yelling into a sheet of tinfoil loudly, you know they are over driving.

If I can tune into your frequency and hear you over driving, and then I hear you beyond the bandwith your mode is supposed to be on, I can sure well guess you are flat topping.

The SDR is being used a means of trying to physically give examples of what is going on during flat topping and splatter. Not necessarily saying it is the only or best way to find it or recognize it.

Being wider, yet clear, when it does happen does not mean over drive, but rather strong signals in some cases. Yes.

But when it is flat topping , it is painfully obvious.

 

Very clear and excellent explanation.

 

And I spelled out the difference between flat-topping and IMD. BOTH can cause a signal to be wider than the intended occupied BW. While you MAY be able to hear one (and you can't always even audibly hear flat-topping, BTW), the other is completely inaudible in-channel.

Also, how can you know that just because you can hear my strong signal in your receiver 3 to 6 kHz away that it is "splatter", or more precisely, illegal? And more importantly, how do you know your receiver isn't being overdriven in one of its stages making you THINK the signal is transmitting IMD, but it's actually one of the amps in your own receiver being overdriven? These are the issues right here, and your post is EXACTLY why I brought this up. People don't fully understand it, and this video doesn't even mention these problems. We all know there are overdriven signals out there, but apparently not everyone understands that for strong signals, legal IMD products can be heard co-channel (and quite strongly, sometimes). This needs to be cleared up, along with the limitations of using something other than a calibrated instrument to call someone out (and especially, some cheap $20 SDR).

 

So, let's see if I have this right...

IMD: Problems in the transmitter itself that create distortion and harmonics in a signal via intermodulation being at the sum and difference of the two or more input tones, even if the signal is correctly driven.

Overmodulation: Distortion caused in the transmitter or receiver because of audio having too much amplitude, being clipped at the top and bottom to prevent blowing something out, and as a byproduct harmonics are created because of the whole deal with Fourier and square waves.

 

Good job. Adaptive Pre Distortion works really great to reduce splatter.
This can greatly reduce even the most audio over driven signal, yes over driven ampler , Yes Christmas tree signal. out there
Put all your energy in the bandpass ............. you are stronger .............. sound stronger, Sound clearer , cleaner and a benefit to the frequency neighborhood

Too bad only ANAN radio has this .

 

If you watch cw signals on any websdr visually, you can think that all stations have fairly strong key clicks, but - with some rare exceptions especially during contests -, they are highly proportional to their signal strength in the receiver. : - )

 

Great explanation on how to evaluate splatter using an SDR panadaptor >>>>>

 

IMD isn't only in a transmitter. In ANY amplifier, which receivers have as well. The presence of strong signals in the receiver path can cause nonlinearities. But keep in mind the mere presence of IMD products aren't necessarily a "problem" -- they are always there, even in the rigs with pre-distortion. They're just lower than a rig without it.

You can go deep down the rabbit hole with this -- the more expensive the rig, the better the amplifiers and circuit designs, and even the phase noise from oscillators can cause measurable loss in performance. So yes, there is a reason why high-end rigs cost so much. You get what you pay for! LOL

 

Good video. Here's a written guide for people who hate videos.



Conclusions:


• The ALC meter is an important tool for finding the best mic gain. Check the operating manual for recommendations.

• ALC = automatic level control. This is your radio acting to prevent intermodulation distortion reaching your radio's final amplifier.

• A wide bandwidth is not splatter. If you listen in the passband of a wide signal, your hearing a part of the signal, not splatter.

• Many, but not all, radios are designed to work best when the ALC meter indicates only minimal activity.

• Keep ALC activity low—set the mic gain so the meter just shows ALC activity on your voice peaks and none when operating digital modes.

• Alternatively, use a wattmeter to find the point where the peak power stops increasing as you turn up the mic gain, and operate just below that gain setting. Note that the average power continues to increase with mic gain, well past the onset of ALC activity. Use the ALC meter, and avoid the temptation to maximize average power.

• Speech compression circuits (sometimes called speech processors) can cause distortion that decreases the intelligibility of your signal. Turn off compression unless your signal to noise level is low because of poor band conditions.

• If possible, ask a friend to use a second radio or SDR to monitor your transceiver and listen (and watch with an SDR) recordings of your audio.

• Collect on-air signal reports in a variety of band conditions.

• Some receivers have noise blanker circuits that create distortion that simulates IMD.

• If you hear "splatter" check your own noise blanker and see if that's the cause before complaining.

• 3rd, 5th, 7th, 9th order distortion products are common on the ham bands. Keep ALC readings low and monitor your signal for distortion products.


https://www.hamradioandvision.com/how-to-use-an-alc-meter/

For More Information:

Explaining Your Transceiver’s ALC and AGC, R.A.B. Freire, PY2RAF,
QST June 2021, 34-5.

Audio Processing and ALC in the FT-897D by G8JNJ
Improving the Intelligibility of SSB Transmissions by G8JNJ
The Abominable ALC by SM5BSZ

What does ALC do in a transceiver?
https://ham.stackexchange.com/questions/17889/what-does-alc-do-on-a-transceiver