Icom IC7300 A to Z #10 Twin Pass Band Tuning (PBT)
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- เผยแพร่เมื่อ 1 ต.ค. 2024
- NOTICE: In July 2021 the channel name changed from HamCuredSmoke
To Ham Radio A2Z. All of the earlier videos (like this one) are still available.
We'll walk through how the Twin PBT function works and what it can do to help you tune out interfering signals. Unfortunately, the demonstration is during challenging band conditions. Not because of many interfering signals, but because there weren't enough signals to find much interference.
me too, I just got my 7300 in 2024 and watching these videos.
Many congrats from user Icom-7300! de UA3NDX, Anton
Fantastic video (and series). Much appreciated!
I viewed your series 3 years ago when I got my radio. I have reviewed them all a couple times since. They are a great reminder and I learn each time.
The name "twin pass-band filters" suggests that they are essentially each 2.4 kHz pass-band filters logically connected in series. The only range that gets through both filters is the middle overlapping section. That is affirmed by your tests. As such ICOM's graphic accurately represents how they are doing it. However I agree with you that it would be clearer to the user if the graphic were showing what was effectively accomplished, which is that you can move both edges of the effective passband around with a maximum width of 2.4 kHz. W5PZT
Some 2.5 years after you recorded this, some of us are new to the 7300 (and amature radio, just got my license in April and my first HF last week). Thanks all of the work you put into this. Anyway, it occured to me that the Twin PBT is a bit like a VIN diagram. You only hear what is inbetween the two circles.73, KJ7YBK
That is a great analogy! I like it.
If you go into expanded view on the spectrum scope then pull up the filter menu the spectrum scope moves up so you can see both.
I have no idea how Icom implemented the feature, but I'm an FPGA programmer, and if I had to do it, I'd code two identical filters in series, because it's simpler and more resource efficient.
Hi,
In my understanding, Twin PBT is similar to parametric equalizer. It control the filter's bandwitdh or Q, and center frequency within the range.
The outer ring controls the bandwitdh,Q and reducing nearby splaters. QRM. Imagine a smaller holes in a tea/coffee filter.
The inner dial controls the 'center' frequency. That's why we hear a tone changes , as we use RIT.
So, Twin PBT is a variable band pass filter + RIT . :)
The best time tu use tiwn PBT is during contest, where there are many stations using frequencies near to each other Or when SWL, listening AM/SW broadcasts, to reducing 'unwanted' signal.
Thank you.
Bahathir 9W2GNU, 73.
As a DSP guy, I would say that that would be the hardest way to do this. I think they have one FIR filter design and they are scaling the coefficients to adjust the center frequency (and the center may be zero because I and Q - i.e a lowpass is a bandpass when you consider negative frequency) while maintaining identical bandwidth and then cascade that into a second identical filter where they do the same thing. They move them independently, the skirts are the same, and they can get any bandwidth they want and at any "center frequency" they want. That is computationally super cheap. That is how they are doing ALL the filters in this radio - they are all just these two filters. It is very effective too. The soft filter is a different filter design and they do the same thing with that. Trying to design a new filter on the fly wouldn't make a lot of sense as the number of taps would have to change. Icom for the win!
I should also say that you can up/down convert a FIR low pass filter by multiplying the coefficients by a complex sine wave (euler's formula) positive or negative relative to zero. That is how they scale them. This is all really different than in the analog world.
Very useful as I have a new IC7300. Settings made it easy from your videos, however on WSJT-X. I had a problem, which I never had on my last rig. That was when trying to work or answer a FT8 call on any band between 2600 and 3000 on the waterfall, resulted in a very muted and low output power mainly on one tone. Having solved this problem with the help of your number #10 on Tuning (PBT). By selecting PBT SSB-D I found this ranged between 300 - 2700. By changing this to 100 - 2900 which was the highest it would go. Ideally needs to be 3000 for max coverage on FT8. This solved most of that problem for me apart from 2900 to 3000 which is not often used. Any suggestion on this. Thanks again. Ralph G4PEY
Sometimes there are operators, who for whatever reason, sound muffled, with their voices sounding like they are missing the higher frequencies in their voices. Perhaps these filters can help with that, by shifting to the higher frequencies of their muffled voice? But of they are eating the mic then probably not. I'll have to try it next time I hear someone ruffled.
Some people just don’t have very good microphones or don’t have their audio set up well. I have heard amazingly good and amazingly bad audio on SSB. The PBT might help, but you aren’t going to be able to hear what isn’t being transmitted to start with.
Thank you, this was most helpful. I'm a new owner of 7300 and I found those controls confusing, coming from analogue transceivers with separate IF Shift and filter bandwidth controls. I think Icom would make things easier if they just used one of those encoders to control the left slope and the other - the right slope of the filter. Or one encoder for the left-right shift and one for the width. Even better if they displayed the filter shape on the scope to match the position and width with the signal spectrum.
Yes, just overlay the filter passband you're tweaking right on the spectrum display. You wouldn't even need to know what the numbers were, just use your eyes and ears at that point. Nice feature though. The filters are a real help during contests when signals overlap.
Dude, the PBT knob is a multi knob, push the knob to bring up the filter screen :)
Yep. Correct. I should have mentioned that in the video. I think I also forgot to point out that pressing and holding it resets the PB offsets back to the center.
Use these two pass band filters on CW to only hear the signal and no QRM or other noise, just pure CW signal. Real helpful to here very weak signals
Good job with filter explanations! I'd been using these, but now I know what I'm doing.
Thank you Tom for this series of videos. I am a new Ham and I just bought a 7300 a couple of months ago. I haven't even switched it on yet as it seems so intimidating and I am so green. I am gaining confidence in watching your videos. Thanks so much for these effort of putting this series together!
Welcome to the ham community Dwight. Nothing to be intimidated about. There are good hams out there that will help you along. Find yourself a good local club if you haven’t already. Thanks for the kind words. Hope to catch you on the air someday. 73, Tom
Your vids are a great service to the community. It would be very helpful if you could position the camera so your hand does not block the portion of the radio you are pointing at. This happens in a number of your vids. 🙃
Hi. Yep, valid comment. You’ll see that is fixed in later videos
Thank you for the video. I never use my filters but now that I have a better understanding of them, I’ll probably begin using them more often.
I am using this video to help learn the IC-705. 73 de K6TJO
Thanks for the comment Tim. I hope they're helpful. I am slowing working on a similar series for the IC-705.
My interpretation of this feature is that it simulates two independent filters in series. That is, the signal must pass through one and then the other. They can be tuned to (centered at) the same frequency, as is the case in the various default conditions, or staggered with one lower or higher in frequency than the other. You corrrectly demonstrate that when you stagger them such that you obtain the very same bandpass bandwidth as one of the defaults, you hear no difference in audio. Signals should and do sound exactly the same in each case. However, the skirt performance will be different in each case. Typically the skirts of IF filters have a significant deep notch fairly close in, and then followed by some re-entry ripple as you go further out. In a situation where you have two interfering signals, a slight tweak of one of the filters can, if you're lucky, move the notch to reject one interferring signal, leaving the notch of the other filter to reject the other interfering signal. in the end you may experience the same audio quality, but enjoy better signal rejection for the situation at hand. What do you think?
I think your analysis of how they are operating sounds pretty reasonable. As I said in the video though, since this function is completely software defined, we’ll never know exactly how it’s implemented unless they let us look at the source code ( or more likely, source figures). I’m not sure you can compare this to “typical” IF filters since the software implementation eliminates many limitations of hardware filters. Regardless, it is remarkable how well it works. I’ll be talking a little more about this in the upcoming episode on how to setup all the IF filter options. Thanks for your feedback.
@@HamRadioA2Z You raise a good point about because it is software, it may in fact be accomplishing its filtering in a manner that is different from the conventional filter design that I am used to when designing a filter with discrete components. Indeed, it may even be in a manner that is totally impossible in the real world. And I am not sure I'd be able to tell this for sure even if it was possible for me to see the source code. Have you seen ever seen the code for typical circuit analysis software, like Spice? It's complex. Still, if that software does use the same mathematical equations as we engineers did when designing filters using discrete components, then there is a good chance that the bandpass and bandstop performance would be exactly the same. I must admit, although I might be biased by my own imagination, as I use the receiver of the 7300 more and more in different QRM conditions, I sometimes have the feeling that the improvement I am realizing when I shift these filters up or down in frequency relative to each other is due to me moving the frequency of the first notch that exists at the bottom edge or skirt of a typical receiver's bandpass filter. And of course that's something that you couldn't do in a world where the bandpass and bandstop characteristics of IF filters were not adjustable. This is truly an amazing rig.
I did some experimenting with FIR and IIR digital filtering some time ago. The details and sophistication of what they’re doing today to make a complete radio in software is way outside of my wheel house. Even so, several modern coding tools for FPGAs and DSPS let you graphically draw your control laws. Matlab-Simulink is one example. So, with a little studying and plenty of Google searches, one could probably get the gist of how the filters are working if anyone would let you look at the diagrams. I can tell you that digital filtering is not just a mathematical model of the equivalent ideal analog components. They actually look at the signal data and process it using signal analysis techniques that involve pretty high level math. That’s why some of the functionality is so amazing. Since the source code is a lot easier to keep secret than schematics I would guess that Icom and the other big manufacturers will each keep their special magic pretty close to the vest to use as sales gimmicks, I mean features. :-)
Thanks! Now I get it.
Thanks for your explanation
Ive been using the TPB for a while now. Great job on the explanation of its use. I find with mors use, I gain an greater understanding of its use. Depend on your ears, not your eyes when adjisting this feature.
Thanks Joe. That’s a great tip to pay more attention to your ears than to your eyes.
Thanks Tom. Your videos on the 7300 are sooooo helpful.
impressive tom..i have learned so much about my new radio which comes this week ty...anyone told you that you sound a little like bill barr ?
I’m glad you’re enjoying the videos. Congratulations on the radio. I’m sure you’re going to enjoy it. On Bill Barr- I believe you’re the first. Hopefully, that doesn’t get me in trouble down the road. :-). 73, Tom
@@HamRadioA2Z Alan Alda for me :) - love the videos Tom, really informative I often recommend these to any new 7300 owners
73's Mark