Power Spectral Density (...Huh?)
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- Опубліковано 24 сер 2024
- I’ve read comments on social media about setting transmit bandwidth to wide, as in 3,000 Hertz or even 4,000 Hertz. People have asked me about it in comments posted to my videos. This video covers that topic of TX bandwidth and why one might want to give some consideration to Power Spectral Density (PSD) when contemplating a wide TX BPF setting.
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73, de N4HNH
I have enjoyed this video ! You are a good teacher, keeping it simple and plain. I have owned my FTDX 10 for about 5 days, I must say it is an outstanding radio. There is something about it, the screen, ease of use, the information gathered listening, adjusting the filters, the way they are displayed, brings to me such a better understanding of radio than I have experienced in the past 6 years of radio. I feel connected with the radio, I have full confidence in its ability to hear as well as its ability to talk. ALready I have gotten thru pile ups like never before. This information combined with your other Ft 10 videos are helping me get the MOST out of my Ham experience with the Rig. Thanks and God Bless !
I appreciate you reaching out to let me know that, Darrell. I just want everyone to get the most from their transceiver, no matter which one they have. But, in your case, you have made a very wise choice. No radio is perfect but the FTdx10 gets close. My son, a Technician class at the moment, noted the same thing as you - being able to see a visual representation of the filter parameters makes it so much easier to understand what is really happening inside the radio.
I hope you are finding the FTdx10 series helpful and informative. It’s also good to explore the other playlists, as you did when you discovered this video.
73, Doug
@@n4hnhradio Yes, thats it, the Visual Representation this Radio Offers is what gives me the understanding I have never had before. Its such a valuable asset that I have not seen any owners talk about in videos. Anyway learning and enjoying is a process , much fun in it all, Thanks again.
You’re very welcome! I look forward to hearing more as you continue to master the FTdx10.
73, Doug
Good explanation. It explains (I think) why digital signals can be transmitted at low power and be heard at very long distances. Thanks Doug. 73
Actually, the digital does have the advantage of taking less bandwidth, as does CW. But FT8/4 is also helped by the fact that it knows what kind of data to expect at a specific point in the receive cycle.
Great video Doug. I love how you break it down. Clear and Consise.
I’m glad you found the video helpful, James. I go for a blend of audio that is good for both rag chew and DX chasing. Plus it helps when your signal is close to the other station’s noise floor.
Doug, very good uncomplicated explanation, makes sense now.
I’m glad Duncan. It was my desire to simplify PSD for practical application.
PSD is a concept that is widely considered in other areas of communications. Hams tend to ignore it or they are simply unaware of the concept. Many try to sound like an FM broadcast disc jockey.
I worked one of the VIP Patreon members last night on 40m. He was in South Dakota, using his FTdx10 from his RV, with the hand mic and 100W. His antenna was a temporary EFHW. He was coming in at 59+15dB, due to his optimized settings that factor in Power Spectral Density. He was maintaining a consistently high amount of output from the 100W. 100W is more effective when the voice is peaking at the optimum frequency range. He was using the exact EQ settings you have available to you in the menu optimizations PDF that is available for Executive and VIP Patreon team members.
73, Doug
@N4HNH you sir are a Genius.
Not really. I just research alot. Bob Heil actually got me looking at Power Spectral Density. He preaches it. He talks about people buying 8-band equalizers to equalize the 3kHz of audio spectrum that SSB occupies. Then they try to make themselves sound like an FM broadcaster, not realizing that they are just making themselves less intelligible in a noisy band scenario and they are causing their transmitter to operate less efficiently.
The Yaesu radios have two separate 3-band parametric equalizers to adjust TX audio. They provide more than enough equalization for the 3kHz SSB occupies. And AM is just both sidebands at the same time, with a carrier. So the same equalizers work for AM.
Excellent video and explanation of PSD
Thank you! 73, de N4HNH
Another great video KB2GCG
I’m glad you liked it Jerry. 73, Doug
Thank you for sharing your thoughts Doug, great info.
Your videos for the FT-DX10 have been helpful in choosing a new radio.
73
N7BFS
Glad to help. 73, Doug
Excellent video. One of the best. I'm heading to the shack right now. --w2nc
Glad you found it helpful. No need to waste energy at frequencies that don’t help project our voice.
73, de N4HNH
@@n4hnhradio what's the relationship between the BPF and the high and low cut freqs? Should they be aligned?
High and Low Cut are for receive. They don’t need to be aligned with the TX BPF. I run TX BPF at 300-2700 for a stock Yaesu mic.
The EQ parameters are important for transmit as well. I cover EQ settings and much more in the menu optimization PDFs that are available for Executive and VIP Patreon team members. Thus far, I have one for the FTdx5000, FT-891, FT-991A, and FTdx10. I plan to add one for the FT-710 also.
73, de N4HNH
@@n4hnhradio 👍
Awsome! I just got educated, i never knew about this. Thank you
Thanks!
You’re very welcome!
Thank you, this was very helpful. I spent some time on 20 meters this weekend and could hardly believe how many terrible sounding signals there were. I think the worst thing I heard was excessive low frequencies (bass), which to me reduced the intelligibility. SSB communication is not the place for high fidelity! I'm going to experiment with narrowing my transmitted audio and see how it works out.
300-2700 TX BPF will usually provide the best TX audio for clarity and punch, without sounding too “tinny”. Then boost 300, 400, or 500 Hz, depending upon your voice. Also boost 1300 Hz a little, and boost 2400 to 2600 Hz a lot. The TX audio video for KC4WZB will be a great starting point. It shows the parameters for Joel’s voice. For my voice, I boosted 300 Hz instead of 500 Hz. That’s just because my voice is different than Joel’s.
You definitely have the right idea about TX audio.
73, de N4HNH
You brought up some interesting points and help ne to put them in perspective, thanks!
Glad it was helpful!
So im watching this after your 891 tx eq settings video.. Both have really helped me understand audio. A question i have is if you set up the eq 1,2,3 with meq on and P-eq1,2,3 is the processors settings. Does setting the tx bpf still change your custom eq or is it more of a genereal preset when you were to leave the MEQ off? Thanks again, I was always told i had a great sound before i ever touched the settings and received even more over the last several weeks. I personally noticed more success during the CQWW SSB last week and i ran qrp over the 2 days making 50 qsos.
Congratulations on the QRP success. I like QRP as well. The 891 is such a fun radio. The TX BPF is always in play, no matter which MEQ is used or not. So, you could have the MEQ on, PRC on, and change the TX BPF to 400-2600 to break a pileup or maximize PSD. Then, when finished, go back to 300-2700 or 200-2800, or whichever you use for a rag chew. BTW, I never operate without the MEQ or processor. I just don’t exceed a setting of 20 for PRC.
There is a video in the FTdx10 playlist that shows how to see what good audio looks like on the scope. It doesn’t matter if you don’t have a FTdx10. It’s just using the scope for educational purposes. Here is a link: ua-cam.com/video/HLxvgfUs-TM/v-deo.html
73, de N4HNH
Very good information sir!
Thank you Allen!
Continuing to earn my Patreon-age. Excellent video sir.
Thank you Todd! I will probably get hate mail from the “wide” crowd. But 100-2900 should be the widest anyone should ever need to transmit.
@@n4hnhradio I gave up wondering why people do the things they do... I barely understand why I do some of the things even I do.
Excellent, thanks Doug
73 Rob G3RCE
You’re very welcome, Rob! Thanks for the good word! 73, Doug
I agree that maximizing PSD allows your signal to be recovered at a greater distance. Running 5 watts on WSPR I am heard in South Africa, thousands of miles from my QTH, where running 5 watts on phone, I'm lucky to be heard in the next county. (Yes, lots of FEC helps with recovery.) But going from 0.033 to 0.041 seems like such a tiny fraction of an S-unit, 10 x log(0.041/0.033) ~= 1dB, seems barely detectable. Is the larger factor the reduction in noise bandwidth rather than the increase in audio PSD?
It’s all of the above. You limit noise on RX with a narrower bandwidth. Of course don’t go too narrow, unless you are combatting QRM from 2kHz away. I normally listen at 2.4kHz but when combatting QRM, I might go a narrow as narrow as 1.5kHz and use Shift. I’ve shown that in numerous videos.
I find that 2.1KHz is a good compromise. It’s not way too narrow but not so wide that it pulls in more noise.
If you are transmitting at 2.4kHz width it makes sense for the receiving station to narrow their bandwidth to match. It will minimize band noise. I find that most people don’t even think like that. Since I chase QRP SOTA stations, I need every option in play to minimize noise.
73, de N4HNH
Great video Doug. I vote for more like this. I have a question. If the Tx station sets their transceiver on 2.4 MHZ and sends a transmission out on SSB while suppressing the carrier, why do I hear his transmission on my transceiver which is set to 2.4 MHz if the carrier is absent? When my VFO is set on 2.4 MHz;,Isn’t my receiver looking for a 2.4 MHz carrier?
I think you are referring to the audio bandwidth of 2.4kHz. If the other station is transmitting with a bandwidth set to 2.4kHz (300-2700 TX BPF), you need only to listen at 2.4kHz or less. 2.4kHz is the width of the other station’s audio sideband.
The carrier is suppressed at the other station. They might be transmitting at a carrier frequency of 7.205MHz, but it is suppressed. In order for your receiver to properly clarify the sideband audio, it needs a carrier at 7.205MHz to center up on. The Beat Frequency Oscillator (BFO) in your receiver injects a low level carrier that provides the detector circuit in your receiver a reference point. Basically, your receiver restores the carrier that the other station suppressed.
SSB is a very close cousin of Amplitude Modulation (AM). AM is less efficient because the power is spread across two sidebands, upper and lower, simultaneously, both carrying the same audio information, plus power is needed to produce a carrier of sufficient strength. Decades ago amateur operators discovered that by suppressing one side band and the carrier, their power could be channeled solely into the remaining sideband. But that approach presented a problem for the receiving station. Their receiver no longer had a carrier to center up on. So, welcome the BFO. It restores the suppressed carrier. So, in essence, SSB is AM, minus the carrier and one sideband that was carrying the same audio anyway. But SSB is a more efficient version of AM.
I hope this helps.
73, de N4HNH
Thank you Doug. So a transmitting radio whose VFO is set at 14.2 MHz removes the 14.2 MHz carrier and sends the the voice signal out to the receiving radio without a 14.2 MHz carrier. Then the receiving antenna picks it up and sends it to the receiving radio. Once in the receiving radio, its BFO restores the carrier so if my VFO is set to 14.2 MHz, I will hear it through my speaker?
You got it my friend! Well put. 73, de N4HNH
If the transmitting radio removes the 14.2 MHz carrier then how does the BFO of the receiving radio know that it needs to restore a 14.2 MHz carrier?
It doesn’t know. You adjust your VFO until their audio sounds clear. If they are transmitting exactly on frequency, it will be 14.2. It they are slightly off frequency, it might sound clear at 14.199.090.
73, de N4HNH