At first, I was just looking around on the web for some simple Rules of Thumb that compare the weak-signal performance of commonly used analog and digital modulation types. I was mostly focused on FT8 and FT4 but I also wanted to compare SSB and CW. I failed to find a simple comparison of these modes but I did find a number of good articles that compared some but not all of them. This article is my attempt to aggregate the available information into something easy to understand.

Disclaimers

I decided to leverage the work of others and to not try deriving everything from basic principles. I am telling myself that I am perfectly capable of doing the analysis but that I would never find the time to actually complete it. (Yeah, that’s my story, and I’m sticking to it.) Where the articles disagree, I tried to identify which one(s) had the most convincing analysis or rationale and used those values.

My goal is to compare common modulation types primarily in terms of weak-signal performance. This means focusing on how well a signal can be detected with low signal-to-noise ratio (SNR). I have ignored other factors, such as signal fading, frequency drift, multipath distortion, etc. Also ignored are factors such as the information rate provided by the modulation type and the required signal bandwidth. This is focused on having the ability to pass just enough info to make the contact.

Literature Survey

Searching the internet provided me with a number of good articles that have examined this topic, listed below in the References section. My approach is to compare the results of these articles and aggregate them into a concise summary. These minimum SNR values are listed in the table shown below, along with my aggregated conclusions in the righthand column.

Most of these articles presented SNR data in terms of a 2500 Hz bandwidth, with the goal of providing an easy comparison between modulation types. SSB is the widest signal discussed, and it roughly fits into a 2500 Hz bandwidth, which is often the IF bandwidth of the receiver being used. Some authors make this explicit by tagging this SNR as SNR2500.  It is common practice in communications work to normalize the bandwidth to 1 Hz, which indicates the modulation’s bandwidth efficiency. However, we’ll stick with SNR2500.

I started with the article by PA3FWM [Ref 1], which provides a look at many of the modes I was interested in comparing. Unfortunately, this article does not include FT4 and FT8. N6MW [Ref 2] has a good treatment of FT4 and FT8 as well as minimum SNR values for SSB and CW. These lined up well with the PA3FWM values, so that was a good sign. N6MW referenced the foundational article about FT4 and FT8, published in QEX, written by the FT4 and FT8 developers [Ref 3]. The KB9II article [Ref 4] focuses on VHF weak-signal performance and provides minimum SNRs for SSB, RTTY, CW, and PSK31. He introduces the concepts of SNR (average) and SNR (peak). I used the SNR (average) numbers in the table. The KF6HI [Ref 5] article provided another set of SNR values that lined up pretty well. Finally, I came across a presentation by K0LB and KK4SNO [Ref 6] that includes a slide summarizing SNR performance. Because it is slideware, it does not include much about the sources of their numbers, but it seems useful to include them in the table.

The authors have somewhat different approaches to determining their SNR2500 numbers, mostly related to the assumptions used. You may want to read through these papers to gain a better understanding of the fine points. Overall, there is good alignment on results, with a few exceptions.

SSB

The single-sideband SNR2500 values are a mix of 10 dB and 6 dB. Frankly, I think 10 dB is a bit high for “minimum SNR” because I’ve spent quite a bit of time making weak-signal VHF/UHF contacts with the signal right at the noise level. I’ve squeezed out radio contacts with SNR much less than 10 dB. I looked at the rationale supplied in the articles for this value and it is mostly just assumed. So I went with my own experience and chose something smaller, 6 dB, aligning with KB9II and KF6HI. Even this number might be a bit conservative.

RTTY

I found only four values for RTTY, and they vary quite a bit. After studying the articles, I judged KB9II to have the best justification, so I went with -9 dB. I suspect that the actual decode performance may vary depending on the type and quality of the detector.

CW

The SNR2500 numbers for CW varied significantly, over a range of 10 dB. One way to estimate CW performance is to use the bandwidth of the receiver and compare it to 2500 Hz. Using a typical CW filter bandwidth of 200 Hz, SNR2500 = 10 log (200/2500) = -11.0 dB. However, it is well-known that the human ear/brain combination provides additional signal processing. The classic article by W2RS [Ref 7] covers this topic quite well. Using actual on-the-air tests, the article explains that the skill of the operator can introduce a variation of 3 to 6 dB. Another interesting note is that if the operator knows in advance the type of information they are expecting (such as the callsign of the other station), it provides a 3-dB advantage.

We can and probably will debate the SNR2500 value for CW until the cows come home, but I decided to adopt -12 dB in the right-hand column. This is probably conservative for a highly skilled operator.

FT8, FT4

For FT8 and FT4, I used the N6MW values, which come directly from the FT4 and FT8 paper [Ref 3]. I rounded off to the nearest decibel to be consistent with the rest of the column.

JT65

The JT65 values are quite consistent. An article by K1JT [Ref 8] says JT65 SNR is “roughly -28 to -24 dB in 2500 Hz,” so I put -24 dB in the righthand column.

WSPR

WSPR is a popular beacon mode and the king of weak-signal reception. Signal reports are collected worldwide and shared via WSPRnet.org. WSPR performance will vary depending on the specific settings used on the software and we have some variation in the table. The K1JT & W1BW article [Ref 9] says, “The WSPR protocol is effective at signal-to-noise ratios as low as –28 dB in a 2500 Hz bandwidth, some 10 to 15 dB below the threshold of audibility.” So I used -28 dB in the aggregated column.

Conclusions

The rightmost column in the table provides a reasonable comparison of the listed modulation types. I don’t claim that the values are perfect, but they should be helpful in understanding the performance of these modes. These data show that SSB is the least sensitive mode, followed by RTTY and PSK31. As mentioned earlier, the CW number is open to debate but it performs better than RTTY and PSK31. This brings us to FT4 and FT8, which are commonly used WSJT protocols with reasonable throughput. (FT4 and FT8 using 7.5 and 15-second transmit/receive intervals.) JT65 operates at lower SNR, but it is really in a different category, It is designed for Earth-Moon-Earth contacts, using one-minute intervals. WSPR is also unique as a beaconing system and not designed for two-way radio contacts, but it does have the best SNR performance on the list.

When using this data, keep in mind that most of these modes degrade slowly so there may not be a sharp cutoff at an exact signal level. The values are Rules of Thumb, accurate to within a few dB.

Thanks to Jim/K5ND and Bob/WØBV for reviewing this article and providing feedback.

73 Bob K0NR

References

1. Signal/noise ratio of digital amateur modes – Pieter-Tjerk de Boer, PA3FWM

2. FT8 Modulation and Decoding – A Dive into SNR interpretation N6MW

3. The FT4 and FT8 Communication Protocols – Steve Franke, K9AN- Bill Somerville, G4WJS – Joe Taylor, K1JT

4. A Comparison of Common Digital Modes for Weak Signal VHF Communications – John Matz, KB9II

5. Signal to Noise Ratio, definition and application to Radio Communications – KF6HI

6. Digital Modes in Amateur Radio – Larry, K0LB and Scott, KK4SNO

7. The Weak-Signal Capability of the Human Ear – Ray Soifer, W2RS

8. EME with JT65 – Joe Taylor, K1JT

9. WSPRing Around the World – Joe Taylor, K1JT, and Bruce Walker, W1BW

The post Weak-Signal Performance of Common Modulation Formats appeared first on The KØNR Radio Site.

I caused a minor kerfuffle on Twitter recently, when I posted this:

This connector, properly called a PL-259, is the most common RF connector for ham radio use. The female counterpart is called the SO-239 connector. While these connectors are often “UHF” connectors, they actually don’t perform very well at those frequencies (300 to 3000 MHz). So I feel justified in disparaging that name.

The tweet generated a large number of replies, mostly in support of my anti-UHF-naming sentiment. It seems that other highly-educated and thoughtful radio amateurs agree with me. (It seems that the wise hams out there always agree with me.) You should be able to view the thread here: https://twitter.com/K0NR/status/1653575723838492672

Some people pushed back on the anti-UHF sentiment, usually saying that it is the common name for this connecter. A few folks pointed out that Amphenol calls these things “UHF Connectors”, which did surprise me. Who am I to disagree with this manufacturer of high-quality connectors? Of course, Amphenol also says this:

Originally intended for use as a video connector in radar applications, UHF coaxial connectors are general purpose units developed for use in low frequency systems from 0.6 – 300 MHz. Invented for use in the radio industry in the 1930’s, UHF is an acronym for Ultra High Frequency because at the time 300 MHz was considered high frequency. They can be used when impedance mating is not required.

Well, there you have it: the connector was named UHF back when UHF meant up to 300 MHz. (Today, UHF means 300 to 3000 MHz). I particularly like the comment “They can be used when impedance mating is not required.” What? That does not sound good for RF applications. I do agree that these connectors can generally be used to 300 MHz, but these days the ITU calls that VHF (30 to 300 MHz).

Wikipedia provides a more complete explanation, worth reading.

OK, so the name “UHF” is archaic but it has kind of stuck, the way old terminology sometimes does. I am still going to avoid using this term because it really should be deprecated.

And don’t use these connectors above 300 MHz (UHF frequencies). Unless you have to. Which I did last weekend when the only cable available for my 440 MHz antenna had a PL-259 connector on it.

73 Bob K0NR

The post About That UHF Connector appeared first on The KØNR Radio Site.

I have my opinion on ARRL asking FCC to grant more HF privileges to Technician-class licensees.

I verbalize them in this video:

[embedyt]https://www.youtube.com/watch?v=BWSAvDWE3Js[/embedyt]

After you hear my comments, please leave your comments.

Thanks, 73 de NW7US dit dit

Some of you wanted to see the complete version, uncut, of this video in which I discuss the differences between CB and the Amateur Radio Service.  This is in response to the recent episode in which the NCIS writers missed a great opportunity to discover the vibrant reality of the current amateur radio service in the United States of America.

The previous version of the video was prematurely cut short by just over three minutes.  This version includes that ending.  I also remove some of the low-end rumblings from the vehicle.  This version should sound a little bit less annoying.  Hopefully, the quality of the video is sharper, as well.  This version was edited by Adobe Premiere CC 2017.

I appreciate the many comments, views, and shares.  Please subscribe, too!

73 from Omaha!

Model 7700 soldering iron

I recently had the opportunity to try out a new ISO-TIP 7700 soldering iron. This is a rechargeable soldering iron without a lot of extra features but it is plenty capable for small soldering tasks. Here’s a few specs from the ISO-TIP web site:

Soldering iron in action

Here’s a short video of the circuit blinking away, proving that I can solder together a simple circuit: Video of circuit blinking Yes, the circuit did work the first time.

The post ISO-TIP 7700 Soldering Iron Review appeared first on The KØNR Radio Site.

We need to get the religion out of ham radio. No, I am not talking about the HF nets that support missionaries or similar activities. (Those people might actually be doing something good for the world.) I am talking about the religious debates concerning new technology…this technology is better than that technology.

Amateur radio is a technical hobby, one based on technology, hobbyist pursuits and mutual interest. One might think that this means issues are looked at objectively and discussions are based on logic, scientific principles and facts. Of course, this is completely wrong. What often shows up in ham radio are religious debates about technology or operating modes.

Here’s a definition of Religion:

a specific fundamental set of beliefs and practices generally agreed upon by a number of persons or sects: the Christian religion; the Buddhist religion.

You can tell when you are stuck in a religious debate…the facts quickly fade and statements like “this is the right way to do it” become louder. Underneath this is a fundamental belief trying to come out that the person may not even be aware they have.

A long running example of a religious debate is Linux versus Windows. On the surface, people argue about which one has more defects, which one is more secure and which one ultimately serves their needs better. Underneath the surface is the religious belief: software should be free, Microsoft is evil, etc. Then there are those Mac enthusiasts (you know who you are)….these folks tend to act like a cult as they attempt to convert other people to their group. (Where is the line between enthusiast and cult member?)

The latest one on the ham radio front is the debate over digital technology in the VHF and higher bands: D-STAR versus DMR (and now Fusion). The debate starts out rational with a discussion of the merits of each but soon the deeply-held beliefs come out: D-STAR is bad because ICOM is pushing it, DMR is good because it is the commercial standard, D-STAR is good because it is an amateur radio standard, D-STAR uses a proprietary vocoder chip so it is bad, etc. Then don’t forget the guys that say “all digital is bad, analog FM is good.”

Again, you can tell when the religion kicks in because the facts start to fade and the beliefs rise to the surface. Usually, these arguments can’t be resolved because you can’t really debate beliefs. What you get instead are flame wars on the various email groups.

What other religious debates are out there? Android versus iOS, Open Source Software versus Commercial Software, My favorite rig versus Your favorite rig, … what else?

-73, Bob K0NR

This post is recycled and updated from a 2007 post. Some things never change.

The post Religion and Ham Radio appeared first on The KØNR Radio Site.

Listening to podcasts has been part of my daily habit for almost a decade. I lean heavily towards audio podcasts (as opposed to video), so I can listen to them while driving. My smartphone is always loaded with hours of content on a variety of topics which is especially useful for international flights.

Podcasts come and go (or podfade) and recently I’ve noticed a few new ham radio podcasts. Well, they might not be all that new…perhaps I just woke up and noticed them. Anyway, I am passing them along in case you have not come across them.

The QSO Today Podcast by Eric 4Z1UG:

QSO Today is a weekly conversation between me,  Eric Guth, 4Z1UG, and my amateur radio operator guest. Each guest tells his or her’s ham radio story to the present time.  I select guests based on their contributions to the hobby through their publishing of articles and books on ham radio, their involvement in the creation of new technologies that enhance the hobby, and the role that they played to bring the amateur radio to others.

The Fo Time – The Other Ham Radio Podcast by Cale K4CDN:

It’s a new Podcast for the Up and Coming Amateur Radio Operator aka Ham Radio Operator. Whether you’re looking for the latest news, a different take on an idea, or just some good humor, Fo Time is the Podcast for you.

If you aren’t sure about the name, this might help.

The 100 Watts and a Wire by Christian KØSTH:

Created by Christian Cudnik, KØSTH in 2015, 100 Watts and a Wire is a program celebrating amateur radio through the eyes of a new ham. The show features topical conversation and interviews, news and an entertaining look at the adventures of a ham trying to figure it all out.

I’ve found all three of these podcasts to be well done and interesting. They all typically run about an hour long. Frankly, that’s a bit much for me, mostly because it does not fit my commute time. Not bad for an airplane ride, but too long for driving to work. More importantly, my smartphone is overflowing with interesting audio content, so I have to be selective.

Other Podcasts

I’ll mention a few other podcasts that deserve attention: The Ham Nation podcast has set a new standard for ham radio video podcasts. Hats off to Bob Heil and crew for their efforts. The Amateur Radio Newsline got its start by delivering audio programs via telephone for hams to play on their local repeater. Many repeaters still play their program but I get their feed via my smartphone. They continue to do an excellent job of stuffing interesting content into a 20-minute format. While not a ham radio podcast, This Week in Tech from TWiT remains a quality source of tech news and opinion (lots of opinion).

Give these podcasts a listen and let me know what you think.

73, Bob K0NR

The post A Few New Ham Radio Podcasts appeared first on The KØNR Radio Site.