Planning for the special event stations commemorating the life-saving food drops to NW Netherlands near the end of World War II is now in full swing. 62 nationalities were part of Bomber Command in WW2.

Please visit Operation Manna @ 80 for a full list of stations around the globe. Here are the Canadian stations participating:

VB7MAN Surrey Amateur Radio Communications

In Canada, Surrey Amateur Radio Communications (SARC) has been granted special event callsign VB7MAN from April 1^st to May 10^th. We will be on the air from our training station and elsewhere prior to, during, and after the event and will seek involvement of the high school students from our RF Communications class. Contacts with Europe can be sporadic from our location but we are generally able to contact North and South America, Asia, and Oceania. We have created a QSL card to commemorate the event. The card bears the $100 Royal Canadian Mint gold and silver coin struck in 2020 for the 75^th anniversary. 

We will update this page as plans progress but hope to make a QSO with you in April or May. Any certified amateur in BC may operate the special event callsign, as long as it is only used in one location at a time. If you wish to use the call on any band or mode, a Google calendar has been set up to reserve the call for your use between April 1st and May 10th. If you wish to book an operating time for VB7MAN, please contact VB7MAN@gmail.com.

John VE7TI
Coordinator VB7MAN@gmail.com

> 

VB6MAN Calgary Amateur Radio Association

CARA will be operating from the Bomber Command Museum of Canada in Nanton, Alberta. They will activate on April 25, 26, and 27th and May 9 and 10. The final dates and hours of operations will depend on the radio amateur operators participating.

> 

VE1MAN Nova Scotia

The Canadian teams closest to Europe will be operating from their club station as VE1MAN. They may be activating from a former WW2 air base or another location of significance to tie in with the event.

Radio Amateurs of Canada published an article about MANNA@80 in the March-April issue of The Canadian Amateur, as did the Radio Society of Great Britain in their national magazine RADCOM.

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If you’re a workbench ham, you like to measure things. Some like to just get a rough cut while others like to be “nuts” about it. There are groups, like Volt-Nuts and Time-Nuts, who focus more on what’s formally called Metrology. Me? I’m somewhere in the middle but tending toward more precise and reliable measurements, although I do get the Cal Lab magazine each month. Perhaps it’s because I taught classical measurement theory to PhD students for over 30 years and understand true-score theory (e.g., every observed measurement is determined by the “true score” plus some error). Adding multiple observed scores and modeling the errors is something I taught and used for a few decades. Reading Bob Witte’s books from HP as well as Joe Carr’s various texts helped me transfer over the statistical base into electronic measurement issues although clearly I have a lot to learn in this realm.

Building out a good test workbench has been one of my priorities over the past few years. I’ve been inspired by many others, mostly on Youtube, but the IMSAI Guy channel is one of my favorites.

The Soldersmoke Blog says his identity is Michael Cassidy W6UAB in Oakland California. He doesn’t exactly say on his Youtube Channel. Whether this is his real name or not, he is very educational in his videos. I have learned a lot but he’s cost me money! He is a clear workbench Elmer to me. I’ve acquired a couple of professional lab-grade test pieces on the used market for far, far less than what they cost new because he first went through them thoroughly on his Youtube Channel. The first was the HP 4735a LCR meter. Here’s my latest one.

The HP 8714ET VNA is a two port VNA. Yes, I have a few NanoVNAs. In addition, the SDR-KITS VNWA 3SE Automatic 2 Port Model with their MagiCal calibration device. Plus, I picked up a LibreVNA with their LibreCAL device. I recommend R&L Electronics for LibreVNA products. Why would I need another VNA? If you are seriously asking this question, my friend the Smoking Ape has some Cat Videos for you to watch. Because I wanted it is the simple answer, LOL.

Shown above is the 8714ET connected to the eight-port test set with an old Barker & Williamson Model 425 Low Pass Filter as the DUT. I purchased it at a hamfest for $5 to use the case but have not yet.The larger monitor on the right serves dually as a second screen to my PC (HDMI port) and as the VGA output with customizable color from the VNA. This is the conversion loss measurement shown. Note the USB floppy drive under the monitor.

Plus, it’s a device with a lot of features that raise the bar for bench testing. It is monochrome green in the internal display but customizable colorized in the VGA output. It’s remotely reachable by HP-IB (I use an HPIB-to-USB adapter), LAN (internal web server), and via a 3.5″ floppy disk. I purchased an inexpensive USB-based floppy drive for the Dell Precision 1700 PC that runs my workbench. And, yes, the 8714ET will indeed format a 3.5″ floppy to DOS. I suspect that I will retrieve screen images, the underlying data, and Touchstone files via the web interface but, heck, I’m kinda digging having a floppy disk in my Lab. In time, I will use some of the many IBASIC programs written for this line of VNAs. The PS/2 keyboard that I just ordered plugs into the rear of the VNA, making editing or writing IBASIC scripts much easier as well as entry for some features on the VNA.

I’ll let IMSAI Guy’s video playlist on his earlier model (HP 8711C upgraded to an 8712) give you the fuller run down on all the things it will do, especially with IBASIC programs that automatic a lot of testing, storage of calibration data, and so forth. But I added something to mine, the Agilent multiport test set, 8-port, 50-ohm model. I found it for $200 on eBay and it is pristine, almost as much as the 8714ET that I found there from a “junk shop” vendor. Very lucky it seems on this set of purchases.

An engineer friend (N5WDG) gave me some high quality test cables when he built a new house and cleared out some extras from his workbench. Good ones can cost almost as much as the used test gear scored online so I’m grateful for the crate of “stuff” that Thomas N5WDG, a WAN Engineer for AT&T, handed to me a couple of years ago. The connections between the VNA and the multiport test set require a standard DB25 male parallel port cable plus two specific firm metal connector jumpers. I found these new-in-box on eBay for $25 each. So with the $1500 price of the 8714ET VNA added to the multiport test set and cables I purchased, I have about $1,750 in this “like new” lab grade VNA from the 1990s.

One thing that the multiport test set provides is a much easier way to tune filters like repeater duplexers and such. The reference materials for the device lay out the wiring diagrams and how to tell the multiport device to configure the ports remotely from the VNA itself. The 100 db dynamic range will help a lot for tuning the standard 2M and 70cm duplexers that are in common use. Covering 300 khz to 3 Ghz, the 8714ET has up to 1600 data points which allows a more thorough sweep for a given frequency span. Nice.

There are always multiple documents to study on new “old” test gear. Each one has a design theory to the things it claims to measure. There are always quirks that support communities (e.g., HP Test Equipment Groups.io; EEVBlog Forum; Youtube) can education you on to more fully utilize gear like this. I also read the archived HP Journal for articles published announcing the release of gear like this. It’s very instructive to have one or more of the design engineers to outline the theory of the device, detailing how they approached the critical aspects of implementing the instrument. Lots of reading and study ahead!

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.

My last post was about my new Icom RC-28 external VFO that I purchased for my 65th birthday. At the time I had not connected it to the radio as I was busy with some home renovations. Once I could sit down and give the new RC-28 a spin I connected it to the front USB port on my Icom 7610 radio. I was very pleased to see that it worked without any issues....so I thought. When I powered down the radio that was when things went south. The Icom 7610 was stuck in power-down mode. I tried to tap the power button and then hold the power button but this did not shut the radio down. I had to turn off the power supply to the radio to finally power-down the radio.

I thought maybe it was a one-off and I powered the radio on again without issue and then attempted to turn it off. Once again the radio was stuck in power-down mode, so I turned the power supply off. Just to make sure it was not a radio issue that happened to show itself at the same time as I plugged in the RC-28 I removed the RC-28 from the Icom USB port. Without the RC-28 connected the radio powered up and powered down without issue, I was hoping there was not an issue with the new RC-28. There is an Icom 7610 group on Groups.IO that I am a member of so I searched there regarding this power-down issue. One suggestion was to make sure my RC-28 has the latest software update. Up to that point, I did not know you could update its software. I downloaded from Icom the latest RC-28 software and connected my RC-28 to my PC USB port and ran the software. I was told I was running the latest software. Next was to make sure the Icom 7610 rig was updated with the latest software. Now this I know for sure is not the case, version 1.42 is mainly a pre-distortion update. Also known as DPD used for SSB and not CW and being I am 100% CW I felt it was a download that was not needed. Now having said that on Icom's update page, it did indicate there were a few minor fixes. In my opinion, my radio was working and I did not see any need for any minor fixes...well until now. 

I downloaded and loaded the latest Icom firmware and it made no difference the radio was still not turning off. Another suggestion from the group was to remove the LAN cable from the rear of the radio. Now for me to remove anything from the rear of the radio is a big undertaking. But it did get me thinking about removing cables so I tried removing the key and headphones from the radio but with the same results failing to shut down. I was thinking for the time being I may have to unplug the RC-28 before turning off the radio as when I did this the Icom 7610 shut down without issue.
As I was plugging my Key back into the front of the radio I noticed a very small device plugged into the other USB port on the radio. It was a Logitech Unifying receiver for my mouse, this allowed me to click on the waterfall of the Icom 7610. I used a wireless mouse as it presented less clutter on the desktop but truth be told I rarely used it. I removed this device and ran a start/shut down again with the radio and low and behold all was fine. 

Problem solved and I must admit I was relieved to have finally found what the issue was. I posted my results on the Icom 7610 Groups.io site. I was informed that on such and such a page in the manual it does say the USB ports do not support wireless receivers. I had no issue with the wireless mouse but once the RC-28 was introduced so was an issue.

In this episode, we join Martin Butler M1MRB, Dan Romanchik KB6NU, Caryn Eve Murray KD2GUT, Edmund Spicer M0MNG, and Ed Durrant DD5LP to discuss the latest Amateur / Ham Radio news. Colin Butler (M6BOY) rounds up the news in brief and the episode's feature is ARRL EE Committee Adventures.

We would like to thank our monthly and annual subscription donors for keeping the podcast advert free. To donate, please visit - http://www.icqpodcast.com/donate

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