Weekend Special — Hamvention & Contest University with Rob Sherwood, NC0B

追加: 2026-05-09

[00:00:00]Hello Facebook fans, YouTube fans of DX Engineering. It is Friday afternoon.

[00:00:06]We're ready for the weekend special.

[00:00:09]Please welcome Rob Sherwood, N C 0 B.

[00:00:13]Rob, how are you? I'm doing well, Tim.

[00:00:17]Rob, it's so great to see you. Rob, give us a a little preview of what we might see at Contest University in Dayton here next week.

[00:00:30]Well, the one thing that's really amazing me has changed in the last couple of years is the the type of radios that are for sale today, the new things that have come out, you know, about a half a dozen.

[00:00:42]And the the designs are just different than we've known for decades.

[00:00:48]So, it's a it's a new day as far as how your radio's going to actually function inside that box.

[00:00:55]Well, you know, tell us some exciting things about you know, how how SDRs and the evolution.

[00:01:05]Well, the biggest evolution was when the Icom 7300 came out because at that point before that had happened, everything was a computer and so you had a computer and you had a box.

[00:01:17]And then now you can have one just with knobs. Now, that's the way I like things cuz I've been a ham since 1961 and all we had was knobs. But, uh that's that's was the major change. But, uh what's happened more recently is all the newer radios have been what we call direct sampling ever since the FTDX 10 came out. That's we'll call it IF sampling. In other words, the analog to digital chip is at the IF unlike an FTDX 10 or a 101D or etc. But, uh all the Mhm, newer ones that I'm going to talk about is CTU. They're all the direct sampling at the antenna. So, it's a big change.

[00:02:03]So, what about you know, changes within Flex, Elecraft, and even the 7300 Mark II?

[00:02:15]Well, they since that these radios are software defined, it's really quite different across the different brands.

[00:02:21]In in the IC-7760 uh expanded on what we were used to with the 7610 and the 7300.

[00:02:32]But, Icom's been pretty much on the top of their game.

[00:02:36]Flex has been a little bit slower and Elecraft for instance uh I believe that Flex finally has pre-distortion. Maybe it's out of beta now. I'm going to have to check with one of the alpha users. But, uh of course, Icom now has had two rigs that run pre-distortion that makes our sideband signal so much cleaner. So, it's really a feature race.

[00:02:58]Uh I don't know when Elecraft is going to offer that cuz they don't even have a alpha product as far as I know. So, it's each OEM, original equipment manufacturer, is focusing on different things to differentiate themselves from the competition. So, they're they're all sort of going in slightly different directions.

[00:03:17]So, Ron, let's let's talk about your lab facilities in Denver and then also at your station in Alt.

[00:03:28]Well, of course, the thing about my lab in Denver is about it would you go back to testing back in the '70s. But, about every 10 years, the lab equipment had to be upgraded to keep uh ahead of the equipment.

[00:03:43]But, I can actually make the same measurements here in Alt. For instance, when the 7300 Mark II came out, I measured it in Denver and there were surprises here and there. So, I measured the same thing at all, got exactly the same numbers, and then was able to test a second sample, thanks to you, and again, same numbers within a couple of DBs. So, um the the lab has been very important, but also on the air operations. For instance, in 2022, I operated an FTDX 10 and an FT-710 at my operating position one and two out of three, and did it for 3 months, October through December. So, that's really important they since I built this station 18 years ago, I've run about 21 radios in contests from here. So, I get not only lab data, but really contest evaluation, and that was a big improvement, a big big addition.

[00:04:43]Yeah, Rob, talk talk about your report, though. When when you get to the top 10, top 20 radios, I mean, how much difference is there?

[00:04:55]I think people are way too focused on one number, and I can be blamed for that, I suppose.

[00:05:01]But, the rankings of the website are by one column, the close in dynamic range, but radios are way more complex than that. But, like I said, I've run 21 of the top 26 radios myself, and I would enjoyed the contests with them. Now, there's differences in the ergonomics, and the menus, and the user interface. So, what I might like because the user interface works well for me, someone else will say, "Well, I like the other user interface from some other company." So, it's uh it's much more subtle now to differentiate on what radio is going to fit for your your operation, and it maybe it's remote or maybe it's uh the VHF UHF whatever. So it's a very it's it's not you don't just take look at a A number and say oh that's the ultimate and really all those top 26 radios you can work contest and DX and rag chewing and with all of them. So the amateur has a phenomenal number of choices today that are going to be more than adequate and I don't mean adequate barely adequate but really they'll work just great.

[00:06:17]You know when you think about it Rob uh you know you talked about having to upgrade some of your equipment over time. I mean that the receiver technology has gotten that much better.

[00:06:32]Oh it is it's night and day difference when if we had a a radio back 20 years ago that had a dynamic range of about 70 that was what we had but now we go from up to 110. Now I don't think we need 110. Right in the middle of my top 26 that is either 99 or 100. So this is almost overkill. So you really need to make a choice based on what what your needs are and what your interests are.

[00:06:59]Maybe you're just running FT8 in which case you can probably run a radio as long as it's got a USB port you can probably run a radio that is fairly old.

[00:07:10]But also you talked about receivers but the other thing is the ARRL finally started using clean signal initiative evaluations.

[00:07:20]And the transmitters compared to 30 years ago have gotten worse in the standpoint of being not as clean as they were in the old days of you know 6146s and crystal band crystals and a PTO.

[00:07:36]So that's something that the OEMs need to catch up but we were kind of interesting to see that as of today, three OEMs, original equipment manufacturers, offer pre-distortion for much cleaner, I mean, significantly cleaner signals on sideband.

[00:07:53]Uh actually, that if we can actually have a strong enough signal and a enough signal-to-noise ratio, then look down on our band scope and our waterfall to see down like 50 dB, we can be 1/3 the bandwidth with pre-distortion at minus 50. Now, three to one reduction in splatter, that's amazing.

[00:08:18]No, that that's huge. And thank you to you for pushing this whole clean sig I mean, the signal get getting the transmitters clean.

[00:08:30]Rob, let's let's go back to Contest University and talk about, you know, now 15, 16, 17 years of you giving presentations at Contest University, how much has that meant to you?

[00:08:46]Well, it's actually number 19, this one coming up out of the 20 that you've offered, so I was one year late to the party, but it it's been so rewarding to see the changes in the document changes over time, to [snorts] get feedback.

[00:09:02]I had one presentation in the UK that the question and answer was 45 minutes, and so I was learning stuff. And so, the the the all the professors at CTU offer amazing information, whether it's tower safety, how to run a waterfall right, or all these things. I mean, the the learning experience is just an outstanding.

[00:09:27]Well, and certainly your experience that you have shared with with the students throughout the years, I mean, you know, we've recorded it. Uh we've got your slide decks. There's a lot of information on your own website as well uh that you have shared with all the measurements and your experiences in contests, Rob.

[00:09:54]Well, it's [snorts] kind of amazing if you do a a little search on NC0B and uh Rob Sherwood or it just it's just amazing the YouTube uh presentations that are up there in the cloud.

[00:10:08]So, you can what or you can of course go to your uh your background of all the uh recorded ones. I mean, it's not all 20, but uh so there the the hams that can't make it to CTU can go watch a presentation from a couple years ago. It's great.

[00:10:25]You know, and and I think back to the 1980s and '90s when you and I were working in in the Sherwood Engineering booth at Hara Arena and and where we are today.

[00:10:40]Yes, that was great and um of course if we go back to the early days of K3LR running Sherwood modified R4Cs and that was great fun.

[00:10:52]But but the funny thing is people say, "Well, how did you ever get into testing radios?" Well, it wasn't like I woke up someday and said, "Uh gee, I should go test radios."

[00:11:02]But I had an R4C and then in a 160-m contest, the thing kind of fell apart.

[00:11:10]Well, if the radio is what it is but if you test it and it tests good and then it's not, then you got to figure out that the test is no good. So, that's where I augmented testing at 20 kHz like was invented 1975. The next year I invented the 2-kHz test which differentiated all these up-conversion radios.

[00:11:31]And so it was 20 or 30 dB difference depending on how you measure it. So, we need to have laboratory testing approximate the best we can what really happens. Like in CQ World Wide, you can't it's it's a challenge to try to duplicate CQ World Wide in a lab with two signal generators.

[00:11:52]But, you know, you have uh affected how radios have progressed, you know, over the last 30 years, 40 years.

[00:12:02]Uh the groundbreaking work that you did with the R4C and and Drake being a US company, but you have steered the evolution of radios, you know, and uh now with transmitters, with the clean signal initiative, and and what you've done with receivers, we have all benefited from Rob Sherwood.

[00:12:30]Well, it's it's been a pleasure to do that, and who would have thought? But, that's that's the reality.

[00:12:36]And on on the mention on the clean signal initiative, okay, I talked about sideband and the amazing benefit of pre-distortion, but also think back some years ago, some of the transmitters had terrible key clicks, just awful key key clicks, and W A J I complained about it, and some cases was able to fix it for like five bucks. But, the OEM didn't get it together until really the last few years.

[00:13:01]And also, transmit noise, which most of the time isn't a big problem, but if you're at Field Day or you've got a ham 10 blocks away or maybe just line of sight. For instance, in Boulder, Colorado, there's a ham up in the mountains that can see down into the city 5 mi away, and due to his transmitter having really bad noise, it's wiping out like 50 m for existence, for example, that's um 5 mi away. So, it's uh we need to really have clean transmitter. We share the bands and if we we shouldn't be taking up space that's not communicating communicating information.

[00:13:43]You know Rob, thanks so much for coming on today and and uh next week at Contest University, I know your presentation is going to be great and it's going to be broadcast live here on the DX Engineering channel. So, thank you once again, Rob, for all your contributions to our great hobby of amateur radio.

[00:14:08]Well, thank you very much, Tim. It's been a pleasure and I'll see you next week.

[00:14:12]All right. And thanks to all of you for watching today. I hope you learn more about Rob Sherwood. Go to his website.

[00:14:20]Go to the Contest University website.

[00:14:23]We'll see you next week from Contest University live. Until then, 73 from DX Engineering.