AmateurRadio.com

or: How I Learned to Stop Worrying and Love the RF Gain

The latest kerfuffle currently brewing on the Elecraft reflector concerns the “Noisy K3 receiver” and, predictably, the commenters have broken down into two opposing factions: the “Me Too!” group is posting comparisons with other receivers that supposedly have less background noise and less listening fatigue, and the “Not Here!” group which swears that their K3 is so quiet that they sometimes think it has been damaged.

Whether any or all of the complaints about background noise are valid, and/or whether these people have radios that are somehow defective or simply misadjusted is beyond my ability to discern. I’m not picking sides here, the guys who think their K3s are noisy may have real issues, and if so I’m confident Elecraft will address these issues as they have done with all others in the past. Perhaps we’ll all end up with better, quieter K3s in a few weeks as a result of this discussion.

That said, what really fascinates me is that some of my fellow amateurs apparently believe the RF Gain control to be an archaic, vestigial appendage left over from ancient days of vacuum tubes, and that it has no place or purpose in a modern receiver. To wit:

“Bill has linked to and quoted Eric’s paper which quite frankly seems way too complicated to me. IMHO, a modern DSP, microprocessor-controlled receiver should figure all of this stuff out automatically and do it for me … If the receiver has a properly designed AGC system then there are only two variables that are potentially the operator’s responsibility: 1) Preamp On/Off and 2) Attenuator On/Off. With the smarts built into modern radios, why can’t the radio do, for example upon band switching, a little routine of turning each of these on and off and measuring the resulting SNR and then setting them accordingly?” — N7WS

And:

“I’m used to leaving the RF gain wide open on the MkV, leaving the audio gain pretty much alone, and maybe switching between SLOW and FAST occasionally. I don’t seem to have any trouble hearing the weak ones under the strong ones. Now I have to fiddle with the RF gain (a small knob hidden amongst the others) while running a pileup. Not enough hands (or enough brains).” — VE7XF

Seriously? Not enough hands? No offense intended to these guys, fine gentlemen both, but we’ve long suffered complaints about how the K3 doesn’t have the all front panel controls one “needs” at his fingertips to tweak a signal to perfection. Now, a single RF Gain knob is too many controls to tweak in order to deliver a good sounding signal? And what N7WS is asking for falls under the general category of “Artificial Intelligence” — I think we’re going to have to wait a few more decades before we start seeing that offered in consumer electronics products!

The fact is, if you run the K3 or any other radio with RF Gain flat out, the result will be a higher level of background noise than if you “ride” the RF Gain. Whether analog or digital, a receiver’s AGC cannot magically discriminate a desired signal from noise. Instead, it will adjust the gain of the IF stages in response to the entirety of what it detects — that is, signal and noise. The purpose of the RF Gain control is to allow the operator to limit the range of the AGC to some degree in order to compensate for this lack of intelligence. RF Gain is like a transmission in a car, and just as an automatic transmission may work well some or perhaps even most of the time, it doesn’t always put the car in the right gear for every road condition. Similarly, the AGC doesn’t — and cannot — always deliver the optimum results under all band conditions. The RF Gain control is the radio’s stick shift. Use it.

Advancements in DSP technology have made it somewhat possible for a processor to detect speech or CW from random noise and perform the requisite voodoo to pass the wanted signal and suppress all else, but this technology still isn’t perfect. I don’t pretend to understand it all, but lot of math is employed to come up with what is still essentially a “best guess” as to what is, or isn’t, wanted. In my experience, it doesn’t always guess correctly; operator input is still required. The reason there are so many different possible settings for the Noise Reduction (NR) on the K3 is so you can choose what works best for you. But if you can’t be bothered riding the RF Gain a little bit, you surely won’t want to mess with the NR parameters.

Is my K3 unusually “noisy?” Honestly, I don’t know for sure. I don’t think it is; when I first got it I did comparisons with the JST-245, a rig which had a pretty damn quiet receiver. At the time I thought the K3 compared quite favorably. However, these tests were not scientific and the antennas used at the time were fairly crappy. Now I have a slightly better antenna… but alas, no more JST-245.

I did a brief A/B test with one of my NRD-515s on 40m SSB switching between both radios with the same antenna, each feeding identical NVA-515 speakers. It was a hands-down win for the K3 even with NR and AFX turned off. Tweaking both radios for best results, the difference in signal quality and intelligibility was pretty significant. Not exactly a fair fight, though… the NRD-515 is a 25 year old design.

Maybe I’d notice this perceived noisiness more if I had a quiet antenna and QTH. Unfortunately, I contend with a constant S7-8 background noise that I attribute to environmental factors (the QRN of suburban hell) and the fact that I have a vertical antenna, by nature more susceptible to electrical noise. In any case, I’ve never experienced how the K3 behaves on a quiet band. Under my typical conditions I can tweak the RF Gain, AF Gain and NR to maximize the quality of signals at or above the high noise level while reducing the background hash to a very acceptable level, but there is no single setting of controls that works on all signals. If I optimize for a relatively strong signal, I can reduce the background noise to practically nil but then weaker signals then become much less readable. Tweaking to separate the weakest signals from the noise is possible but that brings up the background noise as well — all the more so the weaker the signal and the closer it is to the noise floor. Every situation is different, so I’m constantly adjusting RF Gain and other controls to match the conditions much the same way I must downshift my Jeep when I climb a hill or drive through the twisties, or upshift when I reach cruising speed on a highway — no one gear works well all the time.

Once I find the best RF Gain setting for a particular signal, any noise that is still bothering me is handled extremely well by the NR (which, it cannot be overstated, is the whole purpose of having a NR function in the first place!). The K3’s NR has been greatly improved since trusty ol’ #216 arrived on my doorstep in January 2008. The original NR worked well for me as an SSB op, but the CW guys were not satisfied; so Elecraft changed the DSP voodoo to accommodate them. All of a sudden, I (and many others) found the NR didn’t work as well on SSB as it did in previous firmware versions, it made the output sound too hollow. So after we bitched and moaned about this, the boys in Aptos doubled the number of NR settings from 16 to 32, restoring the SSB-optimized NR settings and giving operators enough variety in NR level and aggression to satisfy everyone. I generally prefer very light NR, so I most often use the least aggressive setting in the 8-1 to 8-3 range to make copy comfortable to my ears; rarely do I use 8-4, but occasionally I will try the 7-x range on stronger signals. With the K3’s exceptional noise reduction I find myself adjusting NR more and RF and AF Gain less than I did in the pre-NR days with my JST-245, JST-135 and TS-930.

I hadn’t touched the AGC characteristic settings since the K3 was delivered, but today I decided to experiment with the AGC Slope and Threshold parameters just to see what effects they have. I found that the threshold (AGC THR) parameter makes a big difference in the amount of background noise amplified by AGC during periods of no signal. After a few hours of playing around the settings I ultimately settled on (for now) are:

AGC DCY: SOFT
AGC HLD: 0.20
AGC PLS: NOR (default)
AGC SLP: 012 (default)
AGC THR: 002
AGF-F: 100
AGC-S: 020 (default)

Thus configured, and with noise reduction off, AGC set to Fast, and both AF and RF Gain controls set to 12 o’clock position, I’ve found my sweet spot for tuning around under typical conditions. When find a station, I may switch on NR and/or adjust the AF or RF Gain until what I hear sounds right to my ears.

What it all boils down to is, using the RF Gain isn’t a burden, nor is it rocket science — it’s how I’ve always operated a receiver. Along with NR, Notch, Width and Shift, it’s simply another tool at my disposal to recover the most intelligibility out of a signal. Reaching for the RF Gain comes as naturally to me as it does for the AF Gain or VFO. The idea that some ops feel put out by having to tweak the RF Gain control is beyond incredible to me.

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LHS Episode #029: Evil Empires

deathstar It occurs to me that having an episode discussing evil empires during a celebration- and holiday-filled time of year might be a bit ironic but that's just how things turned out.

Thank you to everyone who has so generously donated to the podcast so that we might have a presence at the upcoming Dayton Hamvention in May, 2010. It was an idea spawned at Ohio Linux Fest in September, 2009 and we've come a long way since then. Every contribution helps and we hope you'll continue to support Linux in the HAM Shack in the future. We also hope to provide timely and essential information to amateur radio enthusiasts and computer users for a long time to come.

From our world to yours, have a Merry Christmas, Happy Hannukah, Joyous Saturnalia, or just a good ol' time--whatever your "thing" might be. We hope you enjoy our latest installment of the podcast, and please: Keep spreading the word. Every month our audience grows, and we predict world takeover by 2014. Well, maybe not, but we are talking about evil empires after all...

73 de Russ, K5TUX

Russ Woodman, K5TUX, co-hosts the Linux in the Ham Shack podcast which is available for download in both MP3 and OGG audio format. Contact him at [email protected].

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RTTY Got Me Into Amateur Radio

When I was a wee little lad in the 70s, I used to go to my grandfather's house on Saturday. He was a ham radio operator since 1956 and had a modest station. There was a 60' tower in the backyard with a Mosley TA-33 Junior tribander and a 6 meter beam at the top and 80 and 40 meter dipoles. His main rig was a set of Kenwood-Trio 599 Twins, probably the last of the silver front Kenwood rigs, with a separate transmitter and receiver. In the shack was also a Clegg Venus VHF rig, a Gonset G-20 6 meter AM rig, and some kind of Hallicrafters receiver from the 60s, all of which he rarely turned on. He was mostly a phone op who would ragchew, though I found out in later years he was quite a CW op in the early days.

After dinner I would be watching TV in the living room (I think Hee Haw or Lawrence Welk was usually on) or perhaps coloring a picture in a coloring book or something little kids would do. Grandpa would be back in the hamshack playing with radios. I'd hear him tuning across an HF band, probably 40 meters considering all of the broadcast station heterodynes you would hear flying by. There might be some phone signals which I always thought sounded funny. And then I'd hear that signal, that undeniable warbling sound. Back then I couldn't really describe the sound, but I always knew immediately that Grandpa would soon be turning on the old Model 15 teletype in the shack.

The Model 15 was nearly spotless and looked new, despite being maybe 30 years old. Grandpa somehow got it after the war, World War II in which he served, brand new in a crate. He built some kind of big metal box that it sat on which contained the electronics to decode the magical signal off the air. It was about three feet tall, about 20" wide, two and a half feet deep, black, and had lots of lights, switches and knobs on it. They weren't those wimpy little knobs and switches you buy today, they were big. Each switch was labeled with a blue colored Dymo label. The big black box had a round CRT picture tube about 3" in diameter that drew a bright green trace on the white screen. The whole box was built like a tank, or at least it seemed to a young aspiring radio engineer like me. The Model 15 was black with a crinkle paint finish and a typewriter-like keyboard on the front with dark green keys that almost looked like bakelight. The keys had the usual assortment of QWERTY keys, but all sorts of other different keys like FIGS, BELL, and BREAK that I never saw on a typewriter but I knew served some special function.

Upon hearing the warbling signal from the living room, I'd drop whatever I was doing and would run into the hamshack. Grandpa would be turning the big knob on the radio to get the signal tuned in just right. He somehow knew exactly what it was supposed to sound like. He would then flip some switches in sequence on the big black box and it would begin to come to life. The CRT screen would warm up and I would see the familiar green dot in the middle appear faintly and then grow bigger and brighter. And then he would flip on a big recessed switch on the Model 15 teletype. The unit would kick on and there was a nice warm hum and whirring sound that would emanate out of it, filling the room. As it warmed up, it had a distinct smell that is hard to describe....that "old radio" smell. The big black box and Model 15 would sit for perhaps a minute warming up, waiting to do its weekly duty.

At the right time, Grandpa would take a cable terminated with a quarter inch headphone plug and plug it into the Kenwood Twins receiver headphone jack. The teletype would spring into action and the CRT display drew all kinds of squiggly lines on the screen, like a madman trying to draw with a spirograph.

I could see and hear the teletype mechanism inside the big Model 15 rhythmically jumping up and down. It was like insides of a typewriter, with little metal arms sitting in a semicircle. The teletype then started tapping away, striking letters on ink tape and writing on the beige colored paper. I would sit there entranced by the whole event, watching the teletype type and looking at the secret message encrypted in the warbling signal travelling over the ether as it was revealed to me. Grandpa might adjust a few knobs on the big black box to tweak the green pattern on the screen.

Sometimes the teletype would make a mistake and miss a letter or two or misspell a word. I would read out the message to Grandpa and figure out what the misspelled words were. Occasionally the teletype would really mess up and would throw a bunch of line feeds out and jump the paper in the middle of a word or paragraph. If the signal was really bad it would start to spew several inches of paper at a time and Grandpa would quickly unplug the jack from the radio, flip some switches on the big black box, or try to tune the signal in better. The show would last 15 or 20 minutes and afterwards Grandpa would sometimes let me put headphones on and tune around the band and listen to Morse code or foreign broadcasts coming in from far off lands.

Later in my teens I got my ticket and operated mainly phone for several years and got into electronics. Years later when I was in my 20s and off to college and making my way into the real world, I became mostly inactive in amateur radio. The Kenwood Twins were displaced with a Kenwood 820 and Grandpa sold the Model 15 and used the extra space for his computer.

Today I'll sometimes fire up DM780 on the computer and tune in a RTTY signal, but I miss the hum, whirl, and clack-clack of the big old Model 15 that got me interested in this strange old hobby. But perhaps someday I'll have a grandson who I can show Hellschreiber and PSK31 and he'll want to click the mouse on the waterfall and decode strange-sounding signals from far off lands.

Anthony Good, K3NG, is a regular contributor to AmateurRadio.com and writes from Pennsylvania, USA. Contact him at [email protected].

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Handiham World for 16 December 2009

Welcome to Handiham World!

What’s on your wish list for the holidays?

Pat at HRO poses with big Icom rig that he can't possibly afford.

Besides world peace, I mean? If you have asked Santa for some new ham radio gear, I hope your wishes are fulfilled. (I’m not holding my breath about getting one of those most excellent $11,000 Icom transceivers like the one I posed with for a photo op at HRO, but then again, I might rate something more affordable for Santa’s budget.)

Yes, I have placed a new HF rig on the wish list at the WA0TDA QTH. The reason is that I’m tying up my Icom IC-706 M2G on 2 meters and 70 cm, sometimes using it as an Echolink node, and that leaves me only an old Yaesu FT-747 for HF. Alas, the Yaesu has seen better days. I had acquired it around 20 years ago as a result of a lightning strike on my tower. My wife and I were at home when the storm moved through the Twin Cities, and we about jumped out of our shoes when the blinding flash of lightning lit up the neighborhood like a million camera flashes. The thunder was instant and loud, and that meant just one thing to me: We had just taken a lightning strike, because the thunder came at the same time as the flash of light. I opened the door to the ham shack and my old FT-101B was smoked. Literally. There was even an outline of the metal louvers on the bottom of the rig burned into the wooden desktop.

So I replaced that rig with the FT-747, which worked like a champ for 10 years. It started flaking out in subtle ways. Once I called CQ on what I thought was a clear frequency, only to be chastised by some guy whose QSO I’d interrupted. A bit of sleuthing with a plastic probe led me to an intermittent on a circuit board that had muted the receiver. After that fix, I had a couple more years of trouble-free operation out of the 747 until the display started to disappear at random, accompanied by a total receiver failure. That was also an intermittent, because you could prod the rig and wiggle connectors to get the display and receiver back to normal. Many tries later, both by me and our shop volunteer CJ, K0CJ, and the problem still crops up at random. But the rig really started to annoy me when it would decide to suddenly shift frequency about 500 Hz or so, also at random. This thing was definitely getting on my nerves!

In the 23 years since the FT-747 came out in 1987, the technology built into ham radio transceivers has evolved – a lot! Although the Icom IC-706M2G is a decade newer, its design is still dated. I would like a better receiver section and more options for signal processing. So a new transceiver in the $1000 class went on my Santa list.

Will Santa deliver? Have I been a good boy? Stay tuned to the Handiham podcast and weekly e-letter news to find out!

For Handiham World, I’m…

Patrick Tice, [email protected]

Pat Tice, WA0TDA, is the manager of HANDI-HAM and a regular contributor to AmateurRadio.com. Contact him at [email protected].

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Why Are Radios Horizontal?

This thought has been keeping me awake at night. Yes, I know I probably need psychiatric help… but that still doesn’t answer the question, now does it?

Radio manufacturers appear to be locked into a belief that radios must be horizontally oriented. I don’t get it — this takes up more desk space and offers no discernible advantage over a vertically-oriented rig. Why not flip radios on their side?

The closest thing we’ve got to vertical radios are some commercial rack-mounted systems, but even then, each of the individual components in the rack are horizontal. The cubish Flex-5000A comes close, it is almost as tall as it is wide, but is still technically a horizontal rig. (Actually, it has no knobs so it’s not a real radio anyway. Never mind.)

Desktop PCs used to come in horizontal cases; now they are all happily ensconced in tidy, attractive vertical towers. Has anyone complained? I don’t think so…

Tallness projects power and demands respect — you never hear people marveling over the world’s widest building, do you? I believe the first radio maker who ventures out into this brave, new design direction will come to rule the market.

You heard it here first, folks.

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Safely Hamming In the Woods In Hunting Season

In recent years it's become popular to operate amateur radio while hiking or in wilderness areas, with activities like the Spartan Sprint and Polar Bear Moonlight Madness. On one reflector last week the topic of hamming in the vicinity of hunters came up. (Unfortunately the moderator squashed the discussion.) Non-hunters often are scared of hunters and fear being harmed, and often in my opinion due to lack of knowledge of the law and some simple common sense practices. There's a lot of misinformation going around which doesn't help the situation. Here are some common hunting myths:

Hunters often shoot at noises. It's illegal (and extremely stupid) to shoot at noise and you would be hard pressed to find any hunter worth their salt who shoots at noise. Anyone who does such a thing isn't a hunter, they're a criminal.

Hunters dislike non-hunters in the woods. Hunters don't want non-hunters to disrupt their hunting, but the more people who enjoy the land means more funding and protection for public wilderness in the future.

Hunters have more rights to be in public woods than non-hunters. At least here in Pennsylvania, all citizens have the same rights to use state land.

Hunting is inherently unsafe and/or is unsafe to non-hunters. According to the 2008 PA Hunting Shooting Incident Report there were 35 hunting-related shooting incidents, 3 of which were fatal. 40% of the total accidents were self-inflicted (not involving anyone but the hunter/victim himself). In only two of the total incidents the victim was a non-hunter, none of which were fatalities. Last year there were 3.84 incidents per 100,000 hunters, nearly the lowest rate on record. The chances of getting injured while hunting or doing a non-hunting activity in a public hunting area is quite low, arguably safer than walking down the street in many urban areas.

So what should you do to safely and successfully operate amateur radio in the woods with hunters around?

When in Rome, do as the Romans do; wear fluorescent orange like hunters do. Hunters may not know of hams, hikers, geocachers, mushroom hunters and mountain bike riders in the woods, but they know how to positively identify humans wearing fluorescent orange. Go to Walmart and buy a fluorescent orange hat and vest combo and wear it in the woods during hunting seasons. This hunting season I bought a new hat and vest set at my local sporting goods store for a mere $8. If a hunter sees orange and it's on you, you're a human, plain and simple. Also, if you want to put orange tape on a tree for good measure, it doesn't hurt, but do it 360 degrees around the tree and up as high as you can get it. But absolutely have an orange cap and a vest on and you're safe in nearly all circumstances. Don't wear red as red looks like brown 100 yards away and certainly don't wear just brown in deer season or just black in beer season.

I'm amazed that in 37 years of hunting, I can't ever recall seeing a non-hunter in the woods who wore fluorescent orange. It's such a small investment and exponentially increases one's safety in the woods in hunting seasons.

Know what the hunting seasons are. Google for your state's game commission or fish and wildlife department website and know what's in season before you out.

Look for hunters before setting up. When you go to setup your operating position in the woods, stop for a minute. Look around 360 degrees. Do you see any orange? If not, wait another minute or two and do another 360. If you don't see any orange, setup your station. If you see orange, relocate. If you're having difficulty finding a location without hunters in it, or you're hearing a lot of close gunfire, you may want to reconsider whether this is an area you want to operate from.

In Pennsylvania, turkey hunters and late season (post Christmas) muzzleloader hunters are not required to wear orange while stationary (although they must have an orange tree marker in place), and they're usually camouflaged, so you may not see them. If you're wearing orange they will see you and they will probably flash orange to make their presence known as they don't want you in the area scaring the turkey away any more than you want to be in their area and in potential danger.

If you take a dog with you, put an orange vest on the dog as well. However, it's a very bad idea to let your dog run loose during hunting seasons. Leave Fido at home during hunting season.

If you hear close gunfire while operating, don't panic. Just stay put and listen. If you see orange from another hunter, take your orange hat and wave it so they're sure to see you. If you are very concerned, let out a yell or a whistle. Whatever you do, don't get up and approach the hunter or pack up and leave until several minutes later. Stay cool, stay put, and wait a bit.

It's quite easy and simple to enjoy the woods in hunting seasons. Buy an orange vest and use some common sense.

Anthony Good, K3NG, is a regular contributor to AmateurRadio.com and writes from Pennsylvania, USA. Contact him at [email protected].

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ICQ Podcast Series Two Episode Twenty-Six (20 December 2009) – A Weekend in Radio

The Noisy K3

LHS Episode #029: Evil Empires

RTTY Got Me Into Amateur Radio

Handiham World for 16 December 2009

Why Are Radios Horizontal?

Safely Hamming In the Woods In Hunting Season