Introduction Some time ago, I read a QRZ forum post by a seasoned Elmer, where he explained how to use the RF gain as your volume control. He proclaimed that he still found it more useful than any Noise Reduction feature out there, and lamented how “upgrades” in DSP functions have caused freshly-minted ham operators to go straight to the Noise Reduction button, without learning the more important basics of RF gain control. As a novice ham, I was both confused and intrigued, because I knew that old Elmer had me pegged. The Useless Knob? In my earlier days, I had experimented, and knew the RF gain helped to reduce background hiss. In my ignorance, I shied away from using it much. I did not see the value in a knob that appeared to be little more than a second, disadvantaged volume control cum squelch. It did cut down on noise, but it degraded DX signals more than the AF gain/volume knob did. Much to the detriment of my hearing, I wrote it off as an inferior, old school pre-DSP throwback from the times when old codgers waited for tubes to warm. Sometimes it helped reduce noise around strong signals, but past that, the only time it saw use was when I accidentally turned it instead of the AF gain. Then, one day, I found myself searching for a video about filters. I was considering the purchase of a “shack-in-the-box” rig, but found myself unhappy with the anemic sound of my friend’s Yaesu FT857D. This led me to a wonderful video by JerryKoch2, where he touched on the basics of RF gain control. Suddenly, the proper use of RF gain made a little more sense. I became more interested in learning about how the RF gain works. I studied more, asked questions in forums, experimented, and learned. Old Tricks with New Twists Since then, I have come to understand that proper control of the RF gain is one of the most powerful tools a ham has for digging weak signals out of the noise. Coupled with true advances in newer SDR technology, learning about the correct use of RF gain is more compelling than ever. In truth, I have found it to be so powerful that I barely use the Noise Reduction features of some radios, at all. When I use my Elecraft KX2, I now “ride the gain” constantly, bringing its full power to bear, in harmony with the often ignored, yet extremely powerful Receive EQ menu function. With AF gain on full, while using the RF gain to control volume, and aggressive EQ settings on upper-middle frequencies, signals barely readable often rise to an easy 56 to 57. Learning how to exploit Elecraft’s cutting-edge SDR technology in this way opens up a whole new world, because you can really boost the snot out of the signals. If you ever hear someone say they tried an Elecraft, but didn't notice a difference between it, and their older rig, it's a safe bet that they didn't attempt what I just explained. With my ICOM 7300, I ride the RF gain less, but employ it alongside the Twin PBT to highlight subtle tweaks, and bring the sounds I need to the front. When necessary, I turn off the AGC with a long press of the AGC button, and a twist of the tuning knob (not explained in earlier manuals). From there, I can increase the AF Gain (be careful, if wearing headphones) and ride the RF gain to dig out signals to my heart’s content. Like the Elecraft KX2, which is also an SDR, the 7300 really helps you boost low signals to amazing levels. On the 7300, I also use Noise Reduction sparingly, but is more effective than on older radios. Please note that the 7300 is a different animal than the Elecraft radios, and time is well spent learning about effective use of the Twin PBT. Older rigs benefit from the use of riding the RF gain, as well. On my Yaesu FT-950, I toggled a strong peak with the DSP Contour, then turned off the AGC, and increased the AF Gain while riding the RF Gain. It got so that if I used the Noise Reduction at all, on that rig, I might set it on level 1 or 3. I still have a lot to learn, but I hope that this story, and the KX2 video following it, will be useful for those a few steps behind me. Watch, and learn how to make use of the RF gain on your radio. if you own an Elecraft, don't forget to use the EQ. It's one of the hidden gems that puts the Elecraft radios in front of most others:
The rule of thumb is still true. If you disconnect the antenna and the noise level goes down, you have more than enough RF gain. Nice tip. More people should take control of the gain in their receivers, especially on the low-bands. Use ATT. Use RF Gain. If you can hear the atmosphere, your radio is working plenty hard enough. I liked to use an outboard MFJ step attenuator with my K3. I'd click in more and more attenuation until the atmospheric noise was just noticeable in the received audio. This had the nice side-effect of placing S0 on the S-meter at the same level as the atmospheric noise, regardless of what antenna I was running, or what band. It sure made listening much more pleasant.
The way most modern noise reduction techniques work is they do a real time subtraction using non-signal spectrum. This is not replaced by riding RF gain. Noise blanking is a type of noise reduction which deals with periodic or quasi periodic signals. One clever method is to do a real time FT--power spectrum and put all periodic components at zero, then reconstruct the inverse domain. Riding the RF gain is a vestige of the days of limited dynamic range and a high noise figure for the receiver itself. I DO NOT miss those days...so sayeth and old timer..
Modern NR techniques have their place, but the problem is that new hams just see the NR button, and go right to it, not understanding that there is more, or how to use it properly. I will say there is a difference between how the Elecraft KX2 sounds, and the 7300 sounds, when using RF Gain. I actually prefer the way Elecraft does it. I can reduce the noise, and more of the signal remains. Does Elecraft handle this in the old way? The two receivers sound very different, as the RF Gain is employed. Both can dig out those weak signals, but it seems like my Icom relies more on the Twin PBT to get there (takes more time to master, but useful).
I've been using the RF gain technique for a while, and was trying to 'splain it to a ham who still had his squelch / RF gain knob set to squelch on SSB. Not sure I got through to him, but hopefully. Did get to play with a recent DSP rig recently, and was not impressed with the noise reduction feature -- it went from readable to stuttering idiot at the lowest setting. Hopefully something a future firmware fix will take care of.
I find that reducing the RF gain setting to a 50% to 75% setting (with increased AF gain) on makes a significant difference in perceived SNR on my K3. There is clearly a benefit to audio quality as well. These were also true for my old IC-751A. (I almost always have the attenuator on for the lower bands as well, and the preamp is used only for 17m and higher.) I don't "ride" the RF gain - that's what AGC is for. I use NR infrequently. It works but my brain seems to do about as good a job, at least for my location and casual operating. The NB is extremely useful for electric fence popping and occasional power line noise.
Agreed on the Elecraft NB. It's really, really nice. Sherwood mentions why Elecraft's NB feature is so good. To quote: http://www.dj0ip.de/app/download/5794201454/Elecraft+KX3+rev+E.pdf
No, that's not what "riding the RF gain" is about, my friend. First, turn the RF gain way down so the radio is near quiet. Then, turn off the AGC. Then boost the AF gain (volume) to full, then ride the RF gain back up, as a volume control -- not to act as your AGC -- but to boost a very faint signal. You aren't "riding" it so much, as using it more to push low signals up, once AGC is turned off. Once I'm done working that signal, I turn the AGC back on again, usually. It's better than the AGC, which ends up suppressing weak signals in the noise. I will say -- one must be careful of sudden loud noises, when using this method!
It sounds like your AGC may be engaging on low level signals, or perhaps the RF gain is too low to begin with? With the AGC settings I use it doesn't engage on low level signals, so no need to turn if off, yet it still operates to keep strong signals in check.
It engages because of the noise around the signal. Hence, the problem with using AGC around faint DX. After releasing the AGC, by turning it off, the method I explained allows you to boost the volume of the entire mess via AF gain, while using the RF gain to drop it/raise it From there, use the EQ (or Twin PBT, in Icom's case) to boost just that part of the noise with the most understandable piece of signal in it. See appx 5:22 into the video for what I'm talking about.
There is a damned good trick being discussed here -- without doubt -- and I use it every day when running my K3. I've been on the air for 60 years but only in the past decade have I really paid surgical attention to RF gain "twiddling" (aka "riding") when working CW stations who are way down in the mud. With the current sagging sunspot situation, there are very frequent opportunities to sharpen skills relevant to "digging out anemic signals". I would like to see a companion discussion regarding the finer points of APF (audio peaking filter) use when working CW. At least on my K3, the impact of this "accessory" is fairly often amazing, to say the least. In contrast, with my Flex 6500 (SUPERB radio for CW work) I have noticed that switching in the APF effect seems definitely much less impressive than when used with the K3 (for whatever reason, and this could be a Flex operator error but I'm not sure). NK7B
Excellent suggestions and that's a neat rig. It sounds good to me. My simple solution with the Icom 7300 on SSB has been to turn the RF gain up, turn the AF up to where it is too loud to be comfortable, then turn the RF gain down to a comfortable audio level. I used the same technique with my Flex.
I understand what you are doing in the video. And I usually operate with the RF gain reduced and AF gain up to reduce receiver noise, I usually have no need to turn off the AGC with my Config: threshold and slope settings- maybe the KX2 AGC is different from the K3. I just did an experiment and find that if I set the AGC for the earliest and most aggressive action available then I can get a little better SNR on a very weak signal by turning AGC off and adjusting the RF gain. But at my normal AGC settings there doesn't seem to be an advantage to doing that. At least that's how mine works, (or my ears.) I'm glad you found a method that works for you.
Very true. RF gain works when the signal to noise radio is high enough so reduction of signal + noise with RF gain can reduce the noise but enough signal is left to be heard. If you're talking to more than one station of varying signal strengths, constantly "riding the rf gain" runs the gamut from being a PITA to just ineffective. When everyone's signal is fairly strong compared to noise, use of RF gain is heavenly. Being an experienced operator means using the right tool for the right job and knowing which is which.
