++++++++++++++++++++ See also K2 Operations Notes ++++++++++++++++++++ Using RF Gain versus AF Gain Control Subject: [Elecraft] Uses for RF Gain Control (was AF Notch filter) John and other K2'ers, One of the best "tips" I *ever* got from my Elmer was to use the RF gain instead of the AF gain to set your listening level. What this does for you is reduces the amount of noise you hear. Its quite amazing to hear signals pop out of the noise when the RF gain is turned down. I set the AF gain at about 9 o'clock on the K2 and use the RF gain for the level setting. Of course by doing this you aren't entertained by the S meter but I feel they are all quite useless except for the rare time when you want to verify that a station is really 20 over S9! hi! Seriously, I could probably do without the AF gain control before giving up any other knob. Next time conditions are quite noisy or you're just trying to dig a signal out of the mud, try "reducing the mud"! 72, Randy WJ4P - --- >John, G3RHP, wrote: "I have never used the RF gain control except when calibrating the S-meter. I do use the attenuator. Am I alone in this?" Personally, I like using the RF gain control instead of the AGC. On the noiser bands, the AGC will tend to bring up the noise to a much higher level "between" signals or when the station I am listening to stops sending for a moment. Using manual RF gain with the AGC off, the receiver sounds much quieter - the noise level stays down where it belongs without an AGC working to crank it up on me. Sure, the "SLOW" function helps with this a little bit, but if you haven't tried tuning a noisy (QRN) band with the AGC off and riding the RF gain while the Audio Gain sits at one spot, try it before throwing that RF gain control away and see how much 'quieter' and 'cleaner' the band sounds. Ron AC7AC K2 # 1289 - --- Subject: Re: [Elecraft] Uses for RF Gain Control (was AF Notch filter) Randy's is good advice. The AGC on the K2 is pretty darned good, but you'll still find much smoother and quieter operation on cw if you put the AF gain up high -- I run mine wide open -- and use the RF control as low as possible to hear the signal of interest. This not only reduces noise, it allows the qsk to be much smoother -- you won't get a puff of noise between words while you're sending. You do lose any meaningful reading from the s meter, but then it's not clear that is a significant negative. Back in the good ol' days of AM phone, both Hallicrafters and National used to suggest in their manuals that, in listening to cw, you turn the AF gain fully up and control with the RF gain, and, in listening to am, you do just the opposite. It was good advice then, and I feel it still is. best wishes, dave belsley, w1euy ++++++++++++++++++++++++++++++++++++++++++++++++++ From: "Bob Lewis" Subject: Re: [Elecraft] K2 - Audio (notch) filter > Using manual RF gain with the AGC off, the receiver sounds much quieter... Actually no need to turn the AGC off in most cases - just turn down the RF gain. That reduces the signals below the AGC threshold and there will be no AGC action. It saves you from having to go in and set the AGC function plus it protects the receiver from overload if a very strong signal does come on. - --- Subject: RE: [Elecraft] Uses for RF Gain Control (was AF Notch filter) dave belsley, w1euy, wrote, "you'll still find much smoother and quieter operation on cw if you put the AF gain up high -- I run mine wide open -- and use the RF control as low as possible to hear the signal of interest. This not only reduces noise, it allows the qsk to be much smoother -- you won't get a puff of noise between words while you're sending." I agree completely, however I do notice that the K2 produces 'thumps' in the audio channel when being keyed with the Audio Gain turned up. I thought it was just the design. Am I the only one who hears this? Ron AC7AC K2 # 1289 - --- Subject: RE: [Elecraft] K2 - Audio (notch) filter John, G3RHP wrote: "I have tried using the AF and RF gain as suggested and agree that it can be helpful in reduction of background noise. It's painful when some local electrical interference comes up suddenly though!" If you were using the Noise Blanker when that happened, you've uncovered an... er.... uh (dare I say it???)... a "weakness" in the K2 design. Many ops here have noticed it when they wondered if their Noise Blanker worked until they encountered a truly strong impulse noise source. The blanker requires a relatively large signal in the i.f. strip to work properly, even at "low threshold". If you don't let the AGC keep the i.f. signal pumped up full blast, the noise blanker often doesn't do a thing. On a few occasions I've been listening - with the RF Gain full 'up' and the AGC on - and a local impulse noise source will boom right through with the Noise Limiter on. Turning on the Preamp, even though it is not otherwise needed, causes the signal to pump up even higher and the Noise Blanker "kicks in" and the interference disappears. It's a lousy way to run a receiver though . Some way for the noise blanker to follow the average i.f. signal level over a wide range would be much better. Sometimes I've been listening on 40 with the Noise Blanker and AGC on, and noticed that there seemed to be a lot of 'odd-sounding' noise on the band. Just broad-band "hash". On a few occasions it sounded like some station with a bad power amp putting out wideband r.f. hash along with the desired signal because the noise was keyed. I could hear Shzzzzzt-zzzzzt. Shzzzzz-t, etc. as the station keyed, and sure 'nuf there'd be an S9 signal somewhere matching that keying. It might be 10 or 20 kHz away, but he's there. Punch the Noise Blanker "OFF" and all the garbage, including the phantom signal disappears! The instruction manual wasn't kidding when they said to turn the Noise Blanker OFF whenever possible! For the odd 'blast' of noise, I prefer an audio limiter and have given some thought to adding one outboard to the K2 phones jack, since I always listen to CW on the phones. The audio limiter only kicks in when the audio level gets too high, so ordinary level signals are not affected at all by it. But if you get hit with an ear-splitting blast while digging for a weak signal, the limiter stops the noise from getting to uncomfortable loudness. One simple such limiter was simply two diodes back to back that would shunt any audio signal above their threshold conduction point of about 0.2 to 0.6 volts (depending upon the diode type) at the 'phones jack. Ron AC7AC K2 # 1289 - --- Date: Mon, 20 Nov 2000 11:05:15 -0800 From: Eric Swartz WA6HHQ - Elecraft Subject: Re: [Elecraft] K2 - Audio (notch) filter Hi Ron, I'm not sure why you are seeing this behavior on your K2. It doesn't show up on our unit here at the factory. The K2's NB is actually located just after the first post mixer IF amp, well ahead of the AGC and IF gain circuitry. Adjusting the RF (actually IF) gain will have no effect on the signal level it sees and blanks on, since the MC1350 variable gain stage is located after the crystal filter - well past the NB circuitry. In addition, the blanker does have its own AGC circuit so to follow the average input signal strength. Could you be confusing reducing the RF gain control with turning on the attenuator? The attenuator -is- before the NB and will drop the level of signal it sees. 73, Eric WA6HHQ +++++++++++++++++++++++++++++++++++ Subject: RE: [Elecraft] Uses for RF Gain Control (was AF Notch filter) No, Ron, I haven't noticed any particular thumping with the AF gain all the way up, at least nothing unusual. I do notice a bit more of a thump when using earphones rather than speaker, but this is because the earphones have significantly better (and unnecessary) low-frequency response. Even with the cans, however, the thumping is not bothersome. However, basically the same effect in using the RF control can be had with the AF gain at its 3/4, say 3 O'clock, setting. best wishes, dave belsley, w1euy ++++++++++++++++++++++++++++++++++++++++++++++++++ Subject: RE: [Elecraft] K2 - Audio (notch) filter OOPS... I wrote: " If you don't let the AGC keep the i.f. signal pumped up full blast, the noise blanker often doesn't do a thing. On a few occasions I've been listening - with the RF Gain full 'up' and the AGC on - and a local impulse noise source will boom right through with the Noise Limiter on." The RF Gain will *not* affect the Noise Blanker operation. The Preamp and the Attenuator settings *do*. My experience is that I have to turn the attenuator off, or turn on the preamp, and bring the signals up much higher than I'd normally ever have them in order for the Noise Blanker to work effectively. That practice reduces the dynamic range of the receiver, so I dislike having to do it to get the noise blanker to work. My apologies to everyone, including Eric who caught my latest Faux Pas. Ron AC7AC K2 # 1289 +++++++++++++++++++++++++++++++++++++++++++