Yes! And to avoid some potential ear damage as well. Normally I wear phones, and I think that blast may have caused bleeding if I'd had them on then.... >:o
Mike NF4L On 11/6/2010 11:51 PM, Joe Subich, W4TV wrote: >>> Since very weak signals (which is what APF is all about) are well below >>> the level that AGC action starts, when trying to dig out such a weak >>> station, it may be wise to turn off AGC altogether (provided you have >>> set the AF limiter beforehand). > It might be wise to ask Wayne and Lyle to consider activating the AF > Limiter when APF is turned on just to prevent a problem it a strong > signal jumps on top of the weak one we're trying to copy. It is not > much of a stretch to think that a local might call that weak UA0 on > 160 or 5R on 80 while we're running "all knobs to the right" trying > to dig it out of the noise. > > Looking at W8OZA's AGC test data, it appears that the audio output > can vary more than 40 dB from a -140 dBm (MDS) signal to a -43 dBm > signal (S9 +30 dB) depending on the user's selection of AGC slope > and threshold. If one adds another 10 dB of APF gain, a sudden 40 > to 50 dB audio "shot" can be quite dangerous depending on the initial > listening level. > > In addition, given reports of damage to the speaker amplifier with > sudden noise bursts with AGC off, enabling AF LIM with APF *might* > prevent some potential amplifier damage. > > 73, > > ... Joe, W4TV > > > On 11/6/2010 9:20 PM, Don Wilhelm wrote: >> Mike, >> >> The AGC works at the IF level, not the audio level. >> What that means is if you crank the AF gain way up to listen to a very >> weak signal, AGC action is probably not even started because the signal >> level is at or near the level of the band noise - In other words, the >> receiver is operation at "full gain, all stops removed". >> >> Under those conditions, if a very strong signal suddenly comes into your >> passband, yes, it will be loud simply because the AF Gain is advanced. >> Yes, the AGC will respond to that new signal - just how much depends on >> how you have the AGC menu parameters set. If it does cause an AGC >> response, it will reduce the gain of the receiver, and you will no >> longer be able to copy the signal at or near the band noise floor. >> >> So perhaps what I am saying is that everyone might run their AGC >> parameters so that all stations, no matter what their relative strengths >> will have the same audio level - that would cure the condition you have >> stated - but I do not really believe that is a good solution - for one, >> it will make band noise the same audio level as the signals - result is >> "noisy K3", and we have been there before. >> >> Myself, I prefer to be able to determine the relative strength of >> various signals "by ear" rather than "by S-meter" - that means the >> strong signals will have greater audio levels than weaker stations - >> that is just the way it is. >> >> Since very weak signals (which is what APF is all about) are well below >> the level that AGC action starts, when trying to dig out such a weak >> station, it may be wise to turn off AGC altogether (provided you have >> set the AF limiter beforehand). With AGC off, the Audio limiter is >> active to protect you from ear-shattering events such as a strong signal >> suddenly coming on frequency. >> >> An additional benefit to copying very weak signals with AGC off is that >> a strong signal coming on within the passband will not de-sense the >> receiver (as it would with AGC on), so you may be able to use the >> "filter between the ears" to continue copying the weak signal. >> >> 73, >> Don W3FPR >> >> On 11/6/2010 7:46 PM, Mike wrote: >>> Thanks Tom. >>> >>> Well, I kinda thought it shouldn't blast my ears that hard. Audio *WASN'T* >>> up too >>> loud for the signal I was after. Maybe I don't understand what AGC does. >>> That's why I >>> asked the questions I did. >>> >>> On 11/6/2010 6:21 PM, Amateur Radio Operator N5GE wrote: >>>> On Sat, 06 Nov 2010 18:04:18 -0400, Mike<[email protected]> wrote: >>>> >>>> Sounds normal to me. >>>> >>>> Audio up too loud and APF on, then a strong signal transmits on the >>>> frequency >>>> you are listening to.... >>>> >>>> What do you think it SHOULD have done? You didn't say. >>>> >>>> Tom >>>> Radio Amateur N5GE >>>> >>>>> On 11/4/2010 9:48 PM, Mike wrote: >>>>>> I'm playing with the new APF, and trying to get a REALLY weak QSO to >>>>>> pop. I have the >>>>>> volume cranked up pretty good, and a REALLY strong station throws in >>>>>> their call. I >>>>>> thought my speakers had blown. Glad I wasn't wearing cans. >>>>>> >>>>>> My CONFIG:AF is 18, AGC = F. >>>>>> >>>>>> Was I doing something wrong? Anybody else experience this? Do we >>>>>> need/can we have >>>>>> better audio limiting? >>>>>> >>>>>> 73, Mike NF4L >>> ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
