[Elecraft] APF and audio limiting

[Mike]

Thanks Don.

No, I wouldn't want all sigs to have the same audio level. I'll play with AGC off, 
and the limiter, and the AGC settings.

Mike

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<nf4l at nf4l.com>    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
>>
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