[Elecraft] Re k3 receive audio

[Guy Olinger K2AV]

Yes, it certainly IS that simple.

I remember the old radios well.  They never had the "problem".  They
didn't have enough gain to have the "problem".  Nor was it possible to
have the AGC recover in such a short interval that the noise sounded
as if it were the same level as the desired signal, even if many S
units weaker.  Using RC timing only and a single voltage bus, really
fast AGC produces really obvious distortion.

So why have digital methodology that can produce setting combinations
that produce roar-in-your-ear behavior?  Very simple.  People wanted
the options and to be able to set it just like they wanted it, so the
available ranges of AGC constants were set to allow people to set it
to taste. If you go back and read the archives, people were pretty
sharp-tongued about having all the options.

But whether consciously or not, many (most?) people were EXPECTING the
K3 to sound like Pappy's analog radio, and divergences were reported
as K3 "troubles", and still are.  AND, as it has always been on the
old radios, once AGC was on the scene, the only setting used for RF
gain was wide open.

And wide open is now 30 db farther down than Pappy's old analog radio,
AND can do all that without distortion.  Someone was asked why he was
running RF gain at max and PRE on on 80 meters.  He thought about it a
while and said he guessed because he always had.  And sure enough,
looking at a now idled older Yakencom rig, that's how it was.  Turned
it on and the older rig *NEEDED* the PRE on 75 meters for morning SSB.
And right beside that was an old Ameco preamp to put in front of the
radio's built-in preamp if you wanted to hear anything weak on 15 and
10 meters.

RF gain maxxed out is just habit and we are taking some time getting
used to stuff that doesn't act like the old radios.

On my K3 on 80 and 160 I use the attenuator on and the preamp off when
listening to the transmit antenna.  I have an on-the-ground loop array
listening antenna, and when listening to that have ATT off and PRE on.
The 20+ dB difference between ATT on and PRE on almost makes up for
the RX antenna's normal very low gain.  If I flip the RX source with
the RX front panel button, the K3 seamlessly switches the ATT and PRE
in and out.  Very nice, very handy.  It also makes for stellar
diversity because the same trick is available for the second RX.

That very useful convenience being in play for anyone who buys a K3,
means that everyone has to understand PRE needs to be OFF and ATT ON
for 80 and 160 listening on transmitting antennas, and adjust
accordingly.

Fail to do that, and somebody has a K3 noise "problem".

But the fix is between the ears, not in the K3.  SETTINGS, which is
what we are really talking about, are the user's problem.

I'm watching my incoming noise tonight on 160.  S5 between strike QRN,
with that up to 20, 30 or 40 over.  That's something like -100 dBm
steady.  -100 dBm just tickles the S-meter on my MP.  On the K3's
S-meter, where calibrated S units ACTUALLY ARE six dB per step, S0
actually *IS* 54 dB below S9, which actually IS -73 dBm. So, watching
both of them, the K3 is five S units noisier than the MP, or that's
how it gets reported -- "my K3 is terribly noisy on 160 and 80".  Add
to that the maxxed out RF gain, plus PRE turned on, plus unfortunate
user-chosen ACG settings and the user expecting it to act like old
analog radios, and not understanding the differences, we have one
unhappy owner.

My MP's S meter is a liar.  What was really going on was that the AGC
and the signal measurement ARE THE SAME CIRCUIT, as they have been in
all the old radios.  The truth of the matter is that S0 (no
deflection) is 54 dB below 50 microvolts across 50 ohms or -73 dBm.
So S0 is -127 dBm.

Our old radios had NO chance of AGC engaging at -127.  A lot could not
even HEAR -127.  So the S-unit scale was a lie TO BEGIN WITH.  What
radio manufacturer is going to tell the truth and start his S-unit
scale at S5?  Now you have explained the MP's compression of S-units
into 20 to 25 dB. And what manufacturer is going to take the AGC bus
and show how cramped the range is on top, and put S9 to 40 over in the
right 1/6th of the scale?  So on the old radios you have a meter that
doesn't show you much more than one signal is louder than another.

Calibrated K3 tells the truth.  The firmware program analyzes multiple
states in the radio, and runs it through a calibration table to
compute the actual signal strength.  Personally, I wish there was a
way to have the K3 (by itself) read out in dBm at the antenna.

The K3 ain't your daddy's analog radio, however much we are
unconsciously looking for that.  But once you learn and get used to
the new stuff, you'll never wanna go back.  No way.

73, Guy.

On Tue, Apr 12, 2011 at 6:45 PM, Barry N1EU <barry.n1eu at gmail.com> wrote:
>
> Bob,w5pvr wrote:
>>
>> The noise between transmissions was like Niagara Falls but not
>> any more.
>>
> Turn down the RF Gain.  It really is that simple.
>
> 73, Barry N1EU

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