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K3 AGC dead spot

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Mike Reublin

K3 AGC dead spot

Tonight I noticed that from about 2:00 to 2:30 on the RF gain encoder, the receiver
goes dead. It's not dependent on the THR or SLP settings which I adjusted to match
some advice given here short time past.

I also realized my S-meter doesn't rise as the RF gain is reduced. I like that, but I
don't know how it got that way. :-P

I have the latest firmware.

It's not really a big deal, but is is puzzling.

73, Mike NF4L
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Vic K2VCO

Re: K3 AGC dead spot

My guess is that you need to do the RF Gain Calibration procedure with the K3 utility. If
you have an XG1 or XG2 you can use it as a calibrated source, or if not you can tell the
utility to use the factory default settings.

On 10/20/2010 8:13 PM, Mike wrote:

> Tonight I noticed that from about 2:00 to 2:30 on the RF gain encoder, the receiver
> goes dead. It's not dependent on the THR or SLP settings which I adjusted to match
> some advice given here short time past.
>
> I also realized my S-meter doesn't rise as the RF gain is reduced. I like that, but I
> don't know how it got that way. :-P
>
> I have the latest firmware.
>
> It's not really a big deal, but is is puzzling.
>
> 73, Mike NF4L
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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Greg - AB7R

Re: K3 AGC dead spot

Also check you CONFIG SMTR MD. May be on ABS vice NOR??

73
Greg

On 10/20/2010 8:50 PM, Vic K2VCO wrote:

> My guess is that you need to do the RF Gain Calibration procedure with the K3 utility. If
> you have an XG1 or XG2 you can use it as a calibrated source, or if not you can tell the
> utility to use the factory default settings.
>
> On 10/20/2010 8:13 PM, Mike wrote:
>> Tonight I noticed that from about 2:00 to 2:30 on the RF gain encoder, the receiver
>> goes dead. It's not dependent on the THR or SLP settings which I adjusted to match
>> some advice given here short time past.
>>
>> I also realized my S-meter doesn't rise as the RF gain is reduced. I like that, but I
>> don't know how it got that way. :-P
>>
>> I have the latest firmware.
>>
>> It's not really a big deal, but is is puzzling.
>>
>> 73, Mike NF4L
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>

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Mike Reublin

Re: K3 AGC dead spot

In reply to this post by Vic K2VCO

Thanks, Vic.

Per Dale's suggestion I did a calibration using factory defaults, and the dead spot
is gone, and the S-meter is back to rising with a decrease of RF gain. Dagnab it.....

73, Mike NF4L

On 10/20/2010 11:50 PM, Vic K2VCO wrote:

Guy, K2AV

Re: K3 AGC dead spot

The thing to note here, this ain't your daddy's analog radio, the only
actual "stage gain" adjustments you have are ATT and PRE. The rest is
all in the numbers, as the front panel knobs are just numerical advice
to the firmware. They don't directly control anything.

What needs to happen is a calibration of what voltage sent to the
variable 8 MHz stage produces a specific number out of the 15 kHz
analog-to-digital converter, etc, and exactly what stage gain change
occurs when PRE enabled, ATT enabled.

Also note here that the PRE and ATT button is also just advice to the
firmware. The button does not directly control a circuit, as opposed
to a DPDT switch carrying RF on its terminals that literally removes a
PRE from the circuit. The in and out is done by a one or zero bit
state from the MCU, converted to a switching voltage which biases
various diodes which change the signal path in the RX.

All of this stuff gets tabled up in the firmware, which constantly
consults it to set levels in the output and optimize IF gain into the
15 kHz ADC. If the numbers in the table are goofy, so will the
behavior be goofy.

Better to calibrate the K3 on a signal source (over the years, the
XG-2 will pay for itself, over and over) and have it right.

If you bought the radio assembled, this was done for you when you got
it. If you assembled it, needs doing.

Personally, sometimes I think the tables get hosed by ??? and needs
redoing. Done it a couple of times to restore normal function and have
no clue what happened to make it that way.

73, Guy.

On Thu, Oct 21, 2010 at 6:41 AM, Mike <[hidden email]> wrote:

>
> Thanks, Vic.
>
> Per Dale's suggestion I did a calibration using factory defaults, and the dead spot
> is gone, and the S-meter is back to rising with a decrease of RF gain. Dagnab it.....
>
> 73, Mike NF4L
>
> On 10/20/2010 11:50 PM, Vic K2VCO wrote:
>> My guess is that you need to do the RF Gain Calibration procedure with the K3 utility. If
>> you have an XG1 or XG2 you can use it as a calibrated source, or if not you can tell the
>> utility to use the factory default settings.
>>
>> On 10/20/2010 8:13 PM, Mike wrote:
>>> Tonight I noticed that from about 2:00 to 2:30 on the RF gain encoder, the receiver
>>> goes dead. It's not dependent on the THR or SLP settings which I adjusted to match
>>> some advice given here short time past.
>>>
>>> I also realized my S-meter doesn't rise as the RF gain is reduced. I like that, but I
>>> don't know how it got that way. :-P
>>>
>>> I have the latest firmware.
>>>
>>> It's not really a big deal, but is is puzzling.
>>>
>>> 73, Mike NF4L
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Mike Reublin

Re: K3 AGC dead spot

I understand that the knob labeled RF doesn't really control RF gain, but since
Elecraft labeled it that way, I think it's better to reference it that way.

I have an XG2, and had done the RF gain calibration using it. Dale recommended doing
it using the factory defaults. I'm waiting to hear back from him why.

It's a kit, just a tad over a year old, with all available mods.

The mechanism by which the tables may get hosed is the same principle which makes
them work. HPFM. (HocusPocusFreakyMagic) :-D .

73, Mike NF4L

On 10/21/2010 7:42 AM, Guy Olinger K2AV wrote:

> The thing to note here, this ain't your daddy's analog radio, the only
> actual "stage gain" adjustments you have are ATT and PRE. The rest is
> all in the numbers, as the front panel knobs are just numerical advice
> to the firmware. They don't directly control anything.
>
> What needs to happen is a calibration of what voltage sent to the
> variable 8 MHz stage produces a specific number out of the 15 kHz
> analog-to-digital converter, etc, and exactly what stage gain change
> occurs when PRE enabled, ATT enabled.
>
> Also note here that the PRE and ATT button is also just advice to the
> firmware. The button does not directly control a circuit, as opposed
> to a DPDT switch carrying RF on its terminals that literally removes a
> PRE from the circuit. The in and out is done by a one or zero bit
> state from the MCU, converted to a switching voltage which biases
> various diodes which change the signal path in the RX.
>
> All of this stuff gets tabled up in the firmware, which constantly
> consults it to set levels in the output and optimize IF gain into the
> 15 kHz ADC. If the numbers in the table are goofy, so will the
> behavior be goofy.
>
> Better to calibrate the K3 on a signal source (over the years, the
> XG-2 will pay for itself, over and over) and have it right.
>
> If you bought the radio assembled, this was done for you when you got
> it. If you assembled it, needs doing.
>
> Personally, sometimes I think the tables get hosed by ??? and needs
> redoing. Done it a couple of times to restore normal function and have
> no clue what happened to make it that way.
>
> 73, Guy.
>
> On Thu, Oct 21, 2010 at 6:41 AM, Mike<[hidden email]> wrote:
>> Thanks, Vic.
>>
>> Per Dale's suggestion I did a calibration using factory defaults, and the dead spot
>> is gone, and the S-meter is back to rising with a decrease of RF gain. Dagnab it.....
>>
>> 73, Mike NF4L
>>
>> On 10/20/2010 11:50 PM, Vic K2VCO wrote:
>>> My guess is that you need to do the RF Gain Calibration procedure with the K3 utility. If
>>> you have an XG1 or XG2 you can use it as a calibrated source, or if not you can tell the
>>> utility to use the factory default settings.
>>>
>>> On 10/20/2010 8:13 PM, Mike wrote:
>>>> Tonight I noticed that from about 2:00 to 2:30 on the RF gain encoder, the receiver
>>>> goes dead. It's not dependent on the THR or SLP settings which I adjusted to match
>>>> some advice given here short time past.
>>>>
>>>> I also realized my S-meter doesn't rise as the RF gain is reduced. I like that, but I
>>>> don't know how it got that way. :-P
>>>>
>>>> I have the latest firmware.
>>>>
>>>> It's not really a big deal, but is is puzzling.
>>>>
>>>> 73, Mike NF4L
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>

Don Wilhelm-4

Re: K3 AGC dead spot

Mike,

Recently a bug was found with the RF Gain Calibration routine in K3
Utility did not properly save the new data.
If you were not using the very latest K3 Utility, that would explain
many anomalies. Moral - download the latest K3 Utility and try again.

73,
Don W3FPR

On 10/21/2010 8:53 AM, Mike wrote:

> I understand that the knob labeled RF doesn't really control RF gain, but since
> Elecraft labeled it that way, I think it's better to reference it that way.
>
> I have an XG2, and had done the RF gain calibration using it. Dale recommended doing
> it using the factory defaults. I'm waiting to hear back from him why.
>
> It's a kit, just a tad over a year old, with all available mods.
>
> The mechanism by which the tables may get hosed is the same principle which makes
> them work. HPFM. (HocusPocusFreakyMagic) :-D .
>

Mike Reublin

Re: K3 AGC dead spot

Don,

I have 1.3.10.15, and in fact had done a calibration using the XG2 with it. Still
waiting to hear why Dale recommended factory defaults. He should be getting to the
office soon.

I assume (yeah I know) when using the XG2, it doesn't matter which of the 3 freqs I
use.....

73, Mike NF4L

On 10/21/2010 9:18 AM, Don Wilhelm wrote:

> Mike,
>
> Recently a bug was found with the RF Gain Calibration routine in K3 Utility did not
> properly save the new data.
> If you were not using the very latest K3 Utility, that would explain many
> anomalies. Moral - download the latest K3 Utility and try again.
>
> 73,
> Don W3FPR
>
> On 10/21/2010 8:53 AM, Mike wrote:
>> I understand that the knob labeled RF doesn't really control RF gain, but since
>> Elecraft labeled it that way, I think it's better to reference it that way.
>>
>> I have an XG2, and had done the RF gain calibration using it. Dale recommended doing
>> it using the factory defaults. I'm waiting to hear back from him why.
>>
>> It's a kit, just a tad over a year old, with all available mods.
>>
>> The mechanism by which the tables may get hosed is the same principle which makes
>> them work. HPFM. (HocusPocusFreakyMagic) :-D .
>>
>

Chuck Shefflette

Re: K3 AGC dead spot

In reply to this post by Guy, K2AV

Guy,

Actually, the RF gain control does have an affect on the analog, as does the AGC. There are 2 types of AGC in the K3, the first is the more obvious that is controlled by the AGC Slow/Fast/Off and the second is a hardware AGC that protects the A/D converters. The "normal" AGC is summed with the hardware AGC to control the gain of the IF amplifier that immediately precedes the 2nd mixer stage. The "normal" AGC is also more than likely used in some of the DSP calculations but that is a little less obvious to the outside observer.

The Pre and Att controls, on the other hand, have real effects on the electronics. The Pre is used to switch the PIN diodes that control the signal path through our around the 11 dB RF Pre-amplifer stage. The Att switches relay K10 which physically switches in and out a 10 dB attenuator circuit.

Granted, all these controls result from switch presses (the Att/Pre) or the A/D results of the RF gain pot that are decoded by the MCU and transmitted to the appropriate control circuits, but they do really have an affect on the radio's operation, not just in the software.

However, you are right when you say this isn't a traditional analog radio, at least beyond the 2nd IF stage!

73,
Chuck, AA3CS
K3 #s 4072 & 4407

Guy, K2AV wrote

The thing to note here, this ain't your daddy's analog radio, the only
actual "stage gain" adjustments you have are ATT and PRE. The rest is
all in the numbers, as the front panel knobs are just numerical advice
to the firmware. They don't directly control anything.

...

73 - Chuck, AA3CS