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K3 Attenuator Turning Itself On

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Dennis Egan

K3 Attenuator Turning Itself On

I have a situation where a K3 with the attenuator off, when bandswitched
to 160M, turns the
attenuator on. I know this is the correct behavior for the K3 if the Rx
signal level is in the range
of +13 to +20dBm. That signal level, by the way, is on the order of
S9+90dB! And, yes, you
would be correct, the receiver is severely blocked and the S-Meter reads
a solid S9 and the
band is mostly intermod. A scan of the MW band shows a dozen stations
that are S9+20,
with the strongest stations being S9+45. I haven't ruled out a very
strong signal that may be
there, but it wasn't in the MW and I have yet to find it.. One of the
first things I intend to do
when I get back to the station is to use a spectrum analyzer (with a
step attenuator in line) to
see if that very strong signal exists.

If I don't find a very strong signal, what conditions, in your
experience, would create a signal
strong enough to turn on the K3 attenuator? Or are there other
circumstances that would cause
the K3 attenuator to turn itself on?

As additional info, if the preamp is on and the radio is switched to
80M, the preamp will turn
itself off. This indicates an RF signal of +3 to +10dBm- or S9+80 or
so- when the radio
is switched to 80M. In both cases, there are no known transmitters
operating within 500 yards
of the antennas in any direction.

Please send replies to me and I'll summarize.

Dennis W1UE

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Joe Subich, W4TV-4

Re: K3 Attenuator Turning Itself On

On 11/15/2015 2:06 PM, Dennis wrote:
> I have a situation where a K3 with the attenuator off, when
> bandswitched to 160M, turns the attenuator on.

The K3 remembers preamp and attenuator status by band. If you want the
attenuator off on 160, turn it off before leaving the band.

73,

... Joe, W4TV

On 11/15/2015 2:06 PM, Dennis wrote:

> I have a situation where a K3 with the attenuator off, when bandswitched
> to 160M, turns the
> attenuator on. I know this is the correct behavior for the K3 if the Rx
> signal level is in the range
> of +13 to +20dBm. That signal level, by the way, is on the order of
> S9+90dB! And, yes, you
> would be correct, the receiver is severely blocked and the S-Meter reads
> a solid S9 and the
> band is mostly intermod. A scan of the MW band shows a dozen stations
> that are S9+20,
> with the strongest stations being S9+45. I haven't ruled out a very
> strong signal that may be
> there, but it wasn't in the MW and I have yet to find it.. One of the
> first things I intend to do
> when I get back to the station is to use a spectrum analyzer (with a
> step attenuator in line) to
> see if that very strong signal exists.
>
> If I don't find a very strong signal, what conditions, in your
> experience, would create a signal
> strong enough to turn on the K3 attenuator? Or are there other
> circumstances that would cause
> the K3 attenuator to turn itself on?
>
> As additional info, if the preamp is on and the radio is switched to
> 80M, the preamp will turn
> itself off. This indicates an RF signal of +3 to +10dBm- or S9+80 or
> so- when the radio
> is switched to 80M. In both cases, there are no known transmitters
> operating within 500 yards
> of the antennas in any direction.
>
> Please send replies to me and I'll summarize.
>
> Dennis W1UE
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
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>
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> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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Dennis Egan

Re: K3 Attenuator Turning Itself On

Joe

Yes, I can turn the attenuator off once I'm on 160M, but within 2
seconds of turning it off
it will turn itself back on.

Dennis W1UE

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Don Wilhelm-4

Re: K3 Attenuator Turning Itself On

In reply to this post by Dennis Egan

Dennis,

The attenuator (and preamp too) setting is per band.
If you have the attenuator on for 160 meters, then leave that band, it
will still be set on when you return to 160 meters.

While switched to 160, turn the attenuator off - change to another band
and then go back to 160m - the attenuator should be off.

Similar for your preamp statement for 80 meters.

73,
Don W3FPR

On 11/15/2015 2:06 PM, Dennis wrote:

> I have a situation where a K3 with the attenuator off, when
> bandswitched to 160M, turns the
> attenuator on. I know this is the correct behavior for the K3 if the
> Rx signal level is in the range
> of +13 to +20dBm. That signal level, by the way, is on the order of
> S9+90dB! And, yes, you
> would be correct, the receiver is severely blocked and the S-Meter
> reads a solid S9 and the
> band is mostly intermod. A scan of the MW band shows a dozen stations
> that are S9+20,
> with the strongest stations being S9+45. I haven't ruled out a very
> strong signal that may be
> there, but it wasn't in the MW and I have yet to find it.. One of the
> first things I intend to do
> when I get back to the station is to use a spectrum analyzer (with a
> step attenuator in line) to
> see if that very strong signal exists.
>
> If I don't find a very strong signal, what conditions, in your
> experience, would create a signal
> strong enough to turn on the K3 attenuator? Or are there other
> circumstances that would cause
> the K3 attenuator to turn itself on?
>
> As additional info, if the preamp is on and the radio is switched to
> 80M, the preamp will turn
> itself off. This indicates an RF signal of +3 to +10dBm- or S9+80 or
> so- when the radio
> is switched to 80M. In both cases, there are no known transmitters
> operating within 500 yards
> of the antennas in any direction.
>

Dennis Egan

Re: K3 Attenuator Turning Itself On

Don

I know that the preamp and attenuator settings are remembered per band.

However, if I am on 160M and turn the attenuator off, it turns itself
back on
within 2 seconds. If I am on 80M and I turn the preamp on, it will
turn itself off within a couple of seconds.

I'm trying to find an explanation for this other than an excessive
strong signal.

Dennis W1UE

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Don Wilhelm-4

Re: K3 Attenuator Turning Itself On

In reply to this post by Dennis Egan

Sounds like you may have a strong AM broadcast signal that is
overwhelming the K3 input.
MW signals will be attenuated by the Low Pass Filter, but those signals
below 160m will not be.
The K3 does have some suppression of AM Broadcast band frequencies, but
it may not be sufficient in your case.

73,
Don W3FPR

On 11/15/2015 3:13 PM, Dennis wrote:
> Joe
>
> Yes, I can turn the attenuator off once I'm on 160M, but within 2
> seconds of turning it off
> it will turn itself back on.
>

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Jack Brindle-2

Re: K3 Attenuator Turning Itself On

In reply to this post by Dennis Egan

What else do you have connected to the K3, specifically the serial port.

Overly strong signals will general kick in a relay to protect the front end of the receiver and not
enable the attenuator. Is it possible that something else is enabling the attenuator, like maybe a command
from a computer program?

- Jack, W6FB

> On Nov 15, 2015, at 12:17 PM, Dennis <[hidden email]> wrote:
>
> Don
>
> I know that the preamp and attenuator settings are remembered per band.
>
> However, if I am on 160M and turn the attenuator off, it turns itself back on
> within 2 seconds. If I am on 80M and I turn the preamp on, it will
> turn itself off within a couple of seconds.
>
> I'm trying to find an explanation for this other than an excessive strong signal.
>
> Dennis W1UE
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]

Bob McGraw - K4TAX

Re: K3 Attenuator Turning Itself On

In reply to this post by Dennis Egan

Try it on a dummy load. If it changes then it is a radio problem. If it
doesn't then it's external.

If you have used the radio with CAT control, sometimes the software
application will not close and exit correctly and will leave "crud" or
fragmented data in the radio and there's no telling what results may
appear.

73
Bob, K4TAX

On 11/15/2015 2:17 PM, Dennis wrote:

> Don
>
> I know that the preamp and attenuator settings are remembered per band.
>
> However, if I am on 160M and turn the attenuator off, it turns itself
> back on
> within 2 seconds. If I am on 80M and I turn the preamp on, it will
> turn itself off within a couple of seconds.
>
> I'm trying to find an explanation for this other than an excessive
> strong signal.
>
> Dennis W1UE

Vic Rosenthal

Re: K3 Attenuator Turning Itself On

In reply to this post by Don Wilhelm-4

I have a 50 kW BC station a few miles away. I had to make a HP filter
because of the IMD. But it was not strong enough to force the attenuator on!

73,
Vic, 4X6GP/K2VCO
Rehovot, Israel
http://www.qsl.net/k2vco/

On 15 Nov 2015 22:22, Don Wilhelm wrote:

> Sounds like you may have a strong AM broadcast signal that is
> overwhelming the K3 input.
> MW signals will be attenuated by the Low Pass Filter, but those signals
> below 160m will not be.
> The K3 does have some suppression of AM Broadcast band frequencies, but
> it may not be sufficient in your case.
>
> 73,
> Don W3FPR
>
> On 11/15/2015 3:13 PM, Dennis wrote:
>> Joe
>>
>> Yes, I can turn the attenuator off once I'm on 160M, but within 2
>> seconds of turning it off
>> it will turn itself back on.