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K3: Receiver recovery time

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NK7Z

K3: Receiver recovery time

Hello,

Anyone able to answer this question please?

In the presence of a strong signal, say -75 db, (or around S9), once
that signal ceases, how long does it take the K3 receiver to return to
normal receive capability again?

--
73s and thanks,
Dave (NK7Z)
https://www.nk7z.net
Award Manager, 30MDG Grid Contest
ARRL Technical Specialist
ARRL Volunteer Examiner
ARRL OOC for Oregon
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Don Wilhelm

Re: K3: Receiver recovery time

Dave,

That depends on slow or fast AGC and the setting of the AGC DCY menu
parameter.
Fast is very quick - just watch the S-meter to get some visual indication.

73,
Don W3FPR

On 1/13/2019 11:49 AM, Dave Cole (NK7Z) wrote:
> Hello,
>
> Anyone able to answer this question please?
>
> In the presence of a strong signal, say -75 db, (or around S9), once
> that signal ceases, how long does it take the K3 receiver to return to
> normal receive capability again?
>
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NK7Z

Re: K3: Receiver recovery time

Sorry, I forgot to add, AGC off...

73s and thanks,
Dave (NK7Z)
https://www.nk7z.net
Award Manager, 30MDG Grid Contest
ARRL Technical Specialist
ARRL Volunteer Examiner
ARRL OOC for Oregon

On 1/13/19 9:06 AM, Don Wilhelm wrote:

> Dave,
>
> That depends on slow or fast AGC and the setting of the AGC DCY menu
> parameter.
> Fast is very quick - just watch the S-meter to get some visual indication.
>
> 73,
> Don W3FPR
>
> On 1/13/2019 11:49 AM, Dave Cole (NK7Z) wrote:
>> Hello,
>>
>> Anyone able to answer this question please?
>>
>> In the presence of a strong signal, say -75 db, (or around S9), once
>> that signal ceases, how long does it take the K3 receiver to return to
>> normal receive capability again?
>>

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NK7Z

Re: K3: Receiver recovery time

In reply to this post by Don Wilhelm

Is it faster than .0001 ms?

73s and thanks,
Dave (NK7Z)
https://www.nk7z.net
Award Manager, 30MDG Grid Contest
ARRL Technical Specialist
ARRL Volunteer Examiner
ARRL OOC for Oregon

On 1/13/19 9:06 AM, Don Wilhelm wrote:

K9MA

Re: K3: Receiver recovery time

On 1/13/2019 12:10, Dave Cole (NK7Z) wrote:
> Is it faster than .0001 ms?

Certainly not. I'm not sure whether it is recovery time or latency, but
in full break-in mode, you hear nothing between the dits above something
like 10 wpm. (Even with AGC off.) With other non-DSP receivers, one can
hear between the dits up to at least 30 wpm with fast AGC. Perhaps it's
just the price we pay for the power of DSP.

Many years ago, when there were sunspots, I recall hearing multiple
echos on 15 meters. I timed them, and the time interval was about 133
ms, just about the time it takes radio waves to circumnavigate the
earth. I heard them go around at least twice, and that was receiving off
the back of a beam. Talk about long path! That would not have been
possible with a DSP receiver.

73,

Scott K9MA

--
Scott K9MA

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NK7Z

Re: K3: Receiver recovery time

Hi again Scott,

Thank you for your answer, but I am not being clear.

Not during break in, just sitting there in receive... If the radio is
hit with an S9+ signal, how long after the S9+ signal terminates before
the K3 receiver recovers enough to show an weak signal on the IF... No
T/R happening, just sitting there in receive.

You are close to what I am looking for... I am investigating the
possibility of using the K3 as the receiver portion in a homebrew
bistatic radar setup running in the HF spectrum.

73s and thanks,
Dave (NK7Z)
https://www.nk7z.net
Award Manager, 30MDG Grid Contest
ARRL Technical Specialist
ARRL Volunteer Examiner
ARRL OOC for Oregon

On 1/13/19 10:25 AM, K9MA wrote:

> On 1/13/2019 12:10, Dave Cole (NK7Z) wrote:
>> Is it faster than .0001 ms?
>
> Certainly not. I'm not sure whether it is recovery time or latency, but
> in full break-in mode, you hear nothing between the dits above something
> like 10 wpm. (Even with AGC off.) With other non-DSP receivers, one can
> hear between the dits up to at least 30 wpm with fast AGC. Perhaps it's
> just the price we pay for the power of DSP.
>
> Many years ago, when there were sunspots, I recall hearing multiple
> echos on 15 meters. I timed them, and the time interval was about 133
> ms, just about the time it takes radio waves to circumnavigate the
> earth. I heard them go around at least twice, and that was receiving off
> the back of a beam. Talk about long path! That would not have been
> possible with a DSP receiver.
>
> 73,
>
> Scott K9MA
>

Don Wilhelm

Re: K3: Receiver recovery time

Dave,

I am trying to think of how you might test it.
The best I can think of is to listen to both a noise source and an XG3
sending a CW string of dots. Increase the speed of the CW sent by the
XG3 until you can no longer hear the noise source between dits.
Then either calculate the off times for the dits or measure it on an
oscilloscope.

73,
Don W3FPR

On 1/13/2019 2:07 PM, Dave Cole (NK7Z) wrote:

> Hi again Scott,
>
> Thank you for your answer, but I am not being clear.
>
> Not during break in, just sitting there in receive... If the radio is
> hit with an S9+ signal, how long after the S9+ signal terminates before
> the K3 receiver recovers enough to show an weak signal on the IF... No
> T/R happening, just sitting there in receive.
>
> You are close to what I am looking for... I am investigating the
> possibility of using the K3 as the receiver portion in a homebrew
> bistatic radar setup running in the HF spectrum.

K9MA

Re: K3: Receiver recovery time

You ought to be able to measure it by simply looking at the audio output
with a scope. Just send some dits and look at how long it takes for the
noise to reappear. You might have to use a noise source, or a low level
carrier at a slightly different frequency.

Of course, with the AGC off and RF gain high enough to detect a weak
signal, things are going to overload. I'd run the test first with a test
signal which does not overload the receiver, and then one equivalent to
a very strong signal. When actually listening to the radio with AGC off,
of course, it is essential to use the audio clipper to prevent hearing
damage. That may or may not affect recovery time.

73,
Scott K9MA

On 1/13/2019 13:53, Don Wilhelm wrote:

> Dave,
>
> I am trying to think of how you might test it.
> The best I can think of is to listen to both a noise source and an XG3
> sending a CW string of dots. Increase the speed of the CW sent by the
> XG3 until you can no longer hear the noise source between dits.
> Then either calculate the off times for the dits or measure it on an
> oscilloscope.
>
> 73,
> Don W3FPR
>
> On 1/13/2019 2:07 PM, Dave Cole (NK7Z) wrote:
>> Hi again Scott,
>>
>> Thank you for your answer, but I am not being clear.
>>
>> Not during break in, just sitting there in receive... If the radio
>> is hit with an S9+ signal, how long after the S9+ signal terminates
>> before the K3 receiver recovers enough to show an weak signal on the
>> IF... No T/R happening, just sitting there in receive.
>>
>> You are close to what I am looking for... I am investigating the
>> possibility of using the K3 as the receiver portion in a homebrew
>> bistatic radar setup running in the HF spectrum.
> ______________________________________________________________
> 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]

--
Scott K9MA

[hidden email]

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NK7Z

Re: K3: Receiver recovery time

In reply to this post by Don Wilhelm

Hi Don,

Thanks for the combined brain power! I have a plan for testing if it
ever gets that far. I am just trying to see if the K3 receiver recovers
sufficiently fast in a general sort of way first.

I believe I could look at RF levels on the IF while transmitting, (using
a different transmitter and a storage scope to look at the K3 IF), then
just drop the carrier while still looking at the levels with that scope.
When I see signals return to the IF I have the recovery time of the
receiver.

I am just trying to skip that step hoping someone actually knows the
recovery time of the receiver, as opposed to actual testing.

If the K3 is even close, I will set up test jig for it, if not, then
I'll look for a better way.

Thanks again for your thoughts here!

73s and thanks,
Dave (NK7Z)
https://www.nk7z.net
Award Manager, 30MDG Grid Contest
ARRL Technical Specialist
ARRL Volunteer Examiner
ARRL OOC for Oregon

On 1/13/19 11:53 AM, Don Wilhelm wrote:

> Dave,
>
> I am trying to think of how you might test it.
> The best I can think of is to listen to both a noise source and an XG3
> sending a CW string of dots. Increase the speed of the CW sent by the
> XG3 until you can no longer hear the noise source between dits.
> Then either calculate the off times for the dits or measure it on an
> oscilloscope.
>
> 73,
> Don W3FPR
>
> On 1/13/2019 2:07 PM, Dave Cole (NK7Z) wrote:
>> Hi again Scott,
>>
>> Thank you for your answer, but I am not being clear.
>>
>> Not during break in, just sitting there in receive... If the radio is
>> hit with an S9+ signal, how long after the S9+ signal terminates
>> before the K3 receiver recovers enough to show an weak signal on the
>> IF... No T/R happening, just sitting there in receive.
>>
>> You are close to what I am looking for... I am investigating the
>> possibility of using the K3 as the receiver portion in a homebrew
>> bistatic radar setup running in the HF spectrum.

Don Wilhelm

Re: K3: Receiver recovery time

Dave,

I would be cautious about looking only at the IF. That is all in front
of the DSP.
Certainly the DSP creates some latency, but that is not what we are
talking about. The DSP latency will delay all signals.

So test in the configuration that you will likely use. If using the IF
output, then test only at the IF.

Your question relates to the recovery time for the entire receiver.
And that does include the filters, both roofing filters and the DSP
filtering.

Don't forget that the Hardware AGC cannot be turned off, but that does
not come into play until the signal is greater than S-9+60

As A result, I believe you need to do actual testing with your
particular K3 under various filtering conditions.
In other words, you are asking a very complex question, and you have not
given us the other configuration settings and filters to be used - other
than AGC OFF. For that reason, your K3 may have a different answer than
others.

73,
Don W3FPR

On 1/13/2019 3:43 PM, Dave Cole (NK7Z) wrote:

> Hi Don,
>
> Thanks for the combined brain power! I have a plan for testing if it
> ever gets that far. I am just trying to see if the K3 receiver recovers
> sufficiently fast in a general sort of way first.
>
> I believe I could look at RF levels on the IF while transmitting, (using
> a different transmitter and a storage scope to look at the K3 IF), then
> just drop the carrier while still looking at the levels with that scope.
> When I see signals return to the IF I have the recovery time of the
> receiver.
>
> I am just trying to skip that step hoping someone actually knows the
> recovery time of the receiver, as opposed to actual testing.
>
> If the K3 is even close, I will set up test jig for it, if not, then
> I'll look for a better way.
>

NK7Z

Re: K3: Receiver recovery time

Thank you Don!! I was trying to get a general feel for what to expect,
a ms, or us type of answer...

I was thinking of using the IF to avoid the DSP filters for just the
reasons you cited. I am sure you are correct about testing-- time to
break out the scope...

Thanks again for your insight!

73s and thanks,
Dave (NK7Z)
https://www.nk7z.net
Award Manager, 30MDG Grid Contest
ARRL Technical Specialist
ARRL Volunteer Examiner
ARRL OOC for Oregon

On 1/13/19 1:08 PM, Don Wilhelm wrote:

> Dave,
>
> I would be cautious about looking only at the IF. That is all in front
> of the DSP.
> Certainly the DSP creates some latency, but that is not what we are
> talking about. The DSP latency will delay all signals.
>
> So test in the configuration that you will likely use. If using the IF
> output, then test only at the IF.
>
> Your question relates to the recovery time for the entire receiver.
> And that does include the filters, both roofing filters and the DSP
> filtering.
>
> Don't forget that the Hardware AGC cannot be turned off, but that does
> not come into play until the signal is greater than S-9+60
>
> As A result, I believe you need to do actual testing with your
> particular K3 under various filtering conditions.
> In other words, you are asking a very complex question, and you have not
> given us the other configuration settings and filters to be used - other
> than AGC OFF. For that reason, your K3 may have a different answer than
> others.
>
> 73,
> Don W3FPR
>
> On 1/13/2019 3:43 PM, Dave Cole (NK7Z) wrote:
>> Hi Don,
>>
>> Thanks for the combined brain power! I have a plan for testing if it
>> ever gets that far. I am just trying to see if the K3 receiver
>> recovers sufficiently fast in a general sort of way first.
>>
>> I believe I could look at RF levels on the IF while transmitting,
>> (using a different transmitter and a storage scope to look at the K3
>> IF), then just drop the carrier while still looking at the levels with
>> that scope. When I see signals return to the IF I have the recovery
>> time of the receiver.
>>
>> I am just trying to skip that step hoping someone actually knows the
>> recovery time of the receiver, as opposed to actual testing.
>>
>> If the K3 is even close, I will set up test jig for it, if not, then
>> I'll look for a better way.
>>