KRX3 questions

[Doug Faunt N6TQS [phone]]

I've finally put the second RX in my K3 #22.

I have 2.7k filters with -0.86 and -0.87 offsets- have I ended up with
filters that are matched enough for diversity reception?  The thought is
that it'd be useful to have two low-band antennas useable
simultaneously when on DXpeditions.  I still need some 8-pole filters,
and my initial choices of 2.1kHz and 400 Hz seem to be slightly
suboptimal, so they may end up on the secondary market.

I only got a strip of foam for the bottom of the speaker, rather than
a square as shown in the KRX3 manual.  OK?

I also added lock washers to my original KSYN to match the mounting
screw configuration of the secondary KSYN.

When you're traveling a lot, it's hard to keep up, so forgive me if
all of this has been discussed in the past.

73, doug

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[KK7P]

> I've finally put the second RX in my K3 #22.
>
> I have 2.7k filters with -0.86 and -0.87 offsets- have I ended up with
> filters that are matched enough for diversity reception?

Yes, but set them both to the same value. A 10 Hz error is not going
matter to the 2.7 kHz filter's passband response, but the 10 Hz
difference in offset may result in an annoying beat effect when both
receivers are tuned to the same indicated frequency.

73,

Lyle KK7P

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[Arie Kleingeld PA3A]

Lyle,

I can understand why the beat effect can happen at certain frequencies.
I read the message about the rounding errors.

My question is: can you give an indication of how often this happens. Of
course it depends on freq and filter offset but still, can you give an
idication how bad it is.
Anyone ?

Thanks.

Arie PA3A



-====================================================

> I've finally put the second RX in my K3 #22.
>
> I have 2.7k filters with -0.86 and -0.87 offsets- have I ended up with

> filters that are matched enough for diversity reception?

Yes, but set them both to the same value. A 10 Hz error is not going
matter to the 2.7 kHz filter's passband response, but the 10 Hz
difference in offset may result in an annoying beat effect when both
receivers are tuned to the same indicated frequency.

73,

Lyle KK7P

__

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[Bill W4ZV]

Arie Kleingeld PA3A wrote

Lyle,

I can understand why the beat effect can happen at certain frequencies.
I read the message about the rounding errors.

My question is: can you give an indication of how often this happens. Of
course it depends on freq and filter offset but still, can you give an
idication how bad it is.
Anyone ?

The beat is not the same as the difference in filter offsets.  Somewhere in the KRX3 documentation I believe it states the beat may only be as bad as a Hz or so.  

73,  Bill

[Bill W4ZV]

Bill W4ZV wrote

Arie Kleingeld PA3A wrote

Lyle,

I can understand why the beat effect can happen at certain frequencies.
I read the message about the rounding errors.

My question is: can you give an indication of how often this happens. Of
course it depends on freq and filter offset but still, can you give an
idication how bad it is.
Anyone ?

The beat is not the same as the difference in filter offsets.  Somewhere in the KRX3 documentation I believe it states the beat may only be as bad as a Hz or so.  

73,  Bill

Found the reference on page 42 of the KRX3 manual (1.6 MB):

Diversity receive performance may be enhanced by
using crystal filters with matched offsets
(CONFIG:FLx FRQ). This ensures that the VFOs
are at exactly the same frequency. Non-matched
filter offsets will result in a difference of about +/- 1
Hz between the two synthesizers, which may be
heard as a “beat note” under some conditions.

http://www.elecraft.com/manual/KRX3_Subreceiver_Install_&_Operate_Rev_A_WEB.pdf

73,  Bill

[N5GE]

On Sat, 30 Aug 2008 05:57:15 -0700 (PDT), Bill W4ZV <[hidden email]>
wrote:

[snip]

>> The beat is not the same as the difference in filter offsets.  Somewhere
>> in the KRX3 documentation I believe it states the beat may only be as bad
>> as a Hz or so.  
>>
>> 73,  Bill
>>
>>
>
>Found the reference on page 42 of the KRX3 manual (1.6 MB):
>
>Diversity receive performance may be enhanced by
>using crystal filters with matched offsets
>(CONFIG:FLx FRQ). This ensures that the VFOs
>are at exactly the same frequency. Non-matched
>filter offsets will result in a difference of about +/- 1
>Hz between the two synthesizers, which may be
>heard as a “beat note” under some conditions.
>
>http://www.elecraft.com/manual/KRX3_Subreceiver_Install_&_Operate_Rev_A_WEB.pdf
>
>73,  Bill

This beat note experience is one of the reasons I got a K3.  My Orion II always
had a 6Hz difference between the A VFO and B VFO.  It was very irritating after
having Kenwoods and Yaesus that did not suffer from that problem.

I am still waiting for my KRX3, but when I heard about the offset possibility I
changed my order for the KRX3 from a 2.7 KHz filter to a 2.8Khz filter (the
others ordered are all 8 pole filters) and replaced the 2.7Khz filter in the K3
with a 2.8Khz filter.


Tom, N5GE - SWOT 3537 - Grid EM12jq

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Essential Liberty to
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just the parts you like.

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[Arie Kleingeld PA3A]

(was subject KRX3 Questions)

Thanks Bill,


I think I have to restate the question for the group.


Just suppose that main and sub receivers have filters with different
off-sets. It is stated that in some cases a 1Hz beatnote occurs due to
rounding errors.

Question is:

How often does the 1 Hz beat 'note'  occur?
Is it on almost all frequencies, or is it only on say 10 frequencies in
a band or is it there in a part of a band (for axample the beatnote is
there from 1.812.009 until 1.815.004)

(Yes, it will depend on band and on filter offsets but I'd like to hear
some experiences from guys who have tried it. Give me the facts  :-)  )


Thanks in advance,
73
Arie PA3A



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[Bill W4ZV]

Tom Childers, N5GE wrote

This beat note experience is one of the reasons I got a K3.  My Orion II always
had a 6Hz difference between the A VFO and B VFO.  It was very irritating after
having Kenwoods and Yaesus that did not suffer from that problem.

I am still waiting for my KRX3, but when I heard about the offset possibility I
changed my order for the KRX3 from a 2.7 KHz filter to a 2.8Khz filter (the
others ordered are all 8 pole filters) and replaced the 2.7Khz filter in the K3
with a 2.8Khz filter.

I  experienced the same problem with my Orion but it had a constant 2.3 Hz offset.  

It's absolutely unnecessary to use only 8-pole filters in the K3 for diversity.  In the case previously cited here by Doug N6TQS, his 2.7k offsets were only off by 10 Hz so it would not cause any problem to set both to the same offset (i.e. 10 Hz out of 2700 Hz is 0.4% and not significant).  

Don't be deceived in thinking 8-pole filters actually have zero Hz offsets...they don't!  Several others (W0YK for one) have reported narrow CW 8-pole filters with offsets of 40-80 Hz.  In a "250 Hz" (actually 370 Hz) 8-pole CW filter, this can be significant (i.e.  80 Hz out of 370 Hz is ~20%).  Also, if you go through the process to zero them, there is no guarantee that any two 8-pole CW filters will actually have the same offset.

When I ordered my new K3 with KRX3, I did not order matched 2.7k and 500 Hz filters, thinking that the 2.7ks would not be far enough off to be significant and hoping the 500s would be about the same since they would probably come from the same manufacturing batch.  The 2.7ks were off by 30 Hz so I split the difference and set both offsets to a number between, as Lyle suggested.  The 500s just happened to be identical.  If they had been off significantly (e.g. 50 Hz), I might have returned one and asked for a matched filter at the additional $30 cost.  

My KRX3 works perfectly in diversity with no beat using only 5-pole filters.

73,  Bill

[David Cutter]

I'm hoping that for diversity I can just switch off my main rx filters and
have both with only the stock 2.7kHz filter.  I only need the narrow roofing
filters when I am near extremely strong local stations, which doesn't happen
much.  I don't see a need to have 2 sets of roofing filters unless there is
very strong local QRM,  perhaps 40m bc at night in some parts of Eu or
on/near a contest station.

David
G3UNA

 

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[Bill W4ZV]

David Cutter wrote

I'm hoping that for diversity I can just switch off my main rx filters and
have both with only the stock 2.7kHz filter.  I only need the narrow roofing
filters when I am near extremely strong local stations, which doesn't happen
much.  I don't see a need to have 2 sets of roofing filters unless there is
very strong local QRM,  perhaps 40m bc at night in some parts of Eu or
on/near a contest station.

Yes you could use the K3 Utility to do that when you wanted to use diversity.  I have 2.7k/1.8k/500/200 in my Main but only 2.7k/500 in the Sub.  When I want to use diversity, I just remember to use a WIDTH which will auto-select either the 2.7k or 500.  This way I can still use the 1.8k/200 for severe QRM situations in non-diversity and the 2.7k/500 for diversity and/or other situations.

73,  Bill

[Joe Subich, W4TV-3]

Bill,

> I have 2.7k/1.8k/500/200 in my Main but
> only 2.7k/500 in the Sub.  When I want to use diversity, I
> just remember to use a WIDTH which will auto-select either
> the 2.7k or 500.  This way I can still use the 1.8k/200 for
> severe QRM situations in non-diversity and the 2.7k/500 for
> diversity and/or other situations.

With some thought would it not be possible to get 500 and 200 Hz
filters with matched offsets so one could use bandwidth diversity
in addition to antenna diversity?  I will not be able to try that
with my first K3 when that KRX3 arrives since the existing 500
and 250 Hz filters have different offsets but I will look at the
200 Hz filter in the second rig to see if it is close enough to
the -790 Hz (measured in radio #1, specified for radio 2) to be
useful.

73,

   ... Joe, W4TV
 

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Bill W4ZV
> Sent: Saturday, August 30, 2008 11:47 AM
> To: [hidden email]
> Subject: Re: [Elecraft] KRX3 questions
>
>
>
>
>
> David Cutter wrote:
> >
> > I'm hoping that for diversity I can just switch off my main
> rx filters
> > and
> > have both with only the stock 2.7kHz filter.  I only need the narrow
> > roofing
> > filters when I am near extremely strong local stations,
> which doesn't
> > happen
> > much.  I don't see a need to have 2 sets of roofing filters
> unless there
> > is
> > very strong local QRM,  perhaps 40m bc at night in some
> parts of Eu or
> > on/near a contest station.
> >
>
> Yes you could use the K3 Utility to do that when you wanted
> to use diversity.  I have 2.7k/1.8k/500/200 in my Main but
> only 2.7k/500 in the Sub.  When I want to use diversity, I
> just remember to use a WIDTH which will auto-select either
> the 2.7k or 500.  This way I can still use the 1.8k/200 for
> severe QRM situations in non-diversity and the 2.7k/500 for
> diversity and/or other situations.
>
> 73,  Bill
>

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[Bill W4ZV]

Joe Subich, W4TV-3 wrote

Bill,

> I have 2.7k/1.8k/500/200 in my Main but
> only 2.7k/500 in the Sub.  When I want to use diversity, I
> just remember to use a WIDTH which will auto-select either
> the 2.7k or 500.  This way I can still use the 1.8k/200 for
> severe QRM situations in non-diversity and the 2.7k/500 for
> diversity and/or other situations.

With some thought would it not be possible to get 500 and 200 Hz
filters with matched offsets so one could use bandwidth diversity
in addition to antenna diversity?  I will not be able to try that
with my first K3 when that KRX3 arrives since the existing 500
and 250 Hz filters have different offsets but I will look at the
200 Hz filter in the second rig to see if it is close enough to
the -790 Hz (measured in radio #1, specified for radio 2) to be
useful.

Sure you could probably do that if the offsets between the 500 and 200 are not too far off.  You'll probably want to set the 500 equal to the 200 rather than vice versa if they aren't identical (i.e. a shift in a 500 Hz BW is not as critical as the same shift in a 200).  I'm not at home now but I recall my 500s are both -0.84 and my 200 is -0.91.  If I wanted to try what you described I would set both 500s to -0.91 since a shift of 70 Hz is still not unreasonable in ~500 Hz total BW.

The magicians at Elecraft are now at work on an improved DUAL PB which will allow more flexibility in the context WIDTH setting, which would accomplish somewhat similar results (but the context BW is attenuated by -24 dB versus the focus BW).

73,  Bill

[Joe Subich, W4TV-3]

> The magicians at Elecraft are now at work on an improved DUAL
> PB which will allow more flexibility in the context WIDTH
> setting, which would accomplish somewhat similar results (but
> the context BW is attenuated by -24 dB versus the focus BW).

I've tried the updated context filter in beta 2.34.  The problem
for me is that the context area is attenuated more than I would
like and the peak (50 Hz?) is a bit narrow.   I would like to
try the transmit antenna on the subreceiver with a relatively
wide filter (600 - 1000 Hz) to get an idea of the overall
activity and a low noise (Beverage, K9AY, phased array, etc.)
receive antenna on the main antenna with a narrow (e.g. 200Hz)
filter to focus on the desired signal.

73,

   ... Joe, W4TV
 

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Bill W4ZV
> Sent: Saturday, August 30, 2008 12:21 PM
> To: [hidden email]
> Subject: RE: [Elecraft] KRX3 questions
>
>
>
>
>
> Joe Subich, W4TV-3 wrote:
> >
> >
> > Bill,
> >
> >> I have 2.7k/1.8k/500/200 in my Main but
> >> only 2.7k/500 in the Sub.  When I want to use diversity, I
> >> just remember to use a WIDTH which will auto-select either
> >> the 2.7k or 500.  This way I can still use the 1.8k/200 for
> >> severe QRM situations in non-diversity and the 2.7k/500 for
> >> diversity and/or other situations.
> >
> > With some thought would it not be possible to get 500 and 200 Hz
> > filters with matched offsets so one could use bandwidth diversity
> > in addition to antenna diversity?  I will not be able to try that
> > with my first K3 when that KRX3 arrives since the existing 500
> > and 250 Hz filters have different offsets but I will look at the
> > 200 Hz filter in the second rig to see if it is close enough to
> > the -790 Hz (measured in radio #1, specified for radio 2) to be
> > useful.
> >
>
> Sure you could probably do that if the offsets between the
> 500 and 200 are
> not too far off.  You'll probably want to set the 500 equal to the 200
> rather than vice versa if they aren't identical (i.e. a shift
> in a 500 Hz BW
> is not as critical as the same shift in a 200).  I'm not at
> home now but I
> recall my 500s are both -0.84 and my 200 is -0.91.  If I
> wanted to try what
> you described I would set both 500s to -0.91 since a shift of
> 70 Hz is still
> not unreasonable in ~500 Hz total BW.
>
> The magicians at Elecraft are now at work on an improved DUAL
> PB which will
> allow more flexibility in the context WIDTH setting, which
> would accomplish
> somewhat similar results (but the context BW is attenuated by
> -24 dB versus
> the focus BW).
>
> 73,  Bill
>

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[Brett Howard]

For me the context area isn't attenuated at all.  I believe its 200Hz
wide in the middle...  The only difference I thought was that it can now
go down to as narrow as 400 on the outer skirts rather than the 600 that
it used to be limited to.  Doesn't seem to make too much difference to
me but I do admit that I like not being limited as I did run it at 600
at times and wished I wasn't being stopped.

I find that for me it may be a dumb idea to do something but I usually
don't like not being allowed to.  Thats one of the reasons why my 250Hz
filter is fully allowed to be used in SSB on my K3.  Not that I'd want
to do that but why limit myself.  

~Brett (KC7OTG)


On Sat, 2008-08-30 at 18:50 -0400, Joe Subich, W4TV wrote:

> > The magicians at Elecraft are now at work on an improved DUAL
> > PB which will allow more flexibility in the context WIDTH
> > setting, which would accomplish somewhat similar results (but
> > the context BW is attenuated by -24 dB versus the focus BW).
>
> I've tried the updated context filter in beta 2.34.  The problem
> for me is that the context area is attenuated more than I would
> like and the peak (50 Hz?) is a bit narrow.   I would like to
> try the transmit antenna on the subreceiver with a relatively
> wide filter (600 - 1000 Hz) to get an idea of the overall
> activity and a low noise (Beverage, K9AY, phased array, etc.)
> receive antenna on the main antenna with a narrow (e.g. 200Hz)
> filter to focus on the desired signal.
>
> 73,
>
>    ... Joe, W4TV
>  
>
>
> > -----Original Message-----
> > From: [hidden email]
> > [mailto:[hidden email]] On Behalf Of Bill W4ZV
> > Sent: Saturday, August 30, 2008 12:21 PM
> > To: [hidden email]
> > Subject: RE: [Elecraft] KRX3 questions
> >
> >
> >
> >
> >
> > Joe Subich, W4TV-3 wrote:
> > >
> > >
> > > Bill,
> > >
> > >> I have 2.7k/1.8k/500/200 in my Main but
> > >> only 2.7k/500 in the Sub.  When I want to use diversity, I
> > >> just remember to use a WIDTH which will auto-select either
> > >> the 2.7k or 500.  This way I can still use the 1.8k/200 for
> > >> severe QRM situations in non-diversity and the 2.7k/500 for
> > >> diversity and/or other situations.
> > >
> > > With some thought would it not be possible to get 500 and 200 Hz
> > > filters with matched offsets so one could use bandwidth diversity
> > > in addition to antenna diversity?  I will not be able to try that
> > > with my first K3 when that KRX3 arrives since the existing 500
> > > and 250 Hz filters have different offsets but I will look at the
> > > 200 Hz filter in the second rig to see if it is close enough to
> > > the -790 Hz (measured in radio #1, specified for radio 2) to be
> > > useful.
> > >
> >
> > Sure you could probably do that if the offsets between the
> > 500 and 200 are
> > not too far off.  You'll probably want to set the 500 equal to the 200
> > rather than vice versa if they aren't identical (i.e. a shift
> > in a 500 Hz BW
> > is not as critical as the same shift in a 200).  I'm not at
> > home now but I
> > recall my 500s are both -0.84 and my 200 is -0.91.  If I
> > wanted to try what
> > you described I would set both 500s to -0.91 since a shift of
> > 70 Hz is still
> > not unreasonable in ~500 Hz total BW.
> >
> > The magicians at Elecraft are now at work on an improved DUAL
> > PB which will
> > allow more flexibility in the context WIDTH setting, which
> > would accomplish
> > somewhat similar results (but the context BW is attenuated by
> > -24 dB versus
> > the focus BW).
> >
> > 73,  Bill
> >
>
>
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[Arie Kleingeld PA3A]

Have not seen any answer to this question yet.
Here it is again.


Just suppose that main and sub receivers have filters with different
off-sets. It is stated that in some cases a 1Hz beatnote occurs due to
rounding errors.

Question is:

How often does the 1 Hz beat 'note'  occur?
Is it on almost all frequencies, or is it only on say 10 frequencies in
a band or is it there in a part of a band (for axample the beatnote is
there from 1.812.009 until 1.815.004)

(Yes, it will depend on band and on filter offsets but I'd like to hear
some experiences from guys who have tried it. What are the facts  :-)  )


Thanks in advance,
73
Arie PA3A

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