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k3 - dual receiver & filters

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tom kenville

k3 - dual receiver & filters

I have a single receiver K3, with various filters.

For adding RCVR#2, do I need to get a set of matched filter pairs to
complete that setup ?

--
thanks and 73
Tom Kenville -- W6TJK
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wayne burdick

Re: k3 - dual receiver & filters

Administrator

Hi Tom,

While matched filters are optimal for matching receiver performance,
they're not strictly necessary if you're only doing non-diversity
receive. The K3 will select an appropriate filter bandwidth for each
receiver independently.

If you want to do diversity receive, you'll need filters with matched
offsets. Our 8-pole filters all have offsets of 0.00, but can also do
this with 5-pole filters as long as the offsets are matched for a
given crystal filter bandwidth. At the time you order the filters, you
can request matched sets.

73,
Wayne
N6KR

On Feb 8, 2011, at 8:25 PM, tom kenville wrote:

> I have a single receiver K3, with various filters.
>
> For adding RCVR#2, do I need to get a set of matched filter pairs to
> complete that setup ?
>
> --
> thanks and 73
> Tom Kenville -- W6TJK
> ______________________________________________________________
> 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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Don Wilhelm-4

Re: k3 - dual receiver & filters

In reply to this post by tom kenville

Tom,

Yes and No.

If you plan to use diversity reception, then the matched filters are
necessary. If you do not plan diversity receive, then they are not
important.

There is a subtle point here that is not often mentioned. For wider
filters, the offset is not as important as for narrow filters. If you
have the 5 pole 2.7 kHz filters (for instance), one with an offset of
+40 and another with an offset of +20, if you set the offset for both
filters at +30, it will be quite usable - only a difference of 10 Hz at
a bandwidth of 2700 Hz - it will not be noticable.
But do not try the same thing with a filter width of 250 Hz - the
results could be quite annoying.

I cannot say where the dividing line should be between wide and narrow
- a big part of it is in your ability to perceive slight differences.

That is the facts as I know them - the choices are yours to make. The
safe answer is YES, you need matched filters for diversity receive.

73,
Don W3FPR

On 2/8/2011 11:25 PM, tom kenville wrote:
> I have a single receiver K3, with various filters.
>
> For adding RCVR#2, do I need to get a set of matched filter pairs to
> complete that setup ?
>
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Ralph Parker

Re: k3 - dual receiver & filters

In reply to this post by tom kenville

>If you plan to use diversity reception, then the matched filters are
necessary...

C'mon, guys, this is not true!
I use diversity reception with one .400 8 pole and one .500 5 pole,
sometimes with one .250 8 pole and one .500 5 pole.
Better performance with matched filters = quite likely.
Necessary = not.

Ralph, VE7XF

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wayne burdick

Re: k3 - dual receiver & filters

Administrator

Ralph,

You're right: even if the filters don't have matched offsets, you can use diversity mode.

But the main and sub synthesizer frequencies will usually be separated by a fraction of a Hz if the offsets are different, leading to a rolling sound in the receivers (phase precessing, a type of beat note). It can be distracting.

This is why most users prefer to use matched filters.

73,
Wayne
N6KR

----
http://www.elecraft.com

On Feb 8, 2011, at 10:14 PM, Ralph Parker <[hidden email]> wrote:

>> If you plan to use diversity reception, then the matched filters are
> necessary...
>
> C'mon, guys, this is not true!
> I use diversity reception with one .400 8 pole and one .500 5 pole,
> sometimes with one .250 8 pole and one .500 5 pole.
> Better performance with matched filters = quite likely.
> Necessary = not.
>
> Ralph, VE7XF
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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Arie Kleingeld PA3A-2

K3 Switching AGC sub-RX (bug?)

In reply to this post by wayne burdick

Hi,

stumbled upon a bug (?) in FW 4.25

Situation:
- VFO's independant
- main on 20m USB
- sub on 20m CW
- both on AGC slow
- Antenna sub = MAIN

Trying to switch the sub RX to AGC-F:
- hold A/B for B SET
- Tip AGC
Expect that AGC of sub would switch to AGC-F ...
BUT... nothing happens, display switches to normal again. Sub still on
AGC-S.

(Work-around to accomplish AGC-F for sub RX in this case: switch both
RX's to CW, switch to diversity, set AGC to F. This way the sub RX is
switched to AGC-F. Then switch off diversity and bring the main RX back
to AGC-S and USB)

73,
Arie PA3A
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Jim Sheldon

Re: K3 Switching AGC sub-RX (bug?)

The band appears to be independent of this apparent bug as I just tried the same thing on 160. Same thing that Arie reports happens with My K3 as well - running latest FW (4.25) as well.

Jim - W0EB

> Hi,
>
> stumbled upon a bug (?) in FW 4.25
>
> Situation:
> - VFO's independant
> - main on 20m USB
> - sub on 20m CW
> - both on AGC slow
> - Antenna sub = MAIN
>
> Trying to switch the sub RX to AGC-F:
> - hold A/B for B SET
> - Tip AGC
> Expect that AGC of sub would switch to AGC-F ...
> BUT... nothing happens, display switches to normal again. Sub still
> on
> AGC-S.
>
>
> (Work-around to accomplish AGC-F for sub RX in this case: switch
> both
> RX's to CW, switch to diversity, set AGC to F. This way the sub RX
> is
> switched to AGC-F. Then switch off diversity and bring the main RX
> back
> to AGC-S and USB)
>
>
> 73,
> Arie PA3A
> ______________________________________________________________
> 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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ha4zd

Re: k3 - dual receiver & filters

In reply to this post by wayne burdick

On 2/9/2011 8:28 AM, Wayne Burdick wrote:

> Ralph,
>
> You're right: even if the filters don't have matched offsets, you can use diversity mode.
>
> But the main and sub synthesizer frequencies will usually be separated by a fraction of a Hz if the offsets are different, leading to a rolling sound in the receivers (phase precessing, a type of beat note). It can be distracting.
>
> This is why most users prefer to use matched filters.
>
> 73,
> Wayne
> N6KR
>
> ----
> http://www.elecraft.com
>
> On Feb 8, 2011, at 10:14 PM, Ralph Parker<[hidden email]> wrote:
>
>>> If you plan to use diversity reception, then the matched filters are
>> necessary...
>>
>> C'mon, guys, this is not true!
>> I use diversity reception with one .400 8 pole and one .500 5 pole,
>> sometimes with one .250 8 pole and one .500 5 pole.
>> Better performance with matched filters = quite likely.
>> Necessary = not.
>>
>> Ralph, VE7XF
>>
>> ______________________________________________________________
>> 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
> ______________________________________________________________
> Elecraft mailing list
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>
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> Please help support this email list:http://www.qsl.net/donate.html

The effect can be heard on youtube, there is a diversity reception
comparison of K3 and FTDX5000 from YO5...
http://www.youtube.com/watch?v=iBGy5HNZxEc K3 is an evident winner in
diversity reception.

73,

István

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