K3: new feature idea / question

[K1LI]

I was just reading about the differing levels of success that people have
with "active noise cancelling" units. It occurred to me that one should be
able to achieve the same kinds of results using the second RX and separate
antenna in the K3 - with the addition of control over the phase (delay) of
the arriving signal. On its face, it would seem that one could achieve
destructive interference between "the noise only" coming from a "sense"
antenna and "the noise + signal" coming from a better receive antenna.

Thoughts?

--
73 -- Brian -- K1LI
______________________________________________________________
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

[Julian, G4ILO]

Brian Machesney wrote

I was just reading about the differing levels of success that people have
with "active noise cancelling" units. It occurred to me that one should be
able to achieve the same kinds of results using the second RX and separate
antenna in the K3 - with the addition of control over the phase (delay) of
the arriving signal. On its face, it would seem that one could achieve
destructive interference between "the noise only" coming from a "sense"
antenna and "the noise + signal" coming from a better receive antenna.

I own one of those units. One thought that immediately springs to mind is that you need at least two extra controls, preferably three, one to vary the phasing of the two signals and the others to adjust the amplitude of the two inputs so that the noise levels cancel exactly. The K3 has no provision for these controls.

[Geoffrey Downs-2]

A good thought Brian. My experience of two such noise cancelling devices is
that, depending on the type and direction of the noise, they can be very
effective in improving the signal/noise ratio although there is some
insertion loss so weak signals are sometimes lost. I always have one
connected to the K3 for use as needed. As I understand it the phase delay of
the signal from the noise antenna and its mixing with the signal from the
main antenna needs to take place before the signal gets to the receiver, so,
with an external device at least, two receivers are not needed. However, I
have been surprised for some years that no rig manufacturers build such a
feature in. Perhaps it could somehow be done with firmware in the K3 using,
say, the RX ANT or the AUX input for the noise antenna?

73 to all

Geoff
G3UCK


----- Original Message -----
From: "Brian Machesney" <[hidden email]>
Subject: [Elecraft] K3: new feature idea / question


>I was just reading about the differing levels of success that people have
> with "active noise cancelling" units. It occurred to me that one should be
> able to achieve the same kinds of results using the second RX and separate
> antenna in the K3 - with the addition of control over the phase (delay) of
> the arriving signal.

______________________________________________________________
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

[Jeff kb2m]

 I just noticed a problem with the main tuning knob on my K3 #1516 this
morning. I noticed it when I was tuning around using the finger dimple. The
odd thing is it only feels rough when you turn the knob counter-clockwise
while applying slight pressure to facilitate using the finger dimple. I took
the knob off, repositioned it(making sure it was clear of the front panel
and not crooked, it wasn't) and still have the problem. It is bad enough
that after several turns it causes the rotation to stick. Once again this
only happens when turning counter-clockwise, with slight finger pressure in
the dimple.
 What I find interesting is that I hardy use the tuning knob as I use an
LP-Pan with PowerSDR and tune around with a mouse. I get the feeling that
the problem is with the VFO A encoder. Any ideas?

73 Jeff kb2m


______________________________________________________________
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

[pd0psb]

Smart thinking!

Though using two receivers for this may be quite difficult to implement.
They have to be *exactly* identical to obtain phase cancellation.
That means AGC timing, roofing filter ripple, signal path gains, everything.
I think this will be hard with the K3 and SubRX.

The outboard noise-cancellation boxes have a much shorter/simpler and wider signal path, making cancellation easier. It may also be a better place to do this at the front-end and not at the back-end of a receiver.

It would be a nice experiment though!
How about just phase reverting the SubRX audio temporarily and give it a try?

73'
Paul
PD0PSB









 

Brian Machesney wrote

I was just reading about the differing levels of success that people have
with "active noise cancelling" units. It occurred to me that one should be
able to achieve the same kinds of results using the second RX and separate
antenna in the K3 - with the addition of control over the phase (delay) of
the arriving signal. On its face, it would seem that one could achieve
destructive interference between "the noise only" coming from a "sense"
antenna and "the noise + signal" coming from a better receive antenna.

Thoughts?

--
73 -- Brian -- K1LI
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[e-mail]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

[Trevor Smithers]

G4ILO said
> you need at least two extra controls, preferably three, one to vary the
>phasing of the two signals and the others to adjust the amplitude of the two
>inputs so that the noise levels cancel exactly.

Sounds like a description of the DX Engineering NCC-1
http://www.dxengineering.com/Parts.asp?ID=1227&PLID=215&SecID=114&DeptID=12&PartNo=
DXE%2DNCC%2D1

Its expensive but if nothing else the manual is worth a read
http://www.dxengineering.com/pdf/NCC-1%20Rev%203.pdf

Trevor  G0KTN
______________________________________________________________
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

[Bill W4ZV]

Brian Machesney wrote

I was just reading about the differing levels of success that people have
with "active noise cancelling" units. It occurred to me that one should be
able to achieve the same kinds of results using the second RX and separate
antenna in the K3 - with the addition of control over the phase (delay) of
the arriving signal.

I believe it should be possible also since the K3 and KRX3 are virtually identical (as required for diversity).  Any gain difference could be compensated using the separate RF Gain controls, but phase differences would require some sort of control knob, which is in short supply on the K3 front panel.

It's simple to do this with an external unit like the MFJ-1025 which is the way I'm heading.  DXE also has a much more expensive unit (NCC-1) but the 1025 can be modified to make it similar (except for strong signal performance).  I've done all the W8JI modifications below (excluding the filter modifications) and I also added impedance converters for the two inputs.  For some reason both inputs on my 1025 show input impedance on 160m of ~160 ohms, so I added 2:1 transformer inputs to get ~80 ohms on both parallel F-connector inputs (another mod).  I'll be using two identical Beverages staggered ~1/4 wl and spaced ~1/8 wl apart, each matched to 75 ohms.  I was concerned about possible reflection issues if the Beverages saw 150 ohms looking back into the 1025.  

http://www.w8ji.com/mfj-1025_1026.htm

Once the crops are out of the field where I plan to install this I'll try to report back on how it's working.

73,  Bill

[Bill W4ZV]

Brian Machesney wrote

I was just reading about the differing levels of success that people have
with "active noise cancelling" units. It occurred to me that one should be
able to achieve the same kinds of results using the second RX and separate
antenna in the K3 - with the addition of control over the phase (delay) of
the arriving signal.

FYI the Flex 5000 has this capability now and may be slightly ahead of the K3's implementation of diversity. They added the ability to adjust phase as well as amplitude differences between the two
channels. This is exactly the capability Brian is asking for above.

http://w9oy-sdr.blogspot.com/2009/07/more-diversity.html

"Above is the latest "polar" control for the diversity project. The control
allows you to adjust phase and gain between 2 antennas and 2 receivers in the
F5K. Here is a shot of the F5K with diversity active"

Hoping this friendly competition will eventually inspire Elecraft to do
something similar! :-) I'm betting it will...maybe using the P3 display.

73, Bill

[Jeff kb2m]

 I had some time today to mess around with my main tuning knob problem. I
once again removed the knob, and felt washer. Everything appeared normal,
there was nothing wrapped around the shaft, all nuts were secure, nothing
needed to be cleaned, etc. So I put it back together and all is working
fine. I also tried several times to change the clearance between the knob
and felt washer to try and reproduce the problem to no avail. I think the
VFO A encoder had some kind of problem from lack of regular use that has now
gone away. Remember, I only had the problem while rotating the knob
counter-clockwise, the tuning knob worked perfectly in the clockwise
direction. Anyway all is now well again in K3/KB2M land......

73 Jeff kb2m


-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Jeff KB2M
Sent: Tuesday, November 10, 2009 7:02 AM
To: 'Elecraft Reflector'
Subject: [Elecraft] Main tuning knob rough


 I just noticed a problem with the main tuning knob on my K3 #1516 this
morning. I noticed it when I was tuning around using the finger dimple. The
odd thing is it only feels rough when you turn the knob counter-clockwise
while applying slight pressure to facilitate using the finger dimple. I took
the knob off, repositioned it(making sure it was clear of the front panel
and not crooked, it wasn't) and still have the problem. It is bad enough
that after several turns it causes the rotation to stick. Once again this
only happens when turning counter-clockwise, with slight finger pressure in
the dimple.
 What I find interesting is that I hardy use the tuning knob as I use an
LP-Pan with PowerSDR and tune around with a mouse. I get the feeling that
the problem is with the VFO A encoder. Any ideas?

73 Jeff kb2m


______________________________________________________________
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