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Connections to K3 ant 1 & 2

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N3XX

Connections to K3 ant 1 & 2

Hi to all on the list,

I just finished building my K3 kit a few weeks ago (4175). All went well,
and the new xcvr is up & running with no problems.
The antenna setup at my qth is a single cable from the entrance panel at the
house going out to tower #1, through a remote antenna switch to select from
antennas on that tower or another connection going to tower #2. At tower #2
is another remote antenna switch to select various antennas on that tower.
In the shack I have an amp for 160-10 meters, and an amp for 6 meters.
I would like to connect my single cable coming in from the entrance panel to
a 2 way coax switch, with one of the ports going to my 160-10 meter amp,
and the other going to my 6 meter amp. Then the 160-10 amp would be
connected to the K3 antenna connector 1, and the 6 meter amp would be
connected to K3 antenna connector 2.
Both amps will operate at the legal limit easily, and my concern is that
when xmitting through one of the antenna connectors & amp, I will put too
much rf back through the coax switch to the unused K3 antenna connector, and
possibly damage the K3.
I have been changing cabling manually but would really like to be able to
just operate a switch to make the change.
So, if anyone on the list doing something similar to what I have in mind, I
sure would like to hear about your setup, what kind of switch you are using,
how much port to port isolation is necessary to be safe, etc.

Tnx & 73,
Tim - N3XX

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juergen piezo

K3:Noise blanker & Chinese radar?

Hi

When the K3 was first released, the noise blanker was very effective on the Chinese Radar on 40 meters. This radar was very active on the CW end of 40 meters. You could totally eliminate this radar signal with the K3's noise blanker.

As the firmware was updated, the K3's noise blanker seemed to become less effective or almost had no effect at all. Anyone else notice this loss in performance? I wonder if this ability to notch this low band radar was removed from the K3's noise blanker algorithm?

It could be that the radars pulse repetition rate or pulse width has changed rendering the noise blanker useless against it.

Anyway when the K3's blanker was working it was outstanding on 160, 80 and 40 meters against this constant QRM source.

John

--- On Thu, 5/20/10, N3XX <[hidden email]> wrote:

> From: N3XX <[hidden email]>
> Subject: [Elecraft] Connections to K3 ant 1 & 2
> To: "Elecraft Reflector" <[hidden email]>
> Date: Thursday, May 20, 2010, 3:18 AM
> Hi to all on the list,
>
> I just finished building my K3 kit a few weeks ago
> (4175). All went well,
> and the new xcvr is up & running with no problems.
> The antenna setup at my qth is a single cable from the
> entrance panel at the
> house going out to tower #1, through a remote antenna
> switch to select from
> antennas on that tower or another connection going to tower
> #2. At tower #2
> is another remote antenna switch to select various antennas
> on that tower.
> In the shack I have an amp for 160-10 meters, and an amp
> for 6 meters.
> I would like to connect my single cable coming in from the
> entrance panel to
> a 2 way coax switch, with one of the ports going to
> my 160-10 meter amp,
> and the other going to my 6 meter amp. Then the
> 160-10 amp would be
> connected to the K3 antenna connector 1, and the 6 meter
> amp would be
> connected to K3 antenna connector 2.
> Both amps will operate at the legal limit easily, and my
> concern is that
> when xmitting through one of the antenna connectors &
> amp, I will put too
> much rf back through the coax switch to the unused K3
> antenna connector, and
> possibly damage the K3.
> I have been changing cabling manually but would really like
> to be able to
> just operate a switch to make the change.
> So, if anyone on the list doing something similar to what I
> have in mind, I
> sure would like to hear about your setup, what kind of
> switch you are using,
> how much port to port isolation is necessary to be safe,
> etc.
>
> Tnx & 73,
> Tim - N3XX
>
> ______________________________________________________________
> 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
>

Philippe Trottet

Re: K3:Noise blanker & Chinese radar?

Hi John,
Do you check all possibilities of the NB and no-one of those are able to block this Radar ?
We are facing time to time in my area such problem and had always founded a reliable position to minimize it, but may be the today's NB is less effective, I have no experience on it and I'm interested by all comments on the subject.
Bst 73's
Philippe A65BI
K3#3616

>>> juergen <[hidden email]> 20-05-2010 15:15 >>>

Hi

When the K3 was first released, the noise blanker was very effective on the Chinese Radar on 40 meters. This radar was very active on the CW end of 40 meters. You could totally eliminate this radar signal with the K3's noise blanker.

As the firmware was updated, the K3's noise blanker seemed to become less effective or almost had no effect at all. Anyone else notice this loss in performance? I wonder if this ability to notch this low band radar was removed from the K3's noise blanker algorithm?

It could be that the radars pulse repetition rate or pulse width has changed rendering the noise blanker useless against it.

Anyway when the K3's blanker was working it was outstanding on 160, 80 and 40 meters against this constant QRM source.

John

--- On Thu, 5/20/10, N3XX <[hidden email]> wrote:

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Don Wilhelm-4

Re: Connections to K3 ant 1 & 2

In reply to this post by N3XX

Tim,

It all depends on the isolation offered by your particular coax relay as
well as the power output from your amplifier.
Assuming you have a 2kW amp (I know 1500 is the max, but the math is
easier with 2k) - then 60 dB of isolation could feed .002 watts into the
non-selected antenna jack. That is a +3dBm signal level.

Now consider that the K3 has front end protective circuitry that begins
at about +3dBm - the receiver preamp is automatically turned off at that
point, and at +13 dBm, the attenuator is automatically switched in.

So I would conclude that up to a +3dBm signal leaking into the receiver
is tolerable and would not cause a problem.
If you further consider that this would only happen when the K3 was in
transmit state, and for the configuration you proposed, the ANT1/ANT2
internal relay offers additional protection (isolation), 60 dB of coax
relay isolation should be overkill. Just how much overkill is cause for
speculation and additional study. If the internal relay offers 20dB or
more isolation, then the required isolation of your coax relay would be
reduced to 40 dB. I would guess that rating the internal relay for 20
dB isolation is conservative, most any relay worth its salt should be at
least that good.

73,
Don W3FPR

N3XX wrote:

> Hi to all on the list,
>
> I just finished building my K3 kit a few weeks ago (4175). All went well,
> and the new xcvr is up & running with no problems.
> The antenna setup at my qth is a single cable from the entrance panel at the
> house going out to tower #1, through a remote antenna switch to select from
> antennas on that tower or another connection going to tower #2. At tower #2
> is another remote antenna switch to select various antennas on that tower.
> In the shack I have an amp for 160-10 meters, and an amp for 6 meters.
> I would like to connect my single cable coming in from the entrance panel to
> a 2 way coax switch, with one of the ports going to my 160-10 meter amp,
> and the other going to my 6 meter amp. Then the 160-10 amp would be
> connected to the K3 antenna connector 1, and the 6 meter amp would be
> connected to K3 antenna connector 2.
> Both amps will operate at the legal limit easily, and my concern is that
> when xmitting through one of the antenna connectors & amp, I will put too
> much rf back through the coax switch to the unused K3 antenna connector, and
> possibly damage the K3.
> I have been changing cabling manually but would really like to be able to
> just operate a switch to make the change.
> So, if anyone on the list doing something similar to what I have in mind, I
> sure would like to hear about your setup, what kind of switch you are using,
> how much port to port isolation is necessary to be safe, etc.
>
> Tnx & 73,
> Tim - N3XX
>
>

Mike Harris

Re: Connections to K3 ant 1 & 2

Hi Tim,

Assuming you are only using the KAT3 A/B ports and not the RX ANT IN
jack on the KXV3A then the RX is already behind two stages of T/R
switching.

However, the Top Ten Devices A/B switch looks interesting.
Unfortunately the manual only gives figures for 30MHz.

Regards,

Mike VP8NO

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Joe Subich, W4TV-4

Re: Connections to K3 ant 1 & 2

> However, the Top Ten Devices A/B switch looks interesting.
> Unfortunately the manual only gives figures for 30MHz.

Some old correspondence with Top Ten systems indicates the
A/BSS has SWR around 1.2;1 at six meters - I don't have any
detail on the measurements and have no way to test one.

Note, unlike most other switches, the A/BSS requires a switched
ground (common source) vs. switched source (common ground).

Another source for usable relays is Surplus Sales of Nebraska
<www.surplussales.com/Relays/rfcoaxialrelays/rfcoaxindex.html>.
Although some versions are a bit expensive, a simple 12V SPDT
relay is an attractive alternative to a manual coax switch.

73,

... Joe, W4TV

On 5/20/2010 9:37 AM, Mike Harris wrote:

> Hi Tim,
>
> Assuming you are only using the KAT3 A/B ports and not the RX ANT IN
> jack on the KXV3A then the RX is already behind two stages of T/R
> switching.
>
> However, the Top Ten Devices A/B switch looks interesting.
> Unfortunately the manual only gives figures for 30MHz.
>
> Regards,
>
> Mike VP8NO
>

KK7P

Re: K3:Noise blanker & Chinese radar?

In reply to this post by juergen piezo

> As the firmware was updated, the K3's noise blanker seemed to become less effective or almost had no effect at all.

I just checked the source codec files of the DSP Noise Blanker back to
May of 2008 - absolutely no change has been made to the algorithm,
*except* the most recent beta which adds a feature but does not take
away any.

73,

Lyle KK7P
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KK7P

Re: K3:Noise blanker & Chinese radar?

>> As the firmware was updated, the K3's noise blanker seemed to become less effective or almost had no effect at all.
>>
>
> I just checked the source code files of the DSP Noise Blanker back to
> May of 2008 - absolutely no change has been made to the algorithm,
> *except* the most recent beta which adds a feature but does not take
> away any.
>

And checked the DSP source code files further back, to October 2007
(first customer shipments). The algorithm is identical.

73,

Lyle KK7P
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Merv Schweigert

Re: K3:Noise blanker & Chinese radar?

In reply to this post by KK7P

Lyle Johnson wrote:

>> As the firmware was updated, the K3's noise blanker seemed to become less effective or almost had no effect at all.
>>
>
> I just checked the source codec files of the DSP Noise Blanker back to
> May of 2008 - absolutely no change has been made to the algorithm,
> *except* the most recent beta which adds a feature but does not take
> away any.
>
> 73,
>
> Lyle KK7P
>

Living in Hawaii gives one a real opportunity to test the NB on the
Hainan radar on 40 meters
and other freqs as well, my K3 #26XX has never been able to remove the
pulses, I can
compare to a couple of other brand X radios and one of them removes the
pulses
very well, the other only so - so. So operating 40 meters when the
radar is on, requires me to
turn on another radio to be able to use the band.
I figure it takes a special set up of timing and algorithm to tackle the
Hainan dragon.
73 Merv KH7C

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Geoffrey Mackenzie-Kennedy

Re: Connections to K3 ant 1 & 2

In reply to this post by Joe Subich, W4TV-4

To add slightly to Joe's suggestion to use a SPDT relay as an alternative,
if a DPDT relay is used one pole can be used to switch the signal path, and
by connecting the second pole to ground the second pole can be used to
ground the unused signal path - which can improve isolation (reduce
crosstalk) if the ground connection to the second pole is short.

73,
Geoff
GM4ESD

On May 20, 2010 at 4:49 PM, Joe Subich, W4TV wrote:

<snip>
> Another source for usable relays is Surplus Sales of Nebraska
> <www.surplussales.com/Relays/rfcoaxialrelays/rfcoaxindex.html>.
> Although some versions are a bit expensive, a simple 12V SPDT
> relay is an attractive alternative to a manual coax switch.

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W8JI

Re: Connections to K3 ant 1 & 2

> To add slightly to Joe's suggestion to use a SPDT relay as
> an alternative,
> if a DPDT relay is used one pole can be used to switch the
> signal path, and
> by connecting the second pole to ground the second pole
> can be used to
> ground the unused signal path - which can improve
> isolation (reduce
> crosstalk) if the ground connection to the second pole is
> short.

I've seen grounding increase crosstalk or feedthrough also,
so it is the overall layout and relay or switch that is key
to whether grounding helps or hurts.

Best to use a form-X or double-make double-break relays and
let the armature ground but not the poles. It's easy to get
into the -90 dB isolation range at HF doing that, and still
be in the 70's and higher at 50 MHz.

I use a manual switch on 6 meters/HF. I have a pair of
3CX800's on six, and a big amp on HF. No problems using some
Diawa 2 pole switches.

If homebrewing I would measure things carefully.

73 Tom

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KK7P

Re: K3:Noise blanker & Chinese radar?

In reply to this post by Merv Schweigert

> Living in Hawaii gives one a real opportunity to test the NB on the
> Hainan radar on 40 meters
> and other freqs as well...

The latest beta has an improved DSP noise blanker that may be more
effective.

73,

Lyle KK7P
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N3XX

Re: Connections to K3 ant 1 & 2

In reply to this post by N3XX

Thanks to everyone for your responses and suggestions.
I have decided to order a "TwoPak" rf switch from Array solutions.
There are less costly ways to go, but I like the specs I see on their
website.
High pwr handling, good well above the highest frequency I intend to use,
and >80 dB isolation between ports.
I will still measure power on the unused port when transmitting through the
other, to see how much I would be putting back into the K3. Only after this
will I connect everything up to both antenna connectors on the K3 if all
looks good.
Will post here again when I have tested and have all connected & working.

73,
Tim - N3XX

----- Original Message -----
From: "N3XX" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Sent: Thursday, May 20, 2010 6:18 AM
Subject: [Elecraft] Connections to K3 ant 1 & 2

> Hi to all on the list,
>
> I just finished building my K3 kit a few weeks ago (4175). All went well,
> and the new xcvr is up & running with no problems.
> The antenna setup at my qth is a single cable from the entrance panel at
> the
> house going out to tower #1, through a remote antenna switch to select
> from
> antennas on that tower or another connection going to tower #2. At tower
> #2
> is another remote antenna switch to select various antennas on that tower.
> In the shack I have an amp for 160-10 meters, and an amp for 6 meters.
> I would like to connect my single cable coming in from the entrance panel
> to
> a 2 way coax switch, with one of the ports going to my 160-10 meter amp,
> and the other going to my 6 meter amp. Then the 160-10 amp would be
> connected to the K3 antenna connector 1, and the 6 meter amp would be
> connected to K3 antenna connector 2.
> Both amps will operate at the legal limit easily, and my concern is that
> when xmitting through one of the antenna connectors & amp, I will put too
> much rf back through the coax switch to the unused K3 antenna connector,
> and
> possibly damage the K3.
> I have been changing cabling manually but would really like to be able to
> just operate a switch to make the change.
> So, if anyone on the list doing something similar to what I have in mind,
> I
> sure would like to hear about your setup, what kind of switch you are
> using,
> how much port to port isolation is necessary to be safe, etc.
>
> Tnx & 73,
> Tim - N3XX
>
> ______________________________________________________________
> 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