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[K3] Detuning antenna per band and QSK

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Jim AB3CV

[K3] Detuning antenna per band and QSK

I use and like QSK on my K3 but I'm now looking at detuning my 160 inverted
L to avoid reradiation into my beverages when in receiving.

I'm looking at what it will take to do that and it appears that if the 160
inv-L is just deselected by the remote DXE relay box it will just be an
ungrounded 1/4 wave which shouldn't present problems on 160.

I could implement a sequencer in the shack to do this by interrupting the
relay select line that controls the 160 antenna on a per band basis but
that leaves the question of what to do about QSK since the relay is
specified to operate no sooner that 15mS. That will likely impact the clean
CW and be undesireable.

I can decode the band info and get the info about whether it is in TX or RX
mode and probably inhibit the K3 until the delay has expired.

But I'd need to kill QSK on 160 alone to do this.

Is there a way to do QSK on a per band basis?

73

jim ab3cv
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Brian Hunt

Re: [K3] Detuning antenna per band and QSK

Another way to do what you want might be to switch some attenuation into the receive path during transmit. I assume you are using the RX antenna port for the beverages. The switching could be done with pin diodes with the timing tuned to allow QSK.

Hope this helps.

Brian, K0DTJ

> On Dec 20, 2014, at 12:45, Jim Miller <[hidden email]> wrote:
>
> I use and like QSK on my K3 but I'm now looking at detuning my 160 inverted
> L to avoid reradiation into my beverages when in receiving.
>
> I'm looking at what it will take to do that and it appears that if the 160
> inv-L is just deselected by the remote DXE relay box it will just be an
> ungrounded 1/4 wave which shouldn't present problems on 160.
>
> I could implement a sequencer in the shack to do this by interrupting the
> relay select line that controls the 160 antenna on a per band basis but
> that leaves the question of what to do about QSK since the relay is
> specified to operate no sooner that 15mS. That will likely impact the clean
> CW and be undesireable.
>
> I can decode the band info and get the info about whether it is in TX or RX
> mode and probably inhibit the K3 until the delay has expired.
>
> But I'd need to kill QSK on 160 alone to do this.
>
> Is there a way to do QSK on a per band basis?
>
> 73
>
> jim ab3cv
> ______________________________________________________________
> 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]

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Wes (N7WS)

Re: [K3] Detuning antenna per band and QSK

In reply to this post by Jim AB3CV

I have no idea how you are feeding the inverted-L but I suspect some kind of
series feed. Nevertheless this seems like a job for some PIN diodes. Depending
of the situation, switching in something that would shift resonant frequency or
otherwise disturb the matching would do it (nearly instantly).

(OT but I once saw a presentation by a Navy reservist who did a summer tour at
NAA. One thing he mentioned (confirmed here:
http://www.navy-radio.com/commsta/cutler.htm) was the fact the antenna was tuned
differently between mark and space of the MSK modulation)

Wes N7WS

On 12/20/2014 1:45 PM, Jim Miller wrote:

> I use and like QSK on my K3 but I'm now looking at detuning my 160 inverted
> L to avoid reradiation into my beverages when in receiving.
>
> I'm looking at what it will take to do that and it appears that if the 160
> inv-L is just deselected by the remote DXE relay box it will just be an
> ungrounded 1/4 wave which shouldn't present problems on 160.
>
> I could implement a sequencer in the shack to do this by interrupting the
> relay select line that controls the 160 antenna on a per band basis but
> that leaves the question of what to do about QSK since the relay is
> specified to operate no sooner that 15mS. That will likely impact the clean
> CW and be undesireable.
>
> I can decode the band info and get the info about whether it is in TX or RX
> mode and probably inhibit the K3 until the delay has expired.
>
> But I'd need to kill QSK on 160 alone to do this.
>
> Is there a way to do QSK on a per band basis?
>
> 73
>
> jim ab3cv
> ______________________________________________________________
>

Vic Rosenthal

Re: [K3] Detuning antenna per band and QSK

In reply to this post by Jim AB3CV

I suggest using a vacuum relay at the antenna. I wouldn't want to switch a relay box even with a sequencer at a semi-QSK rate.

Vic K2VCO /4X6GP

> On Dec 20, 2014, at 10:45 PM, Jim Miller <[hidden email]> wrote:
>
> I use and like QSK on my K3 but I'm now looking at detuning my 160 inverted
> L to avoid reradiation into my beverages when in receiving.
>
> I'm looking at what it will take to do that and it appears that if the 160
> inv-L is just deselected by the remote DXE relay box it will just be an
> ungrounded 1/4 wave which shouldn't present problems on 160.
>
> I could implement a sequencer in the shack to do this by interrupting the
> relay select line that controls the 160 antenna on a per band basis but
> that leaves the question of what to do about QSK since the relay is
> specified to operate no sooner that 15mS. That will likely impact the clean
> CW and be undesireable.
>
> I can decode the band info and get the info about whether it is in TX or RX
> mode and probably inhibit the K3 until the delay has expired.
>
> But I'd need to kill QSK on 160 alone to do this.
>
> Is there a way to do QSK on a per band basis?
>
> 73
>
> jim ab3cv
> ______________________________________________________________
> 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]