VFO IND in the KX3?

[KB5NJD]

Good Afternoon,

I recently received my KX3 and its amazing.

I am very active on the 630m band as a Part 5 experimental station and use an outboard transmit downconverter with an 80m IF to generate a signal.  While I have RX upconverters that port to various bands, the native RX seems ok so at least at first I plan on using the internal general coverage RX.

I just ran into a problem, however.  I need to be able to TX on one band and RX on another, literally VFO A is RX at 475 KHz and VFO B is TX at 3675 Khz running split.  Every time I manually enter a freq, when I presee enter, it changes both VFO's to the same band.  I have been told that in the K3, there is a menu setting (VFO IND) to allow independent VFO's but I dont see that option with the KX3.

How do I do this?  The manual does not indicate any instructions for crossband operation but I do it with my Yaesu's and they seem very happy with this type of operation so I suspect there is a way to make this happen.

Thanks so much!

John Langridge KB5NJD / WG2XIQ

[wayne burdick]

John,

The KX3 has "dual watch" (up to +/- 15 kHz VFO A and B separation within the current band). But it does not allow the VFOs to be on different bands. (The K3 allows VFO INDependent in conjunction with the sub receiver, which also has its own front end filters, allowing simultaneous receive on two different bands).

To do what I think you require on the KX3, you could set up 160 m and 80 m for the desired frequencies, then hit BAND+ or BAND- to go from TX to RX. It's still just a single switch press.

Regarding 475 kHz receive: My guess is you'll want to use the up-converter. The KX3's sensitivity and image rejection is optimized for the ham bands, and I'm not sure it will meet your needs at this frequency.

73,
Wayne
N6KR


On Oct 25, 2014, at 4:27 PM, KB5NJD <[hidden email]> wrote:

> Good Afternoon,
>
> I recently received my KX3 and its amazing.
>
> I am very active on the 630m band as a Part 5 experimental station and use
> an outboard transmit downconverter with an 80m IF to generate a signal.
> While I have RX upconverters that port to various bands, the native RX seems
> ok so at least at first I plan on using the internal general coverage RX.
>
> I just ran into a problem, however.  I need to be able to TX on one band and
> RX on another, literally VFO A is RX at 475 KHz and VFO B is TX at 3675 Khz.
> Every time I manually enter a freq, when I presee enter, it changes both
> VFO's to the same band.  I have been told that in the K3, there is a menu
> setting (VFO IND) to allow independent VFO's but I dont see that option with
> the KX3.
>
> How do I do this?  The manual does not indicate any instructions for
> crossband operation but I do it with my Yaesu's and they seem very happy
> with this type of operation so I suspect there is a way to make this happen.
>
> Thanks so much!
>
> John Langridge KB5NJD / WG2XIQ
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/VFO-IND-in-the-KX3-tp7594189.html
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[KB5NJD]

Thanks Wayne.  I have an RX converter I can put in line that ports to 80m also. I will just have to create the relay logic for RX/TX but I have all the info and materials I need to do that.

Interestingly enough, the RX seems "ok" down there but I have outboard filters in place.  Sensitivity is down a bit but its not a show stopper, or it has not been so far.  More real time evaluation is in order.

thanks again for the clarification.  I am very happy with the KX3 and can apply my workaround to make this fill my need.

73!

John KB5NJD / WG2XIQ

[Dave-3]

I found similar at GW0FRE. The kx3 HAD to have an external BPF but was still
outperformed on the band by my IC706mkIIG which didn't need one. I now use
the KX3 with a 30m IF Xverter which works fine

Dave

WW2R

Date: Sat, 25 Oct 2014 17:01:52 -0700 (PDT)
From: KB5NJD <[hidden email]>
To: [hidden email]
Subject: Re: [Elecraft] VFO IND in the KX3?
Message-ID: <[hidden email]>
Content-Type: text/plain; charset=us-ascii

Thanks Wayne.  I have an RX converter I can put in line that ports to 80m
also. I will just have to create the relay logic for RX/TX but I have all
the info and materials I need to do that.

Interestingly enough, the RX seems "ok" down there but I have outboard
filters in place.  Sensitivity is down a bit but its not a show stopper, or
it has not been so far.  More real time evaluation is in order.

thanks again for the clarification.  I am very happy with the KX3 and can
apply my workaround to make this fill my need.

73!

John KB5NJD / WG2XIQ




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[wayne burdick]

Hi Dave,

To resurrect a technical description about LF-band receive I posted earlier this year:

* * *

The KX3 does not have filtering specifically for the lower portion of the AM radio band. It is intended primarily as a ham-band transceiver, and covers nearly the entire SWL range. But to completely eliminate low AM-band 3rd-overtone LO images such as the one you're hearing would require at least two and possibly three more filters (more on that below). Complicating this is the high-pass filter in the T/R switch, which is intended to protect the PIN diodes from very strong signals below 1 MHz or so. This attenuates low-AM-band signals. (To quote the KX3 product brochure on our web site: "...also covers 0.31 - 1.5 MHz with reduced sensitivity….)

The KXAT3 ATU provides some additional filtering for the lower AM range when correctly configured. But at 500 kHz, the LO still isn't filtered enough to eliminate strong signals.

* * *

The IC706mkIIG probably uses a keying relay rather than PIN diodes in the main T/R path.

73,
Wayne
N6KR


On Oct 27, 2014, at 1:47 AM, Dave <[hidden email]> wrote:

> I found similar at GW0FRE. The kx3 HAD to have an external BPF but was still
> outperformed on the band by my IC706mkIIG which didn't need one. I now use
> the KX3 with a 30m IF Xverter which works fine
>
> Dave
>
> WW2R



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