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KX-1: Broadcast breakthrough on 20m

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Stephen Prior

KX-1: Broadcast breakthrough on 20m

I have just returned from a few days away in Italy with my xyl. Being
limited with what we could take (we were flying, usually we drive), I took
along my KX-1. It was the first time that I had used it this year- blame
the K3 for that!

When I used it last (in CT and EA in summer 2008) I posted to the reflector
that I had suffered Broadcast interference on 20m after the radio had
suffered a rather severe blow caused by my son tripping up over the antenna
wire and launching the KX-1 some distance! As a result of this mishap I
discovered that I had a broken bnc socket which I have since replaced. I
imagined that this might have been at the root of the problem and that all
would be well.

However, on the aforementioned trip I threw about 10m of wire out of the
hotel window (just to listen) and was surprised to find three or four strong
broadcast stations around 14.2MHz, so strong in fact that they were badly
interfering with QSOs. I cannot help but think that there is something else
awry with the KX-1. I have checked the filter alignment and all seems okay
according to the manual. Is there anything else I should check for? I
don't expect the kind of performance I get from the K2 or K3, but it seems
to me that the KX-1 should be performing better than this. It also seems a
little quiet.

Any suggestions appreciated

73 Stephen G4SJP

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Dick Dickinson

Re: KX-1: Broadcast breakthrough on 20m

"...three or four strong broadcast stations around 14.2MHz"

Harmonics of 40 meter BC stations..?

Best regards,

Dick - KA5KKT

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Stephen Prior

Re: KX-1: Broadcast breakthrough on 20m

Hi Dick

Maybe they are, but I don't hear anything on the K3 (or even my FT-817) on a
much bigger antenna, and anyway there is not much BC activity I can hear on
7.1MHz these days. I should add that the KX-1 has the 30/40 board and the
internal ATU fitted.

73 Stephen

On 27/10/2009 20:35, "Edward Dickinson, III" <[hidden email]>
wrote:

>
> "...three or four strong broadcast stations around 14.2MHz"
>
> Harmonics of 40 meter BC stations..?
>
>
> Best regards,
>
> Dick - KA5KKT
>
> ______________________________________________________________
> Elecraft mailing list
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wayne burdick

Re: KX-1: Broadcast breakthrough on 20m

Administrator

In reply to this post by Stephen Prior

Hi Stephen,

The KX1, like most low-current QRP transceivers, uses an active mixer
in the front end. IMD products can appear in the mixer's output
spectra when large signals are present at the input, especially if the
LO (local oscillator) injection is insufficient.

Try backing down the RF GAIN control on the KX1. If the "breakthrough"
signals you're referring to decrease in amplitude faster than the
desired signals, chances are you're hearing IMD. If all signals
decrease in amplitude at about the same rate, you could have a problem
with LO injection, or the 20-m band-pass filter may need realignment.
The KX1's DDS LO has some level of harmonic content, and if the input
filtering is not sufficient, LO harmonics might mix with very strong
signals to produce outputs that show up in the ham band.

If you have an oscilloscope I can give you a few test points to look
at. But you could also try peaking the band pass filter per the KX1
owner's manual.

73,
Wayne
N6KR

On Oct 27, 2009, at 1:23 PM, Stephen Prior wrote:

> ...I threw about 10m of wire out of the
> hotel window (just to listen) and was surprised to find three or
> four strong
> broadcast stations around 14.2MHz...
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Don Wilhelm-4

Re: KX-1: Broadcast breakthrough on 20m

In reply to this post by Stephen Prior

Stephen,

The first thing I would suggest is to see if the KX1 is really receiving
on 20 meters, or perhaps on some other frequency band. What I am
thinking is that the firmware chip may not be fully seated in the
socket, which will cause to DDS output to be on some unknown frequency.

Another thing that could cause similar problem is a distorted DDS output
waveshape - check inductors L4 and L5 for damage and capacitors C50, C51
and C52.

The other possibility is that the KX1 was actually responding to the
image. When tuned to USB at 14.2, the DDS output is 4.9 kHz below the
received frequency, and there could be leak-through of strong signals
near 4.4 MHz.

73,
Don W3FPR

Stephen Prior wrote:

> I have just returned from a few days away in Italy with my xyl. Being
> limited with what we could take (we were flying, usually we drive), I took
> along my KX-1. It was the first time that I had used it this year- blame
> the K3 for that!
>
> When I used it last (in CT and EA in summer 2008) I posted to the reflector
> that I had suffered Broadcast interference on 20m after the radio had
> suffered a rather severe blow caused by my son tripping up over the antenna
> wire and launching the KX-1 some distance! As a result of this mishap I
> discovered that I had a broken bnc socket which I have since replaced. I
> imagined that this might have been at the root of the problem and that all
> would be well.
>
> However, on the aforementioned trip I threw about 10m of wire out of the
> hotel window (just to listen) and was surprised to find three or four strong
> broadcast stations around 14.2MHz, so strong in fact that they were badly
> interfering with QSOs. I cannot help but think that there is something else
> awry with the KX-1. I have checked the filter alignment and all seems okay
> according to the manual. Is there anything else I should check for? I
> don't expect the kind of performance I get from the K2 or K3, but it seems
> to me that the KX-1 should be performing better than this. It also seems a
> little quiet.
>
> Any suggestions appreciated
>
> 73 Stephen G4SJP
>
>
>
>
> ______________________________________________________________
> 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
> ------------------------------------------------------------------------
>
>
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>
>

Stephen Prior

Re: KX-1: Broadcast breakthrough on 20m

Many thanks Don, I have also had some input from Wayne on this one and have
some things to check with the scope. I shall combine your reply with his
and see where it takes me.

Thanks again

73 Stephen

On 27/10/2009 21:57, "Don Wilhelm" <[hidden email]> wrote:

>
> Stephen,
>
> The first thing I would suggest is to see if the KX1 is really receiving
> on 20 meters, or perhaps on some other frequency band. What I am
> thinking is that the firmware chip may not be fully seated in the
> socket, which will cause to DDS output to be on some unknown frequency.
>
> Another thing that could cause similar problem is a distorted DDS output
> waveshape - check inductors L4 and L5 for damage and capacitors C50, C51
> and C52.
>
> The other possibility is that the KX1 was actually responding to the
> image. When tuned to USB at 14.2, the DDS output is 4.9 kHz below the
> received frequency, and there could be leak-through of strong signals
> near 4.4 MHz.
>
> 73,
> Don W3FPR
>

Peter, DL2FI

Re: KX-1: Broadcast breakthrough on 20m

Good morning all,
I assume there is nothing defect nor misalignment in the KX1 but a special
situation as we find it in some European Areas during winter conditions. At
different places in Europe we have different levels of Broadcast signals. It
depends on the distance between your actual location and the BC stn
location. Especially BC stn located somewhere in Russia can produce extreme
high field strength in the evening because if it is the right distance and
if it is darkness between them and you. For example I measured more the
350mV sum RF at 50 Ohm using a 2x 20m dipole here in Berlin.

The KX1 is an excellent little transceiver but for such situations it´s
preselect ion sometimes is not good enough to handle such strong off band
signals without producing some intermodulations. Remember, even for the much
bigger K2 we published a "European 40m Band Modification" because in seldom
cases even the fantastic K2 suffered by Intermodulations.

The KX1 is as it is, it would be a hard job to give it some extra front end
selectivity, but an easy way to avoid this intermodulations is to use a
selective ATU. Normal T or L ATU designs do add only poor extra selectivity,
but if you use a parallel design like the ZM2 or ZM4
(http://www.qrpproject.biz/UK/ZM4.html) or the "Fuchs ATU"
(http://www.qrpproject.biz/UK/multifuchs.htm) you will have the same amount
of selectivity as with a complete preselector.

73/2 de Peter, DL2FI

> -----Original Message-----
> From: [hidden email] [mailto:elecraft-
> [hidden email]] On Behalf Of Stephen Prior
> Sent: Tuesday, October 27, 2009 11:02 PM
> To: [hidden email]; elecraft
> Subject: Re: [Elecraft] KX-1: Broadcast breakthrough on 20m
>
> Many thanks Don, I have also had some input from Wayne on this one and
> have
> some things to check with the scope. I shall combine your reply with
> his
> and see where it takes me.
>
> Thanks again
>
> 73 Stephen
>
>
> On 27/10/2009 21:57, "Don Wilhelm" <[hidden email]> wrote:
>
> >
> > Stephen,
> >
> > The first thing I would suggest is to see if the KX1 is really
> receiving
> > on 20 meters, or perhaps on some other frequency band. What I am
> > thinking is that the firmware chip may not be fully seated in the
> > socket, which will cause to DDS output to be on some unknown
> frequency.
> >
> > Another thing that could cause similar problem is a distorted DDS
> output
> > waveshape - check inductors L4 and L5 for damage and capacitors C50,
> C51
> > and C52.
> >
> > The other possibility is that the KX1 was actually responding to the
> > image. When tuned to USB at 14.2, the DDS output is 4.9 kHz below
> the
> > received frequency, and there could be leak-through of strong signals
> > near 4.4 MHz.
> >
> > 73,
> > Don W3FPR
> >
>
>
>
>
> ______________________________________________________________
> 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

Guy, K2AV

Re: KX-1: Broadcast breakthrough on 20m

I have to confirm that.

It would not surprise me if the voltage on the front end of a radio device
went higher than a volt given conditions and antenna, particularly so in
Europe.

One time quite a while ago at W4BVV in northern Virginia, we measured 5
volts RF on an oscilloscope attached to the feedline coming in from a 3
element 40m yagi up 70m pointed at Europe. Was back in the day of megawatt
transmitters into 20 plus dB curtain arrays from Radio Moscow and VOA and
such.

On that band we put a series trap in front of the RX tuned to 7125 to quiet
things 7050 and below. That made a difference even for Collins 75S gear.

I still see very high miscellaneous signal voltage on antennas for other
frequencies at locations well distanced from metropolitan areas.

73, Guy.

On Wed, Oct 28, 2009 at 5:14 AM, Peter, DL2FI <[hidden email]> wrote:

> Good morning all,
> I assume there is nothing defect nor misalignment in the KX1 but a special
> situation as we find it in some European Areas during winter conditions. At
> different places in Europe we have different levels of Broadcast signals.
> It
> depends on the distance between your actual location and the BC stn
> location. Especially BC stn located somewhere in Russia can produce extreme
> high field strength in the evening because if it is the right distance and
> if it is darkness between them and you. For example I measured more the
> 350mV sum RF at 50 Ohm using a 2x 20m dipole here in Berlin.
>
> The KX1 is an excellent little transceiver but for such situations it´s
> preselect ion sometimes is not good enough to handle such strong off band
> signals without producing some intermodulations. Remember, even for the
> much
> bigger K2 we published a "European 40m Band Modification" because in seldom
> cases even the fantastic K2 suffered by Intermodulations.
>
> The KX1 is as it is, it would be a hard job to give it some extra front end
> selectivity, but an easy way to avoid this intermodulations is to use a
> selective ATU. Normal T or L ATU designs do add only poor extra
> selectivity,
> but if you use a parallel design like the ZM2 or ZM4
> (http://www.qrpproject.biz/UK/ZM4.html) or the "Fuchs ATU"
> (http://www.qrpproject.biz/UK/multifuchs.htm) you will have the same
> amount
> of selectivity as with a complete preselector.
>
> 73/2 de Peter, DL2FI
>
> > -----Original Message-----
> > From: [hidden email] [mailto:elecraft-
> > [hidden email]] On Behalf Of Stephen Prior
> > Sent: Tuesday, October 27, 2009 11:02 PM
> > To: [hidden email]; elecraft
> > Subject: Re: [Elecraft] KX-1: Broadcast breakthrough on 20m
> >
> > Many thanks Don, I have also had some input from Wayne on this one and
> > have
> > some things to check with the scope. I shall combine your reply with
> > his
> > and see where it takes me.
> >
> > Thanks again
> >
> > 73 Stephen
> >
> >
> > On 27/10/2009 21:57, "Don Wilhelm" <[hidden email]> wrote:
> >
> > >
> > > Stephen,
> > >
> > > The first thing I would suggest is to see if the KX1 is really
> > receiving
> > > on 20 meters, or perhaps on some other frequency band. What I am
> > > thinking is that the firmware chip may not be fully seated in the
> > > socket, which will cause to DDS output to be on some unknown
> > frequency.
> > >
> > > Another thing that could cause similar problem is a distorted DDS
> > output
> > > waveshape - check inductors L4 and L5 for damage and capacitors C50,
> > C51
> > > and C52.
> > >
> > > The other possibility is that the KX1 was actually responding to the
> > > image. When tuned to USB at 14.2, the DDS output is 4.9 kHz below
> > the
> > > received frequency, and there could be leak-through of strong signals
> > > near 4.4 MHz.
> > >
> > > 73,
> > > Don W3FPR
> > >
> >
> >
> >
> >
> > ______________________________________________________________
> > 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
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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>