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Intermod filter for the KX3

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Mike Parkes

Intermod filter for the KX3

Hey group
I have an issue here and am wondering if a good band pass filter would
help? I pick up so much sqawks and buzzing weird interference, grating
machine sounds, on my KX3 on all HF bands, it is horrible in my setting
(ground floor apartment in the city). I have the same issues on 2 meter
handhelds, noise all over the band, trips the squelch making it nigh
impossible to scan without the radio stopping on some ghost signal that is
only intermod. Same story with the KX3 2 mtr module though I can turn the
squelch up enough to keep the radio scanning without stopping on noise for
the most part. Is there any hope for HF? Would some sort of HF band pass
filter help my KX3? Or is the filtering in the KX3 already good enough? I
can't make it go away with the built in KX3 noise filters. There is this
one company across the street from me, some internet megalith place with
sat dishes on the roof and I wonder if some of the noise is coming from
that establishment. Anyway... thanks for any ideas... head for a park, a
mountain peak... I know... :)

73's Mike AB7RU DN17gp
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wayne burdick

Re: Intermod filter for the KX3

Administrator

Mike,

What you’re describing sounds like noise that is in-band and would be debilitating for any radio. Not intermod. But just to be sure, set MENU:RX SHFT to 8.0 and turn off the noise blanker. This is the most resilient setup if you have monster signals actually causing IMD.

Also try turning off the preamp.

If the above steps don’t help, you could simply have a case of very high noise floor. Here are a few more things you can try:

1. Use very narrow filter bandwidths. In CW mode, use the APF feature (audio peaking filter).

2. Move the antenna farther from identified noise sources.

3. Try a magnetic loop. These are very narrow banded, and may have directional characteristics you can make use of.

If all else fails, try taking your KX3 portable as an experiment. A location far from massive noise sources can be a breath of fresh air, both atmospherically and ion-ically. It’s not a long-term solution unless, like me, you discover that field operation is a blast. But it’ll give you some perspective about your noise at home.

73,
Wayne
N6KR

----
http://www.elecraft.com

> On Jun 3, 2018, at 9:49 AM, Mike Parkes <[hidden email]> wrote:
>
> Hey group
> I have an issue here and am wondering if a good band pass filter would
> help? I pick up so much sqawks and buzzing weird interference, grating
> machine sounds, on my KX3 on all HF bands, it is horrible in my setting
> (ground floor apartment in the city). I have the same issues on 2 meter
> handhelds, noise all over the band, trips the squelch making it nigh
> impossible to scan without the radio stopping on some ghost signal that is
> only intermod. Same story with the KX3 2 mtr module though I can turn the
> squelch up enough to keep the radio scanning without stopping on noise for
> the most part. Is there any hope for HF? Would some sort of HF band pass
> filter help my KX3? Or is the filtering in the KX3 already good enough? I
> can't make it go away with the built in KX3 noise filters. There is this
> one company across the street from me, some internet megalith place with
> sat dishes on the roof and I wonder if some of the noise is coming from
> that establishment. Anyway... thanks for any ideas... head for a park, a
> mountain peak... I know... :)
>
> 73's Mike AB7RU DN17gp
> ______________________________________________________________
> 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]

Elecraft mailing list

Re: Intermod filter for the KX3

Wayne,
You missed one. Depending on operation whether it is internal battery or external supply. I have had problems with a lot of external source, so always put a dummy load on the antenna a see if the noise is conducted or radiated. Just one more reason to go solar/battery in the field. Yummmm.
Mel, K6KBE with KX3 is all applications

From: Wayne Burdick <[hidden email]>
To: Mike Parkes <[hidden email]>
Cc: [hidden email]
Sent: Sunday, June 3, 2018 10:15 AM
Subject: Re: [Elecraft] Intermod filter for the KX3

Mike,

What you’re describing sounds like noise that is in-band and would be debilitating for any radio. Not intermod. But just to be sure, set MENU:RX SHFT to 8.0 and turn off the noise blanker. This is the most resilient setup if you have monster signals actually causing IMD.

Also try turning off the preamp.

If the above steps don’t help, you could simply have a case of very high noise floor. Here are a few more things you can try:

1. Use very narrow filter bandwidths. In CW mode, use the APF feature (audio peaking filter).

2. Move the antenna farther from identified noise sources.

3. Try a magnetic loop. These are very narrow banded, and may have directional characteristics you can make use of.

If all else fails, try taking your KX3 portable as an experiment. A location far from massive noise sources can be a breath of fresh air, both atmospherically and ion-ically. It’s not a long-term solution unless, like me, you discover that field operation is a blast. But it’ll give you some perspective about your noise at home.

73,
Wayne
N6KR

----
http://www.elecraft.com

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Nicklas Johnson

Re: Intermod filter for the KX3

Second that. I have one external power supply from a well-known ham-gear
manufacturer of somewhat questionable repute which throws off S9 racket all
over everything, or did until I gave the output cord about 10 turns through
a hefty ferrite.

I'd forgotten about the RX Shift feature being per-band somehow... it could
be my imagination but it seems to take down the omnipresent 30Hz impulse
noise a few dB at my QTH in San Mateo. (I've of course gone through
turning off power to the house and driving around in portable operation...
I think the problem is generally being anywhere near PG&E transmission
lines, which is something that's hard to avoid anywhere in the SF
peninsula. The noise blanker also does a pretty decent job of suppressing
it even further.)

Nick

On 3 June 2018 at 10:45, Mel Farrer via Elecraft <[hidden email]>
wrote:

> Wayne,
> You missed one. Depending on operation whether it is internal battery or
> external supply. I have had problems with a lot of external source, so
> always put a dummy load on the antenna a see if the noise is conducted or
> radiated. Just one more reason to go solar/battery in the field. Yummmm.
> Mel, K6KBE with KX3 is all applications
>
> From: Wayne Burdick <[hidden email]>
> To: Mike Parkes <[hidden email]>
> Cc: [hidden email]
> Sent: Sunday, June 3, 2018 10:15 AM
> Subject: Re: [Elecraft] Intermod filter for the KX3
>
> Mike,
>
> What you’re describing sounds like noise that is in-band and would be
> debilitating for any radio. Not intermod. But just to be sure, set MENU:RX
> SHFT to 8.0 and turn off the noise blanker. This is the most resilient
> setup if you have monster signals actually causing IMD.
>
> Also try turning off the preamp.
>
> If the above steps don’t help, you could simply have a case of very high
> noise floor. Here are a few more things you can try:
>
> 1. Use very narrow filter bandwidths. In CW mode, use the APF feature
> (audio peaking filter).
>
> 2. Move the antenna farther from identified noise sources.
>
> 3. Try a magnetic loop. These are very narrow banded, and may have
> directional characteristics you can make use of.
>
> If all else fails, try taking your KX3 portable as an experiment. A
> location far from massive noise sources can be a breath of fresh air, both
> atmospherically and ion-ically. It’s not a long-term solution unless, like
> me, you discover that field operation is a blast. But it’ll give you some
> perspective about your noise at home.
>
> 73,
> Wayne
> N6KR
>
>
>
>
>
> ----
> http://www.elecraft.com
>
> > On Jun 3, 2018, at 9:49 AM, Mike Parkes <[hidden email]> wrote:
> >
> > Hey group
> > I have an issue here and am wondering if a good band pass filter would
> > help? I pick up so much sqawks and buzzing weird interference, grating
> > machine sounds, on my KX3 on all HF bands, it is horrible in my setting
> > (ground floor apartment in the city). I have the same issues on 2 meter
> > handhelds, noise all over the band, trips the squelch making it nigh
> > impossible to scan without the radio stopping on some ghost signal that
> is
> > only intermod. Same story with the KX3 2 mtr module though I can turn the
> > squelch up enough to keep the radio scanning without stopping on noise
> for
> > the most part. Is there any hope for HF? Would some sort of HF band pass
> > filter help my KX3? Or is the filtering in the KX3 already good enough? I
> > can't make it go away with the built in KX3 noise filters. There is this
> > one company across the street from me, some internet megalith place with
> > sat dishes on the roof and I wonder if some of the noise is coming from
> > that establishment. Anyway... thanks for any ideas... head for a park, a
> > mountain peak... I know... :)
> >
> > 73's Mike AB7RU DN17gp
> > ______________________________________________________________
> > 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]
> ______________________________________________________________
> 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]
>
>
> ______________________________________________________________
> 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]
>

--
*N6OL*
Saying something doesn't make it true. Belief in something doesn't make it
real. And if you have to lie to support a position, that position is not
worth supporting.
______________________________________________________________
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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Please help support this email list: http://www.qsl.net/donate.html
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Mike Parkes

Re: Intermod filter for the KX3

Thanks Nick for that info, I have a lot of power lines all around this apt
building and I have wondered if a lot of the noise is coming from that.
I like the idea of turning the power off, and locating the source of
noise... at least then you have the satisfaction of knowing where it is
coming from or what it is.
73's Mike AB7RU

On Sun, Jun 3, 2018 at 11:13 AM, Nicklas Johnson <[hidden email]> wrote:

> Second that. I have one external power supply from a well-known ham-gear
> manufacturer of somewhat questionable repute which throws off S9 racket all
> over everything, or did until I gave the output cord about 10 turns through
> a hefty ferrite.
>
> I'd forgotten about the RX Shift feature being per-band somehow... it could
> be my imagination but it seems to take down the omnipresent 30Hz impulse
> noise a few dB at my QTH in San Mateo. (I've of course gone through
> turning off power to the house and driving around in portable operation...
> I think the problem is generally being anywhere near PG&E transmission
> lines, which is something that's hard to avoid anywhere in the SF
> peninsula. The noise blanker also does a pretty decent job of suppressing
> it even further.)
>
> Nick
>
> On 3 June 2018 at 10:45, Mel Farrer via Elecraft <[hidden email]
> >
> wrote:
>
> > Wayne,
> > You missed one. Depending on operation whether it is internal battery or
> > external supply. I have had problems with a lot of external source, so
> > always put a dummy load on the antenna a see if the noise is conducted or
> > radiated. Just one more reason to go solar/battery in the field.
> Yummmm.
> > Mel, K6KBE with KX3 is all applications
> >
> > From: Wayne Burdick <[hidden email]>
> > To: Mike Parkes <[hidden email]>
> > Cc: [hidden email]
> > Sent: Sunday, June 3, 2018 10:15 AM
> > Subject: Re: [Elecraft] Intermod filter for the KX3
> >
> > Mike,
> >
> > What you’re describing sounds like noise that is in-band and would be
> > debilitating for any radio. Not intermod. But just to be sure, set
> MENU:RX
> > SHFT to 8.0 and turn off the noise blanker. This is the most resilient
> > setup if you have monster signals actually causing IMD.
> >
> > Also try turning off the preamp.
> >
> > If the above steps don’t help, you could simply have a case of very high
> > noise floor. Here are a few more things you can try:
> >
> > 1. Use very narrow filter bandwidths. In CW mode, use the APF feature
> > (audio peaking filter).
> >
> > 2. Move the antenna farther from identified noise sources.
> >
> > 3. Try a magnetic loop. These are very narrow banded, and may have
> > directional characteristics you can make use of.
> >
> > If all else fails, try taking your KX3 portable as an experiment. A
> > location far from massive noise sources can be a breath of fresh air,
> both
> > atmospherically and ion-ically. It’s not a long-term solution unless,
> like
> > me, you discover that field operation is a blast. But it’ll give you some
> > perspective about your noise at home.
> >
> > 73,
> > Wayne
> > N6KR
> >
> >
> >
> >
> >
> > ----
> > http://www.elecraft.com
> >
> > > On Jun 3, 2018, at 9:49 AM, Mike Parkes <[hidden email]> wrote:
> > >
> > > Hey group
> > > I have an issue here and am wondering if a good band pass filter would
> > > help? I pick up so much sqawks and buzzing weird interference, grating
> > > machine sounds, on my KX3 on all HF bands, it is horrible in my setting
> > > (ground floor apartment in the city). I have the same issues on 2 meter
> > > handhelds, noise all over the band, trips the squelch making it nigh
> > > impossible to scan without the radio stopping on some ghost signal that
> > is
> > > only intermod. Same story with the KX3 2 mtr module though I can turn
> the
> > > squelch up enough to keep the radio scanning without stopping on noise
> > for
> > > the most part. Is there any hope for HF? Would some sort of HF band
> pass
> > > filter help my KX3? Or is the filtering in the KX3 already good
> enough? I
> > > can't make it go away with the built in KX3 noise filters. There is
> this
> > > one company across the street from me, some internet megalith place
> with
> > > sat dishes on the roof and I wonder if some of the noise is coming from
> > > that establishment. Anyway... thanks for any ideas... head for a park,
> a
> > > mountain peak... I know... :)
> > >
> > > 73's Mike AB7RU DN17gp
> > > ______________________________________________________________
> > > 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]
> > ______________________________________________________________
> > 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]
> >
> >
> > ______________________________________________________________
> > 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]
> >
>
>
>
> --
> *N6OL*
> Saying something doesn't make it true. Belief in something doesn't make it
> real. And if you have to lie to support a position, that position is not
> worth supporting.
> ______________________________________________________________
> 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]

Elecraft mailing list

Re: Intermod filter for the KX3

In reply to this post by Mike Parkes

Rather than band pass filters, maybe try a good ‘ole low pass filter? Won’t work on two meters or maybe six meters, but I suspect most of the ambient RF is up in the VHF/UHF or above. And if it’s in-band interference, a band pass filter won’t help either.

Used for the opposite reason - protecting us rather than our neighbors - than for what those LPFs were originally made and purchased.

73 - Jim K8MR

> On Jun 3, 2018, at 12:49 PM, Mike Parkes <[hidden email]> wrote:
>
> Hey group
> I have an issue here and am wondering if a good band pass filter would
> help? I pick up so much sqawks and buzzing weird interference, grating
> machine sounds, on my KX3 on all HF bands, it is horrible in my setting
> (ground floor apartment in the city). I have the same issues on 2 meter
> handhelds, noise all over the band, trips the squelch making it nigh
> impossible to scan without the radio stopping on some ghost signal that is
> only intermod. Same story with the KX3 2 mtr module though I can turn the
> squelch up enough to keep the radio scanning without stopping on noise for
> the most part. Is there any hope for HF? Would some sort of HF band pass
> filter help my KX3? Or is the filtering in the KX3 already good enough? I
> can't make it go away with the built in KX3 noise filters. There is this
> one company across the street from me, some internet megalith place with
> sat dishes on the roof and I wonder if some of the noise is coming from
> that establishment. Anyway... thanks for any ideas... head for a park, a
> mountain peak... I know... :)
>
> 73's Mike AB7RU DN17gp
> ______________________________________________________________
> 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]

Bob McGraw - K4TAX

Re: Intermod filter for the KX3

If the interference is a product of 2 or more out of band signals mixing
together, then a band pass filter would help.    If this the case, use
of noise reduction or noise blanking in the KX3 will likely make the
issue worse, not better. One test is to use a step attenuator
between the antenna and the receiver input. Thus selecting some value
of attenuation for all signals, thus equally reducing the 2 or more out
of band signals. If this improves your issues with regard to the
interference, one can attribute to strong signals mixing and entering
the receiver. A band pass filter will likely help and allow you to
transmit on that band as well as receive on that band.   A band pass
filter will be required for each band you intend to operate.   A full
set, they aren't cheap.

Likewise on 2M, many paging and public service systems are now
transmitting digital data streams. These cause me havoc on 2M as I am
600 ft from the local 911 communications tower. Only 12 total of
antennas, VHF and UHF, on that tower.   A band reject or notch filter
corrects the issue.   But again, one needs to know the exact frequencies
of the signals which are causing the interference as that is the
frequency the notch must be applied. I use a filter from PAR Electronics
which is a notch filter. The insertion loss on 2M is very low allowing
me to receive and transmit with the filter in the line between the radio
and the antenna but provides about a 40 dB notch at the offending
frequency. In general handheld radios do not have adequate space
internally to design in and implement good front end filters.   They in
general are very subject to interference and do not perform well with RF
from nearby services operating above or below the ham bands.

If the interference is in the pass band of the receiver, finding and
eliminating the source is the optimum approach. If the mixing
components are in the PA of a transmitter and thus being radiated and
picked up by your receiver, finding the source is about the only
solution.   This could be the product of 2 FM stations in the building
or a building of close proximity.   As an example, 99.5 MHz and 106.7
MHz mixed together produce two signals being a sum and a difference.
The difference is 7.2 MHz.....smack in the 40M band. Probably due to
harmonics affect 20M and 15M to some extent. Depending on exactly
where the mixing is taking place, a corroded pipe on or in the building,
in the PA of one of the transmitters, or some other device which becomes
non linear when excited with RF, then it radiates the signal. Finding
and correcting the issue is about the only solution.

Third choice.............move.     Which in fact might be easier.   Just
be sure one doesn't move into an RF plagued area.

73

Bob, K4TAX

On Jun 3, 2018, at 12:49 PM, Mike Parkes <[hidden email]> wrote:

>> Hey group
>> I have an issue here and am wondering if a good band pass filter would
>> help? I pick up so much sqawks and buzzing weird interference, grating
>> machine sounds, on my KX3 on all HF bands, it is horrible in my setting
>> (ground floor apartment in the city). I have the same issues on 2 meter
>> handhelds, noise all over the band, trips the squelch making it nigh
>> impossible to scan without the radio stopping on some ghost signal that is
>> only intermod. Same story with the KX3 2 mtr module though I can turn the
>> squelch up enough to keep the radio scanning without stopping on noise for
>> the most part. Is there any hope for HF? Would some sort of HF band pass
>> filter help my KX3? Or is the filtering in the KX3 already good enough? I
>> can't make it go away with the built in KX3 noise filters. There is this
>> one company across the street from me, some internet megalith place with
>> sat dishes on the roof and I wonder if some of the noise is coming from
>> that establishment. Anyway... thanks for any ideas... head for a park, a
>> mountain peak... I know... :)
>>
>> 73's Mike AB7RU DN17gp
>>