Elecraft › [HAM]

Intermod or mixing?

Classic

List

Threaded

16 messages Options

Larry Godek

Intermod or mixing?

I've got some local noise around here that sounds like a water heater or sorts or something along that line. Anyway it's really giving me fits on 6 meters. I ahve to run the NB almost all the time and that distorts the signals and sometimes it doesn't even clean up the noise. Doesn't matter if i use the preamp, attenuator, Noise reduction or what. Plus when i turn the NB on i get all sorts of crap from SSb signals 40 plus kc up in the band. If i turn the NB off the SSb crud is gone. I operate mostly in the CW portion of the band. When the NB is off i don't ahve this problem. Other than finding the noise out there in the 0-90 degree quadrant anyone have any idea as to whats going on? I'm really getting sick of the SSb crud showing up when the NB is on down in the CW portion of the band. I only have one antenna hooked to the radio. What else can i tell you?

Larry
W0OGH

______________________________________________________________
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

Matt Zilmer

Re: Intermod or mixing?

DFing the problem is probably your best bet. I had to do that with a
S9+30 noise source on freqs lower than 10 MHz. It was an unused
irrigation transformer with open leads (arcing). It was almost
1/2-mile from the shack. Crud like this carries a long distance.

Your local electrical utility should be able to help with this, since
almost all of them have "electrical supply quality" departments. In
most US states, the utility can also force a customer to fix the
problem if it's not utility-owned equipment. The field personnel that
do this professionally are very capable, and yes - many of them really
can find a needle in a haystack.

73 and Good Luck!

matt zilmer, W6NIA

On Sat, 12 Jun 2010 14:34:06 -0700 (PDT), you wrote:

>I've got some local noise around here that sounds like a water heater or sorts or something along that line. Anyway it's really giving me fits on 6 meters. I ahve to run the NB almost all the time and that distorts the signals and sometimes it doesn't even clean up the noise. Doesn't matter if i use the preamp, attenuator, Noise reduction or what. Plus when i turn the NB on i get all sorts of crap from SSb signals 40 plus kc up in the band. If i turn the NB off the SSb crud is gone. I operate mostly in the CW portion of the band. When the NB is off i don't ahve this problem. Other than finding the noise out there in the 0-90 degree quadrant anyone have any idea as to whats going on? I'm really getting sick of the SSb crud showing up when the NB is on down in the CW portion of the band. I only have one antenna hooked to the radio. What else can i tell you?
>
>Larry
>W0OGH
>
>______________________________________________________________
>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]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

Joe Planisky

Re: Intermod or mixing?

In reply to this post by Larry Godek

Hi Larry,

I assume you've tried playing with different settings of both the IF
and DSP noise blankers. If not, by all means try it and use the least
aggressive settings that make the situation tolerable.

I'm not sure how the DSP NB works, but the IF NB works by essentially
shutting off the signal path in the IF stage for the duration of the
noise pulse. For relatively infrequent pulses, these brief blank
spots in the received signal aren't very noticeable to our ears.
However, if the blanking action is frequent (either because of the
nature of the noise or because the threshold is set too low), the
blanker effectively becomes a mixer combining the desired signal at
the IF frequency with the frequency of the noise pulses (and harmonics
thereof, etc.) When this happens, you'll hear distortion and
"intermod" just as you've described. I'm afraid it's the nature of
the beast.

Your best bet in the long run is to find and fix the source of the
noise. A distant second best is backing off the NB settings to find a
compromise between the noise and the intermod that's at least tolerable.

73
--
Joe KB8AP

On Jun 12, 2010, at 2:34 PM, Larry Godek wrote:

> I've got some local noise around here that sounds like a water
> heater or sorts or something along that line. Anyway it's really
> giving me fits on 6 meters. I ahve to run the NB almost all the
> time and that distorts the signals and sometimes it doesn't even
> clean up the noise. Doesn't matter if i use the preamp, attenuator,
> Noise reduction or what. Plus when i turn the NB on i get all sorts
> of crap from SSb signals 40 plus kc up in the band. If i turn the
> NB off the SSb crud is gone. I operate mostly in the CW portion of
> the band. When the NB is off i don't ahve this problem. Other than
> finding the noise out there in the 0-90 degree quadrant anyone have
> any idea as to whats going on? I'm really getting sick of the SSb
> crud showing up when the NB is on down in the CW portion of the
> band. I only have one antenna hooked to the radio. What else can i
> tell you?
>
> Larry
> W0OGH
>
> ______________________________________________________________
> 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

Richard Davis-5

Re: Intermod or mixing?

In reply to this post by Larry Godek

Would someone please furnish definitions of these two terms, and
explain the difference between them--if there really is a difference.

Sent from my iPhone

______________________________________________________________
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

raroth7

Re: Intermod or mixing?

Mixing is a general term for combining any two or more signals through
the process of heterodyning.

Intermod is a specific form of mixing which combines harmonic products
of two RF signals: the desired receive signal and an undesired,
accidental signal, yielding a series of harmonically related RF
byproducts that can impair the receive pass band.

I hope I stated this correctly and that it helps to differentiate the
two terms adequately.

Richard wrote:
> Would someone please furnish definitions of these two terms, and
> explain the difference between them--if there really is a difference.
>
> Sent from my iPhone
>

[snip]

--
73,
Dick ka1oz
Middleborough, MA

Radio: Elecraft K3/100(Kit) SN 859
Antenna: Titan-DX
______________________________________________________________
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

raroth7

Re: Intermod or mixing?>>>CORRECTION!

In reply to this post by Richard Davis-5

Regarding Intermod, I misspoke when stating that there was a harmonic
relationship. I meant to say a relationship between the sum and
difference frequencies that yield products up and down the band spaced
these difference frequencies.

Sorry,

Dick

Mixing is a general term for combining any two or more signals through
the process of heterodyning.

Intermod is a specific form of mixing which combines harmonic products
of two RF signals: the desired receive signal and an undesired,
accidental signal, yielding a series of harmonically related RF
byproducts that can impair the receive pass band.

I hope I stated this correctly and that it helps to differentiate the
two terms adequately.

Richard wrote:
> Would someone please furnish definitions of these two terms, and
> explain the difference between them--if there really is a difference.
>
> Sent from my iPhone
>

[snip]

--
73,
Dick ka1oz
Middleborough, MA

Radio: Elecraft K3/100(Kit) SN 859
Antenna: Titan-DX
______________________________________________________________
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

Richard Davis-5

Re: Intermod or mixing?>>>CORRECTION!

Thank you Dick. Nicely done.

Sent from my iPhone

On Jun 12, 2010, at 21:30, "Dick Roth, KA1OZ" <[hidden email]>
wrote:

> Regarding Intermod, I misspoke when stating that there was a
> harmonic relationship. I meant to say a relationship between the
> sum and difference frequencies that yield products up and down the
> band spaced these difference frequencies.
>
> Sorry,
>
> Dick
>
>
>
> Mixing is a general term for combining any two or more signals
> through the process of heterodyning.
>
> Intermod is a specific form of mixing which combines harmonic
> products of two RF signals: the desired receive signal and an
> undesired, accidental signal, yielding a series of harmonically
> related RF byproducts that can impair the receive pass band.
>
> I hope I stated this correctly and that it helps to differentiate
> the two terms adequately.
>
>
> Richard wrote:
>> Would someone please furnish definitions of these two terms, and
>> explain the difference between them--if there really is a difference.
>>
>> Sent from my iPhone
>>
>
> [snip]
>
> --
> 73,
> Dick ka1oz
> Middleborough, MA
>
> Radio: Elecraft K3/100(Kit) SN 859
> Antenna: Titan-DX

Geoffrey Mackenzie-Kennedy

Re: Intermod or mixing?

In reply to this post by Larry Godek

Larry,

Is there a Channel 2 TV station in your vicinity?

73,
Geoff
GM4ESD

Larry Godek wrote on Saturday, June 12, 2010 at 10:34 PM:

I've got some local noise around here that sounds like a water heater or
sorts or something along that line. Anyway it's really giving me fits on 6
meters. I ahve to run the NB almost all the time and that distorts the
signals and sometimes it doesn't even clean up the noise.

<snip>

______________________________________________________________
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

ka9zap

Re: Intermod or mixing?

I was using another brand transverter which suffered big time from
channel 2 tv signal, I live about 25 miles
from the transmitter. The transverter needed a notch filter installed in
it to take out the tv signal.

Regards
Art
ka9zap

On 6/13/2010 7:42 AM, Geoffrey Mackenzie-Kennedy wrote:

> Larry,
>
> Is there a Channel 2 TV station in your vicinity?
>
> 73,
> Geoff
> GM4ESD
>
>
> Larry Godek wrote on Saturday, June 12, 2010 at 10:34 PM:
>
>
> I've got some local noise around here that sounds like a water heater or
> sorts or something along that line. Anyway it's really giving me fits on 6
> meters. I ahve to run the NB almost all the time and that distorts the
> signals and sometimes it doesn't even clean up the noise.
>
> <snip>
>
>
> ______________________________________________________________
> 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
>
>

W8JI

Re: Intermod or mixing?

The low-band TV signals are all QRT now, so that shouldn't be an issue
anymore. There is only one VHF high station in range for me. I think it is
up around 200 MHz.

----- Original Message -----
From: "ka9zap" <[hidden email]>
To: "K3 list" <[hidden email]>
Sent: Sunday, June 13, 2010 9:51 AM
Subject: Re: [Elecraft] Intermod or mixing?

>I was using another brand transverter which suffered big time from
> channel 2 tv signal, I live about 25 miles
> from the transmitter. The transverter needed a notch filter installed in
> it to take out the tv signal.
>
> Regards
> Art
> ka9zap
>
> On 6/13/2010 7:42 AM, Geoffrey Mackenzie-Kennedy wrote:
>> Larry,
>>
>> Is there a Channel 2 TV station in your vicinity?
>>
>> 73,
>> Geoff
>> GM4ESD
>>
>>
>> Larry Godek wrote on Saturday, June 12, 2010 at 10:34 PM:
>>
>>
>> I've got some local noise around here that sounds like a water heater or
>> sorts or something along that line. Anyway it's really giving me fits on
>> 6
>> meters. I ahve to run the NB almost all the time and that distorts the
>> signals and sometimes it doesn't even clean up the noise.
>>
>> <snip>
>>
>>
>> ______________________________________________________________
>> 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]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

Phil Kane-2

Re: Intermod or mixing?

In reply to this post by ka9zap

On 6/13/2010 6:51 AM, ka9zap wrote:

> I was using another brand transverter which suffered big time
> from channel 2 tv signal, I live about 25 miles from the
> transmitter. The transverter needed a notch filter installed in
> it to take out the tv signal.

Is the Channel 2 TV station still on the air after the
transition to digital TV a year ago? In this area, 6 meters
has been rarely used because of proximity until the Channel 2
station left the air after the transition.

Last year we used the by-then unused Channel 2 six bay antenna
for the VHF phone contest. We were running a 500 W amplifier
only because we couldn't get the promised 1500 W amplifier in
time. There was more loss in the 35 feet of RG-8 coax between
the amplifier and the antenna patch bay than there was in the
almost 1000 feet of 8-inch coax to the antenna.

We (inadvertently) overloaded six meter receivers for about
20 miles around. Needless to say, we scored Number One. We
can't do it again this year because the antenna has been
disconnected and it and the feed line capped off.

-- 73 de K2ASP - Phil Kane
Skyline Tower Amateur Radio Club
Portland, OR
______________________________________________________________
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

Joe Subich, W4TV-4

Re: Intermod or mixing?

In reply to this post by W8JI

> The low-band TV signals are all QRT now,

There are more than four dozen full power DTV licenses (including
WMAZ-DT on channel 4 in your back yard) and quite a few low power
DTV stations. The biggest cities with licensed "full power" low
VHF DTV are Cleveland OH (WKYC, channel 2), Chicago IL (WBBM,
channel 3), Nashville TN (WTVF, channel 5), and New Haven CT (WEDY,
channel 6). There are construction permits or special temporary
authorizations for a couple other large/middle market stations as
well.

A good reference to US, Canadian and Mexican allocations is
Doug Smith's web site: www.w9wi.com.

73,

... Joe, W4TV

On 6/13/2010 10:06 AM, Tom W8JI wrote:
> The low-band TV signals are all QRT now, so that shouldn't be an issue
> anymore. There is only one VHF high station in range for me. I think it is
> up around 200 MHz.
>
>

______________________________________________________________
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

Mike WA8BXN

Re: Intermod or mixing?

Some careful reading W9WI data may be in order. For example, from the WKYC
(analog channel 3) web site:

July 12, 2009: Channel 3 moves to "all digital" broadcasting on digital
channel 17 at 10 a.m. (Previously, the station was broadcasting on digital
channel 2.) The station would continue its analog broadcast as the
nightlight" station in Cleveland, broadcasting only transition information
through July 26th when the analog transmitter was permenantly shut off.

I would suggest going to the individual web sites for stations that are
shown as being on channel 2 to see where they really are now.

73 - Mike WA8BXN

______________________________________________________________
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

Joe Subich, W4TV-4

Re: Intermod or mixing?

> I would suggest going to the individual web sites for stations that
> are shown as being on channel 2 to see where they really are now.

Some stations may have moved away from low VHF licenses but there
are as many who have active applications and/or construction permits
to move back to low VHF. The issue is lack of coverage due to bad
model data that resulted in excessively low "equivalent coverage"
ERP.

73,

... Joe, W4TV

On 6/13/2010 12:43 PM, Mike WA8BXN wrote:

> Some careful reading W9WI data may be in order. For example, from the
> WKYC (analog channel 3) web site:
>
>
>
> July 12, 2009: Channel 3 moves to "all digital" broadcasting on
> digital channel 17 at 10 a.m. (Previously, the station was
> broadcasting on digital channel 2.) The station would continue its
> analog broadcast as the nightlight" station in Cleveland,
> broadcasting only transition information through July 26th when the
> analog transmitter was permenantly shut off.
>
>
>
> I would suggest going to the individual web sites for stations that
> are shown as being on channel 2 to see where they really are now.
>
>
>
> 73 - Mike WA8BXN
>
>
>
>
>

Mike Harris

Re: Intermod or mixing?

Hi,

Yet another good reason for a K3 bifurcation of the list.

Regards,

Mike VP8NO

----- Original Message -----
From: "Joe Subich, W4TV" <[hidden email]>
To: "Mike WA8BXN" <[hidden email]>
Cc: <[hidden email]>
Sent: Sunday, June 13, 2010 1:24 PM
Subject: Re: [Elecraft] Intermod or mixing?

>
>> I would suggest going to the individual web sites for stations
>> that
>> are shown as being on channel 2 to see where they really are now.
>
> Some stations may have moved away from low VHF licenses but there
> are as many who have active applications and/or construction
> permits
> to move back to low VHF. The issue is lack of coverage due to bad
> model data that resulted in excessively low "equivalent coverage"
> ERP.
>
> 73,
>
> ... Joe, W4TV
>
> On 6/13/2010 12:43 PM, Mike WA8BXN wrote:
>> Some careful reading W9WI data may be in order. For example, from
>> the
>> WKYC (analog channel 3) web site:
>>
>>
>>
>> July 12, 2009: Channel 3 moves to "all digital" broadcasting on
>> digital channel 17 at 10 a.m. (Previously, the station was
>> broadcasting on digital channel 2.) The station would continue
>> its
>> analog broadcast as the nightlight" station in Cleveland,
>> broadcasting only transition information through July 26th when
>> the
>> analog transmitter was permenantly shut off.
>>
>>
>>
>> I would suggest going to the individual web sites for stations
>> that
>> are shown as being on channel 2 to see where they really are now.
>>
>>
>>
>> 73 - Mike WA8BXN
>>
>>
>>
>>
>>
> ______________________________________________________________
> 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

--------------------------------------------------------------------------------

No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 9.0.829 / Virus Database: 271.1.1/2934 - Release Date:
06/13/10 02:35:00

______________________________________________________________
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

Jim Brown-10

Re: Intermod or mixing?

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

On Sun, 13 Jun 2010 11:21:49 -0400, Joe Subich, W4TV wrote:

The info below is only partially correct. WBBM-TV has a CP
(construction permit) to move to Channel 12. WKYC-TV has a CP to
move to Channel 17. Both chose to move to avoid impulse noise that
is present on the low-band VHF channels, and causes break-up of the
digital signal. Another factor in WBBM-TV's move was problems with
close-in high rise buildings. WTVF has a CP for channel 50. WEDY is
the only one of those cited who appears to be happy with their low-
band VHF assignment. Tom is right -- low band VHF is now used by
only a handful of broadcasters in the US.

For REAL FCC data, see

http://www.fcc.gov/fcc-bin/audio/tvq.html

and

http://www.fcc.gov/dtv/markets/

73, Jim K9YC

> > The low-band TV signals are all QRT now,

>There are more than four dozen full power DTV licenses (including
>WMAZ-DT on channel 4 in your back yard) and quite a few low power
>DTV stations. The biggest cities with licensed "full power" low
>VHF DTV are Cleveland OH (WKYC, channel 2), Chicago IL (WBBM,
>channel 3), Nashville TN (WTVF, channel 5), and New Haven CT (WEDY,
>channel 6). There are construction permits or special temporary
>authorizations for a couple other large/middle market stations as
>well.

______________________________________________________________
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