Topics

Ground noise on 23cm?


Andy G4JNT
 

Messages in this thread are continually being diverted to my Spam folder, from which I have to declare each one as being Not Spam.  
It's because of the link to G4ZTR's site [now deleted in this 'reply to'] that is being repeated in all replies.

When you reply to a message, to prevent rapid growth, why not just delete all quoted text except for the sentence or two that says what you're referring to.



Paul G8AQA
 

I had a lot of wideband noise particularly in one direction. I temporarily put in a switchable bandpass filter before the Bulgarian SG Lab masthead preamp. In the worst direction the drop in background noise with the filter in was about 24dB.  It is now in permanently.  It was a surplus silver plated interdigital filter that I modified to increase the frequency.  The loss was too small to measure reliably.

Paul G8AQA


G4
DBN wrote:

I've used one of John's filters for ages. Through loss is tiny, something around 0.15dB increase in NF when I put it in front of a DDK preamp on my HP8970B compared with an SMA barrel connector.

I am 51km LOS from Emley Moor and there are no cellphone masts within 2km, but the problem was severe. I had about 15 noise spikes in many directions before I added the interdigital filter. It has SMA connectors.

http://www.g4ztr.co.uk/amateur-radio/23cms/

Neil G4DBN


On 17/09/2020 10:05, Anthony Coldman via groups.io wrote:

Morning all

 

I would agree with others that a filter in front of a preamp is an almost must now, I have built ones for 23cm and 13cm using the information on this site and the difference is night and day, If you prefer to buy you can also have a look at PE1RKI site he produces nice filters as well.

 

Regards

 

Anthony G7LRQ




Neil Smith G4DBN
 

I've used one of John's filters for ages. Through loss is tiny, something around 0.15dB increase in NF when I put it in front of a DDK preamp on my HP8970B compared with an SMA barrel connector.

I am 51km LOS from Emley Moor and there are no cellphone masts within 2km, but the problem was severe. I had about 15 noise spikes in many directions before I added the interdigital filter. It has SMA connectors.

http://www.g4ztr.co.uk/amateur-radio/23cms/

Neil G4DBN


On 17/09/2020 10:05, Anthony Coldman via groups.io wrote:

Morning all

 

I would agree with others that a filter in front of a preamp is an almost must now, I have built ones for 23cm and 13cm using the information on this site and the difference is night and day, If you prefer to buy you can also have a look at PE1RKI site he produces nice filters as well.

 

Regards

 

Anthony G7LRQ



Anthony Coldman
 

Morning all

 

I would agree with others that a filter in front of a preamp is an almost must now, I have built ones for 23cm and 13cm using the information on this site and the difference is night and day, If you prefer to buy you can also have a look at PE1RKI site he produces nice filters as well.

 

Regards

 

Anthony G7LRQ

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of John Lemay
Sent: 17 September 2020 07:49
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Ground noise on 23cm?

 

Morning all

 

I completely agree with Richard’s analysis of the likely cause of interference on 23cms. My QTH is line of sight with the Sudbury TV transmitter, and it gave me lots of grief until I introduced a bandpass filter. A notch filter at 650MHz provided an element of improvement and indicated I was on the right track.

 

You can read about my findings at http://www.g4ztr.co.uk/amateur-radio/23cms/ , just scroll down past the yagi info.

 

Maybe I can use this mail as a thinly disguised commercial for my own interdigital filter, which can be found at www.aerial-parts.co.uk. Quite a few of these are in use around the country and I’ve yet to hear of anyone who has not been able to improve reception.

 

Regards

 

John G4ZTR

 

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Colin Ranson
Sent: 16 September 2020 23:09
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Ground noise on 23cm?

 

Hi all,

 

I have a filter designed by G3XDY plumbed into my system after the amplifier.     https://www.qsl.net/g3xdy/QRO%2023cm%20Harmonic%20Filter%20and%20Reflectometer.htm

 

On RX I have an (almost) mast head pre-amp (located in loft, with the amplifier, under the antenna outside, a Tonna 35ele that seems to be intermittent at times so something else is needed). The pre-amp has an onboard hairpin bandpass filter and this also feeds an interdigital filter which connects via 30ft of coax to the SG Labs transverter.   Other than radar pulses I have never noticed any unusual noise from any direction – even with a well loaded water tower only 400 yards away. Mind you not saying this won’t change when I get a decent antenna up there.

 

Regards to all,

 

Colin de G8LBS.

 

 

 

 

 

Sent from Mail for Windows 10

 

From: Richard GD8EXI
Sent: 16 September 2020 22:27
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Ground noise on 23cm?

 

I doubt it can be ground noise if it is S5. On 23cms you are unlikely to see more than 3dB change in noise, between beaming into a hillside and beaming down hill. The antenna noise temp going from say 100 to 200K, so even with a RX noise temperature of 50K, only expect a 2.2dB difference.
 
As Andy stated more likely the presence of one or more very strong signals, mixing in your RX at the /P location.
 
Another common culprit is a DTV transmitter centred on about 650MHz. The intermodulation products look like white noise in a 3kHz bandwidth on 1296MHz. Also do not assume your beam will tell you where the source is, as the polar diagram will look very different on 650MHz.
 
Best test is a good 1296MHz bandpass filter in front of any amplification. The trouble is the path loss of about 1dB. I use a 650MHz notch filter in front of my masthead preamp and an interdigital one after it. The noise floor drops by 10dB on some beam headings, on adding this combination, even after correcting for insertion loss.

73s
Richard
GD8EXI




On 16/09/2020, 20:20, "Andy G4JNT" <andy.g4jnt@...> wrote:

The product is 2160MHz  [which is on the edge of a 3G channel]  -   2 x 1152 [LO]  =  144MHz

Andy
www.g4jnt.com <http://www.g4jnt.com>



On Wed, 16 Sep 2020 at 20:18, Andy Talbot <andy.g4jnt@...> wrote:

If you're using aa 144MHz IF, there's a chance you're seeing IM products between your mixer LO and one of the 3G base station channels.   I'd have to look up the channel that cases the problems, but it was bad here until I added an additional filter in the Rx chain

Andy
www.g4jnt.com <http://www.g4jnt.com>



On Wed, 16 Sep 2020 at 20:13, G0FVI via groups.io <http://groups.io>  <Andrew.gilfillan@...> wrote:

I'm still learning being relatively new to uwaves so apologies if this question seems a bit 'dumb'. I'm noticing fairly high noise levels on 23cm UKAC from my /P location (S5) but it's not constant in all directions and tails off to zero in several directions particularly due east to the continent (ground slope away to east and there are no obvious nearby man made sources of noise although there are HT pylons about 100 yards away). I'm not getting this at home with the same setup mounted on mast at about 35 feet (/P mast is only 20 feet), so I'm guessing it is perhaps ground noise? 

Andy G0FVI

 

 

 

Virus-free. www.avg.com


John Lemay
 

Morning all

 

I completely agree with Richard’s analysis of the likely cause of interference on 23cms. My QTH is line of sight with the Sudbury TV transmitter, and it gave me lots of grief until I introduced a bandpass filter. A notch filter at 650MHz provided an element of improvement and indicated I was on the right track.

 

You can read about my findings at http://www.g4ztr.co.uk/amateur-radio/23cms/ , just scroll down past the yagi info.

 

Maybe I can use this mail as a thinly disguised commercial for my own interdigital filter, which can be found at www.aerial-parts.co.uk. Quite a few of these are in use around the country and I’ve yet to hear of anyone who has not been able to improve reception.

 

Regards

 

John G4ZTR

 

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Colin Ranson
Sent: 16 September 2020 23:09
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Ground noise on 23cm?

 

Hi all,

 

I have a filter designed by G3XDY plumbed into my system after the amplifier.     https://www.qsl.net/g3xdy/QRO%2023cm%20Harmonic%20Filter%20and%20Reflectometer.htm

 

On RX I have an (almost) mast head pre-amp (located in loft, with the amplifier, under the antenna outside, a Tonna 35ele that seems to be intermittent at times so something else is needed). The pre-amp has an onboard hairpin bandpass filter and this also feeds an interdigital filter which connects via 30ft of coax to the SG Labs transverter.   Other than radar pulses I have never noticed any unusual noise from any direction – even with a well loaded water tower only 400 yards away. Mind you not saying this won’t change when I get a decent antenna up there.

 

Regards to all,

 

Colin de G8LBS.

 

 

 

 

 

Sent from Mail for Windows 10

 

From: Richard GD8EXI
Sent: 16 September 2020 22:27
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Ground noise on 23cm?

 

I doubt it can be ground noise if it is S5. On 23cms you are unlikely to see more than 3dB change in noise, between beaming into a hillside and beaming down hill. The antenna noise temp going from say 100 to 200K, so even with a RX noise temperature of 50K, only expect a 2.2dB difference.
 
As Andy stated more likely the presence of one or more very strong signals, mixing in your RX at the /P location.
 
Another common culprit is a DTV transmitter centred on about 650MHz. The intermodulation products look like white noise in a 3kHz bandwidth on 1296MHz. Also do not assume your beam will tell you where the source is, as the polar diagram will look very different on 650MHz.
 
Best test is a good 1296MHz bandpass filter in front of any amplification. The trouble is the path loss of about 1dB. I use a 650MHz notch filter in front of my masthead preamp and an interdigital one after it. The noise floor drops by 10dB on some beam headings, on adding this combination, even after correcting for insertion loss.

73s
Richard
GD8EXI




On 16/09/2020, 20:20, "Andy G4JNT" <andy.g4jnt@...> wrote:

The product is 2160MHz  [which is on the edge of a 3G channel]  -   2 x 1152 [LO]  =  144MHz

Andy
www.g4jnt.com <http://www.g4jnt.com>



On Wed, 16 Sep 2020 at 20:18, Andy Talbot <andy.g4jnt@...> wrote:

If you're using aa 144MHz IF, there's a chance you're seeing IM products between your mixer LO and one of the 3G base station channels.   I'd have to look up the channel that cases the problems, but it was bad here until I added an additional filter in the Rx chain

Andy
www.g4jnt.com <http://www.g4jnt.com>



On Wed, 16 Sep 2020 at 20:13, G0FVI via groups.io <http://groups.io>  <Andrew.gilfillan@...> wrote:

I'm still learning being relatively new to uwaves so apologies if this question seems a bit 'dumb'. I'm noticing fairly high noise levels on 23cm UKAC from my /P location (S5) but it's not constant in all directions and tails off to zero in several directions particularly due east to the continent (ground slope away to east and there are no obvious nearby man made sources of noise although there are HT pylons about 100 yards away). I'm not getting this at home with the same setup mounted on mast at about 35 feet (/P mast is only 20 feet), so I'm guessing it is perhaps ground noise? 

Andy G0FVI

 

 


Virus-free. www.avg.com


Colin Ranson
 

Hi all,

 

I have a filter designed by G3XDY plumbed into my system after the amplifier.     https://www.qsl.net/g3xdy/QRO%2023cm%20Harmonic%20Filter%20and%20Reflectometer.htm

 

On RX I have an (almost) mast head pre-amp (located in loft, with the amplifier, under the antenna outside, a Tonna 35ele that seems to be intermittent at times so something else is needed). The pre-amp has an onboard hairpin bandpass filter and this also feeds an interdigital filter which connects via 30ft of coax to the SG Labs transverter.   Other than radar pulses I have never noticed any unusual noise from any direction – even with a well loaded water tower only 400 yards away. Mind you not saying this won’t change when I get a decent antenna up there.

 

Regards to all,

 

Colin de G8LBS.

 

 

 

 

 

Sent from Mail for Windows 10

 

From: Richard GD8EXI
Sent: 16 September 2020 22:27
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Ground noise on 23cm?

 

I doubt it can be ground noise if it is S5. On 23cms you are unlikely to see more than 3dB change in noise, between beaming into a hillside and beaming down hill. The antenna noise temp going from say 100 to 200K, so even with a RX noise temperature of 50K, only expect a 2.2dB difference.
 
As Andy stated more likely the presence of one or more very strong signals, mixing in your RX at the /P location.
 
Another common culprit is a DTV transmitter centred on about 650MHz. The intermodulation products look like white noise in a 3kHz bandwidth on 1296MHz. Also do not assume your beam will tell you where the source is, as the polar diagram will look very different on 650MHz.
 
Best test is a good 1296MHz bandpass filter in front of any amplification. The trouble is the path loss of about 1dB. I use a 650MHz notch filter in front of my masthead preamp and an interdigital one after it. The noise floor drops by 10dB on some beam headings, on adding this combination, even after correcting for insertion loss.

73s
Richard
GD8EXI




On 16/09/2020, 20:20, "Andy G4JNT" <andy.g4jnt@...> wrote:

The product is 2160MHz  [which is on the edge of a 3G channel]  -   2 x 1152 [LO]  =  144MHz

Andy
www.g4jnt.com <http://www.g4jnt.com>



On Wed, 16 Sep 2020 at 20:18, Andy Talbot <andy.g4jnt@...> wrote:

If you're using aa 144MHz IF, there's a chance you're seeing IM products between your mixer LO and one of the 3G base station channels.   I'd have to look up the channel that cases the problems, but it was bad here until I added an additional filter in the Rx chain

Andy
www.g4jnt.com <http://www.g4jnt.com>



On Wed, 16 Sep 2020 at 20:13, G0FVI via groups.io <http://groups.io>  <Andrew.gilfillan@...> wrote:

I'm still learning being relatively new to uwaves so apologies if this question seems a bit 'dumb'. I'm noticing fairly high noise levels on 23cm UKAC from my /P location (S5) but it's not constant in all directions and tails off to zero in several directions particularly due east to the continent (ground slope away to east and there are no obvious nearby man made sources of noise although there are HT pylons about 100 yards away). I'm not getting this at home with the same setup mounted on mast at about 35 feet (/P mast is only 20 feet), so I'm guessing it is perhaps ground noise? 

Andy G0FVI

 

 


G0FVI
 

Thanks for replies guys. The world's dtv transmitter mast is is plane sight about 15 miles away, from your input Richard I'm guessing that could be the problem. Filter time I guess.


From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of Richard GD8EXI <perwick@...>
Sent: Wednesday, September 16, 2020 10:27:26 PM
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] Ground noise on 23cm?
 
I doubt it can be ground noise if it is S5. On 23cms you are unlikely to see more than 3dB change in noise, between beaming into a hillside and beaming down hill. The antenna noise temp going from say 100 to 200K, so even with a RX noise temperature of 50K, only expect a 2.2dB difference.
 
As Andy stated more likely the presence of one or more very strong signals, mixing in your RX at the /P location.
 
Another common culprit is a DTV transmitter centred on about 650MHz. The intermodulation products look like white noise in a 3kHz bandwidth on 1296MHz. Also do not assume your beam will tell you where the source is, as the polar diagram will look very different on 650MHz.
 
Best test is a good 1296MHz bandpass filter in front of any amplification. The trouble is the path loss of about 1dB. I use a 650MHz notch filter in front of my masthead preamp and an interdigital one after it. The noise floor drops by 10dB on some beam headings, on adding this combination, even after correcting for insertion loss.

73s
Richard
GD8EXI




On 16/09/2020, 20:20, "Andy G4JNT" <andy.g4jnt@...> wrote:

The product is 2160MHz  [which is on the edge of a 3G channel]  -   2 x 1152 [LO]  =  144MHz

Andy
www.g4jnt.com <http://www.g4jnt.com>



On Wed, 16 Sep 2020 at 20:18, Andy Talbot <andy.g4jnt@...> wrote:
If you're using aa 144MHz IF, there's a chance you're seeing IM products between your mixer LO and one of the 3G base station channels.   I'd have to look up the channel that cases the problems, but it was bad here until I added an additional filter in the Rx chain

Andy
www.g4jnt.com <http://www.g4jnt.com>



On Wed, 16 Sep 2020 at 20:13, G0FVI via groups.io <http://groups.io>  <Andrew.gilfillan@...> wrote:
I'm still learning being relatively new to uwaves so apologies if this question seems a bit 'dumb'. I'm noticing fairly high noise levels on 23cm UKAC from my /P location (S5) but it's not constant in all directions and tails off to zero in several directions particularly due east to the continent (ground slope away to east and there are no obvious nearby man made sources of noise although there are HT pylons about 100 yards away). I'm not getting this at home with the same setup mounted on mast at about 35 feet (/P mast is only 20 feet), so I'm guessing it is perhaps ground noise? 

Andy G0FVI




Richard GD8EXI
 

I doubt it can be ground noise if it is S5. On 23cms you are unlikely to see more than 3dB change in noise, between beaming into a hillside and beaming down hill. The antenna noise temp going from say 100 to 200K, so even with a RX noise temperature of 50K, only expect a 2.2dB difference.
 
As Andy stated more likely the presence of one or more very strong signals, mixing in your RX at the /P location.
 
Another common culprit is a DTV transmitter centred on about 650MHz. The intermodulation products look like white noise in a 3kHz bandwidth on 1296MHz. Also do not assume your beam will tell you where the source is, as the polar diagram will look very different on 650MHz.
 
Best test is a good 1296MHz bandpass filter in front of any amplification. The trouble is the path loss of about 1dB. I use a 650MHz notch filter in front of my masthead preamp and an interdigital one after it. The noise floor drops by 10dB on some beam headings, on adding this combination, even after correcting for insertion loss.

73s
Richard
GD8EXI




On 16/09/2020, 20:20, "Andy G4JNT" <andy.g4jnt@...> wrote:

The product is 2160MHz  [which is on the edge of a 3G channel]  -   2 x 1152 [LO]  =  144MHz

Andy
www.g4jnt.com <http://www.g4jnt.com>



On Wed, 16 Sep 2020 at 20:18, Andy Talbot <andy.g4jnt@...> wrote:
If you're using aa 144MHz IF, there's a chance you're seeing IM products between your mixer LO and one of the 3G base station channels.   I'd have to look up the channel that cases the problems, but it was bad here until I added an additional filter in the Rx chain

Andy
www.g4jnt.com <http://www.g4jnt.com>



On Wed, 16 Sep 2020 at 20:13, G0FVI via groups.io <http://groups.io>  <Andrew.gilfillan@...> wrote:
I'm still learning being relatively new to uwaves so apologies if this question seems a bit 'dumb'. I'm noticing fairly high noise levels on 23cm UKAC from my /P location (S5) but it's not constant in all directions and tails off to zero in several directions particularly due east to the continent (ground slope away to east and there are no obvious nearby man made sources of noise although there are HT pylons about 100 yards away). I'm not getting this at home with the same setup mounted on mast at about 35 feet (/P mast is only 20 feet), so I'm guessing it is perhaps ground noise? 

Andy G0FVI




Andy G4JNT
 

The product is 2160MHz  [which is on the edge of a 3G channel]  -  2 x 1152 [LO]  =  144MHz



On Wed, 16 Sep 2020 at 20:18, Andy Talbot <andy.g4jnt@...> wrote:
If you're using aa 144MHz IF, there's a chance you're seeing IM products between your mixer LO and one of the 3G base station channels.   I'd have to look up the channel that cases the problems, but it was bad here until I added an additional filter in the Rx chain



On Wed, 16 Sep 2020 at 20:13, G0FVI via groups.io <Andrew.gilfillan=ntlworld.com@groups.io> wrote:
I'm still learning being relatively new to uwaves so apologies if this question seems a bit 'dumb'. I'm noticing fairly high noise levels on 23cm UKAC from my /P location (S5) but it's not constant in all directions and tails off to zero in several directions particularly due east to the continent (ground slope away to east and there are no obvious nearby man made sources of noise although there are HT pylons about 100 yards away). I'm not getting this at home with the same setup mounted on mast at about 35 feet (/P mast is only 20 feet), so I'm guessing it is perhaps ground noise? 

Andy G0FVI


Andy G4JNT
 

If you're using aa 144MHz IF, there's a chance you're seeing IM products between your mixer LO and one of the 3G base station channels.   I'd have to look up the channel that cases the problems, but it was bad here until I added an additional filter in the Rx chain



On Wed, 16 Sep 2020 at 20:13, G0FVI via groups.io <Andrew.gilfillan=ntlworld.com@groups.io> wrote:
I'm still learning being relatively new to uwaves so apologies if this question seems a bit 'dumb'. I'm noticing fairly high noise levels on 23cm UKAC from my /P location (S5) but it's not constant in all directions and tails off to zero in several directions particularly due east to the continent (ground slope away to east and there are no obvious nearby man made sources of noise although there are HT pylons about 100 yards away). I'm not getting this at home with the same setup mounted on mast at about 35 feet (/P mast is only 20 feet), so I'm guessing it is perhaps ground noise? 

Andy G0FVI


G0FVI
 

I'm still learning being relatively new to uwaves so apologies if this question seems a bit 'dumb'. I'm noticing fairly high noise levels on 23cm UKAC from my /P location (S5) but it's not constant in all directions and tails off to zero in several directions particularly due east to the continent (ground slope away to east and there are no obvious nearby man made sources of noise although there are HT pylons about 100 yards away). I'm not getting this at home with the same setup mounted on mast at about 35 feet (/P mast is only 20 feet), so I'm guessing it is perhaps ground noise? 

Andy G0FVI