Date   

Re: Tactics in microwave contest with very few planes.

Mark GM4ISM
 

Hi Andy, yes indeed Ardgour also has a passive reflector but was not in this particular chain.  However you are correct RK is indeed Rosemarkie


Look West    The station in the valley  is near Luichart hydro power station its passive links must have been at an elevation of 25-30 deg

Afraid MB21 wont help with these sites as they were never actually broadcast sites and have not been captured .

The losses associated with passive deflectors / reflectors are pretty horrendous but  still often lower than the  normal path.

The reason that they work best at one end is simply that you have to use the distance square law for field strength twice.. once to  get a signal to your intermediate point and then again (with a  much lower  starting signal) from there to the destination.

The amount of re-radiated signal  is easy to calculate from a purpose designed  passive repeater but far less so from an aircraft or similar.  The re-radiated signal from an aircraft  is highly variable in level and dependent on incident angles.  It scatters the signal in many directions but is far from Lambertian.   Some really big reflection  can be obtained when specular reflection occurs (ie a lot of the planes' reflecting surfaces all send a signal in the same direction roughly in phase)

 These  peaks are often observed as a significant but short duration increase in the  reflected signal.. much akin to watching a passing plane glint in the sunlight or observing an irridium flare.


So  arrange for your scatter point to be as close as possible to one end, give it as much gain as you can in your direction and then hit it with as high an ERP as you can muster

As for the re-radiated pattern from your  passive repeater,  if you can control that too with high gain( and say a remote rotator) then you will gain a big advantage in  signal strength over an omni, as with any antenna system.


As has been pointed out   these systems are practicable from VHF up to SHF and if you really do live in an RF black hole,  will make a significant difference.


I feel that anyone  engineering such a system   is worthy of the contest points  that they may gain from use of  a non-prohibited man-made reflector


Mark GM4ISM


On 19/05/2020 13:27, Andy wrote:
There was 7GHz link using a passive reflector down near Ardgour a long time ago. So is RK Rosemarkie ?

Andy




From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of Mark GM4ISM via groups.io <gm4ism@...>
Sent: Tuesday, May 19, 2020 4:27 AM
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] Tactics in microwave contest with very few planes.
 


I too have  worked with professional passive systems

The pictured passive  deflector at 7GHz used back to back 3.7m dishes on a mountain top  (Point 'SM').  About 1 km or so away was a huge passive reflector (big flat lump of metal)

The signal from point 'RK' (some 20km away if i recall) was bounced down to the valley floor by the reflector, where a powered link station  re-transmitted at about 5W up to the back to back dishes.  There were several mW in the waveguide at this point.  The passive deflector output  then went on to another link stations  point 'GD'  some 28km away with another 3.7m dish.

 This link carried  broadcast video and  radio signals.

The  key thing to note is that the passive sections were both close to one end  of their respective paths (2km or so) to keep the signal levels as high as possible

having a reflector mid way potentially increases range if you have a good link budget but it is far from optimum  from a signal strength perspective.

The system would not have been viable with a mid point passive system.

In this case the  signals were  adequate but had lower than normal fade margins and we did suffer from  snow / ice build-up on the radomes.

These have long since been decomissioned.

  Quiz question.. Name  RK, SM  and GD  + the station in the valley

Bonus points for spelling SM correctly without looking it up  Ken?


Mark GM4ISM




On 19/05/2020 11:24, Nick Peckett G4KUX wrote:

I have actually used commercial passive reflectors to get links into awkward locations before, where it’s just not feasible to build an active repeater. They need very accurate foundation engineering but work very well. Information here.

https://az276019.vo.msecnd.net/valmontstaging/vsna-resources/microflect-passive-repeater-catalog.pdf?sfvrsn=6

 

Regards & 73s

 

Nick G4KUX/YA4F

Sent from Mail for Windows 10

 

From: Murray Niman
Sent: 18 May 2020 12:55
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Tactics in microwave contest with very few planes.

 


So thinking laterally for a contest/QSO-aid (and a loophole in the rules) - you could deliberately fly a a fairly static drone or metallised balloon as a medium altitude passive reflector....
and not just a random scatterer either - there are surface designs that can help refocus the scattered beam

73

 Murray G6JYB  :)

 


Virus-free. www.avg.com


Re: Passive Relay's

Andy G4JNT
 

Probably because it gives maximum distance rather than maximum signal.
? ? ? ?  ...



On Tue, 19 May 2020 at 14:21, Phil Guttridge G3TCU <p.guttridge@...> wrote:
Andy,

So why does Airscout suggest the optimum place for a plane is mid way on the path then? And that seems to work in practice, if you're ever lucky enough to have a plane flying exactly along the path.

I'm aware there are special cases, like when one station is in a valley and can only 'see' the plane when it's pretty close.

I assume an aircraft must be a form of passive reflector or is there a difference between aircraft *scatter* and a passive repeater that is a deliberate reflector?

Thanks & 73, Phil G3TCU



On 19/05/2020 12:11, Andy G4JNT via groups.io wrote:
Correction:
If the repeater is exactly on the direct line from Tx to Rx,  MAXIMUM loss occurs if it is placed mid way
Better to have it close to one end or the other

Spreadsheet for a simplistic view will follow shortly



On Tue, 19 May 2020 at 11:29, Andy Talbot <andy.g4jnt@...> wrote:
I feel a spreadsheet coming on ..
Seem to recall doing this calculation back in the dim and distant past for work, and IIRC the mid point gave furthest range extension.   But that would have been for a naval scenario and no hills !



On Tue, 19 May 2020 at 10:58, Iain Young <g7iii@...> wrote:
Hi Nick,

On 19/05/20 10:24, Nick Gregory G0HIK via groups.io wrote:

> I have been told that you cant have the passive repeater anywhere near
> the middle of the link and has to be right at one end of it. Not sure
> how the logic works, as several of the communities fed by these are not
> that close to them, say up to 2 to 5 miles away.

I beg to differ. While this was done on 144MHz, and 433MHz, last time I
checked the rules of physics don't change at 1.2GHz and up,so here are
a couple of links tto a presentation that I did based on an experiment a
couple of years ago:

http://hal.g7iii.net/ppt/Passive_Repeater_Experiment.pdf
http://hal.g7iii.net/ppt/Passive_Repeater.pdf

Personally, I think it's all about overcoming the extra path loss, so
you need gain in the antennas. I must try it on 23cms and up sometime...


73s

Iain




Virus-free. www.avg.com


Re: Passive Relay's

Phil Guttridge G3TCU
 

Andy,

So why does Airscout suggest the optimum place for a plane is mid way on the path then? And that seems to work in practice, if you're ever lucky enough to have a plane flying exactly along the path.

I'm aware there are special cases, like when one station is in a valley and can only 'see' the plane when it's pretty close.

I assume an aircraft must be a form of passive reflector or is there a difference between aircraft *scatter* and a passive repeater that is a deliberate reflector?

Thanks & 73, Phil G3TCU



On 19/05/2020 12:11, Andy G4JNT via groups.io wrote:
Correction:
If the repeater is exactly on the direct line from Tx to Rx,  MAXIMUM loss occurs if it is placed mid way
Better to have it close to one end or the other

Spreadsheet for a simplistic view will follow shortly



On Tue, 19 May 2020 at 11:29, Andy Talbot <andy.g4jnt@...> wrote:
I feel a spreadsheet coming on ..
Seem to recall doing this calculation back in the dim and distant past for work, and IIRC the mid point gave furthest range extension.   But that would have been for a naval scenario and no hills !



On Tue, 19 May 2020 at 10:58, Iain Young <g7iii@...> wrote:
Hi Nick,

On 19/05/20 10:24, Nick Gregory G0HIK via groups.io wrote:

> I have been told that you cant have the passive repeater anywhere near
> the middle of the link and has to be right at one end of it. Not sure
> how the logic works, as several of the communities fed by these are not
> that close to them, say up to 2 to 5 miles away.

I beg to differ. While this was done on 144MHz, and 433MHz, last time I
checked the rules of physics don't change at 1.2GHz and up,so here are
a couple of links tto a presentation that I did based on an experiment a
couple of years ago:

http://hal.g7iii.net/ppt/Passive_Repeater_Experiment.pdf
http://hal.g7iii.net/ppt/Passive_Repeater.pdf

Personally, I think it's all about overcoming the extra path loss, so
you need gain in the antennas. I must try it on 23cms and up sometime...


73s

Iain




Virus-free. www.avg.com


Chris & Andy please...... [split from: Tactics in microwave contest with very few planes. ]

G8DQX list
 

Alan, Andy,

1) the articles on aircraft reflection were in the '60s, by a monk in Douai Abbey. The RSGB on-line Archive doesn't offer a hit;

2) those articles greatly appealed to me. They were much more fun than 80m AM nets, whose participants seemed to have an in-built fear of releasing the PTT switch;

3) I've always thought of Amateur Radio as a broad church. ITU Radio Regulation 1.56 would seem concordant:

1.56
amateur service: A radiocommunication service for the purpose of self-training,
intercommunication and technical investigations carried out by amateurs, that is, by duly authorized persons interested in radio technique solely with a personal aim and without pecuniary interest.
put another way, Amateur Radio is for:

* learning and personal development

* communicating between Amateur Radio stations, including providing emergency communications

* performing technical experiments, of one sort and another

4) other than the ITU, no-one has the right to constrain the scope of Amateur Radio;

5) or put more positively, Amateur Radio is the sum of each of us, our curiosity, technical knowledge, operating skills, constructional ability, &c. &c.

73, Stay Safe,

Robin, G8DQX

PS: Alan, next time you hi-jack a long-and-lengthy thread, think of us with threaded readers and start a fresh thread, pretty please!


Alan said:

Andy, Chris please dont assume because you don't get 1000+ farcebook-like ''likes'' nobody is interested ! Yes there may be the odd ''Letters Page'' responder who feels he is qualified to define what is and what is not ''amateur radio'' for the rest of us. 
 
There must be a large number of us, particularly at LF and microwaves, who mentally file these gems away as part of our accumulating knowledge of the technical side of the hobby. I remember a series of interesting articles in the 70s by a monk  who wrote about 2m aircraft reflections. Way before ''planefinder'' and such were even thought of. Yes the letters page of Radcom got a comment asking what that was to do with ''amateur radio''!  I remember considering 2m meteor scatter the ''lunatic fringe'' at about the same period. However with the general improvement in readily available high technology many of these ideas slowly come into regular use, even to the state were they are sought out by Professional users for help. Most notably for me, Paul Nicholson's VLF whistler streaming network (LIGO), and Wolf 's SpecrumLab on the search for the lost Malaysian Airlines plane. I am sure demand for Andy's new book compilation of his column will match that for the popular Technical Topics of Pat Hawker.
 
''You don't need to be able to strip and rebuild an engine or the transmission system to drive a car, but knowledge of how it works sure makes you a better driver''
 
Please don't stop trying to educate us all !
 
Alan
G3NYK
 
 
----- Original Message -----
From: Andy G4JNT
Sent: Monday, May 18, 2020 11:04 AM
Subject: Re: [UKMicrowaves] Tactics in microwave contest with very few planes.

Chris
If it doesn't involve a two way SSB or CW QSO it usually doesn't interest most people
One of the reasons I despair of the majority of the amateur radio community and am slowly going off the hobby more and more

My little 70MHz beacon, just 400mW to a dipole,  located at the Bell Hill beacon site has just been reported on Beaconspot as being heard by 9A2SB locator JN95GM distance 1652km.   This isn't even a record, it gets reported from that sort of distance several times per year.   But it's not a kew-ess-oh is it, so no one cares




Re: Tactics in microwave contest with very few planes.

Andy
 

Sgurr Marcasaidh


From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of Mark GM4ISM via groups.io <gm4ism@...>
Sent: Tuesday, May 19, 2020 4:27 AM
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] Tactics in microwave contest with very few planes.
 


I too have  worked with professional passive systems

The pictured passive  deflector at 7GHz used back to back 3.7m dishes on a mountain top  (Point 'SM').  About 1 km or so away was a huge passive reflector (big flat lump of metal)

The signal from point 'RK' (some 20km away if i recall) was bounced down to the valley floor by the reflector, where a powered link station  re-transmitted at about 5W up to the back to back dishes.  There were several mW in the waveguide at this point.  The passive deflector output  then went on to another link stations  point 'GD'  some 28km away with another 3.7m dish.

 This link carried  broadcast video and  radio signals.

The  key thing to note is that the passive sections were both close to one end  of their respective paths (2km or so) to keep the signal levels as high as possible

having a reflector mid way potentially increases range if you have a good link budget but it is far from optimum  from a signal strength perspective.

The system would not have been viable with a mid point passive system.

In this case the  signals were  adequate but had lower than normal fade margins and we did suffer from  snow / ice build-up on the radomes.

These have long since been decomissioned.

  Quiz question.. Name  RK, SM  and GD  + the station in the valley

Bonus points for spelling SM correctly without looking it up  Ken?


Mark GM4ISM




On 19/05/2020 11:24, Nick Peckett G4KUX wrote:

I have actually used commercial passive reflectors to get links into awkward locations before, where it’s just not feasible to build an active repeater. They need very accurate foundation engineering but work very well. Information here.

https://az276019.vo.msecnd.net/valmontstaging/vsna-resources/microflect-passive-repeater-catalog.pdf?sfvrsn=6

 

Regards & 73s

 

Nick G4KUX/YA4F

Sent from Mail for Windows 10

 

From: Murray Niman
Sent: 18 May 2020 12:55
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Tactics in microwave contest with very few planes.

 


So thinking laterally for a contest/QSO-aid (and a loophole in the rules) - you could deliberately fly a a fairly static drone or metallised balloon as a medium altitude passive reflector....
and not just a random scatterer either - there are surface designs that can help refocus the scattered beam

73

 Murray G6JYB  :)

 


Virus-free. www.avg.com


Re: Tactics in microwave contest with very few planes.

Andy
 

There was 7GHz link using a passive reflector down near Ardgour a long time ago. So is RK Rosemarkie ?

Andy




From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of Mark GM4ISM via groups.io <gm4ism@...>
Sent: Tuesday, May 19, 2020 4:27 AM
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] Tactics in microwave contest with very few planes.
 


I too have  worked with professional passive systems

The pictured passive  deflector at 7GHz used back to back 3.7m dishes on a mountain top  (Point 'SM').  About 1 km or so away was a huge passive reflector (big flat lump of metal)

The signal from point 'RK' (some 20km away if i recall) was bounced down to the valley floor by the reflector, where a powered link station  re-transmitted at about 5W up to the back to back dishes.  There were several mW in the waveguide at this point.  The passive deflector output  then went on to another link stations  point 'GD'  some 28km away with another 3.7m dish.

 This link carried  broadcast video and  radio signals.

The  key thing to note is that the passive sections were both close to one end  of their respective paths (2km or so) to keep the signal levels as high as possible

having a reflector mid way potentially increases range if you have a good link budget but it is far from optimum  from a signal strength perspective.

The system would not have been viable with a mid point passive system.

In this case the  signals were  adequate but had lower than normal fade margins and we did suffer from  snow / ice build-up on the radomes.

These have long since been decomissioned.

  Quiz question.. Name  RK, SM  and GD  + the station in the valley

Bonus points for spelling SM correctly without looking it up  Ken?


Mark GM4ISM




On 19/05/2020 11:24, Nick Peckett G4KUX wrote:

I have actually used commercial passive reflectors to get links into awkward locations before, where it’s just not feasible to build an active repeater. They need very accurate foundation engineering but work very well. Information here.

https://az276019.vo.msecnd.net/valmontstaging/vsna-resources/microflect-passive-repeater-catalog.pdf?sfvrsn=6

 

Regards & 73s

 

Nick G4KUX/YA4F

Sent from Mail for Windows 10

 

From: Murray Niman
Sent: 18 May 2020 12:55
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Tactics in microwave contest with very few planes.

 


So thinking laterally for a contest/QSO-aid (and a loophole in the rules) - you could deliberately fly a a fairly static drone or metallised balloon as a medium altitude passive reflector....
and not just a random scatterer either - there are surface designs that can help refocus the scattered beam

73

 Murray G6JYB  :)

 


Virus-free. www.avg.com


Re: Passive Relays

Andy G4JNT
 

To the handful of people who downloaded the .XLS before I made this correction, download  it again
IN the original, amplifier gain was added to pass LOSS rather than subtracted

(Also subject line apostophacalypse repaired)



On Tue, 19 May 2020 at 12:35, Andy Talbot <andy.g4jnt@...> wrote:

This assumes Line of Sight Tx to passive repeater, and from there to Rx
All antennas see terrestrial noise temperatures



On Tue, 19 May 2020 at 12:11, Andy Talbot <andy.g4jnt@...> wrote:
Correction:
If the repeater is exactly on the direct line from Tx to Rx,  MAXIMUM loss occurs if it is placed mid way
Better to have it close to one end or the other

Spreadsheet for a simplistic view will follow shortly



On Tue, 19 May 2020 at 11:29, Andy Talbot <andy.g4jnt@...> wrote:
I feel a spreadsheet coming on ..
Seem to recall doing this calculation back in the dim and distant past for work, and IIRC the mid point gave furthest range extension.   But that would have been for a naval scenario and no hills !



On Tue, 19 May 2020 at 10:58, Iain Young <g7iii@...> wrote:
Hi Nick,

On 19/05/20 10:24, Nick Gregory G0HIK via groups.io wrote:

> I have been told that you cant have the passive repeater anywhere near
> the middle of the link and has to be right at one end of it. Not sure
> how the logic works, as several of the communities fed by these are not
> that close to them, say up to 2 to 5 miles away.

I beg to differ. While this was done on 144MHz, and 433MHz, last time I
checked the rules of physics don't change at 1.2GHz and up,so here are
a couple of links tto a presentation that I did based on an experiment a
couple of years ago:

http://hal.g7iii.net/ppt/Passive_Repeater_Experiment.pdf
http://hal.g7iii.net/ppt/Passive_Repeater.pdf

Personally, I think it's all about overcoming the extra path loss, so
you need gain in the antennas. I must try it on 23cms and up sometime...


73s

Iain




Re: Chris & Andy please......

Chris Bartram G4DGU
 

I used to see similar signals from GB3NGI, also on 144MHz - I still do but with much less frequency. The interesting aspect is that there was little doppler, implying that the aircraft were crossing the path more-or-less at right angles - which is not exactly surprising given the structure of the airways.

This bodes well for the microwave bands when I'm able to get QRV via terrestrial propagation.

BTW the monk who wrote the Radcom (or was it still the 'Bull' at that time?) was Fr. Paul Sollom, G3BGL. I believe he taught physics at Douai Abbey School.

73

Chris G4DGU

On 19/05/2020 11:52, Neil Smith G4DBN wrote:

Back in "normal" times, the GB3MCB beacon on 144 MHz looked like this in late afternoon.  Path is 430 km. There are very few times when there wasn't at least *some* aircraft reflection and signal enhancement.  Time runs downwards, total of 6.5 minutes. It is probably fair to say that the majority of the received signal was enhanced via plane reflections.


Re: Passive Relay's

Andy G4JNT
 


This assumes Line of Sight Tx to passive repeater, and from there to Rx
All antennas see terrestrial noise temperatures



On Tue, 19 May 2020 at 12:11, Andy Talbot <andy.g4jnt@...> wrote:
Correction:
If the repeater is exactly on the direct line from Tx to Rx,  MAXIMUM loss occurs if it is placed mid way
Better to have it close to one end or the other

Spreadsheet for a simplistic view will follow shortly



On Tue, 19 May 2020 at 11:29, Andy Talbot <andy.g4jnt@...> wrote:
I feel a spreadsheet coming on ..
Seem to recall doing this calculation back in the dim and distant past for work, and IIRC the mid point gave furthest range extension.   But that would have been for a naval scenario and no hills !



On Tue, 19 May 2020 at 10:58, Iain Young <g7iii@...> wrote:
Hi Nick,

On 19/05/20 10:24, Nick Gregory G0HIK via groups.io wrote:

> I have been told that you cant have the passive repeater anywhere near
> the middle of the link and has to be right at one end of it. Not sure
> how the logic works, as several of the communities fed by these are not
> that close to them, say up to 2 to 5 miles away.

I beg to differ. While this was done on 144MHz, and 433MHz, last time I
checked the rules of physics don't change at 1.2GHz and up,so here are
a couple of links tto a presentation that I did based on an experiment a
couple of years ago:

http://hal.g7iii.net/ppt/Passive_Repeater_Experiment.pdf
http://hal.g7iii.net/ppt/Passive_Repeater.pdf

Personally, I think it's all about overcoming the extra path loss, so
you need gain in the antennas. I must try it on 23cms and up sometime...


73s

Iain




Re: Tactics in microwave contest with very few planes.

Mark GM4ISM
 


I too have  worked with professional passive systems

The pictured passive  deflector at 7GHz used back to back 3.7m dishes on a mountain top  (Point 'SM').  About 1 km or so away was a huge passive reflector (big flat lump of metal)

The signal from point 'RK' (some 20km away if i recall) was bounced down to the valley floor by the reflector, where a powered link station  re-transmitted at about 5W up to the back to back dishes.  There were several mW in the waveguide at this point.  The passive deflector output  then went on to another link stations  point 'GD'  some 28km away with another 3.7m dish.

 This link carried  broadcast video and  radio signals.

The  key thing to note is that the passive sections were both close to one end  of their respective paths (2km or so) to keep the signal levels as high as possible

having a reflector mid way potentially increases range if you have a good link budget but it is far from optimum  from a signal strength perspective.

The system would not have been viable with a mid point passive system.

In this case the  signals were  adequate but had lower than normal fade margins and we did suffer from  snow / ice build-up on the radomes.

These have long since been decomissioned.

  Quiz question.. Name  RK, SM  and GD  + the station in the valley

Bonus points for spelling SM correctly without looking it up  Ken?


Mark GM4ISM




On 19/05/2020 11:24, Nick Peckett G4KUX wrote:

I have actually used commercial passive reflectors to get links into awkward locations before, where it’s just not feasible to build an active repeater. They need very accurate foundation engineering but work very well. Information here.

https://az276019.vo.msecnd.net/valmontstaging/vsna-resources/microflect-passive-repeater-catalog.pdf?sfvrsn=6

 

Regards & 73s

 

Nick G4KUX/YA4F

Sent from Mail for Windows 10

 

From: Murray Niman
Sent: 18 May 2020 12:55
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Tactics in microwave contest with very few planes.

 


So thinking laterally for a contest/QSO-aid (and a loophole in the rules) - you could deliberately fly a a fairly static drone or metallised balloon as a medium altitude passive reflector....
and not just a random scatterer either - there are surface designs that can help refocus the scattered beam

73

 Murray G6JYB  :)

 


Virus-free. www.avg.com


Re: Passive Relay's

Andy G4JNT
 

Correction:
If the repeater is exactly on the direct line from Tx to Rx,  MAXIMUM loss occurs if it is placed mid way
Better to have it close to one end or the other

Spreadsheet for a simplistic view will follow shortly



On Tue, 19 May 2020 at 11:29, Andy Talbot <andy.g4jnt@...> wrote:
I feel a spreadsheet coming on ..
Seem to recall doing this calculation back in the dim and distant past for work, and IIRC the mid point gave furthest range extension.   But that would have been for a naval scenario and no hills !



On Tue, 19 May 2020 at 10:58, Iain Young <g7iii@...> wrote:
Hi Nick,

On 19/05/20 10:24, Nick Gregory G0HIK via groups.io wrote:

> I have been told that you cant have the passive repeater anywhere near
> the middle of the link and has to be right at one end of it. Not sure
> how the logic works, as several of the communities fed by these are not
> that close to them, say up to 2 to 5 miles away.

I beg to differ. While this was done on 144MHz, and 433MHz, last time I
checked the rules of physics don't change at 1.2GHz and up,so here are
a couple of links tto a presentation that I did based on an experiment a
couple of years ago:

http://hal.g7iii.net/ppt/Passive_Repeater_Experiment.pdf
http://hal.g7iii.net/ppt/Passive_Repeater.pdf

Personally, I think it's all about overcoming the extra path loss, so
you need gain in the antennas. I must try it on 23cms and up sometime...


73s

Iain




Re: Passive Relay's

Nick Gregory G0HIK
 

Thanks for the PDF's, no time today, but I'll print them off and read later.

All sounds good though.

I'll have to dig some aerials out and see what I have and can throw up for a quick and dirt test.

Nick G0HIK


Re: Chris & Andy please......

Neil Smith G4DBN
 

Back in "normal" times, the GB3MCB beacon on 144 MHz looked like this in late afternoon.  Path is 430 km. There are very few times when there wasn't at least *some* aircraft reflection and signal enhancement.  Time runs downwards, total of 6.5 minutes.  It is probably fair to say that the majority of the received signal was enhanced via plane reflections.

Neil G4DBN

On 19/05/2020 11:10, alwyn.seeds1 wrote:
Dear Alan,

Totally agree with you.

The original aircraft reflections papers in the RSGB were even earlier- the 1960s- “A little flutter on VHF” Douai School. 

They are great papers- all done with analytical geometry- I apologise that I have forgotten the author’s name.

This leads me to some questions for the microwavers: At my site in IO92FA GB3VHF and GB3UHF are received over an obstructed 154km path.

Under flat conditions the penalty relative to free space used to be 30 dB relative to free space on 2m and 33 dB relative to free space on 70cm.

Re-checking in our little aircraft scatter world the GB3VHF signal strength is little altered, except that QSB is greater (was 1 dB with period around 5s) now fades of 6 dB plus common.

GB3UHF, however is much weaker- seems to be about 15 dB down and the pervasive aircraft doppler now missing, fades also much deeper (was 2 dB with period around 1 s) now 6db to 10 dB.

My questions are:

1. Have others noticed this?

2. Can someone who is LOS of these beacons confirm whether the GB3UHF signal strength is normal?

3. What do people receiving at greater distances observe?

Regards, and thanks, as ever, to Chris and everyone who made these and our other beacons possible.

Alwyn G8DOH 


_____________________________________________________

Alwyn Seeds, Director
SynOptika Ltd.,
114 Beaufort Street,
London,
SW3 6BU,
England.


SynOptika Ltd., Registered in England and Wales: No. 04606737
Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom.
_____________________________________________________

-- 
Neil
http://g4dbn.uk


Re: Stacking frames

ian hope (2E0IJH)
 

Watch your antennas, not every make requires one inverted, for example our comet cya 16's all have to be the same way up
 
Ian
2E0IJH

 
 
Sent: Tuesday, May 19, 2020 at 9:47 AM
From: "Pete - GM4BYF via groups.io" <gm4byf@...>
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Stacking frames

Important at those frequencies to ensure that any conducting frame does not intrude on the line of the elements.

For a stack of four, this is easy to do provided you invert one antenna and then get the phasing correct. Been there and got it wrong !!

73
Pete GM4BYF
On 18/05/20 20:39, Robin Szemeti wrote:
Aluminium every time.
 
 
On Mon, 18 May 2020 at 19:51, chris ruddy via groups.io <mm0kos=yahoo.co.uk@groups.io> wrote:
Hi All

just a quick question, would you build your stacking frames from Aluminium of Carbon Fibre for 23 and 13cm

Thanks Chris


--
Best regards,

Robin Szemeti

Redpoint Consulting Limited

E: robin@...
T: +44 (0) 1299 405028
M: +44 (0) 7971 883371

CONFIDENTIALITY NOTICE
The information contained in this e-mail is intended only for the
confidential use of the above named recipient. If you are not the
intended recipient or person responsible for delivering it to the
intended recipient, you have received this communication in error
and must not distribute or copy it.
Please accept the sender's apologies, notify the sender immediately
by return e-mail and delete this communication.

Thank you. 

--
vry 73
Pete GM4BYF


Re: RF getting into cheap LED meters?

Andy G4JNT
 

Oh dear, if the meters are what I think they are then look to see where teh current shunt is.  Commonly in the negative lead.   Since there's every chance the negative lead (ground) goes via several roundabout routes, all bets are off as to what current you're actually measuring

For decent I measurement, you can beat proper high-side current monitoring chips (covered in an episode of DNotes a while back)
 


On Tue, 19 May 2020 at 11:23, Andy GD1MIP <gd1mip@...> wrote:
I have just finished putting together a 23cm amplifier based on a PE1RKI 150w amp.
In my case I now have switch mode PSU's for 28v DC (amplifier)  and 12v DC (relays, sequencer and fans).

All works well as an amplifier.  Except I fitted some cheap LED dual A / V meters from a rally. These meters work fine out of the confines of the case but in the case their display on Amps only  reduces (rather than rises) as the amplifiers output wattage increases. At levels beyond 50watts the meters effectively start going 'backwards' until by 100watts they read zero. (volts readings remain stable / true).

I assume RF is getting where it shouldn't,  the meters are not screened, the PCB's are held in a plastic frame. I tried decoupling caps at the meters with some effect, but not enough.  A mixture of clip on ferrites on the LED meter leads seems to have tamed this issue and today I will fabricate some screening boxes for the meters.

Is there anything else I should look at (other than buying better meters).

Thanks Andy GD1MIP 

PS a link to my meters.... https://drive.google.com/folderview?id=1YBujeGcEnsWeOeAZxSjfBZWJMp00yydh


Re: Passive Relay's

Andy G4JNT
 

I feel a spreadsheet coming on ..
Seem to recall doing this calculation back in the dim and distant past for work, and IIRC the mid point gave furthest range extension.   But that would have been for a naval scenario and no hills !



On Tue, 19 May 2020 at 10:58, Iain Young <g7iii@...> wrote:
Hi Nick,

On 19/05/20 10:24, Nick Gregory G0HIK via groups.io wrote:

> I have been told that you cant have the passive repeater anywhere near
> the middle of the link and has to be right at one end of it. Not sure
> how the logic works, as several of the communities fed by these are not
> that close to them, say up to 2 to 5 miles away.

I beg to differ. While this was done on 144MHz, and 433MHz, last time I
checked the rules of physics don't change at 1.2GHz and up,so here are
a couple of links tto a presentation that I did based on an experiment a
couple of years ago:

http://hal.g7iii.net/ppt/Passive_Repeater_Experiment.pdf
http://hal.g7iii.net/ppt/Passive_Repeater.pdf

Personally, I think it's all about overcoming the extra path loss, so
you need gain in the antennas. I must try it on 23cms and up sometime...


73s

Iain




Re: Tactics in microwave contest with very few planes.

Nick Peckett G4KUX
 

I have actually used commercial passive reflectors to get links into awkward locations before, where it’s just not feasible to build an active repeater. They need very accurate foundation engineering but work very well. Information here.

https://az276019.vo.msecnd.net/valmontstaging/vsna-resources/microflect-passive-repeater-catalog.pdf?sfvrsn=6

 

Regards & 73s

 

Nick G4KUX/YA4F

Sent from Mail for Windows 10

 

From: Murray Niman
Sent: 18 May 2020 12:55
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Tactics in microwave contest with very few planes.

 


So thinking laterally for a contest/QSO-aid (and a loophole in the rules) - you could deliberately fly a a fairly static drone or metallised balloon as a medium altitude passive reflector....
and not just a random scatterer either - there are surface designs that can help refocus the scattered beam

73

 Murray G6JYB  :)

 


RF getting into cheap LED meters?

Andy GD1MIP
 

I have just finished putting together a 23cm amplifier based on a PE1RKI 150w amp.
In my case I now have switch mode PSU's for 28v DC (amplifier)  and 12v DC (relays, sequencer and fans).

All works well as an amplifier.  Except I fitted some cheap LED dual A / V meters from a rally. These meters work fine out of the confines of the case but in the case their display on Amps only  reduces (rather than rises) as the amplifiers output wattage increases. At levels beyond 50watts the meters effectively start going 'backwards' until by 100watts they read zero. (volts readings remain stable / true).

I assume RF is getting where it shouldn't,  the meters are not screened, the PCB's are held in a plastic frame. I tried decoupling caps at the meters with some effect, but not enough.  A mixture of clip on ferrites on the LED meter leads seems to have tamed this issue and today I will fabricate some screening boxes for the meters.

Is there anything else I should look at (other than buying better meters).

Thanks Andy GD1MIP 

PS a link to my meters.... https://drive.google.com/folderview?id=1YBujeGcEnsWeOeAZxSjfBZWJMp00yydh


Re: Chris & Andy please......

alwyn.seeds1
 

Dear Alan,

Totally agree with you.

The original aircraft reflections papers in the RSGB were even earlier- the 1960s- “A little flutter on VHF” Douai School. 

They are great papers- all done with analytical geometry- I apologise that I have forgotten the author’s name.

This leads me to some questions for the microwavers: At my site in IO92FA GB3VHF and GB3UHF are received over an obstructed 154km path.

Under flat conditions the penalty relative to free space used to be 30 dB relative to free space on 2m and 33 dB relative to free space on 70cm.

Re-checking in our little aircraft scatter world the GB3VHF signal strength is little altered, except that QSB is greater (was 1 dB with period around 5s) now fades of 6 dB plus common.

GB3UHF, however is much weaker- seems to be about 15 dB down and the pervasive aircraft doppler now missing, fades also much deeper (was 2 dB with period around 1 s) now 6db to 10 dB.

My questions are:

1. Have others noticed this?

2. Can someone who is LOS of these beacons confirm whether the GB3UHF signal strength is normal?

3. What do people receiving at greater distances observe?

Regards, and thanks, as ever, to Chris and everyone who made these and our other beacons possible.

Alwyn G8DOH 


_____________________________________________________

Alwyn Seeds, Director
SynOptika Ltd.,
114 Beaufort Street,
London,
SW3 6BU,
England.


SynOptika Ltd., Registered in England and Wales: No. 04606737
Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom.
_____________________________________________________


23 m UKAC 19th May 2020

Andy GD1MIP
 

Tonight I plan to unleash my new 100 watt amplifier on the unsuspecting UKAC folk. After feeder loss I probably have 55w masthead (30m LDF450) ,  so hopefully a healthy increase over the 5w last month. 

I will be on KST. Hope to get a few of you (and looking at my 2m UBNS hope to accurately log 🤯).

Andy GD1MIP 
45 ele Q loop from NE GD.

7361 - 7380 of 62935