Date   

KST2Me very simple and TACLog too

Bo, OZ2M
 

Hi

Attached is a picture of KST2Me for RFzero. It has a really simple user interface. Two rotary encoders for X-Y selection of station and letters, numbers and other characters.

For those who use TACLog there is even a solution for this too.

(:
Bo


Re: Activity List for the UK Microwave Group 24/47/76GHz Contests - Sunday 19th July

Phil Boorman G0JBA
 

A fair point.

I looked down the list of stations active and the only one who hadn’t put 2m Talkback was myself.

The only contact I am likely to make is potentially with G3XDY who is a another fixed station with KST.  If I went out portable to a hilltop site then I totally agree and would have KST and 2m Talkback capability.

If anyone wishes to try a QSO with me down on the Kent coast then please use KST or call my mobile 07973 227560.  (Incidentally I am using my 144MHz feeder as the I.F cable for 24GHz gear).

Many thanks and I hope everyone manages some QSOs as the weather is looking variable.

73 Phil G0JBA




On Saturday, July 18, 2020, 8:15 am, Martyn G3UKV <ukv@...> wrote:

Good (but wet) morning
I notice several ops. for tomorrow's microwave activity are not including 2m talkback. That's likely to result in missed opportunities.
Why ? Well for 24G and up, successful paths are almost always shorter than on 10G and down, so a very modest 2m stn is all that is required..
Even in 2019, 2m was still used by a majority of regular stations at 24G and above, since only a very small station (eg HB9CV with 5W) was quite adequate for talkback and much easier for dish alignment and beaconing arrangements. Typing never matches analogue voice for rapid comms !
Please try to have 2m talkback available (or even Zello SHF chat) if at all possible! A mobile phone number is also a last resort when 'white noise' reigns.
73 Martyn G3UKV

On 17/07/2020 21:27, Noel G8GTZ wrote:
Callsign: G8GTZ/P
Locator: IO91KF and roaming
Bands: 24GHz, 76GHz and possibly 122 GHz
Times: Depending on local activity/conditions
Talkback: ON4KST & 144.390

Virus-free. www.avg.com


Activity List for the UK Microwave Group 24/47/76GHz Contests - Sunday 19th July

Martyn G3UKV
 

Good (but wet) morning
I notice several ops. for tomorrow's microwave activity are not including 2m talkback. That's likely to result in missed opportunities.
Why ? Well for 24G and up, successful paths are almost always shorter than on 10G and down, so a very modest 2m stn is all that is required..
Even in 2019, 2m was still used by a majority of regular stations at 24G and above, since only a very small station (eg HB9CV with 5W) was quite adequate for talkback and much easier for dish alignment and beaconing arrangements. Typing never matches analogue voice for rapid comms !
Please try to have 2m talkback available (or even Zello SHF chat) if at all possible! A mobile phone number is also a last resort when 'white noise' reigns.
73 Martyn G3UKV

On 17/07/2020 21:27, Noel G8GTZ wrote:
Callsign: G8GTZ/P
Locator: IO91KF and roaming
Bands: 24GHz, 76GHz and possibly 122 GHz
Times: Depending on local activity/conditions
Talkback: ON4KST & 144.390


Virus-free. www.avg.com


Re: mmWave Bands from IO70

groupio@...
 

Hi Chris,

 

I live in Falmouth – IO70LD- so about 35KM away. Only 5.6GHz here. Working on GB3NQ with DATV and analogue ATV . Repeater is about the same distance away just about line of sight!

Got some 10GHz radar type alarms from way back and a few other bits but never got around to going up in frequency as Cornwall is not very active up there. Oscar 100 is the only good 10 GHz source! And I can work through that.
I have neighbours too and a flat roof full of aerials.I tend to watch TV when transmitting so I know if I upset them. DATV on 437MHz tends to swamp the TV!
g8lce.com for  live video of rx etc.

 

Martin  G8LCE


Re: mmWave Bands from IO70

G1DFL
 

You raise an intereting point Chris, in that there is no central UK list or database of who has what GHz capabilities, from what locations, and on what bands.

Donkeys years ago, I remember there was a list of stations in Scotland and Northern England on 23cm on the web.

Below 10GHz most folks are active in UKAC's once a month and then in the UKuG weekend contests. You can also see in KST sometimes what bands people have equipment for. Scatterpoint has activity reports. But it's all a bit random! 

We could a lot more as a niche interest group to help each other to create QSO's and activity. And to use all that DB6NT kit that must be out there somewhere sat unused, gathering dust?!

Above 10Ghz there are regionally pockets of folks. I'm fortunate that we have a small local group active in IO91 for 24GHz. 

Maybe UKuG could have a simple secure database members could log in to. We could all use it to search for stations nearby to test paths and equipmemt on various bands. Also to work out if its viable to invest in bands. ..Just an idea.

Regards..Pete
G1DFL



On Fri, 17 Jul 2020 at 21:44, Ed G3VPF
<g3vpf@...> wrote:
Chris

At present I only have my old WB gear for 24GHz. However, given someone to test with I could be persuaded to get going on 24GHz NB. Havn't bothered so far as there has been no local activity. Path from here is good to Dartmoor, then a large lump of granite gets in the way! If you are operational on 10GHz or 5.7GHz I can be active on those bands very quickly and this would allow an assessment of the path to be started.

Ed G3VPF IO80RQ


From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of Chris Bartram G4DGU <chris@...>
Sent: 17 July 2020 19:17
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] mmWave Bands from IO70
 

Hello Paul,

Yours was the only reply to my post, so I think that concentrating on 24G EME will be most profitable once I've managed to get QRV on 10GHz EME again. It's taking a while, partly because I want to finish the work I'm doing on our house before giving 10GHz EME serious time!

I look forward to the signal from whatever you put on your 80ft tower! I'm rather restricted here, and the only antenna I have at the moment is a very low (and very old!) 9ele Tonna for 144MHz. While the site isn't quite as difficult as the old Carno location, I do have closer neighbours, and I don't want to get into neighbour conflicts! I think that I can get PP for an extendable mast mounted on the end of the house, and I'll probably put up a 1m dish with a dual feeds for 1.3 and 10GHz, as I'm limited there by a potential neighbour overhang to antenna lengths of ~3m.

I suppose it's fun!

73 to you both. Hope to see you sometime.

Chris 'DGU


On 17/07/2020 12:07, PAUL NICKALLS via groups.io wrote:
Hi Chris,

Pity you are so far away (280km).  I have a 24GHz system that needs repair - it has a lock issue.
I trust you are keeping well.

73
Paul G8AQA

On 17/07/2020 11:27, Chris Bartram G4DGU wrote:
Reading the comments regarding the UKuG mmWave contest prompted these thoughts.

It would be at least very interesting to discover if there is anyone within, say, 200km of IO70pj who has 24GHz gear and would like to run tests in the future? I have fully working kit built over a decade ago (2W, 2dBNF and usually a 0.9m dish) sitting in a box in my workshop, and it would be good to use it! I have had only one QSO since returning to IO70. I'm quite happy to go out portable, but I don't want to have to drive too far ...

I also have a beacon for 24GHz (200mW to a 16dBi sectoral horn) which it would be good to put to use. That requires a major update to the synthesier, and possibly a new keyer but that could be arranged if someone in IO70/IN69 with a suitable site would like to offer it a home. A cross-channel, low level beacon might be an interesting project!

I also did quite a lot of preparation work for a 47GHz system before I left Wales, and I'd be interested in finishing that if I had had someone to play mmWave games with!

73

Chris G4DGU






KST Update

Robin Szemeti - G1YFG
 

Just in case anyone is interested, I added auto-reconnect, so it will log you back in if the link is interrupted for any reason,  the user list/map/chat continues as if nothing had happened.



--
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.


Re: Activity List for the UK Microwave Group 24/47/76GHz Contests - Sunday 19th July

Phil Boorman G0JBA
 


Callsign: G0JBA
Locator: JO01PG63
Bands: 24GHz 40cm off set 1.8W
Times: Depending on local activity/conditions
Talkback: ON4KST 

Phil G0JBA 


On Friday, July 17, 2020, 9:27 pm, Noel G8GTZ <noel@...> wrote:

Callsign: G8GTZ/P
Locator: IO91KF and roaming
Bands: 24GHz, 76GHz and possibly 122 GHz
Times: Depending on local activity/conditions
Talkback: ON4KST & 144.390


Re: Horn madness

Robin Szemeti - G1YFG
 

Well, that *nearly* worked ... the flat patterns worked out correctly, all the rivet holes lined up ... but, the sheet of material I happened to have was 7082T6, and *far* too brittle to take a tight 90 degree bend. after 2 of the bends broke off, I didn't bother putting the bends on the front edges.. I'll buy a sheet of 5083 or something like that, a little softer.  Another prototype for the scrap pile ...

image.png

image.png

image.png


On Fri, 17 Jul 2020 at 14:39, Gordon REASON via groups.io <gordonj.reason=virgin.net@groups.io> wrote:

I was always taught , that a waveguide horn , should be as long as is possible , with smooth sides ,  that makes for even enlargement of the wave , which lead to less sidelobes ......

It's that simple .

You can always put some matching screws , at or near the waveguide-horn junction , to match any errors , which will be small ..... if tour horn is well made .......

My one and only horn , for 3 cems , was made using an old waveguide flange , filed to shape , and an emplty (!) Duchams oil can ( those were the days ) , and it worked very well ..........

Keep it simple .

On 17 July 2020 at 00:02 Robin Szemeti - G1YFG <robin@...> wrote:

Well, I am clearly not getting something, as I cannot see how, regardless of the shape (rectangular or square)  the joint between the rectangular waveguide and the horn can be anything other than a simple planar joint, (ie a straight saw cut through the rectangular section) ... I think I'll try this out of cardboard before committing it to metal!

On Thu, 16 Jul 2020 at 23:49, G8DQX list < list@...> wrote:

Robin,

I think that the calculator is, in principle, correct, because the horn itself is rectangular rather than square, and the feeding waveguide meets the planes of the horn at different locations, due to linear geometry. (The angles of the two planes could be freely chosen, for instance to optimise gain or bandwidth.) An isometric projection would show it much more clearly!

HTH, 73, Stay Safe,

Robin, G8DQX

PS: Sadly, the likely text books are currently unavailable to me, so can't comment on the "optimal" nature of the offered design mantra.

On 16/07/2020 22:58, Robin Szemeti - G1YFG wrote:
Before I go slightly potty ...  the horn calculator on this page, am I misunderstanding it, or is it broken?

The horizontal values for PE and PH appear to not be equal,  which is doing my head in, as surely, assuming normal Euclidian geometry,  the exit of the rectangular waveguide must be planar, so surely PE and PH must be identical (assuming the horn front face is planar ... )  or is the joint between the rectangular section and the horn no planar?



image.png


--
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. 

 

 


Re: G/T for parabolic dishes

KENT BRITAIN
 

I recently saw an HF antenna with dimensions in .01 mm.

Someone need to crush that lads scientific calculator!!

Kent

On Friday, July 17, 2020, 3:11:29 PM CDT, Dr. David Kirkby, Kirkby Microwave Ltd <drkirkby@...> wrote:


On Fri, 17 Jul 2020 at 20:19, KENT BRITAIN <WA5VJB@...> wrote:

There has been some interesting work with very long, very narrow banded, log periodics
with excellent gain and low sidelobes.    But all the work I have seen was simulations,
looking forward to the day someone brings one to the antenna range.   Kent WA5VJB-2E0VAA

If it’s very long, the chances are it’s impossible to hold the elements in position. Our radio club had a Yagi-Uda type antenna with elements cut to +/- 0.5 mm, but which move around several hundred mm. It would probably have been okay for MEM (moon earth moon), as the much lower gravity and little atmosphere on the moon  would mean it could probably be supported on the moon. 😂😂😢 Buf on earth it was not useful. 

Dave
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...
https://www.kirkbymicrowave.co.uk/
Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom


Re: G/T for parabolic dishes

KENT BRITAIN
 

Easier in my back yard.   I've got 100 Meters to work with.
A photo of my butt testing a 3 cm antenna is on the cover of the next CQ magazine.
Yes, lots of comments about showing my best side.

Kent

On Friday, July 17, 2020, 3:41:40 PM CDT, Robin Szemeti - G1YFG <robin@...> wrote:


That reminds me .. is there an "accessible" antenna range in the UK where idiots such as myself can bring their construction and come away with a graph to laugh at?  I've thought about putting something together in the filed at the back of the house, but as always, it never quite happens.

On Fri, 17 Jul 2020 at 20:19, KENT BRITAIN <WA5VJB@...> wrote:
There has been some interesting work with very long, very narrow banded, log periodics
with excellent gain and low sidelobes.    But all the work I have seen was simulations,
looking forward to the day someone brings one to the antenna range.   Kent WA5VJB-2E0VAA

On Friday, July 17, 2020, 2:16:45 PM CDT, Dr. David Kirkby, Kirkby Microwave Ltd <drkirkby@...> wrote:


On Thu, 16 Jul 2020 at 21:57, Chris Bartram G4DGU <chris@...> wrote:
Hello Dave,

> what physics comes into play here? It's either something I never knew,
> or have forgotten.

It's all to do with diffraction. Optical telescope designers know all
about it, but I'd have to go back to a text to refresh my limited
understanding in order to say more.

73

Chris G4DGU

I’m not convinced that one can arrive at the same levels for a Yagi-Uda though, which I believe was mentioned earlier.  You can compute a capture area, which is itself not circular. 

I have thought about trying to reduce the first sidelobe on a Yagi-Uda type antenna, perhaps with a small bend on the ends of the elements. I personally find that sidelobe annoying as if one knows the general direction of a station one can rotate the beam and think one has the peak but doesn’t.

You can argue sidelobes are advantageous in a contest. 

Anyway, I will not take the argument too far from the dish. Yagis are a quite different beast. 

Dave
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...
https://www.kirkbymicrowave.co.uk/
Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom


Re: mmWave Bands from IO70

Ed G3VPF
 

Chris

At present I only have my old WB gear for 24GHz. However, given someone to test with I could be persuaded to get going on 24GHz NB. Havn't bothered so far as there has been no local activity. Path from here is good to Dartmoor, then a large lump of granite gets in the way! If you are operational on 10GHz or 5.7GHz I can be active on those bands very quickly and this would allow an assessment of the path to be started.

Ed G3VPF IO80RQ


From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of Chris Bartram G4DGU <chris@...>
Sent: 17 July 2020 19:17
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] mmWave Bands from IO70
 

Hello Paul,

Yours was the only reply to my post, so I think that concentrating on 24G EME will be most profitable once I've managed to get QRV on 10GHz EME again. It's taking a while, partly because I want to finish the work I'm doing on our house before giving 10GHz EME serious time!

I look forward to the signal from whatever you put on your 80ft tower! I'm rather restricted here, and the only antenna I have at the moment is a very low (and very old!) 9ele Tonna for 144MHz. While the site isn't quite as difficult as the old Carno location, I do have closer neighbours, and I don't want to get into neighbour conflicts! I think that I can get PP for an extendable mast mounted on the end of the house, and I'll probably put up a 1m dish with a dual feeds for 1.3 and 10GHz, as I'm limited there by a potential neighbour overhang to antenna lengths of ~3m.

I suppose it's fun!

73 to you both. Hope to see you sometime.

Chris 'DGU


On 17/07/2020 12:07, PAUL NICKALLS via groups.io wrote:
Hi Chris,

Pity you are so far away (280km).  I have a 24GHz system that needs repair - it has a lock issue.
I trust you are keeping well.

73
Paul G8AQA

On 17/07/2020 11:27, Chris Bartram G4DGU wrote:
Reading the comments regarding the UKuG mmWave contest prompted these thoughts.

It would be at least very interesting to discover if there is anyone within, say, 200km of IO70pj who has 24GHz gear and would like to run tests in the future? I have fully working kit built over a decade ago (2W, 2dBNF and usually a 0.9m dish) sitting in a box in my workshop, and it would be good to use it! I have had only one QSO since returning to IO70. I'm quite happy to go out portable, but I don't want to have to drive too far ...

I also have a beacon for 24GHz (200mW to a 16dBi sectoral horn) which it would be good to put to use. That requires a major update to the synthesier, and possibly a new keyer but that could be arranged if someone in IO70/IN69 with a suitable site would like to offer it a home. A cross-channel, low level beacon might be an interesting project!

I also did quite a lot of preparation work for a 47GHz system before I left Wales, and I'd be interested in finishing that if I had had someone to play mmWave games with!

73

Chris G4DGU






Re: G/T for parabolic dishes

Robin Szemeti - G1YFG
 

That reminds me .. is there an "accessible" antenna range in the UK where idiots such as myself can bring their construction and come away with a graph to laugh at?  I've thought about putting something together in the filed at the back of the house, but as always, it never quite happens.

On Fri, 17 Jul 2020 at 20:19, KENT BRITAIN <WA5VJB@...> wrote:
There has been some interesting work with very long, very narrow banded, log periodics
with excellent gain and low sidelobes.    But all the work I have seen was simulations,
looking forward to the day someone brings one to the antenna range.   Kent WA5VJB-2E0VAA

On Friday, July 17, 2020, 2:16:45 PM CDT, Dr. David Kirkby, Kirkby Microwave Ltd <drkirkby@...> wrote:


On Thu, 16 Jul 2020 at 21:57, Chris Bartram G4DGU <chris@...> wrote:
Hello Dave,

> what physics comes into play here? It's either something I never knew,
> or have forgotten.

It's all to do with diffraction. Optical telescope designers know all
about it, but I'd have to go back to a text to refresh my limited
understanding in order to say more.

73

Chris G4DGU

I’m not convinced that one can arrive at the same levels for a Yagi-Uda though, which I believe was mentioned earlier.  You can compute a capture area, which is itself not circular. 

I have thought about trying to reduce the first sidelobe on a Yagi-Uda type antenna, perhaps with a small bend on the ends of the elements. I personally find that sidelobe annoying as if one knows the general direction of a station one can rotate the beam and think one has the peak but doesn’t.

You can argue sidelobes are advantageous in a contest. 

Anyway, I will not take the argument too far from the dish. Yagis are a quite different beast. 

Dave
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...
https://www.kirkbymicrowave.co.uk/
Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom


Re: Activity List for the UK Microwave Group 24/47/76GHz Contests - Sunday 19th July

Noel G8GTZ
 

Callsign: G8GTZ/P
Locator: IO91KF and roaming
Bands: 24GHz, 76GHz and possibly 122 GHz
Times: Depending on local activity/conditions
Talkback: ON4KST & 144.390


Re: G/T for parabolic dishes

 

On Fri, 17 Jul 2020 at 20:19, KENT BRITAIN <WA5VJB@...> wrote:

There has been some interesting work with very long, very narrow banded, log periodics
with excellent gain and low sidelobes.    But all the work I have seen was simulations,
looking forward to the day someone brings one to the antenna range.   Kent WA5VJB-2E0VAA

If it’s very long, the chances are it’s impossible to hold the elements in position. Our radio club had a Yagi-Uda type antenna with elements cut to +/- 0.5 mm, but which move around several hundred mm. It would probably have been okay for MEM (moon earth moon), as the much lower gravity and little atmosphere on the moon  would mean it could probably be supported on the moon. 😂😂😢 Buf on earth it was not useful. 

Dave
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...
https://www.kirkbymicrowave.co.uk/
Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom


Re: G/T for parabolic dishes

KENT BRITAIN
 

There has been some interesting work with very long, very narrow banded, log periodics
with excellent gain and low sidelobes.    But all the work I have seen was simulations,
looking forward to the day someone brings one to the antenna range.   Kent WA5VJB-2E0VAA

On Friday, July 17, 2020, 2:16:45 PM CDT, Dr. David Kirkby, Kirkby Microwave Ltd <drkirkby@...> wrote:


On Thu, 16 Jul 2020 at 21:57, Chris Bartram G4DGU <chris@...> wrote:
Hello Dave,

> what physics comes into play here? It's either something I never knew,
> or have forgotten.

It's all to do with diffraction. Optical telescope designers know all
about it, but I'd have to go back to a text to refresh my limited
understanding in order to say more.

73

Chris G4DGU

I’m not convinced that one can arrive at the same levels for a Yagi-Uda though, which I believe was mentioned earlier.  You can compute a capture area, which is itself not circular. 

I have thought about trying to reduce the first sidelobe on a Yagi-Uda type antenna, perhaps with a small bend on the ends of the elements. I personally find that sidelobe annoying as if one knows the general direction of a station one can rotate the beam and think one has the peak but doesn’t.

You can argue sidelobes are advantageous in a contest. 

Anyway, I will not take the argument too far from the dish. Yagis are a quite different beast. 

Dave
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...
https://www.kirkbymicrowave.co.uk/
Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom


Re: mmWave Bands from IO70

Chris Bartram G4DGU
 

Hello Paul,

Yours was the only reply to my post, so I think that concentrating on 24G EME will be most profitable once I've managed to get QRV on 10GHz EME again. It's taking a while, partly because I want to finish the work I'm doing on our house before giving 10GHz EME serious time!

I look forward to the signal from whatever you put on your 80ft tower! I'm rather restricted here, and the only antenna I have at the moment is a very low (and very old!) 9ele Tonna for 144MHz. While the site isn't quite as difficult as the old Carno location, I do have closer neighbours, and I don't want to get into neighbour conflicts! I think that I can get PP for an extendable mast mounted on the end of the house, and I'll probably put up a 1m dish with a dual feeds for 1.3 and 10GHz, as I'm limited there by a potential neighbour overhang to antenna lengths of ~3m.

I suppose it's fun!

73 to you both. Hope to see you sometime.

Chris 'DGU


On 17/07/2020 12:07, PAUL NICKALLS via groups.io wrote:
Hi Chris,

Pity you are so far away (280km).  I have a 24GHz system that needs repair - it has a lock issue.
I trust you are keeping well.

73
Paul G8AQA

On 17/07/2020 11:27, Chris Bartram G4DGU wrote:
Reading the comments regarding the UKuG mmWave contest prompted these thoughts.

It would be at least very interesting to discover if there is anyone within, say, 200km of IO70pj who has 24GHz gear and would like to run tests in the future? I have fully working kit built over a decade ago (2W, 2dBNF and usually a 0.9m dish) sitting in a box in my workshop, and it would be good to use it! I have had only one QSO since returning to IO70. I'm quite happy to go out portable, but I don't want to have to drive too far ...

I also have a beacon for 24GHz (200mW to a 16dBi sectoral horn) which it would be good to put to use. That requires a major update to the synthesier, and possibly a new keyer but that could be arranged if someone in IO70/IN69 with a suitable site would like to offer it a home. A cross-channel, low level beacon might be an interesting project!

I also did quite a lot of preparation work for a 47GHz system before I left Wales, and I'd be interested in finishing that if I had had someone to play mmWave games with!

73

Chris G4DGU






Re: G/T for parabolic dishes

 

On Thu, 16 Jul 2020 at 21:57, Chris Bartram G4DGU <chris@...> wrote:
Hello Dave,

> what physics comes into play here? It's either something I never knew,
> or have forgotten.

It's all to do with diffraction. Optical telescope designers know all
about it, but I'd have to go back to a text to refresh my limited
understanding in order to say more.

73

Chris G4DGU

I’m not convinced that one can arrive at the same levels for a Yagi-Uda though, which I believe was mentioned earlier.  You can compute a capture area, which is itself not circular. 

I have thought about trying to reduce the first sidelobe on a Yagi-Uda type antenna, perhaps with a small bend on the ends of the elements. I personally find that sidelobe annoying as if one knows the general direction of a station one can rotate the beam and think one has the peak but doesn’t.

You can argue sidelobes are advantageous in a contest. 

Anyway, I will not take the argument too far from the dish. Yagis are a quite different beast. 

Dave
--
Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...
https://www.kirkbymicrowave.co.uk/
Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom


Re: G/T for parabolic dishes

Brian Howie GM4DIJ
 

It's not quite as bad as that. The optical side lobes assumes the limiting aperture (lens etc) is uniformly illuminated. In RF land the dish is illuminated by a spatially non-uniform field. I imagine the illumination is some sort of sine function from a horn. The level at the edges of is meant to be ( rule of thumb) about -10db from the centre. So finger in the air, the sidelobes are going to to be 10dB lower than the Airy Disc solution. Of course you get sidelobes from both the horn and dish edge.

The maths must be horrible.

I used to do this sort of stuff for laser beam diffraction, The difference between a top-Hat beam and a truncated Gaussian beam is about 12dB for an example I have. Infinite Gaussian has the lowest sidelobe, but you need a big lens for that ;-)

Maths for this is a lot easier, an decent ray-tracing programs can do it.

Brian GM4DIJ

On 16/07/2020 22:09, Andy G4JNT wrote:
Good pictures of optical sidelobes
https://www.photokonnexion.com/definition-diffraction-pinhole-diffraction/
http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/cirapp2.html
image.png
Andy
www.g4jnt.com <http://www.g4jnt.com>
On Thu, 16 Jul 2020 at 21:57, Chris Bartram G4DGU <chris@chris-bartram.co.uk <mailto:chris@chris-bartram.co.uk>> wrote:
Hello Dave,

> what physics comes into play here? It's either something I never
knew,
> or have forgotten.
It's all to do with diffraction. Optical telescope designers know all
about it, but I'd have to go back to a text to refresh my limited
understanding in order to say more.
73
Chris G4DGU
--
Brian


Re: Activity List for the UK Microwave Group 24/47/76GHz Contests - Sunday 19th July

David Robinson
 

Callsign: G4FRE/P 
Locator: IO81XW (Cleeve common)
Bands: 24/47 GHz and possibly 76GHz
Times: 10:00 until around 1300 (BST)
Talkback: KST and Zello SHF chat


22ghz odu and dish

Reg Woolley
 

If any of you want a Huawei  22ghz odu with .3 dish all as one unit my freind has one for sale.

E mail r-halliday@... 

Reg g8vhi 



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