Horn for 3.4GHz


Gareth G4XAT
 

My local repeater GB3JV (DATV) (Petts Wood SE London) is pretty much LOS to me at home, so rather than tie up my Titanium PLL LNB I picked up a NOS Nortel DRO commercial unit. As it needs some form of weather protection I thought I might as well add some gain too. Using this software https://www.raytechx.com/antenna-calc I then designed a 3-D printed 10dBd horn, which came out like the picture. Interior surface finish has been improved by flat filing and I will then cover with aluminium tape. 
A couple of questions....
1. It seems very 'wide' compared to horns I've seen on 10GHz stuff - maybe why its 'only' 10dBd.
2. I have some PTFE sheet, would this be suitable as a gasket to keep the weather out of the LNB cavity, if not would HDPE from a milk carton work?
The horn sizes very quickly got very large (longer print time/too big for the printer) if I upped the target gain figure. I was surprised by this...not like adding a couple of elements to a yagi....
Comments welcome...
Gareth


Andy G4JNT
 

I use the old software written by G8AGN decades ago for horn design, updated for 32 bit OS and now with graphical output including a cutting template.
Here are my values for a 12.1 dBi gain Horn (Why, ever, specify gains in dBd ??????)

image.png


image.png


On Tue, 22 Jun 2021 at 08:28, Gareth G4XAT via groups.io <g4xat=ntlworld.com@groups.io> wrote:
My local repeater GB3JV (DATV) (Petts Wood SE London) is pretty much LOS to me at home, so rather than tie up my Titanium PLL LNB I picked up a NOS Nortel DRO commercial unit. As it needs some form of weather protection I thought I might as well add some gain too. Using this software https://www.raytechx.com/antenna-calc I then designed a 3-D printed 10dBd horn, which came out like the picture. Interior surface finish has been improved by flat filing and I will then cover with aluminium tape. 
A couple of questions....
1. It seems very 'wide' compared to horns I've seen on 10GHz stuff - maybe why its 'only' 10dBd.
2. I have some PTFE sheet, would this be suitable as a gasket to keep the weather out of the LNB cavity, if not would HDPE from a milk carton work?
The horn sizes very quickly got very large (longer print time/too big for the printer) if I upped the target gain figure. I was surprised by this...not like adding a couple of elements to a yagi....
Comments welcome...
Gareth


Colin Ranson
 

Yes please. Ideas for thin 10GHz transparent materials for weather proofing horns, feeds etc. Milk bottle material sounds good and is plentiful !

 

Colin de G8LBS.

 

Sent from Mail for Windows 10

 

From: Andy G4JNT
Sent: 22 June 2021 08:40
To: UK Microwaves groups.io
Subject: Re: [UKMicrowaves] Horn for 3.4GHz

 

I use the old software written by G8AGN decades ago for horn design, updated for 32 bit OS and now with graphical output including a cutting template.

Here are my values for a 12.1 dBi gain Horn (Why, ever, specify gains in dBd ??????)

 

 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 08:28, Gareth G4XAT via groups.io <g4xat=ntlworld.com@groups.io> wrote:

My local repeater GB3JV (DATV) (Petts Wood SE London) is pretty much LOS to me at home, so rather than tie up my Titanium PLL LNB I picked up a NOS Nortel DRO commercial unit. As it needs some form of weather protection I thought I might as well add some gain too. Using this software https://www.raytechx.com/antenna-calc I then designed a 3-D printed 10dBd horn, which came out like the picture. Interior surface finish has been improved by flat filing and I will then cover with aluminium tape. 
A couple of questions....
1. It seems very 'wide' compared to horns I've seen on 10GHz stuff - maybe why its 'only' 10dBd.
2. I have some PTFE sheet, would this be suitable as a gasket to keep the weather out of the LNB cavity, if not would HDPE from a milk carton work?
The horn sizes very quickly got very large (longer print time/too big for the printer) if I upped the target gain figure. I was surprised by this...not like adding a couple of elements to a yagi....
Comments welcome...
Gareth

 


Neil Smith G4DBN
 

"Styrene" modelling sheet from model suppliers is actually polystyrene and performs well. HDPE has a loss tangent almost as good as polystyrene and PTFE.  PS is nice because it is reasonably stiff.  Ideally you want something hydrophobic so water drops just fall off. Polyurethane also works, and even fairly-lossy Kapton is OK, so long as it is very thin.

I've bought some CCTV camera domes that work well as radomes.  They may be acrylic, but they are thin and appear to have no measurable loss up to 10 GHz.

Neil G4DBN

On 22/06/2021 11:57, Colin Ranson wrote:

Yes please. Ideas for thin 10GHz transparent materials for weather proofing horns, feeds etc. Milk bottle material sounds good and is plentiful !

 




Andy G4JNT
 

Interesting your comment on kapton.   It seems to be used a lot in electrical work and imn spacecraft, yet you suggest it's not very good microwave-wise?
Must have very good other properties

Andy


On Tue, 22 Jun 2021 at 12:56, Neil Smith G4DBN <neil@...> wrote:

"Styrene" modelling sheet from model suppliers is actually polystyrene and performs well. HDPE has a loss tangent almost as good as polystyrene and PTFE.  PS is nice because it is reasonably stiff.  Ideally you want something hydrophobic so water drops just fall off. Polyurethane also works, and even fairly-lossy Kapton is OK, so long as it is very thin.

I've bought some CCTV camera domes that work well as radomes.  They may be acrylic, but they are thin and appear to have no measurable loss up to 10 GHz.

Neil G4DBN

On 22/06/2021 11:57, Colin Ranson wrote:

Yes please. Ideas for thin 10GHz transparent materials for weather proofing horns, feeds etc. Milk bottle material sounds good and is plentiful !

 




KENT BRITAIN
 

Hi Colin

I usually put the window between the horn and the WG Transition.    Much smaller piece and it's out of the weather.
I like to use a sheet of Mica, but that's for X-Band and higher.  Hard to find Mica sheet big enough for 9cm but the bits for the larger power transistors is OK for WG16.  Also the Teflon Tape used in plumbing works well.  But again a pretty big piece for 9 cm but the standard tape works well at 3 cm and higher.   73 Kent

On Tuesday, June 22, 2021, 05:57:25 AM CDT, Colin Ranson <g8lbs@...> wrote:


Yes please. Ideas for thin 10GHz transparent materials for weather proofing horns, feeds etc. Milk bottle material sounds good and is plentiful !

 

Colin de G8LBS.

 

Sent from Mail for Windows 10

 

From: Andy G4JNT
Sent: 22 June 2021 08:40
To: UK Microwaves groups.io
Subject: Re: [UKMicrowaves] Horn for 3.4GHz

 

I use the old software written by G8AGN decades ago for horn design, updated for 32 bit OS and now with graphical output including a cutting template.

Here are my values for a 12.1 dBi gain Horn (Why, ever, specify gains in dBd ??????)

 

 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 08:28, Gareth G4XAT via groups.io <g4xat=ntlworld.com@groups.io> wrote:

My local repeater GB3JV (DATV) (Petts Wood SE London) is pretty much LOS to me at home, so rather than tie up my Titanium PLL LNB I picked up a NOS Nortel DRO commercial unit. As it needs some form of weather protection I thought I might as well add some gain too. Using this software https://www.raytechx.com/antenna-calc I then designed a 3-D printed 10dBd horn, which came out like the picture. Interior surface finish has been improved by flat filing and I will then cover with aluminium tape. 
A couple of questions....
1. It seems very 'wide' compared to horns I've seen on 10GHz stuff - maybe why its 'only' 10dBd.
2. I have some PTFE sheet, would this be suitable as a gasket to keep the weather out of the LNB cavity, if not would HDPE from a milk carton work?
The horn sizes very quickly got very large (longer print time/too big for the printer) if I upped the target gain figure. I was surprised by this...not like adding a couple of elements to a yagi....
Comments welcome...
Gareth

 


Neil Smith G4DBN
 

Kapton tape is very thin, so hardly any effect if it is in the fairly dilute field at the opening of a horn. Kent is right about it being more practical putting a window between guide and horn, but I'd want to use something lower loss than Kapton in the stronger field at the throat of the horn at higher frequencies.  Kapton's loss tangent is about 0.02 at 10 GHz, about 50 times worse than "proper" dielectrics, but is hugely stiffer and stronger than most of them, and survives sunlight better than PS or PU. For a 0.125 mm film of Kapton, I suspect the loss would be low enough for the bands below 10 GHz by clamping it between two flanges.  It has a higher relative permittivity than PE, PS or PTFE, but wins on the mechanical properties.

Neil G4DBN

On 22/06/2021 13:00, Andy G4JNT wrote:
Interesting your comment on kapton.   It seems to be used a lot in electrical work and imn spacecraft, yet you suggest it's not very good microwave-wise?
Must have very good other properties



Raymond Brooks
 

For Sheet mica look at microwave oven spears.

 

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of KENT BRITAIN
Sent: 22 June 2021 13:09
To: UKMicrowaves@groups.io; UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Horn for 3.4GHz

 

Hi Colin

 

I usually put the window between the horn and the WG Transition.    Much smaller piece and it's out of the weather.

I like to use a sheet of Mica, but that's for X-Band and higher.  Hard to find Mica sheet big enough for 9cm but the bits for the larger power transistors is OK for WG16.  Also the Teflon Tape used in plumbing works well.  But again a pretty big piece for 9 cm but the standard tape works well at 3 cm and higher.   73 Kent

 

On Tuesday, June 22, 2021, 05:57:25 AM CDT, Colin Ranson <g8lbs@...> wrote:

 

 

Yes please. Ideas for thin 10GHz transparent materials for weather proofing horns, feeds etc. Milk bottle material sounds good and is plentiful !

 

Colin de G8LBS.

 

Sent from Mail for Windows 10

 

From: Andy G4JNT
Sent: 22 June 2021 08:40
To: UK Microwaves groups.io
Subject: Re: [UKMicrowaves] Horn for 3.4GHz

 

I use the old software written by G8AGN decades ago for horn design, updated for 32 bit OS and now with graphical output including a cutting template.

Here are my values for a 12.1 dBi gain Horn (Why, ever, specify gains in dBd ??????)

 

 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 08:28, Gareth G4XAT via groups.io <g4xat=ntlworld.com@groups.io> wrote:

My local repeater GB3JV (DATV) (Petts Wood SE London) is pretty much LOS to me at home, so rather than tie up my Titanium PLL LNB I picked up a NOS Nortel DRO commercial unit. As it needs some form of weather protection I thought I might as well add some gain too. Using this software https://www.raytechx.com/antenna-calc I then designed a 3-D printed 10dBd horn, which came out like the picture. Interior surface finish has been improved by flat filing and I will then cover with aluminium tape. 
A couple of questions....
1. It seems very 'wide' compared to horns I've seen on 10GHz stuff - maybe why its 'only' 10dBd.
2. I have some PTFE sheet, would this be suitable as a gasket to keep the weather out of the LNB cavity, if not would HDPE from a milk carton work?
The horn sizes very quickly got very large (longer print time/too big for the printer) if I upped the target gain figure. I was surprised by this...not like adding a couple of elements to a yagi....
Comments welcome...
Gareth

 


--
Raymond G8KPS


DF6NA Rainer
 

Hi,

look for Capton tape or capton foil. Works very good !

3 samples from RS online catalog:
Hi-Bond HB830 Isolierband, Polyimid-Folie Bernstein, 0.07mm x 25mm x 33m, -20°C bis +260°C
RS PRO AT4160,Polyimid-Folie Abdeckband bronzen, 25mm x 33m
3M 5413,Polyimid-Folie Abdeckband Bernstein, 50mm x 33mm

Youeven can ask DuPond for samples of the 3M 5413 !!!

73, Rainer


Am 22.06.2021 um 14:58 schrieb Raymond Brooks:

For Sheet mica look at microwave oven spears.

 

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of KENT BRITAIN
Sent: 22 June 2021 13:09
To: UKMicrowaves@groups.io; UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Horn for 3.4GHz

 

Hi Colin

 

I usually put the window between the horn and the WG Transition.    Much smaller piece and it's out of the weather.

I like to use a sheet of Mica, but that's for X-Band and higher.  Hard to find Mica sheet big enough for 9cm but the bits for the larger power transistors is OK for WG16.  Also the Teflon Tape used in plumbing works well.  But again a pretty big piece for 9 cm but the standard tape works well at 3 cm and higher.   73 Kent

 

On Tuesday, June 22, 2021, 05:57:25 AM CDT, Colin Ranson <g8lbs@...> wrote:

 

 

Yes please. Ideas for thin 10GHz transparent materials for weather proofing horns, feeds etc. Milk bottle material sounds good and is plentiful !

 

Colin de G8LBS.

 

Sent from Mail for Windows 10

 

From: Andy G4JNT
Sent: 22 June 2021 08:40
To: UK Microwaves groups.io
Subject: Re: [UKMicrowaves] Horn for 3.4GHz

 

I use the old software written by G8AGN decades ago for horn design, updated for 32 bit OS and now with graphical output including a cutting template.

Here are my values for a 12.1 dBi gain Horn (Why, ever, specify gains in dBd ??????)

 

 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 08:28, Gareth G4XAT via groups.io <g4xat=ntlworld.com@groups.io> wrote:

My local repeater GB3JV (DATV) (Petts Wood SE London) is pretty much LOS to me at home, so rather than tie up my Titanium PLL LNB I picked up a NOS Nortel DRO commercial unit. As it needs some form of weather protection I thought I might as well add some gain too. Using this software https://www.raytechx.com/antenna-calc I then designed a 3-D printed 10dBd horn, which came out like the picture. Interior surface finish has been improved by flat filing and I will then cover with aluminium tape. 
A couple of questions....
1. It seems very 'wide' compared to horns I've seen on 10GHz stuff - maybe why its 'only' 10dBd.
2. I have some PTFE sheet, would this be suitable as a gasket to keep the weather out of the LNB cavity, if not would HDPE from a milk carton work?
The horn sizes very quickly got very large (longer print time/too big for the printer) if I upped the target gain figure. I was surprised by this...not like adding a couple of elements to a yagi....
Comments welcome...
Gareth

 


--
Raymond G8KPS


DF6NA Rainer
 

Hi Colin,

you're lucky. I found my capton foil supply. Give me your address and I can send you some.

73, Rainer


Am 22.06.2021 um 15:10 schrieb DF6NA Rainer:

Hi,

look for Capton tape or capton foil. Works very good !

3 samples from RS online catalog:
Hi-Bond HB830 Isolierband, Polyimid-Folie Bernstein, 0.07mm x 25mm x 33m, -20°C bis +260°C
RS PRO AT4160,Polyimid-Folie Abdeckband bronzen, 25mm x 33m
3M 5413,Polyimid-Folie Abdeckband Bernstein, 50mm x 33mm

Youeven can ask DuPond for samples of the 3M 5413 !!!

73, Rainer


Am 22.06.2021 um 14:58 schrieb Raymond Brooks:

For Sheet mica look at microwave oven spears.

 

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of KENT BRITAIN
Sent: 22 June 2021 13:09
To: UKMicrowaves@groups.io; UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Horn for 3.4GHz

 

Hi Colin

 

I usually put the window between the horn and the WG Transition.    Much smaller piece and it's out of the weather.

I like to use a sheet of Mica, but that's for X-Band and higher.  Hard to find Mica sheet big enough for 9cm but the bits for the larger power transistors is OK for WG16.  Also the Teflon Tape used in plumbing works well.  But again a pretty big piece for 9 cm but the standard tape works well at 3 cm and higher.   73 Kent

 

On Tuesday, June 22, 2021, 05:57:25 AM CDT, Colin Ranson <g8lbs@...> wrote:

 

 

Yes please. Ideas for thin 10GHz transparent materials for weather proofing horns, feeds etc. Milk bottle material sounds good and is plentiful !

 

Colin de G8LBS.

 

Sent from Mail for Windows 10

 

From: Andy G4JNT
Sent: 22 June 2021 08:40
To: UK Microwaves groups.io
Subject: Re: [UKMicrowaves] Horn for 3.4GHz

 

I use the old software written by G8AGN decades ago for horn design, updated for 32 bit OS and now with graphical output including a cutting template.

Here are my values for a 12.1 dBi gain Horn (Why, ever, specify gains in dBd ??????)

 

 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 08:28, Gareth G4XAT via groups.io <g4xat=ntlworld.com@groups.io> wrote:

My local repeater GB3JV (DATV) (Petts Wood SE London) is pretty much LOS to me at home, so rather than tie up my Titanium PLL LNB I picked up a NOS Nortel DRO commercial unit. As it needs some form of weather protection I thought I might as well add some gain too. Using this software https://www.raytechx.com/antenna-calc I then designed a 3-D printed 10dBd horn, which came out like the picture. Interior surface finish has been improved by flat filing and I will then cover with aluminium tape. 
A couple of questions....
1. It seems very 'wide' compared to horns I've seen on 10GHz stuff - maybe why its 'only' 10dBd.
2. I have some PTFE sheet, would this be suitable as a gasket to keep the weather out of the LNB cavity, if not would HDPE from a milk carton work?
The horn sizes very quickly got very large (longer print time/too big for the printer) if I upped the target gain figure. I was surprised by this...not like adding a couple of elements to a yagi....
Comments welcome...
Gareth

 


--
Raymond G8KPS



Colin Ranson
 

Hi All, this is the ‘horn’ I hope to use at 10GHz – the mouth is 75mm and the other end 40mm for easy mounting.  A 22mm copper pipe with an SMA transition will complete. No idea what the gain will be or if it will even be suitable for an 80cm round offset dish.  I have lost the original weather proofing cap hence ideas for weather proofing material.

 

Thanks for all your suggestions.

 

Absolute beginner at 10GHz !  de G8LBS.

 

Sent from Mail for Windows 10

 

From: Neil Smith G4DBN
Sent: 22 June 2021 12:56
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Horn for 3.4GHz

 

"Styrene" modelling sheet from model suppliers is actually polystyrene and performs well. HDPE has a loss tangent almost as good as polystyrene and PTFE.  PS is nice because it is reasonably stiff.  Ideally you want something hydrophobic so water drops just fall off. Polyurethane also works, and even fairly-lossy Kapton is OK, so long as it is very thin.

I've bought some CCTV camera domes that work well as radomes.  They may be acrylic, but they are thin and appear to have no measurable loss up to 10 GHz.

Neil G4DBN

On 22/06/2021 11:57, Colin Ranson wrote:

Yes please. Ideas for thin 10GHz transparent materials for weather proofing horns, feeds etc. Milk bottle material sounds good and is plentiful !

 

 

 

 


dave G8SFU
 

Also worth a look at toaster element supports. Often about 5inches square.
Dave g8sfu

Sent from BlueMail

On 22 Jun 2021, at 14:53, Raymond Brooks <g8kps@...> wrote:

For Sheet mica look at microwave oven spears.

 

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of KENT BRITAIN
Sent: 22 June 2021 13:09
To: UKMicrowaves@groups.io; UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Horn for 3.4GHz

 

Hi Colin

 

I usually put the window between the horn and the WG Transition.    Much smaller piece and it's out of the weather.

I like to use a sheet of Mica, but that's for X-Band and higher.  Hard to find Mica sheet big enough for 9cm but the bits for the larger power transistors is OK 

 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 08:28, Gareth G4XAT via groups.io <g4xat=ntlworld.com@groups.io> wrote:

My local repeater GB3JV (DATV) (Petts Wood SE London) is pretty much LOS to me at home, so rather than tie up my Titanium PLL LNB I picked up a NOS Nortel DRO commercial unit. As it needs some form of weather protection I thought I might as well add some gain too. Using this software https://www.raytechx.com/antenna-calc I then designed a 3-D printed 10dBd horn, which came out like the picture. Interior surface finish has been improved by flat filing and I will then cover with aluminium tape. 
A couple of questions....
1. It seems very 'wide' compared to horns I've seen on 10GHz stuff - maybe why its 'only' 10dBd.
2. I have some PTFE sheet, would this be suitable as a gasket to keep the weather out of the LNB cavity, if not would HDPE from a milk carton work?
The horn sizes very quickly got very large (longer print time/too big for the printer) if I upped the target gain figure. I was surprised by this...not like adding a couple of elements to a yagi....
Comments welcome...
Gareth

 


--
Raymond G8KPS


Colin Ranson
 

Dave, just retired a big triple toaster, its in the loft.....wonder if the missus will miss it ?

 

73’s   Colin.

 

Sent from Mail for Windows 10

 

From: dave G8SFU via groups.io
Sent: 22 June 2021 16:13
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Horn for 3.4GHz

 

Also worth a look at toaster element supports. Often about 5inches square.

Dave g8sfu

Sent from BlueMail

On 22 Jun 2021, at 14:53, Raymond Brooks <g8kps@...> wrote:

For Sheet mica look at microwave oven spears.

 

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of KENT BRITAIN
Sent: 22 June 2021 13:09
To: UKMicrowaves@groups.io; UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Horn for 3.4GHz

 

Hi Colin

 

I usually put the window between the horn and the WG Transition.    Much smaller piece and it's out of the weather.

I like to use a sheet of Mica, but that's for X-Band and higher.  Hard to find Mica sheet big enough for 9cm but the bits for the larger power transistors is OK 

 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 08:28, Gareth G4XAT via groups.io <g4xat=ntlworld.com@groups.io> wrote:

My local repeater GB3JV (DATV) (Petts Wood SE London) is pretty much LOS to me at home, so rather than tie up my Titanium PLL LNB I picked up a NOS Nortel DRO commercial unit. As it needs some form of weather protection I thought I might as well add some gain too. Using this software https://www.raytechx.com/antenna-calc I then designed a 3-D printed 10dBd horn, which came out like the picture. Interior surface finish has been improved by flat filing and I will then cover with aluminium tape. 
A couple of questions....
1. It seems very 'wide' compared to horns I've seen on 10GHz stuff - maybe why its 'only' 10dBd.
2. I have some PTFE sheet, would this be suitable as a gasket to keep the weather out of the LNB cavity, if not would HDPE from a milk carton work?
The horn sizes very quickly got very large (longer print time/too big for the printer) if I upped the target gain figure. I was surprised by this...not like adding a couple of elements to a yagi....
Comments welcome...
Gareth

 


--
Raymond G8KPS

 


Gareth G4XAT
 

Sorry I didn't make that clear - I was always going to mount the 'gasket' between the WG and the Horn as it has a nice neoprene gasket in the WG already and will be very well clamped and holfully sealed. Got the aluminium tape today from screwfix and have covered the horn. Looks fine and the surface if very smooth too. 
Regarding dBd, I always understood that dBi refers to isotropic and that 'real' gain starts when it gets better than a dipole ;-)
Gareth


Andy G4JNT
 

dBd is just gain referred to a dipole; which already has 2.15dBi gain.
So gain referred to in dBd is 2.15dB lower than gain specified in dBi.
There is this daft idea that at freqencies below 1GHz, that once upon a time when antennas were measured by substitution, because a dipole was used as a reference, the resulting gain measurement should then be referred to it.
When you need antenna gain in link budget calculations, or use it to get beamwidths, or whatever, you always need dBi.   So why on Earth do not just amateurs, but others too still persist in specifying gain reltive to some arbitrary dipole escapes me.

TO add real daftness to reality, in the amateur licence radiated powers for the two lowest bands are specified using both standards:
On 137kHz its 1 Watt EDRP (ie = 1W to a dipole),   but on 475kHz its 5W EIRP (ie 5W to an isotropic antenna)

WHY ???????????????



On Tue, 22 Jun 2021 at 19:59, Gareth G4XAT via groups.io <g4xat=ntlworld.com@groups.io> wrote:
Regarding dBd, I always understood that dBi refers to isotropic and that 'real' gain starts when it gets better than a dipole ;-)
Gareth


dave G8SFU
 

If the rules are the same as in our house the boss would say that should go on a skip. My stock answer is "stop swearing".
We don't use the sk.. word here.

If the parts are useful they should be used.

Regards.  Dave.   Sfu

Sent from BlueMail

On 22 Jun 2021, at 18:38, Colin Ranson <g8lbs@...> wrote:

Dave, just retired a big triple toaster, its in the loft.....wonder if the missus will miss it ?

 

73’s   Colin.

 

Sent from Mail for Windows 10

 

From: dave G8SFU via groups.io
Sent: 22 June 2021 16:13
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Horn for 3.4GHz

 

Also worth a look at toaster element supports. Often about 5inches square.

Dave g8sfu

Sent from BlueMail

On 22 Jun 2021, at 14:53, Raymond Brooks <g8kps@...> wrote:

For Sheet mica look at microwave oven spears.

 

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of KENT BRITAIN
Sent: 22 June 2021 13:09
To: UKMicrowaves@groups.io; UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Horn for 3.4GHz

 

Hi Colin

 

I usually put the window between the horn and the WG Transition.    Much smaller piece and it's out of the weather.

I like to use a sheet of Mica, but that's for X-Band and higher.  Hard to find Mica sheet big enough for 9cm but the bits for the larger power transistors is OK 

 

 

Andy

 

 

 

On Tue, 22 Jun 2021 at 08:28, Gareth G4XAT via groups.io <g4xat=ntlworld.com@groups.io> wrote:

My local repeater GB3JV (DATV) (Petts Wood SE London) is pretty much LOS to me at home, so rather than tie up my Titanium PLL LNB I picked up a NOS Nortel DRO commercial unit. As it needs some form of weather protection I thought I might as well add some gain too. Using this software https://www.raytechx.com/antenna-calc I then designed a 3-D printed 10dBd horn, which came out like the picture. Interior surface finish has been improved by flat filing and I will then cover with aluminium tape. 
A couple of questions....
1. It seems very 'wide' compared to horns I've seen on 10GHz stuff - maybe why its 'only' 10dBd.
2. I have some PTFE sheet, would this be suitable as a gasket to keep the weather out of the LNB cavity, if not would HDPE from a milk carton work?
The horn sizes very quickly got very large (longer print time/too big for the printer) if I upped the target gain figure. I was surprised by this...not like adding a couple of elements to a yagi....
Comments welcome...
Gareth

 


--
Raymond G8KPS