Date   
Re: It's gone very quiet. Is no one Microwaving (other than their (porridge)

Ed G3VPF
 

Regarding Zello, I too get the same problem as Denis. I am connected but hear nothing. In a week of monitoring it sprung to life for about an hour last Monday but otherwise nothing. Echo works OK. SHFchat has two blue circles against it. Any help with how to make it work would be welcome.

Zello is installed on an Android phone.

On Thursday, November 22, 2018, 19:39, G3UVR Denis via Groups.Io <g3uvr@...> wrote:

All.

Now this microwave activity thread has diverted to Zello can I seize the oppertunity to ask a question about its configuration.

Since I installed the application just a few weeks ago (thanks Neil DBN for the suggestion) I did hear people talking during the last Sunday Microwave group contest (G4DBN G4UVZ GM0USI and G4CBW) in the GM microwave chat.  I now discover that there is also the SHFchat. Since that last contest a few weeks back I have never heard anybody talking since in hours of monitoring.

Right now I have connected to GM Microwave seeing four users and SHF chat seeing fifteen users but I hear no conversation traffic. I cant even see a list of connected users logged in.

Am I missing something?

73 de Denis G3UVR

Re: dis-assembling an octogon lnb

Richard <richard@...>
 

Hi John
Thanks for the info, especially on the holes.
I got a dual head so that one can be modified for NB and the other for wide band,
ie plug in to a normal Sat RX
I'm making the assumption its two separate Rx boards as each can be independently powered
I'll use a separate dish for Tx, should it survive up there, I've spare 1.2mtr prime focus dish
thats somewhere around 26dB of gain, so a couple of watts at 2400 should do .
I'm glad its now 25MHz for the LO as that make life easier, I can either divide the 100MHz o/p from the SV1AFN GPSDO
by 4 or multiple the 5MHz from a OCXO by 5 . probably the latter as it will be cleaner.


On Fri, 2018-11-23 at 10:39 +0000, John Fell wrote:
Unless you are modifying the horn of the Octagon DO NOT remove the horn cap ( Hermetic seal) .The body covers are snap locked together and can be separated with careful insertion of a thin blade at the rear (socket) end .You can then clip it back on later .The screws are Torx type to retain the diecast lid .
The small holes seen around the F types area are breather vents only and do not have screws inside .

John
G0API

On Fri, 23 Nov 2018 at 10:00, Richard <richard@...> wrote:
Thanks Alan
That saves damaging the unit while getting it apart.

On Fri, 2018-11-23 at 09:53 +0000, Alan Melia via Groups.Io wrote:
> Hi Richard the single OSLO version I just took apart required the
> white
> plastic cover removing. I did this by prising the horn cover forward
> and
> gently splitting the rearcover down the seam. You are then faced with
> a cast
> ali (?) body with a flat lid held by 3 small bolts and sealed with a
> red
> silicone. The bolts have what looks like a hex head, but it is in
> fact a
> slightly star-shaped ''secutity'' bolt. I found the smallest tool in
> the
> Draper SEC33 security socket set fits them nicely. I scraped the
> sealant
> clear with a craft knife. but dont think this is necessary. Removing
> the lid
> with the craft knife (take it carefully !!) exposes the pcb with a
> 25MHz
> surface mount crystal. That is as far as I got!
>
> Alan
> G3NYK
>
>
> ----- Original Message -----
> From: "Richard" <richard@...>
> To: <UKMicrowaves@groups.io>
> Sent: Thursday, November 22, 2018 11:25 PM
> Subject: [UKMicrowaves] dis-assembling an octogon lnb
>
>
> > Hi
> > I've now got one of these,, and a quick look shows 6 little holes
> > around the F type connectors.
> > Are there tiny screws at the bottom of those holes or do the covers
> > just clip together, and pressure needs putting on the joins to pop
> > apart ?
> > --
> > Best wishes /73
> > Richard Bown
> >
> > Email : richard@...
> >
> > HTTP  :  http://www.g8jvm.com
> >
> > ###################################################################
> > ###
> >
> > Ham Call: G8JVM . QRV: 50-432 MHz + Microwave
> > Maidenhead QRA: IO82SP38, LAT. 52 39.720' N LONG. 2 28.171 W
> > QRV 6mtrs 200W, 4mtrs 150W, 2mtrs 300W, 70cms 200W,
> > Microwave 1296MHz 140W, 2320MHz 100W & 10368MHz 5W
> > OS: Linux Mint 19 x86_64 Tara, on a Dell Inspiron N5030 laptop
> > ###################################################################
> > ###
> >
> >
> >
> >
> >
>
>
>
>

-- 
 Best wishes /73 
 Richard Bown
 
 Email : richard@...

 HTTP  :  http://www.g8jvm.com
 
 ######################################################################

 Ham Call: G8JVM . QRV: 50-432 MHz + Microwave 
 Maidenhead QRA: IO82SP38, LAT. 52 39.720' N LONG. 2 28.171 W
 QRV 6mtrs 200W, 4mtrs 150W, 2mtrs 300W, 70cms 200W, 
Microwave 1296MHz 140W, 2320MHz 100W & 10368MHz 5W
 OS: Linux Mint 19 x86_64 Tara, on a Dell Inspiron N5030 laptop
 ######################################################################

Re: Using PU foam in feedhorns?

Alan Melia
 


Hi Simon, yes I remember Hydrogen......I received a valve at DH from the shore end of CANTAT where we could not get the cathode  to emit. When we cracked the valve in the mass spectrometer it was full of hydrogen. This had reduced the metal-oxide-glass seal round the pins allowing the valve to suck in hydrogen from the repeater body. It was produced by electrochemical reaction between the repeater casing and the sacrificial anode, meant to stop the steel case rusting.
 
Alan
G3NYK
 

----- Original Message -----
Sent: Friday, November 23, 2018 12:42 AM
Subject: Re: [UKMicrowaves] Using PU foam in feedhorns?

Back in the 70s we realised how Ions can penetrate “solid plastic” – working on submarine cables with PC insulation the amount of hydrogen that appeared in the centre conductor was surprising and interesting – to repair a joint you could (but did not) use the Hydrogen flame to melt the solder for a joint repair.  All right the cables were very deep so pressure is a consideration however the ingress of H atoms was observed in cables laid in shallow waters.
 
One or two cable failures were more of a puzzle as lengths of  cable were missing – something to do with foreign trawlers I understand.
 
Simon
G8ATB
 
 
From: Alan Melia via Groups.Io
Sent: Thursday, November 22, 2018 10:34 PM
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Using PU foam in feedhorns?
 
Neil even if the foam is ''closed'', even ''solid'' plastic is really a load of holes tied together with chains of carbon, water vapour or more specifically OH ions are quite small and will diffuse in driven by the concentration gradient. Eventually every hole in the foam will be filled with water vapour or liquid water depending in the temperature. This will not do much for RF transparency I suspect. (I was involved in plastic encapsulated IC reliability and conformal coatings at BTRL.)  Dunking in water for 24 hours wont tell you much about the long term.
 
When feed horns are out of reach this is a pain but overall it is probably best to just let it drain out occasionally.
 
Alan
G3NYK.
----- Original Message -----
From: Neil Smith G4DBN
To: UKMicrowaves@groups.io
Sent: Thursday, November 22, 2018 8:50 PM
Subject: Re: [UKMicrowaves] Using PU foam in feedhorns?
 

I am confident that the only feasible ingress path is water vapour in damp air through the joints.  The open end of the horn is sealed with a PE cap, and the interior of the waveguide/horn is connected to the steel equipment box with some serious seals.  The box has a semi-permeable breather, but the waveguid is the lowest point, so any damp air might gather there.  The potential for diurnal pumping *should* be very low, but I've seen surprisingly large volumes of water inside "sealed" compartments after a year or two of temperature cycling in damp air.   As (hopefully) only water vapour (and any other fluids in the vapour-phase) will be able to get in between the joints in the aluminium parts, I think I can discount much by way of salts and other rubbish getting inside.

One simple option is just to TIG the seams on the outside of the horn, but that seems a bit extreme compared with a squirt of magic foam.

I know where there is some excess foam which has been exposed to the outside air for 5 years, so I'll carve a bit of that off and try the microwave test on it to see if there is water inside the foam.  I tried the foam in tghe microwave with no obvious heating seen, and I've got a lump of it weighted down in a bucket so I'll test that in a few days.

I need to do some work on the antenna system in a week or two anyway, so I'll have a careful check for any water droplets inside the waveguide and horn.  Ultimately, a dry air overpressure system is the solution, but I don't want to go to those lengths.

Neil G4DBN


On 22/11/2018 19:08, Richard wrote:
I'd be inclined to use your local rain water for the second part.
Tap water is pretty pure , unlike what falls out of the sky , salt ,bits of carbon etc, which could contaminate the surface.
It would avoid any misleading results
Unless of course if you are in the London area where they reckon the water has been through many kidneys before it come out of the tap.
 
On Thu, 2018-11-22 at 18:56 +0000, Richard GD8EXI wrote:
Can I suggest an experiment with B and Q polyurethane foam. Put a freshly made lump of it in a microwave oven along with a dummy load (cup of water) and see how hot it gets after say 3 minutes at full power. Then take the same the lump of foam, soak it in water for 24 hours or more, dry its surface and repeat the experiment in the microwave.

PU foam is used for microwave application as you already know for example.

https://www.generalplastics.com/wp-content/uploads/2016/12/White-Paper-PU-Foam-Dielectric-Materials-for-Use-in-Radomes-and-Other_Applications.pdf

However some of the additives in B and Q foam may make it less suitable. It only takes 1% or less of something with a high dielectric loss or something in there that make it hydroscopic to ruin the performance in a horn.


Richard
GD8EXI



On 22/11/2018, 17:16, "Barry Chambers" <wlmailhtml:b.chambers@...> wrote:

> Neil
>
> I suspect the Er will be around 1.05 at worst but you will need to think
> about whether the pores in the foam are open or closed. I'm thinking
> about water getting into the foam.
>
> 73
>
> Barry, G8AGN
>
>
>
>
-- 
Best wishes /73
Richard Bown
 
Email : richard@...
 
 
######################################################################

Ham Call: G8JVM . QRV: 50-432 MHz + Microwave
Maidenhead QRA: IO82SP38, LAT. 52 39.720' N LONG. 2 28.171 W
QRV 6mtrs 200W, 4mtrs 150W, 2mtrs 300W, 70cms 200W,
Microwave 1296MHz 140W, 2320MHz 100W & 10368MHz 5W
OS: Linux Mint 19 x86_64 Tara, on a Dell Inspiron N5030 laptop
######################################################################
 

Re: dis-assembling an octogon lnb

John Fell
 

Unless you are modifying the horn of the Octagon DO NOT remove the horn cap ( Hermetic seal) .The body covers are snap locked together and can be separated with careful insertion of a thin blade at the rear (socket) end .You can then clip it back on later .The screws are Torx type to retain the diecast lid .
The small holes seen around the F types area are breather vents only and do not have screws inside .

John
G0API

On Fri, 23 Nov 2018 at 10:00, Richard <richard@...> wrote:
Thanks Alan
That saves damaging the unit while getting it apart.

On Fri, 2018-11-23 at 09:53 +0000, Alan Melia via Groups.Io wrote:
> Hi Richard the single OSLO version I just took apart required the
> white
> plastic cover removing. I did this by prising the horn cover forward
> and
> gently splitting the rearcover down the seam. You are then faced with
> a cast
> ali (?) body with a flat lid held by 3 small bolts and sealed with a
> red
> silicone. The bolts have what looks like a hex head, but it is in
> fact a
> slightly star-shaped ''secutity'' bolt. I found the smallest tool in
> the
> Draper SEC33 security socket set fits them nicely. I scraped the
> sealant
> clear with a craft knife. but dont think this is necessary. Removing
> the lid
> with the craft knife (take it carefully !!) exposes the pcb with a
> 25MHz
> surface mount crystal. That is as far as I got!
>
> Alan
> G3NYK
>
>
> ----- Original Message -----
> From: "Richard" <richard@...>
> To: <UKMicrowaves@groups.io>
> Sent: Thursday, November 22, 2018 11:25 PM
> Subject: [UKMicrowaves] dis-assembling an octogon lnb
>
>
> > Hi
> > I've now got one of these,, and a quick look shows 6 little holes
> > around the F type connectors.
> > Are there tiny screws at the bottom of those holes or do the covers
> > just clip together, and pressure needs putting on the joins to pop
> > apart ?
> > --
> > Best wishes /73
> > Richard Bown
> >
> > Email : richard@...
> >
> > HTTP  :  http://www.g8jvm.com
> >
> > ###################################################################
> > ###
> >
> > Ham Call: G8JVM . QRV: 50-432 MHz + Microwave
> > Maidenhead QRA: IO82SP38, LAT. 52 39.720' N LONG. 2 28.171 W
> > QRV 6mtrs 200W, 4mtrs 150W, 2mtrs 300W, 70cms 200W,
> > Microwave 1296MHz 140W, 2320MHz 100W & 10368MHz 5W
> > OS: Linux Mint 19 x86_64 Tara, on a Dell Inspiron N5030 laptop
> > ###################################################################
> > ###
> >
> >
> >
> >
> >
>
>
>
>

--
 Best wishes /73
 Richard Bown

 Email : richard@...

 HTTP  :  http://www.g8jvm.com

 ######################################################################

 Ham Call: G8JVM . QRV: 50-432 MHz + Microwave
 Maidenhead QRA: IO82SP38, LAT. 52 39.720' N LONG. 2 28.171 W
 QRV 6mtrs 200W, 4mtrs 150W, 2mtrs 300W, 70cms 200W,
 Microwave 1296MHz 140W, 2320MHz 100W & 10368MHz 5W
 OS: Linux Mint 19 x86_64 Tara, on a Dell Inspiron N5030 laptop
 ######################################################################





Re: dis-assembling an octogon lnb

Mike Willis
 

I think the bolt is a Torx head. Can be quite tight. Remove all the silicone first.

If (and only if) you are interested in using the same dish for TX and TX you can convert to a dual band feed. I used a parting tool on my lathe to remove the LNB horn but a hacksaw would work too. Once you remove the horn there is a ~20mm tube that is the waveguide. This can be extended and a patch antenna attached for 2.4GHz. DJ7GP sent me some very useful info on an easy to make square patch antenna for a dualband feed for 10.5 / 2.4 GHz. 


See this link for some ideas https://www.oe7forum.at/viewtopic.php?t=284&start=135
--
Mike G0MJW

23cm driver kits update

John Worsnop
 

The PCBs have been handed to DHL in China for shipping.

73 John 

Re: It's gone very quiet. Is no one Microwaving (other than their (porridge)

John Fell
 

Looking at the Labgear pic it seems to allow a DC path through each branch of the split ports .
This implies that there is no DC blocking cap to stop Volts arriving at the input to the 618MHZ  RX . 
A basic USB dongle may well have an input DC blocking cap , but several of the more advanced SDR devices allow selectable DC output to antenna pre-amps . Damage could occur if the 12V+DC injected for the LNB got into this other source.


A bias T would normally insert a DC blocking Cap in the 618MHZ port to prevent the above and a suitable choke in the DC injection port to stop the wanted 618MHZ going into the DC feed circuit , causing attenuation .

73
John
G0API


On Thu, 22 Nov 2018 at 20:55, Mike G4TVP <mike_cat_taylor@...> wrote:
Thank you for the advice John much appreciated. Some it went over my head a little, but we will see where I get to.

I seem to have a two way splitter (Labgear FBS402s), which I must of used in the past. Is there any benefit/drawback on this approach rather than using a biasT?

Re: dis-assembling an octogon lnb

Richard <richard@...>
 

Thanks Alan
That saves damaging the unit while getting it apart.

On Fri, 2018-11-23 at 09:53 +0000, Alan Melia via Groups.Io wrote:
Hi Richard the single OSLO version I just took apart required the
white
plastic cover removing. I did this by prising the horn cover forward
and
gently splitting the rearcover down the seam. You are then faced with
a cast
ali (?) body with a flat lid held by 3 small bolts and sealed with a
red
silicone. The bolts have what looks like a hex head, but it is in
fact a
slightly star-shaped ''secutity'' bolt. I found the smallest tool in
the
Draper SEC33 security socket set fits them nicely. I scraped the
sealant
clear with a craft knife. but dont think this is necessary. Removing
the lid
with the craft knife (take it carefully !!) exposes the pcb with a
25MHz
surface mount crystal. That is as far as I got!

Alan
G3NYK


----- Original Message -----
From: "Richard" <richard@...>
To: <UKMicrowaves@groups.io>
Sent: Thursday, November 22, 2018 11:25 PM
Subject: [UKMicrowaves] dis-assembling an octogon lnb


Hi
I've now got one of these,, and a quick look shows 6 little holes
around the F type connectors.
Are there tiny screws at the bottom of those holes or do the covers
just clip together, and pressure needs putting on the joins to pop
apart ?
--
Best wishes /73
Richard Bown

Email : richard@...

HTTP : http://www.g8jvm.com

###################################################################
###

Ham Call: G8JVM . QRV: 50-432 MHz + Microwave
Maidenhead QRA: IO82SP38, LAT. 52 39.720' N LONG. 2 28.171 W
QRV 6mtrs 200W, 4mtrs 150W, 2mtrs 300W, 70cms 200W,
Microwave 1296MHz 140W, 2320MHz 100W & 10368MHz 5W
OS: Linux Mint 19 x86_64 Tara, on a Dell Inspiron N5030 laptop
###################################################################
###






--
Best wishes /73
Richard Bown

Email : richard@...

HTTP : http://www.g8jvm.com

######################################################################

Ham Call: G8JVM . QRV: 50-432 MHz + Microwave
Maidenhead QRA: IO82SP38, LAT. 52 39.720' N LONG. 2 28.171 W
QRV 6mtrs 200W, 4mtrs 150W, 2mtrs 300W, 70cms 200W,
Microwave 1296MHz 140W, 2320MHz 100W & 10368MHz 5W
OS: Linux Mint 19 x86_64 Tara, on a Dell Inspiron N5030 laptop
######################################################################

Re: dis-assembling an octogon lnb

Alan Melia
 

Hi Richard the single OSLO version I just took apart required the white plastic cover removing. I did this by prising the horn cover forward and gently splitting the rearcover down the seam. You are then faced with a cast ali (?) body with a flat lid held by 3 small bolts and sealed with a red silicone. The bolts have what looks like a hex head, but it is in fact a slightly star-shaped ''secutity'' bolt. I found the smallest tool in the Draper SEC33 security socket set fits them nicely. I scraped the sealant clear with a craft knife. but dont think this is necessary. Removing the lid with the craft knife (take it carefully !!) exposes the pcb with a 25MHz surface mount crystal. That is as far as I got!

Alan
G3NYK

----- Original Message -----
From: "Richard" <richard@...>
To: <UKMicrowaves@groups.io>
Sent: Thursday, November 22, 2018 11:25 PM
Subject: [UKMicrowaves] dis-assembling an octogon lnb


Hi
I've now got one of these,, and a quick look shows 6 little holes
around the F type connectors.
Are there tiny screws at the bottom of those holes or do the covers
just clip together, and pressure needs putting on the joins to pop
apart ?
--
Best wishes /73
Richard Bown

Email : richard@...

HTTP : http://www.g8jvm.com

######################################################################

Ham Call: G8JVM . QRV: 50-432 MHz + Microwave
Maidenhead QRA: IO82SP38, LAT. 52 39.720' N LONG. 2 28.171 W
QRV 6mtrs 200W, 4mtrs 150W, 2mtrs 300W, 70cms 200W,
Microwave 1296MHz 140W, 2320MHz 100W & 10368MHz 5W
OS: Linux Mint 19 x86_64 Tara, on a Dell Inspiron N5030 laptop
######################################################################



Re: Using PU foam in feedhorns?

F6DRO
 

Hi All ,

I am using this , I have it pasted on my 3cm horn for something like 10 years and never got the sligthest trace of water.
73
Dom

Le 22/11/2018 18:16, Barry Chambers a écrit :
Neil

I suspect the Er will be around 1.05 at worst but you will need to think about whether the pores in the foam are open or closed. I'm thinking about water getting into the foam.

73

Barry, G8AGN



Re: Using PU foam in feedhorns?

simonchettle
 

Back in the 70s we realised how Ions can penetrate “solid plastic” – working on submarine cables with PC insulation the amount of hydrogen that appeared in the centre conductor was surprising and interesting – to repair a joint you could (but did not) use the Hydrogen flame to melt the solder for a joint repair.  All right the cables were very deep so pressure is a consideration however the ingress of H atoms was observed in cables laid in shallow waters.
 
One or two cable failures were more of a puzzle as lengths of  cable were missing – something to do with foreign trawlers I understand.
 
Simon
G8ATB
 
 

From: Alan Melia via Groups.Io
Sent: Thursday, November 22, 2018 10:34 PM
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Using PU foam in feedhorns?
 
Neil even if the foam is ''closed'', even ''solid'' plastic is really a load of holes tied together with chains of carbon, water vapour or more specifically OH ions are quite small and will diffuse in driven by the concentration gradient. Eventually every hole in the foam will be filled with water vapour or liquid water depending in the temperature. This will not do much for RF transparency I suspect. (I was involved in plastic encapsulated IC reliability and conformal coatings at BTRL.)  Dunking in water for 24 hours wont tell you much about the long term.
 
When feed horns are out of reach this is a pain but overall it is probably best to just let it drain out occasionally.
 
Alan
G3NYK.
----- Original Message -----
From: Neil Smith G4DBN
To: UKMicrowaves@groups.io
Sent: Thursday, November 22, 2018 8:50 PM
Subject: Re: [UKMicrowaves] Using PU foam in feedhorns?
 

I am confident that the only feasible ingress path is water vapour in damp air through the joints.  The open end of the horn is sealed with a PE cap, and the interior of the waveguide/horn is connected to the steel equipment box with some serious seals.  The box has a semi-permeable breather, but the waveguid is the lowest point, so any damp air might gather there.  The potential for diurnal pumping *should* be very low, but I've seen surprisingly large volumes of water inside "sealed" compartments after a year or two of temperature cycling in damp air.   As (hopefully) only water vapour (and any other fluids in the vapour-phase) will be able to get in between the joints in the aluminium parts, I think I can discount much by way of salts and other rubbish getting inside.

One simple option is just to TIG the seams on the outside of the horn, but that seems a bit extreme compared with a squirt of magic foam.

I know where there is some excess foam which has been exposed to the outside air for 5 years, so I'll carve a bit of that off and try the microwave test on it to see if there is water inside the foam.  I tried the foam in tghe microwave with no obvious heating seen, and I've got a lump of it weighted down in a bucket so I'll test that in a few days.

I need to do some work on the antenna system in a week or two anyway, so I'll have a careful check for any water droplets inside the waveguide and horn.  Ultimately, a dry air overpressure system is the solution, but I don't want to go to those lengths.

Neil G4DBN


On 22/11/2018 19:08, Richard wrote:
I'd be inclined to use your local rain water for the second part.
Tap water is pretty pure , unlike what falls out of the sky , salt ,bits of carbon etc, which could contaminate the surface.
It would avoid any misleading results
Unless of course if you are in the London area where they reckon the water has been through many kidneys before it come out of the tap.
 
On Thu, 2018-11-22 at 18:56 +0000, Richard GD8EXI wrote:
Can I suggest an experiment with B and Q polyurethane foam. Put a freshly made lump of it in a microwave oven along with a dummy load (cup of water) and see how hot it gets after say 3 minutes at full power. Then take the same the lump of foam, soak it in water for 24 hours or more, dry its surface and repeat the experiment in the microwave.

PU foam is used for microwave application as you already know for example.

https://www.generalplastics.com/wp-content/uploads/2016/12/White-Paper-PU-Foam-Dielectric-Materials-for-Use-in-Radomes-and-Other_Applications.pdf

However some of the additives in B and Q foam may make it less suitable. It only takes 1% or less of something with a high dielectric loss or something in there that make it hydroscopic to ruin the performance in a horn.


Richard
GD8EXI



On 22/11/2018, 17:16, "Barry Chambers" <wlmailhtml:b.chambers@...> wrote:

> Neil
>
> I suspect the Er will be around 1.05 at worst but you will need to think
> about whether the pores in the foam are open or closed. I'm thinking
> about water getting into the foam.
>
> 73
>
> Barry, G8AGN
>
>
>
>
-- 
Best wishes /73
Richard Bown
 
Email : richard@...
 
 
######################################################################

Ham Call: G8JVM . QRV: 50-432 MHz + Microwave
Maidenhead QRA: IO82SP38, LAT. 52 39.720' N LONG. 2 28.171 W
QRV 6mtrs 200W, 4mtrs 150W, 2mtrs 300W, 70cms 200W,
Microwave 1296MHz 140W, 2320MHz 100W & 10368MHz 5W
OS: Linux Mint 19 x86_64 Tara, on a Dell Inspiron N5030 laptop
######################################################################
 

dis-assembling an octogon lnb

Richard <richard@...>
 

Hi
I've now got one of these,, and a quick look shows 6 little holes
around the F type connectors.
Are there tiny screws at the bottom of those holes or do the covers
just clip together, and pressure needs putting on the joins to pop
apart ?
--
Best wishes /73
Richard Bown

Email : richard@...

HTTP : http://www.g8jvm.com

######################################################################

Ham Call: G8JVM . QRV: 50-432 MHz + Microwave
Maidenhead QRA: IO82SP38, LAT. 52 39.720' N LONG. 2 28.171 W
QRV 6mtrs 200W, 4mtrs 150W, 2mtrs 300W, 70cms 200W,
Microwave 1296MHz 140W, 2320MHz 100W & 10368MHz 5W
OS: Linux Mint 19 x86_64 Tara, on a Dell Inspiron N5030 laptop
######################################################################

Re: Using PU foam in feedhorns?

Alan Melia
 


Neil even if the foam is ''closed'', even ''solid'' plastic is really a load of holes tied together with chains of carbon, water vapour or more specifically OH ions are quite small and will diffuse in driven by the concentration gradient. Eventually every hole in the foam will be filled with water vapour or liquid water depending in the temperature. This will not do much for RF transparency I suspect. (I was involved in plastic encapsulated IC reliability and conformal coatings at BTRL.)  Dunking in water for 24 hours wont tell you much about the long term.
 
When feed horns are out of reach this is a pain but overall it is probably best to just let it drain out occasionally.
 
Alan
G3NYK.

----- Original Message -----
Sent: Thursday, November 22, 2018 8:50 PM
Subject: Re: [UKMicrowaves] Using PU foam in feedhorns?

I am confident that the only feasible ingress path is water vapour in damp air through the joints.  The open end of the horn is sealed with a PE cap, and the interior of the waveguide/horn is connected to the steel equipment box with some serious seals.  The box has a semi-permeable breather, but the waveguid is the lowest point, so any damp air might gather there.  The potential for diurnal pumping *should* be very low, but I've seen surprisingly large volumes of water inside "sealed" compartments after a year or two of temperature cycling in damp air.   As (hopefully) only water vapour (and any other fluids in the vapour-phase) will be able to get in between the joints in the aluminium parts, I think I can discount much by way of salts and other rubbish getting inside.

One simple option is just to TIG the seams on the outside of the horn, but that seems a bit extreme compared with a squirt of magic foam.

I know where there is some excess foam which has been exposed to the outside air for 5 years, so I'll carve a bit of that off and try the microwave test on it to see if there is water inside the foam.  I tried the foam in tghe microwave with no obvious heating seen, and I've got a lump of it weighted down in a bucket so I'll test that in a few days.

I need to do some work on the antenna system in a week or two anyway, so I'll have a careful check for any water droplets inside the waveguide and horn.  Ultimately, a dry air overpressure system is the solution, but I don't want to go to those lengths.

Neil G4DBN


On 22/11/2018 19:08, Richard wrote:
I'd be inclined to use your local rain water for the second part.
Tap water is pretty pure , unlike what falls out of the sky , salt ,bits of carbon etc, which could contaminate the surface.
It would avoid any misleading results
Unless of course if you are in the London area where they reckon the water has been through many kidneys before it come out of the tap.

On Thu, 2018-11-22 at 18:56 +0000, Richard GD8EXI wrote:
Can I suggest an experiment with B and Q polyurethane foam. Put a freshly made lump of it in a microwave oven along with a dummy load (cup of water) and see how hot it gets after say 3 minutes at full power. Then take the same the lump of foam, soak it in water for 24 hours or more, dry its surface and repeat the experiment in the microwave.

PU foam is used for microwave application as you already know for example.

https://www.generalplastics.com/wp-content/uploads/2016/12/White-Paper-PU-Foam-Dielectric-Materials-for-Use-in-Radomes-and-Other_Applications.pdf

However some of the additives in B and Q foam may make it less suitable. It only takes 1% or less of something with a high dielectric loss or something in there that make it hydroscopic to ruin the performance in a horn.


Richard
GD8EXI



On 22/11/2018, 17:16, "Barry Chambers" <b.chambers@...> wrote:

> Neil
>
> I suspect the Er will be around 1.05 at worst but you will need to think
> about whether the pores in the foam are open or closed. I'm thinking
> about water getting into the foam.
>
> 73
>
> Barry, G8AGN
>
>
>
>
-- 
 Best wishes /73 
 Richard Bown
 
 Email : richard@...

 HTTP  :  http://www.g8jvm.com
 
 ######################################################################

 Ham Call: G8JVM . QRV: 50-432 MHz + Microwave 
 Maidenhead QRA: IO82SP38, LAT. 52 39.720' N LONG. 2 28.171 W
 QRV 6mtrs 200W, 4mtrs 150W, 2mtrs 300W, 70cms 200W, 
Microwave 1296MHz 140W, 2320MHz 100W & 10368MHz 5W
 OS: Linux Mint 19 x86_64 Tara, on a Dell Inspiron N5030 laptop
 ######################################################################


Re: It's gone very quiet. Is no one Microwaving (other than their (porridge)

Mike G4TVP <mike_cat_taylor@...>
 

Thank you for the advice John much appreciated. Some it went over my head a little, but we will see where I get to.

I seem to have a two way splitter (Labgear FBS402s), which I must of used in the past. Is there any benefit/drawback on this approach rather than using a biasT?

Re: Using PU foam in feedhorns?

Neil Smith G4DBN
 

I am confident that the only feasible ingress path is water vapour in damp air through the joints.  The open end of the horn is sealed with a PE cap, and the interior of the waveguide/horn is connected to the steel equipment box with some serious seals.  The box has a semi-permeable breather, but the waveguid is the lowest point, so any damp air might gather there.  The potential for diurnal pumping *should* be very low, but I've seen surprisingly large volumes of water inside "sealed" compartments after a year or two of temperature cycling in damp air.   As (hopefully) only water vapour (and any other fluids in the vapour-phase) will be able to get in between the joints in the aluminium parts, I think I can discount much by way of salts and other rubbish getting inside.

One simple option is just to TIG the seams on the outside of the horn, but that seems a bit extreme compared with a squirt of magic foam.

I know where there is some excess foam which has been exposed to the outside air for 5 years, so I'll carve a bit of that off and try the microwave test on it to see if there is water inside the foam.  I tried the foam in tghe microwave with no obvious heating seen, and I've got a lump of it weighted down in a bucket so I'll test that in a few days.

I need to do some work on the antenna system in a week or two anyway, so I'll have a careful check for any water droplets inside the waveguide and horn.  Ultimately, a dry air overpressure system is the solution, but I don't want to go to those lengths.

Neil G4DBN


On 22/11/2018 19:08, Richard wrote:
I'd be inclined to use your local rain water for the second part.
Tap water is pretty pure , unlike what falls out of the sky , salt ,bits of carbon etc, which could contaminate the surface.
It would avoid any misleading results
Unless of course if you are in the London area where they reckon the water has been through many kidneys before it come out of the tap.

On Thu, 2018-11-22 at 18:56 +0000, Richard GD8EXI wrote:
Can I suggest an experiment with B and Q polyurethane foam. Put a freshly made lump of it in a microwave oven along with a dummy load (cup of water) and see how hot it gets after say 3 minutes at full power. Then take the same the lump of foam, soak it in water for 24 hours or more, dry its surface and repeat the experiment in the microwave.

PU foam is used for microwave application as you already know for example.

https://www.generalplastics.com/wp-content/uploads/2016/12/White-Paper-PU-Foam-Dielectric-Materials-for-Use-in-Radomes-and-Other_Applications.pdf

However some of the additives in B and Q foam may make it less suitable. It only takes 1% or less of something with a high dielectric loss or something in there that make it hydroscopic to ruin the performance in a horn.


Richard
GD8EXI



On 22/11/2018, 17:16, "Barry Chambers" <b.chambers@...> wrote:

> Neil
>
> I suspect the Er will be around 1.05 at worst but you will need to think
> about whether the pores in the foam are open or closed. I'm thinking
> about water getting into the foam.
>
> 73
>
> Barry, G8AGN
>
>
>
>
-- 
 Best wishes /73 
 Richard Bown
 
 Email : richard@...

 HTTP  :  http://www.g8jvm.com
 
 ######################################################################

 Ham Call: G8JVM . QRV: 50-432 MHz + Microwave 
 Maidenhead QRA: IO82SP38, LAT. 52 39.720' N LONG. 2 28.171 W
 QRV 6mtrs 200W, 4mtrs 150W, 2mtrs 300W, 70cms 200W, 
Microwave 1296MHz 140W, 2320MHz 100W & 10368MHz 5W
 OS: Linux Mint 19 x86_64 Tara, on a Dell Inspiron N5030 laptop
 ######################################################################


Re: It's gone very quiet. Is no one Microwaving (other than their (porridge)

G3UVR Denis
 

All.

Now this microwave activity thread has diverted to Zello can I seize the oppertunity to ask a question about its configuration.

Since I installed the application just a few weeks ago (thanks Neil DBN for the suggestion) I did hear people talking during the last Sunday Microwave group contest (G4DBN G4UVZ GM0USI and G4CBW) in the GM microwave chat.  I now discover that there is also the SHFchat. Since that last contest a few weeks back I have never heard anybody talking since in hours of monitoring.

Right now I have connected to GM Microwave seeing four users and SHF chat seeing fifteen users but I hear no conversation traffic. I cant even see a list of connected users logged in.

Am I missing something?

73 de Denis G3UVR

Re: Using PU foam in feedhorns?

Richard <richard@...>
 

I'd be inclined to use your local rain water for the second part.
Tap water is pretty pure , unlike what falls out of the sky , salt ,bits of carbon etc, which could contaminate the surface.
It would avoid any misleading results
Unless of course if you are in the London area where they reckon the water has been through many kidneys before it come out of the tap.

On Thu, 2018-11-22 at 18:56 +0000, Richard GD8EXI wrote:
Can I suggest an experiment with B and Q polyurethane foam. Put a freshly made lump of it in a microwave oven along with a dummy load (cup of water) and see how hot it gets after say 3 minutes at full power. Then take the same the lump of foam, soak it in water for 24 hours or more, dry its surface and repeat the experiment in the microwave.

PU foam is used for microwave application as you already know for example.

https://www.generalplastics.com/wp-content/uploads/2016/12/White-Paper-PU-Foam-Dielectric-Materials-for-Use-in-Radomes-and-Other_Applications.pdf

However some of the additives in B and Q foam may make it less suitable. It only takes 1% or less of something with a high dielectric loss or something in there that make it hydroscopic to ruin the performance in a horn.


Richard
GD8EXI



On 22/11/2018, 17:16, "Barry Chambers" <b.chambers@...> wrote:

> Neil
>
> I suspect the Er will be around 1.05 at worst but you will need to think
> about whether the pores in the foam are open or closed. I'm thinking
> about water getting into the foam.
>
> 73
>
> Barry, G8AGN
>
>
>
>
-- 
 Best wishes /73 
 Richard Bown
 
 Email : richard@...

 HTTP  :  http://www.g8jvm.com
 
 ######################################################################

 Ham Call: G8JVM . QRV: 50-432 MHz + Microwave 
 Maidenhead QRA: IO82SP38, LAT. 52 39.720' N LONG. 2 28.171 W
 QRV 6mtrs 200W, 4mtrs 150W, 2mtrs 300W, 70cms 200W, 
Microwave 1296MHz 140W, 2320MHz 100W & 10368MHz 5W
 OS: Linux Mint 19 x86_64 Tara, on a Dell Inspiron N5030 laptop
 ######################################################################

Re: Using PU foam in feedhorns?

Richard GD8EXI
 

Can I suggest an experiment with B and Q polyurethane foam. Put a freshly made lump of it in a microwave oven along with a dummy load (cup of water) and see how hot it gets after say 3 minutes at full power. Then take the same the lump of foam, soak it in water for 24 hours or more, dry its surface and repeat the experiment in the microwave.

PU foam is used for microwave application as you already know for example.

https://www.generalplastics.com/wp-content/uploads/2016/12/White-Paper-PU-Foam-Dielectric-Materials-for-Use-in-Radomes-and-Other_Applications.pdf

However some of the additives in B and Q foam may make it less suitable. It only takes 1% or less of something with a high dielectric loss or something in there that make it hydroscopic to ruin the performance in a horn.


Richard
GD8EXI



On 22/11/2018, 17:16, "Barry Chambers" <b.chambers@...> wrote:

> Neil
>
> I suspect the Er will be around 1.05 at worst but you will need to think
> about whether the pores in the foam are open or closed. I'm thinking
> about water getting into the foam.
>
> 73
>
> Barry, G8AGN
>
>
>
>

Re: 144MHz Gain block

Andy G4JNT
 

Farnell do that device - a mere £3.65 each (plus VAT )
Although having ordered one of the modules, I'll get a couple for the junk box

At > 10V rail, a 50 ohm load resistance is 1 Watt out - which appears to be exactly how the Ebay module are doing it.
 


On Thu, 22 Nov 2018 at 17:16, Chris Bartram G4DGU <chris@...> wrote:



On 22/11/18 17:09, Andy G4JNT wrote:

Hopefully the raw device will be identifiable
It's been a PD84002 (manufactured by ST) in those I've used. They are a very useful little amp when building instrumentation.

73
Chris
-- 
Chris Bartram
Luxulyan, Bodmin, Cornwall

chris@...

Re: 144MHz Gain block

Conrad, PA5Y
 

If you want good linearity a good choice for a 2nd stage would be a HELA10B they have around 11 dB gain on 144MHz, so PGA103+ then HELA10B would work SV1AFN has kits.

 

73

 

Conrad PA5Y

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of Andy G4JNT
Sent: 22 November 2018 17:27
To: UK Microwaves groups.io <ukmicrowaves@groups.io>
Subject: [UKMicrowaves] 144MHz Gain block

 

I need a gain block to go from a little under 0dBm up to a bit over 27dBm or 500mW.   This is needed to make my Elad FDM-DUO "look like" the FT817 for driving transverters.

But it's a very inconvenient gain arrangement to get using gain blocks

PGA-103 etc go to 50mW and needs the input attenuating.  Then any discrete device after that has to be wound back so much it gets silly. 

Meaning :   Atten - Gain - Atten Gain

 

Is there an off the shelf solution to 27dB - 30dB gain  up to 1 Watt output?  Or will it have to be a pair of bipolars with old-fashioned discrete circuitry

 

 

Andy