Date   
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 IO83KH
 

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

 

Re: 144MHz Gain block

Andy G4JNT
 

Transerter interfacing is a bit of a pain

Of course, starting from scratch the 1mW output from the Elad on its LP port is perfect for driving Tx mixers directly.   The RF is generated at a sampling rate of 368MHz, so only a bit of alias filtering is needed - a three section elliptic with the zero at 223MHz is more than adequate.   (On Rx it needs 30dB or more of gain and bandpass filtering to get rid of other alias responses).

But with all my transverters designed for FT817 compatibility, that's the way they're staying



On Thu, 22 Nov 2018 at 17:17, SAM JEWELL via Groups.Io <jewell=btinternet.com@groups.io> wrote:
That’s what I thought. I was disappointed (perhaps not surprised though) that i could not get 2W out at any frequency,  but the gain was a surprise. As used on the output of one of my transverters, I decided to ditch the first stage and just run the second stage. I am not sure what the device is. Possibly RFMOS fet. It does need forward bias, whereas the first stage is just a high gain MMIC? The second stage bias is on the  board. The whole thing runs happily on 12V. It brings the Iceni or Anglian transverter output up enough to drive one of the SGLabs 23 or 13cm transverters if you don’t want to modify one of those for the lower input. 
Sam,   G4DDK




Sent from Yahoo Mail for iPad

On Thursday, November 22, 2018, 5:09 pm, Andy G4JNT <andy.g4jnt@...> wrote:

Danke ...

I've ordered one.   1MHz to 1GHz , 2 Watt saturated.   https://www.ebay.com/itm/112991082065

Hopefully the raw device will be identifiable, but as usual with these Chinese modules, probably cheaper buying ready built like this than it is to get the components.



On Thu, 22 Nov 2018 at 17:00, SAM JEWELL via Groups.Io <jewell=btinternet.com@groups.io> wrote:
Yes, Andy the little ‘2 Watt’ 2 stage wideband amplifiers on EBay will do 1W at very good linearity. Really awful much above that and excellent at 500mW. They will do HF through 500MHz. Performance is much worse above that. If you need low gain then ditch the first stage. Over 50dB gain at low HF!
They have a small, but adequate heatsink on the rear of the board.
I don’t have an Ebay reference, but you can’t fail to see them once you start looking.......

Sam, G4DDK




Sent from Yahoo Mail for iPad

On Thursday, November 22, 2018, 4:26 pm, Andy G4JNT <andy.g4jnt@...> wrote:

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


Re: 144MHz Gain block

SAM JEWELL
 

That’s what I thought. I was disappointed (perhaps not surprised though) that i could not get 2W out at any frequency,  but the gain was a surprise. As used on the output of one of my transverters, I decided to ditch the first stage and just run the second stage. I am not sure what the device is. Possibly RFMOS fet. It does need forward bias, whereas the first stage is just a high gain MMIC? The second stage bias is on the  board. The whole thing runs happily on 12V. It brings the Iceni or Anglian transverter output up enough to drive one of the SGLabs 23 or 13cm transverters if you don’t want to modify one of those for the lower input. 
Sam,   G4DDK

On Thursday, November 22, 2018, 5:09 pm, Andy G4JNT <andy.g4jnt@...> wrote:

Danke ...

I've ordered one.   1MHz to 1GHz , 2 Watt saturated.   https://www.ebay.com/itm/112991082065

Hopefully the raw device will be identifiable, but as usual with these Chinese modules, probably cheaper buying ready built like this than it is to get the components.



On Thu, 22 Nov 2018 at 17:00, SAM JEWELL via Groups.Io <jewell=btinternet.com@groups.io> wrote:
Yes, Andy the little ‘2 Watt’ 2 stage wideband amplifiers on EBay will do 1W at very good linearity. Really awful much above that and excellent at 500mW. They will do HF through 500MHz. Performance is much worse above that. If you need low gain then ditch the first stage. Over 50dB gain at low HF!
They have a small, but adequate heatsink on the rear of the board.
I don’t have an Ebay reference, but you can’t fail to see them once you start looking.......

Sam, G4DDK




Sent from Yahoo Mail for iPad

On Thursday, November 22, 2018, 4:26 pm, Andy G4JNT <andy.g4jnt@...> wrote:

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


Re: Using PU foam in feedhorns?

Barry Chambers
 

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

Chris Bartram G4DGU
 



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

Andy G4JNT
 

Danke ...

I've ordered one.   1MHz to 1GHz , 2 Watt saturated.   https://www.ebay.com/itm/112991082065

Hopefully the raw device will be identifiable, but as usual with these Chinese modules, probably cheaper buying ready built like this than it is to get the components.



On Thu, 22 Nov 2018 at 17:00, SAM JEWELL via Groups.Io <jewell=btinternet.com@groups.io> wrote:
Yes, Andy the little ‘2 Watt’ 2 stage wideband amplifiers on EBay will do 1W at very good linearity. Really awful much above that and excellent at 500mW. They will do HF through 500MHz. Performance is much worse above that. If you need low gain then ditch the first stage. Over 50dB gain at low HF!
They have a small, but adequate heatsink on the rear of the board.
I don’t have an Ebay reference, but you can’t fail to see them once you start looking.......

Sam, G4DDK




Sent from Yahoo Mail for iPad

On Thursday, November 22, 2018, 4:26 pm, Andy G4JNT <andy.g4jnt@...> wrote:

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


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

Adrian G4UVZ
 

Hi Dennis ..thanks for the info on your locator

Re Zello ....I would highly recommend this to you ..Neil DBN and myself have been using to great effect on 10GHz aircraft scatter the last 3 Monday Nights...We have made contact every time!   Once you have sorted yourself out on Zello sign into SHFCHAT channel...you will hear stations on 'talkback' there who would not otherwise be able to communicate. We use our own callsigns and it is extremely civilised!

Look forward to hearing you in due course

Adrian

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

Richard <richard@...>
 

I've learnt to distrust moderators I don't know, and a few I do.

On Thu, 2018-11-22 at 16:59 +0000, Andy G4JNT wrote:
Once you've spoken to them once its open


Andy
www.g4jnt.com






On Thu, 22 Nov 2018 at 16:57, Richard <richard@...> wrote:

I set up Zello
signed on to shf chat
got the messsage you can only talk to the moderator , so
uninstalled

On Thu, 2018-11-22 at 16:53 +0000, Andy G4JNT wrote:
> Yes you should :-)
>
>
> I leave the Inrico handheld on all the time logged into
Zello.
> Tuesday evening, happily sitting there watching TV and
suddenly at
> 20:00 voices start booming out
>
>
> Andy
> www.g4jnt.com
>
>
>
>
>
> On Thu, 22 Nov 2018 at 16:50, Neil Smith G4DBN
<neil@...> wrote:
>
>
> a few others join in, and we use Zello for talkback.
We
> should really
> move to a private session once we are in QSO, but
when the
> service isn't
> busy with multiple users talking about different
paths, it is
> useful to
> hear what others are up to.
>
> Neil
>
>




--
Best wishes /73
Richard Bown

Email : richard@...


HTTP : http://www.g8jvm.com

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

Neil Smith G4DBN
 

You say "Hi" to the mods with a name and call and they grant you access, usually fairly rapidly. Means we don't get random people joining to talk about the weather or radio politics or lumbago, just folks interested in SHF operation.

Neil

On 22/11/2018 16:57, Richard wrote:
I set up Zello
signed on to shf chat
got the messsage you can only talk to the moderator , so uninstalled

On Thu, 2018-11-22 at 16:53 +0000, Andy G4JNT wrote:
Yes you should :-)


I leave the Inrico handheld on all the time logged into Zello.
Tuesday evening, happily sitting there watching TV and suddenly at
20:00 voices start booming out


Andy
www.g4jnt.com





On Thu, 22 Nov 2018 at 16:50, Neil Smith G4DBN <neil@...> wrote:

a few others join in, and we use Zello for talkback. We
should really
move to a private session once we are in QSO, but when the
service isn't
busy with multiple users talking about different paths, it is
useful to
hear what others are up to.
Neil

Re: 144MHz Gain block

SAM JEWELL
 

Yes, Andy the little ‘2 Watt’ 2 stage wideband amplifiers on EBay will do 1W at very good linearity. Really awful much above that and excellent at 500mW. They will do HF through 500MHz. Performance is much worse above that. If you need low gain then ditch the first stage. Over 50dB gain at low HF!
They have a small, but adequate heatsink on the rear of the board.
I don’t have an Ebay reference, but you can’t fail to see them once you start looking.......

Sam, G4DDK

On Thursday, November 22, 2018, 4:26 pm, Andy G4JNT <andy.g4jnt@...> wrote:

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