Date   

Re: Wave guide dummy load.

Andy G4JNT
 

I'd have thought the uWave Column would be a better place.   

Is there really much interest in unknown quality loads in waveguide ?



On Thu, 4 Mar 2021 at 18:28, Greg - ZL3IX <zl3ix@...> wrote:
Since few of us will have a copy going so far back, how about repeating the design in RadCom. An idea for Design Notes, Andy (JNT)....?


Re: Wave guide dummy load.

Greg - ZL3IX
 

Since few of us will have a copy going so far back, how about repeating the design in RadCom. An idea for Design Notes, Andy (JNT)....?


Re: Bodgers Guide to Patio Moonbounce

John Fell
 

Interesting talk notes from John.
My olde school was Leeds Grammar  , which was just up the road from the fruit Salads - we were the Banana skins (Yellow cross on the cap) .Taught me how to swim , cricket and Rugby . Too young then for RF .

73
John
G0API 

On Thu, 4 Mar 2021 at 16:21, Dave G6HEF <hardknottdave@...> wrote:

Following on from last nights discussions here is the rather interesting EME article by John Worsnop.

I'm hoping to be a notch more ambitious, but whether I'll get there or not remains to be seen.

Bodger's Guide to Patio Moonbounce

Now all I need to do is remember what was advised re: interfacing a vibroplex bug with JT65b ;)


Re: ICNIRP

Dave G6HEF
 
Edited

"Political comments on this uWave Group  OM :-)"

I'd like to think it's clever satirical comedy. There are always crazy things at both ends of the spectrum. Same with EM radiation.


Ofcom -important message about your licence

Andy G4JNT
 




---------- Forwarded message ---------
From: John Rogers <m0jav@...>
Date: Thu, 4 Mar 2021 at 15:16
Subject: Ofcom -important message about your licence
To: Volunteer Leadership Team <LeadershipTeam@...>
Cc: Elaine Richards, G4LFM <Elaine.Richards@...>, Heather Parsons <heather.parsons@...>


Please use this information to respond to any questions you get on this topic:

 

-----------------

 

If you have received an email from Ofcom to your personal email address you will be aware of the new EMF area of their website: ofcom.org.uk/emf

 

Please direct people there if they have questions about the variation process and EMF conditions.  

 

The RSGB EMC Committee will share more information about assessments you can make over the coming weeks but they can’t reply to all individual queries at the moment.

 

If you didn’t receive an email, check your spam filter and ensure that Ofcom has your correct contact details. Please also encourage your club members to look for their copy of the email.

 

People should be aware that the RSGB information on EMF Exposure will be updated on rsgb.org.uk/emf

 

Tell people not to panic they have at least until November (May 2022 for <10Mhz bands) before they need to comply with these requirements.

 

----------------

 

Regards and 73 de
John Rogers (M0JAV/NHS)
RSGB Director

E: m0jav@...
W: www.rsgb.org.uk
Follow us on Twitter: @theRSGB

Patron: HRH The Prince Philip, Duke of Edinburgh, KG, KT.
Registered Office: 3 Abbey Court, Fraser Road, Priory Business Park, Bedford MK44 3WH, UK 
RSGB was founded in 1913 and incorporated in 1926. Registered Number: 216431

The information in this internet email is copyright of the Radio Society of Great Britain (RSGB), confidential and is intended solely for the addressee(s). Access, copying, dissemination to or re-use of information in it to or by anyone else is unauthorised unless stated clearly at the top of the email. Any views expressed in this email are those of the individual sender, except where the sender specifically states these to be the views of the RSGB.

 

 

John Rogers
Radio Society of Great Britain
 
 
 

 

John Rogers

Radio Society of Great Britain

m0jav@...
rsgb.org/board

RSGB Newsfeed RSGB on Facebook RSGB on Twitter RSGB on YouTube
Patron: HRH The Prince Philip, Duke of Edinburgh, KG, KT.
Registered Office: 3 Abbey Court, Fraser Road, Priory Business Park, Bedford MK44 3WH, UK
RSGB was founded in 1913 and incorporated in 1926. Registered Number: 216431
The information in this internet email is copyright of the Radio Society of Great Britain (RSGB), confidential and is intended solely for the addressee(s). Access, copying, dissemination to or re-use of information in it to or by anyone else is unauthorised unless stated clearly at the top of the email. Any views expressed in this email are those of the individual sender, except where the sender specifically states these to be the views of the RSGB.



 


Re: microwave absorbent adhesive polymer?

Paul Evans W4/VP9KF
 

Conductivity between the back of the absorber and the metal chassis (or normally, inside of the lid) may not be important. Normally the absorber is used to stop reflections inside the box when the lid is on, not to absorb 'all' the emitted power.

Bet Gordon got through gobs of the 3140 and absorber material from 'next door' in Towcester.
--
73, Paul Evans G4BKI [VP9KF]


Re: microwave absorbent adhesive polymer?

SAM JEWELL
 

Andy,



I can't send a bodge like that out to paying customers!!!

:>Q


Sam





------ Original Message ------
From: "Andy G4JNT" <andy.g4jnt@...>
To: "UK Microwaves groups.io" <UKMicrowaves@groups.io>
Sent: Thursday, 4 Mar, 21 At 13:34
Subject: Re: [UKMicrowaves] microwave absorbent adhesive polymer?

Have you tried just taping over with magic Tape (*) ?
It really does work well

(*) Other thin plastic self adhesive tapes are available.



On Thu, 4 Mar 2021 at 13:31, Gordon REASON via groups.io <gordonj.reason=virgin.net@groups.io> wrote:

RTV 3140 was our favourite adhesive .............

On 04 March 2021 at 09:32 "SAM JEWELL via groups.io" <jewell=btinternet.com@groups.io> wrote:

I would like to echo that comment about finding suitable adhesive to use with the polyurethane/silicon absorber materials. I was given a few sheets of 'plain' absorber of the sort I use with my VLNA preamps. I have tried all sorts of adhesives, but none of them adhere properly and several of them caused the absorber sheet to curl up.
I went back to the self adhesive type, expensive as it is.

73 de Sam, G4DDK





On 4 Mar 2021, at 08:18, Dave G8KHU <david@...> wrote:

Neil
Before you order check with Mouser that their material has the pressure sensitive adhesisve tape option - the Mouser description just says mounting is "adhesive". Does that mean it's got the adhesive film or that you need adhesive to glue it in place? The Digikey version does at least says that the adhesive is non-conductive single sided so I'm assuming that this is the factory fitted adhesive sheet . The base number just referes to the material and the laird site lists the psa as an option - https://www.laird.com/products/microwave-absorbers/microwave-absorbing-elastomers-and-films/eccosorb-mcs/21109145
The non-adhesive stuff is a pig for amateur use as nothing seems to stick it reliably, carpet tape falls off and superglue / rtv fail rapidly. The proper adhesive is a two part mix that's fiendishly expensive, comes in a one litre can which has very limited shelf life and has enough skull and crossbones warning symbols to sink a pirate ship. I had to use it once and swore never, ever, again.
HTH Dave G8KHU




Re: Eltek Flatpack2 PSU 3KW set to 48V or whatever you want.

Andy G4JNT
 

What inline fuse :-)
Don't see the point when you run things from PSUs with current limits / trips

Only two FETs blew out of the four, and by some fluke I had several devices spare in the junk box - must have anticipated blowing some.  So all repaired and I can have a linear 300 Watts on 137 & 475kHz kHz if needed.




On Thu, 4 Mar 2021 at 13:53, Mike Willis <willis.mj@...> wrote:
I suppose as long as you don't ask it to provide any more than 3kW it will be happy. For future reference I think you can set limits via the CAN Bus. Surprised your inline fuse didn't blow.
--
Mike G0MJW


Re: Pump up Masts

Clive Elliott GW4MBS
 

50kg head load looks useful, does it have a keyway I wonder?
--
Clive GW4MBS (ex-G8ADP)
Pottering on 6m - 3cm in a valley in IO71XW where any QSO is a triumph of optimism over geography!


Re: Pump up Masts

ian hope (2E0IJH)
 

Talk to Total Masts as that looks identical to the units they supply
 
Ian
M5IJH

 
 
Sent: Thursday, March 04, 2021 at 1:50 PM
From: "Mike Willis" <willis.mj@...>
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Pump up Masts
After some googling it looks very much like it is one of these with the compressor and valve accessories

http://www.nrentech.com/pneumatic-telescopic-mast/9m-SecurityCCTV-PneumaticTelescopicMast

--
Mike G0MJW


Re: Eltek Flatpack2 PSU 3KW set to 48V or whatever you want.

Mike Willis
 

I suppose as long as you don't ask it to provide any more than 3kW it will be happy. For future reference I think you can set limits via the CAN Bus. Surprised your inline fuse didn't blow.
--
Mike G0MJW


Re: Pump up Masts

Mike Willis
 

After some googling it looks very much like it is one of these with the compressor and valve accessories

http://www.nrentech.com/pneumatic-telescopic-mast/9m-SecurityCCTV-PneumaticTelescopicMast

--
Mike G0MJW


Re: Wave guide dummy load.

John E. Beech
 

Probably more than enough; the more carbon the higher the conductivity & the less lossy it is. I'm guessing the pukka
foam works well because the foam structure has longer, narrow conducting parts which go in all directions which will
have cancelling electric & magnetic fields - a bit like wire wool at HF. And probably has high dielectric losses as well. ( Its
dielectric constant is fairly high at 2.5 - higher than polythene but lower than polymethyl methacrylate (Perspex).

de John G8SEQ

-------Original Message-------
From: Neil Douglas via groups.io <neil.douglas=ntlworld.com@groups.io>
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] Wave guide dummy load.
Sent: Mar 04 '21 11:57

All,

RS sell this material

THERMAL INTERFACE SHEET, GRAPHITE, 10W/M·K, 150 X 150MM 0.16MM,
SELF-ADHESIVE

£13.31 FOR 150 X 150 MM

Would this be enough carbon?

73 NeilD G4SHJ

FROM: UKMicrowaves@groups.io <UKMicrowaves@groups.io> ON BEHALF OF
KENT BRITAIN
SENT: 04 March 2021 02:03
TO: ukmicrowaves@groups.io; UKMicrowaves@groups.io
SUBJECT: Re: [UKMicrowaves] Wave guide dummy load.

Only, Only if there is enough Carbon to make the epoxy electrically
conductive.

The particles have to be touching. A little Carbon does nothing. Kent

On Wednesday, March 3, 2021, 07:22:13 PM CST, Gordon REASON via
groups.io <gordonj.reason=virgin.net@groups.io> wrote:

would'nt some carbon powder , mixed into one part of an epoxy , such
as araldite , have a good absorbtion >>>>> just thinking !
> On 03 March 2021 at 19:18 "John E. Beech" <john@g8seq.com> wrote:
>
>
> Tnx John,
> I eventually found it on page 8.20 of the 1969 edition. No mention
of it in the index under micro- or wave-
> though.
>
> de John G8SEQ
>
> > -------Original Message-------
> > From: John Fell <john.g0api@gmail.com>
> > To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
> > Subject: Re: [UKMicrowaves] microwave absorbent adhesive polymer?
> > Sent: Mar 03 '21 10:57
> >
> > RSGB VHF Manual - Microwave section .Wood in guide dummy load .
> >
> > John
> > G0API
> >
> > On Wed, 3 Mar 2021 at 10:11, John E. Beech <john@g8seq.com>
wrote:
> >
> > > Don't laugh, but has anyone tried a thin strip of balsa wood or
> > > plywood for the absorber? ( Perhaps covered in
> > > graphite pencil lead?) I once made an effective waveguide dummy
> > > load for 10 GHz out of wood - a specially shaped
> > > wedge. I don't know where the design came from but I got it
from
> > > G8MWR (SK).
> > >
> > > de John G8SEQ
> > >
> > >> -------Original Message-------
> > >> From: Neil Smith G4DBN <neil@g4dbn.uk>
> > >> To: BVA-transverters-uk@groups.io
> > > <BVA-transverters-uk@groups.io>, UKMicrowaves@groups.io
> > > <UKMicrowaves@groups.io>
> > >> Subject: [UKMicrowaves] microwave absorbent adhesive polymer?
> > >> Sent: Mar 02 '21 23:27
> > >>
> > >> Are there any secret sources of microwave absorbant material
> > > which will
> > >> work from 2.5 to 10 GHz with good reflection loss and bulk
loss,
> > > around
> > >> 1mm thick and self-adhesive?
> > >>
> > >> For the F6BVA 3cm to UHF transverters, we need a bit about 150
x
> > > 50 mm.
> > >>
> > >> I see RF Microwave has some at around £330 for a 600 mm
square
> > > sheet of
> > >> silicone 1mm carbonyl/iron, which makes 48 pieces at around
> > > £8.50 per
> > >> piece including VAT etc. The price from Mouser etc for similar
> > > stuff
> > >> works out about the same. Is that the right sort of price or
is
> > > there
> > >> some low cost magic stuff of which I am unaware? The gap above
> > > the PCB
> > >> is only 7mm, and some of the components are a few mm tall, so
> > > 1/16" or
> > >> about 1.5 mm is the max I can fit in.
> > >>
> > >> Neil G4DBN
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> >
> >
>
>
>
>
>


Re: ICNIRP

Dave
 

Thanks Neil,
I had a look at the RSGB calculator and see what you mean regarding the 6 minutes and the duty cycle in there.
73
Dave G4GLT.

On 4 Mar 2021, at 09:01, Neil Smith G4DBN <neil@g4dbn.uk> wrote:

of


Re: microwave absorbent adhesive polymer?

Andy G4JNT
 

Have you tried just taping over with magic Tape (*) ?
It really does work well

(*)  Other thin plastic self adhesive tapes are available.



On Thu, 4 Mar 2021 at 13:31, Gordon REASON via groups.io <gordonj.reason=virgin.net@groups.io> wrote:

RTV 3140 was our favourite adhesive .............

On 04 March 2021 at 09:32 "SAM JEWELL via groups.io" <jewell=btinternet.com@groups.io> wrote:

I would like to echo that comment about finding suitable adhesive to use with the polyurethane/silicon absorber materials. I was given a few sheets of 'plain' absorber of the sort I use with my VLNA preamps. I have tried all sorts of adhesives, but none of them adhere properly and several of them caused the absorber sheet to curl up.
I went back to the self adhesive type, expensive as it is.

73 de Sam, G4DDK



 

On 4 Mar 2021, at 08:18, Dave G8KHU <david@...> wrote:

Neil
Before you order check with Mouser that their material has the pressure sensitive adhesisve tape option - the Mouser description just says mounting is "adhesive". Does that mean it's got the adhesive film or that you need adhesive to glue it in place? The Digikey version does at least says that the adhesive is non-conductive single sided so I'm assuming that this is the factory fitted adhesive sheet . The base number just referes to the material and the laird site lists the psa as an option - https://www.laird.com/products/microwave-absorbers/microwave-absorbing-elastomers-and-films/eccosorb-mcs/21109145
The non-adhesive stuff is a pig for amateur use as nothing seems to stick it reliably, carpet tape falls off and superglue / rtv fail rapidly. The proper adhesive is a two part mix that's fiendishly expensive, comes in a one litre can which has very limited shelf life and has enough skull and crossbones warning symbols to sink a pirate ship. I had to use it once and swore never, ever, again.
HTH Dave G8KHU


 


 


Re: microwave absorbent adhesive polymer?

Gordon REASON <gordonj.reason@...>
 

RTV 3140 was our favourite adhesive .............

On 04 March 2021 at 09:32 "SAM JEWELL via groups.io" <jewell@...> wrote:

I would like to echo that comment about finding suitable adhesive to use with the polyurethane/silicon absorber materials. I was given a few sheets of 'plain' absorber of the sort I use with my VLNA preamps. I have tried all sorts of adhesives, but none of them adhere properly and several of them caused the absorber sheet to curl up.
I went back to the self adhesive type, expensive as it is.

73 de Sam, G4DDK



 

On 4 Mar 2021, at 08:18, Dave G8KHU <david@...> wrote:

Neil
Before you order check with Mouser that their material has the pressure sensitive adhesisve tape option - the Mouser description just says mounting is "adhesive". Does that mean it's got the adhesive film or that you need adhesive to glue it in place? The Digikey version does at least says that the adhesive is non-conductive single sided so I'm assuming that this is the factory fitted adhesive sheet . The base number just referes to the material and the laird site lists the psa as an option - https://www.laird.com/products/microwave-absorbers/microwave-absorbing-elastomers-and-films/eccosorb-mcs/21109145
The non-adhesive stuff is a pig for amateur use as nothing seems to stick it reliably, carpet tape falls off and superglue / rtv fail rapidly. The proper adhesive is a two part mix that's fiendishly expensive, comes in a one litre can which has very limited shelf life and has enough skull and crossbones warning symbols to sink a pirate ship. I had to use it once and swore never, ever, again.
HTH Dave G8KHU


 


 


Re: Wave guide dummy load.

KENT BRITAIN
 

I have made and even published how to make loads using that IC Carbon foam.

Some of the foam is 'Static Dissipative' and does not work well as a microwave absorber.

Get out your Ohm Meter and poke the foam with the probes about 5-10 mm apart.   If you read a few hundred Ohms it will work well.  If it reads thousands of Ohms, it will not.   Then form the foam into a wedge shape and put it in the waveguide.   Kent WA5VJB/G8EMY

On Thursday, March 4, 2021, 04:48:44 AM CST, Wilko <wkb@...> wrote:


And the old style anti-static carbon-filled foam for IC's, would that work? Something that has crossed my mind but forgot to ask for a while now

Wilko
PA1WBU






Re: microwave absorbent adhesive polymer?

SAM JEWELL
 

My experience of fridge magnet 'stuff' is not that good. I know others have reported positive results. When compared to the 'right stuff', in my various preamps, it's like chalk and cheese!
Sam, G4DDK

On 4 Mar 2021, at 10:51, John E. Beech <john@g8seq.com> wrote:

I forgot we were talking about silicone foam. Contact adhesive won't work very well either. I have some silicone glue
made by DMC which would probably stick it BUT reading the warnings on the label, I think it contains acetic acid which is
not a good idea around electronics, so if you are thinking of using silicone sealer as glue it should be the sort that
DOESEN'T smell of vinegar.

I haven't studied the detail of this project but doesn't this absorber go inside the tin plate box lid? So wouldn't the fridge
stuff be a good option?

de John G8SEQ

-------Original Message-------
From: john <john@g8seq.com>
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] microwave absorbent adhesive polymer?
Sent: Mar 04 '21 10:17

I would have thought contact adhesive such as Evostick, Bostik or Thixofix would be a good option. Snag is you only
get
one chance to stick it in the right place otherwise it is rip it off & start again.

de John G8SEQ

-------Original Message-------
From: Dave G8KHU <david@fielding-electronics.co.uk>
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] microwave absorbent adhesive polymer?
Sent: Mar 04 '21 08:18

Neil
Before you order check with Mouser that their material has the
pressure sensitive adhesisve tape option - the Mouser description just
says mounting is "adhesive". Does that mean it's got the adhesive film
or that you need adhesive to glue it in place? The Digikey version
does at least says that the adhesive is non-conductive single sided so
I'm assuming that this is the factory fitted adhesive sheet . The base
number just referes to the material and the laird site lists the psa
as an option -
https://www.laird.com/products/microwave-absorbers/microwave-absorbing-elastomers-and-films/eccosorb-
mcs/21109145
The non-adhesive stuff is a pig for amateur use as nothing seems to
stick it reliably, carpet tape falls off and superglue / rtv fail
rapidly. The proper adhesive is a two part mix that's fiendishly
expensive, comes in a one litre can which has very limited shelf life
and has enough skull and crossbones warning symbols to sink a pirate
ship. I had to use it once and swore never, ever, again.
HTH Dave G8KHU




Re: 23cm warm cable

Rien Eradus PA0JME
 

Hi all,

My experience 0.25 inch at 1296MHz and 120 Watt RF is OK, it certainly is better since 0.141 will become to hot too

Short ends (20 to 30cms) can be found at fleamarkets, often used as phasing lines in antenna's for UMTS and the like

Pityfull fleamarkets are far from common at the moment, I know

Aliexpress also supplies new cable RG401, though not really cheap (around USD18/m), and waiting time can be long

Best regards Rien PA0JME

Op 4-3-2021 om 12:53 schreef militaryoperator via groups.io:


You should be using .141 at that level / frequency

Andy


Yes, I guessed that Andy.I can see N plugs on ebay but couldn't see any cable, will keep searching. 

Thanks, Ben. 


Re: Wave guide dummy load.

Neil Douglas
 

All,

 

RS sell this material

 

Thermal Interface Sheet, Graphite, 10W/m·K, 150 x 150mm 0.16mm, Self-Adhesive

£13.31 for 150 x 150 mm

Would this be enough carbon?

73 NeilD G4SHJ

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of KENT BRITAIN
Sent: 04 March 2021 02:03
To: ukmicrowaves@groups.io; UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Wave guide dummy load.

 

Only, Only if there is enough Carbon to make the epoxy electrically conductive.

The particles have to be touching.       A little Carbon does nothing.    Kent

 

On Wednesday, March 3, 2021, 07:22:13 PM CST, Gordon REASON via groups.io <gordonj.reason@...> wrote:

 

 

would'nt some carbon powder , mixed into one part of an epoxy , such as araldite , have a good absorbtion >>>>>  just thinking !
> On 03 March 2021 at 19:18 "John E. Beech" <john@...> wrote:
>
>
> Tnx John,
>                I eventually found it on page 8.20 of the 1969 edition. No mention of it in the index under micro- or wave-
> though.
>
> de John G8SEQ
>
> >  -------Original Message-------
> >  From: John Fell <john.g0api@...>
> >  To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
> >  Subject: Re: [UKMicrowaves] microwave absorbent adhesive polymer?
> >  Sent: Mar 03 '21 10:57
> >
> >  RSGB VHF Manual - Microwave section .Wood in guide dummy load .
> >
> >  John
> >  G0API
> >
> >  On Wed, 3 Mar 2021 at 10:11, John E. Beech <john@...> wrote:
> >
> >  > Don't laugh, but has anyone tried a thin strip of balsa wood or
> >  > plywood for the absorber? ( Perhaps covered in
> >  > graphite pencil lead?) I once made an effective waveguide dummy
> >  > load for 10 GHz out of wood - a specially shaped
> >  > wedge. I don't know where the design came from but I got it from
> >  > G8MWR (SK).
> >  >
> >  > de John G8SEQ
> >  >
> >  >> -------Original Message-------
> >  >> From: Neil Smith G4DBN <neil@...>
> >  >> To: BVA-transverters-uk@groups.io
> >  > <BVA-transverters-uk@groups.io>, UKMicrowaves@groups.io
> >  > <UKMicrowaves@groups.io>
> >  >> Subject: [UKMicrowaves] microwave absorbent adhesive polymer?
> >  >> Sent: Mar 02 '21 23:27
> >  >>
> >  >> Are there any secret sources of microwave absorbant material
> >  > which will
> >  >> work from 2.5 to 10 GHz with good reflection loss and bulk loss,
> >  > around
> >  >> 1mm thick and self-adhesive?
> >  >>
> >  >> For the F6BVA 3cm to UHF transverters, we need a bit about 150 x
> >  > 50 mm.
> >  >>
> >  >> I see RF Microwave has some at around £330 for a 600 mm square
> >  > sheet of
> >  >> silicone 1mm carbonyl/iron, which makes 48 pieces at around
> >  > £8.50 per
> >  >> piece including VAT etc. The price from Mouser etc for similar
> >  > stuff
> >  >> works out about the same. Is that the right sort of price or is
> >  > there
> >  >> some low cost magic stuff of which I am unaware? The gap above
> >  > the PCB
> >  >> is only 7mm, and some of the components are a few mm tall, so
> >  > 1/16" or
> >  >> about 1.5 mm is the max I can fit in.
> >  >>
> >  >> Neil G4DBN
> >  >>
> >  >>
> >  >>
> >  >>
> >  >>
> >  >>
> >
> >
>
>
>
>
>




2701 - 2720 of 64061