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
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> >
> >
>
>
>
>
>

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