Date   

Re: microwave absorbent adhesive polymer?

SAM JEWELL
 

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?

Neil Smith G4DBN
 

Response from Hitek suggests DD-11143 silicone absorber. I've asked for a quote.

Spec sheet attached.

Neil


Re: ICNIRP

Neil Smith G4DBN
 

typo, 88% should be 83% obvs

On 04/03/2021 09:01, Neil Smith G4DBN wrote:
The duty cycle should be the worst-case average over 6 minutes. If you transmit continuously for five minutes, then listen for 55 minutes, your duty cycle is 88% over six minutes


Re: microwave absorbent adhesive polymer?

Neil Smith G4DBN
 

I've sent them a tech query

Thanks Dave

Neil

On 04/03/2021 08:18, Dave G8KHU 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: ICNIRP

Neil Smith G4DBN
 

The duty cycle should be the worst-case average over 6 minutes. If you transmit continuously for five minutes, then listen for 55 minutes, your duty cycle is 88% over six minutes if you transmit for 5 seconds on and 55 seconds off, then it is 8.3% over six minutes, just put the duty cycle number into the RSGB sheet. If you use a beacon mode for dish alignment with dots and sometimes send for more than six minutes, even if only once every couple of hours, then it is 50%, if you use dashes, it is 75%, carrer, 100%.

I'm using 100% to be sure, then for anything where the spreadsheets suggest I am near the ICNIRP levels, I do a proper calculation using the real beam pattern, accessibility and taking into account my compensating controls like controlling access, and interlocks to prevent transmission towards neighbouring properties below a certain angle, and not using my 70cm beam unless it is at least 9 metres above ground, so the main lobe goes over the top of my neighbour's house (which makes sense anyway)

If you look at a 1m dish on a patio sending 40 watts of DATV on 2.4 GHz to QO-100, the raw numbers are a bit, er, exciting.  The spreadsheets are using some very broad-brush assumptions and are only an indicator of where we need to check more closely.

Neil G4DBN

On 04/03/2021 08:28, Dave via groups.io wrote:
I agree with you Martin,
As I spend a lot of time listening my duty cycle for an over estimation of 5 mins every 60 mins then the duty cycle is 8.3% and I have made a representation to Ofcom on this basis, asking for this to be taken into account.
Dave G4GLT.


On 4 Mar 2021, at 06:17, GM6VXB via groups.io <martin.andrew=btinternet.com@groups.io> wrote:

Watching this thread with interest and will not reply to comments.
Have done two RF safety courses in my commercial life so do understand what is
and is not safe to be close to RF wise.
Have looked at both the RSGB (who are they) and OFCOM 'calculators' which although
almost correct do not really take into account the duty cycles involved in amateur radio.

Martin, GM6VXB


Re: ICNIRP

Dave
 

I agree with you Martin,
As I spend a lot of time listening my duty cycle for an over estimation of 5 mins every 60 mins then the duty cycle is 8.3% and I have made a representation to Ofcom on this basis, asking for this to be taken into account.
Dave G4GLT. 


On 4 Mar 2021, at 06:17, GM6VXB via groups.io <martin.andrew@...> wrote:

Watching this thread with interest and will not reply to comments.
Have done two RF safety courses in my commercial life so do understand what is
and is not safe to be close to RF wise.
Have looked at both the RSGB (who are they) and OFCOM 'calculators' which although
almost correct do not really take into account the duty cycles involved in amateur radio.

Martin, GM6VXB


Re: microwave absorbent adhesive polymer?

Andy G4JNT
 

I had that stuff once - nothing would stick it.
I just taped it on with magic tape, completely overlapping the absorber piece.

Good stuff , Magic Tape.   Sticks forever.



On Thu, 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?

Dave G8KHU
 

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: ICNIRP

GM6VXB
 

Watching this thread with interest and will not reply to comments.
Have done two RF safety courses in my commercial life so do understand what is
and is not safe to be close to RF wise.
Have looked at both the RSGB (who are they) and OFCOM 'calculators' which although
almost correct do not really take into account the duty cycles involved in amateur radio.

Martin, GM6VXB


Re: ICNIRP

Robin Szemeti - G1YFG
 

It is on my "to do" list, right after "paper the lawn" and "paint the road"

I've worked on sites with "medium" RF levels, like Droitwich.    When pigeons land on the insulators of the open wire feeder to the LF aerial, the arc detector in the field briefly turns the transmitter off to clear the arc and then fires up again. 

That is now my standard test. If it is loud enough to fry pigeons, I'll worry about it.


On Wed, 3 Mar 2021 at 22:51, Graham G3VKV via groups.io <g3vkv=btinternet.com@groups.io> wrote:
I have used this one for a long while, if it works in VK land using ICNIRP data then should be OK here
VK3UM downloads (vk5dj.com)
EMRcalc
Graham G3VKV


--
Robin Szemeti - G1YFG


Re: Wave guide dummy load.

KENT BRITAIN
 

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






Re: Wave guide dummy load.

Gordon REASON <gordonj.reason@...>
 

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: microwave absorbent adhesive polymer?

Neil Smith G4DBN
 

Thanks Dave, Mouser have Eccosorb MCS 1mm in 12 x 12 inch sheets for £89.51 in 5-off, part number 739-21109145, a bit cheaper than Digikey at £104.

Assume 2 x 6 inch sections, that means 12 units per sheet. With the VAT, that is £8.95 per transverter for the full-fat high-end proper material, and free carriage, no carrier fees.

I did buy a couple of A4 sheets of fridge magnet material, but I'll probably use them to fix things to whiteboards and tin cupboards and maybe even fridges.

Neil G4DBN

On 03/03/2021 20:33, Dave G8KHU wrote:
Personaly I'd go for Eccosorb MCS, it's almost 80dB/cm absorbtion at 10 GHz cf the < 20 dB/cm of the chomerics CHO-MUTE

(digikey 903-1498-ND)
_._,_._,_



Re: 23cm warm cable

Phil Guttridge G3TCU
 

I find 0.25" semi-rigid (real RG401) gets warm at 400W on 23cm.

73, Phil. G3TCU



On 03/03/2021 22:55, Andy G4JNT via groups.io wrote:
To be a bit more scientific about it :

Loss in  .086 Simi Rigid is  0.73dB / metre at 1296MHz.   SO in a 100mm length, that's   1 - 10^(-.0073)   = 0.0167 of the input power dissipated.

At 100 Watts that's 1.7 Watts dissipated in 100mm of cable.   You'd expect it to be getting warm




On Wed, 3 Mar 2021 at 22:45, ian hope (2E0IJH) <ian@...> wrote:
I remember melting a Rg213 patch lead with a K2RIW, BTW if anyone's got a neglected one laying about PM me
 
Ian
M5IJH
 
 
Sent: Wednesday, March 03, 2021 at 10:33 PM
From: "Andy G4JNT" <andy.g4jnt@...>
To: "UK Microwaves groups.io" <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] 23cm warm cable
You'd expect .086 SR to get warm at 100W of L-Band
 
Back in the days of playing with a K2RIW, I remember the thicker .141 SR gets warm at 400W of 432MHz
And the same stuff warms with 10W of 10GHz
 
You should be using .141 at that level / frequency
 
Andy
 
 
On Wed, 3 Mar 2021 at 21:18, militaryoperator via groups.io <Military1944=aol.com@groups.io> wrote:
Ok, my new 23cm 100W set seems to be working but noticed the cable from amp to isolator is getting warm, its blue mini bend, and the cable from ant relay to socket on case wall, semi-rigid (0.086) is also warm. 
 
I'm going N to sma adapter, sma mini-bend to sma iso, iso is sma o/p to sma to N adp into relay, N to sma adp then semi rigid to N chassis socket.
 
What else can I use? RG402?  I could use N type soldered to RG402 to sma for Amp to Iso and  Soldered N RG402 to N and use a N to N bulkhead I guess. That would remove a couple of adaptors.
 
Ben

 

 


Virus-free. www.avg.com


Re: 23cm warm cable

Andy G4JNT
 

To be a bit more scientific about it :

Loss in  .086 Simi Rigid is  0.73dB / metre at 1296MHz.   SO in a 100mm length, that's   1 - 10^(-.0073)   = 0.0167 of the input power dissipated.

At 100 Watts that's 1.7 Watts dissipated in 100mm of cable.   You'd expect it to be getting warm




On Wed, 3 Mar 2021 at 22:45, ian hope (2E0IJH) <ian@...> wrote:
I remember melting a Rg213 patch lead with a K2RIW, BTW if anyone's got a neglected one laying about PM me
 
Ian
M5IJH
 
 
Sent: Wednesday, March 03, 2021 at 10:33 PM
From: "Andy G4JNT" <andy.g4jnt@...>
To: "UK Microwaves groups.io" <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] 23cm warm cable
You'd expect .086 SR to get warm at 100W of L-Band
 
Back in the days of playing with a K2RIW, I remember the thicker .141 SR gets warm at 400W of 432MHz
And the same stuff warms with 10W of 10GHz
 
You should be using .141 at that level / frequency
 
Andy
 
 
On Wed, 3 Mar 2021 at 21:18, militaryoperator via groups.io <Military1944=aol.com@groups.io> wrote:
Ok, my new 23cm 100W set seems to be working but noticed the cable from amp to isolator is getting warm, its blue mini bend, and the cable from ant relay to socket on case wall, semi-rigid (0.086) is also warm. 
 
I'm going N to sma adapter, sma mini-bend to sma iso, iso is sma o/p to sma to N adp into relay, N to sma adp then semi rigid to N chassis socket.
 
What else can I use? RG402?  I could use N type soldered to RG402 to sma for Amp to Iso and  Soldered N RG402 to N and use a N to N bulkhead I guess. That would remove a couple of adaptors.
 
Ben

 

 


Re: ICNIRP

Graham G3VKV
 

I have used this one for a long while, if it works in VK land using ICNIRP data then should be OK here
VK3UM downloads (vk5dj.com)
EMRcalc
Graham G3VKV


Re: 23cm warm cable

ian hope (2E0IJH)
 

I remember melting a Rg213 patch lead with a K2RIW, BTW if anyone's got a neglected one laying about PM me
 
Ian
M5IJH

 
 
Sent: Wednesday, March 03, 2021 at 10:33 PM
From: "Andy G4JNT" <andy.g4jnt@...>
To: "UK Microwaves groups.io" <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] 23cm warm cable
You'd expect .086 SR to get warm at 100W of L-Band
 
Back in the days of playing with a K2RIW, I remember the thicker .141 SR gets warm at 400W of 432MHz
And the same stuff warms with 10W of 10GHz
 
You should be using .141 at that level / frequency
 
Andy
 
 
On Wed, 3 Mar 2021 at 21:18, militaryoperator via groups.io <Military1944=aol.com@groups.io> wrote:
Ok, my new 23cm 100W set seems to be working but noticed the cable from amp to isolator is getting warm, its blue mini bend, and the cable from ant relay to socket on case wall, semi-rigid (0.086) is also warm. 
 
I'm going N to sma adapter, sma mini-bend to sma iso, iso is sma o/p to sma to N adp into relay, N to sma adp then semi rigid to N chassis socket.
 
What else can I use? RG402?  I could use N type soldered to RG402 to sma for Amp to Iso and  Soldered N RG402 to N and use a N to N bulkhead I guess. That would remove a couple of adaptors.
 
Ben

 

 


Re: ICNIRP

Colin Ranson
 

I tend to agree with John, G3SEQ.... just give them some input to keep them happy. Anyway who’s going to look at it when they do get it ? and like John said, who’s going to police it ?  

 

Personally I’m too old to worry about such things.

 

 

Colin de G8LBS.

 

Sent from Mail for Windows 10

 

From: John E. Beech
Sent: 03 March 2021 19:32
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] ICNIRP

 

It was clear to me. You have got until April 18th 2021 to complain/offer suugestions etc. And in future there will be no
personal letters from them - you will either have to be clairvoyant or log on to their website "from time to time" - their
words which amounts to the same thing when you won't know what you are looking for because they haven't told you.
London Gazetteer? Does it still exist? ANyone read it?
         Personally I'm inclined to ignore this latest from Ofcom. How are they going to police it? If it went to court they
would have to prove their case by making actual measurements to show emf values have been exceeded.

de John G8SEQ

>  -------Original Message-------
>  From: ian hope (2E0IJH) <ian@...>
>  To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
>  Subject: Re: [UKMicrowaves] ICNIRP
>  Sent: Mar 03 '21 17:19

>  The letters about as clear as mud, but this is ofcom's calculator
https://www.ofcom.org.uk/__data/assets/excel_doc/0021/214455/emf-calculator-v0.1.2.xlsx,
>  stick your details in here and note result

>  ian
>  M5IJH

>  SENT: Wednesday, March 03, 2021 at 5:14 PM
>  FROM: "Andy G4JNT" <andy.g4jnt@...>
>  TO: "UK Microwaves groups.io" <UKMicrowaves@groups.io>
>  SUBJECT: Re: [UKMicrowaves] ICNIRP

>  You read what they sent you, and note you don't do anything yet

>  Andy
www.g4jnt.com

>  On Wed, 3 Mar 2021 at 17:10, geoffrey pike via groups.io
>  <gi0gdp@...> wrote:

>  > I have just received an e-mail from Ofcom telling me that i must
>  > observe the ICNIRP rules, so do i go to their
>  > website and fill in my details or what?
>  > cheers
>  > Geoff
>  > GI0GDP






 


Re: 23cm warm cable

Andy G4JNT
 

You'd expect .086 SR to get warm at 100W of L-Band

Back in the days of playing with a K2RIW, I remember the thicker .141 SR gets warm at 400W of 432MHz
And the same stuff warms with 10W of 10GHz

You should be using .141 at that level / frequency



On Wed, 3 Mar 2021 at 21:18, militaryoperator via groups.io <Military1944=aol.com@groups.io> wrote:
Ok, my new 23cm 100W set seems to be working but noticed the cable from amp to isolator is getting warm, its blue mini bend, and the cable from ant relay to socket on case wall, semi-rigid (0.086) is also warm. 

I'm going N to sma adapter, sma mini-bend to sma iso, iso is sma o/p to sma to N adp into relay, N to sma adp then semi rigid to N chassis socket.

What else can I use? RG402?  I could use N type soldered to RG402 to sma for Amp to Iso and  Soldered N RG402 to N and use a N to N bulkhead I guess. That would remove a couple of adaptors.

Ben


Re: 23cm warm cable

militaryoperator
 


Are you sure it’s not just conducted heat?
 

It is, its conducting from inside the cable out. 


B

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