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13cm filter

G0FCU
 

I built a pipe cap filter for 13cm but it has an insertion loss of 12dB when measured. Possibly this is down to my lack of sub-mm accuracy in construction. Does anyone have suggestions for a design that is reproducible, ideally that I could build before Sunday. I couldn't find pipe caps locally so bought from eBay but stupidly only bought one.

Thanks
Simon
G0FCU.
David Redman
 

If you have plotted the response it's probably very tight i.e. Narrow, hence the  high insertion loss, which means if you have built it correctly the 2 probes are too short.
Search on the Internet for Paul Wades W1GHz info on the correct size end caps for 13cms and higher bands and the effect of probe length v insertion loss and filter response.

Be aware of American end cap dimensions v UK / EU, they are different but manageable.

With your insertion loss on 13cm  I suspect your probes are short by 2 to 3mm and maybe your tune screw is very well inserted into the cavity.

I have made pipecap filters for 9 and 6cm and always use 2.5 or 3mm copper for the base plate with SMA connectors screwed into tapped hokes in the base plate. This way if the probe is too long you can adjust etc

Make sure your soldering of all parts is good and ensure your measurement method is as consistent as possible. 

Just my thoughts

Dave
G4IDR 




On Fri, 6 May 2022, 18:35 G0FCU, <simon@...> wrote:
I built a pipe cap filter for 13cm but it has an insertion loss of 12dB when measured. Possibly this is down to my lack of sub-mm accuracy in construction. Does anyone have suggestions for a design that is reproducible, ideally that I could build before Sunday. I couldn't find pipe caps locally so bought from eBay but stupidly only bought one.

Thanks
Simon
G0FCU.
militaryoperator
 

I built a pipe cap filter for 13cm but it has an insertion loss of 12dB when measured. Possibly this is down to my lack of sub-mm accuracy in construction. Does anyone have suggestions for a design that is reproducible, ideally that I could build before Sunday. I couldn't find pipe caps locally so bought from eBay but stupidly only bought one.

Thanks
Simon
G0FCU.

I built one of these with basic tools Simon and it seemed to work ok, cured my interference on 9Cms. Cant'state its loss/swr etc but it seemed to work.

Ben G4BXD

2.jpg
1.jpg
Stefan
 


Hi Simon and the group
 
From all my personal experience Pipecap filters are unfortunately a bit lossy specially when you want them narrow band.
 
I have build many and have stepped away from copper cap filters due being too lossy and also they are poor in stopband rejection,
while they are great in multiplier chains, they in general are unsuitable for input filtering.
 
But dont let that deter you they are fun to learn and simple to use for any lab setups, most plumbing supply stores should be able to help with spare caps.
 
Stefan VK4CSD

----- Original Message -----
From: G0FCU
Sent: Saturday, May 07, 2022 3:35 AM
Subject: [UKMicrowaves] 13cm filter

I built a pipe cap filter for 13cm but it has an insertion loss of 12dB when measured. Possibly this is down to my lack of sub-mm accuracy in construction. Does anyone have suggestions for a design that is reproducible, ideally that I could build before Sunday. I couldn't find pipe caps locally so bought from eBay but stupidly only bought one.

Thanks
Simon
G0FCU.
G0FCU
 

Hi Dave, Ben and Stefan,

Thanks for the inputs, I've just re-read Paul's paper but now have a much better understanding. I'll try lengthening the probes by a few mm tomorrow.

I've searched for pipe caps on the Screwfix website (and they sell everything for tradesmen) but can't find any or at least any of the needed size hence resorting to eBay.

73 Simon
G0FCU.

On Fri, 6 May 2022, 22:38 Stefan, <comlab@...> wrote:
Hi Simon and the group
 
From all my personal experience Pipecap filters are unfortunately a bit lossy specially when you want them narrow band.
 
I have build many and have stepped away from copper cap filters due being too lossy and also they are poor in stopband rejection,
while they are great in multiplier chains, they in general are unsuitable for input filtering.
 
But dont let that deter you they are fun to learn and simple to use for any lab setups, most plumbing supply stores should be able to help with spare caps.
 
Stefan VK4CSD
----- Original Message -----
From: G0FCU
Sent: Saturday, May 07, 2022 3:35 AM
Subject: [UKMicrowaves] 13cm filter

I built a pipe cap filter for 13cm but it has an insertion loss of 12dB when measured. Possibly this is down to my lack of sub-mm accuracy in construction. Does anyone have suggestions for a design that is reproducible, ideally that I could build before Sunday. I couldn't find pipe caps locally so bought from eBay but stupidly only bought one.

Thanks
Simon
G0FCU.
Alan Melia
 


Try search ''end feed pipefittings'' (pg 473 in my paper cat)  part# for 15mm 90441   ''flowmasta''
 
Alan
G3NY

----- Original Message -----
From: G0FCU
Sent: Friday, May 06, 2022 10:49 PM
Subject: Re: [UKMicrowaves] 13cm filter

Hi Dave, Ben and Stefan,

Thanks for the inputs, I've just re-read Paul's paper but now have a much better understanding. I'll try lengthening the probes by a few mm tomorrow.

I've searched for pipe caps on the Screwfix website (and they sell everything for tradesmen) but can't find any or at least any of the needed size hence resorting to eBay.

73 Simon
G0FCU.

On Fri, 6 May 2022, 22:38 Stefan, <comlab@...> wrote:
Hi Simon and the group
 
From all my personal experience Pipecap filters are unfortunately a bit lossy specially when you want them narrow band.
 
I have build many and have stepped away from copper cap filters due being too lossy and also they are poor in stopband rejection,
while they are great in multiplier chains, they in general are unsuitable for input filtering.
 
But dont let that deter you they are fun to learn and simple to use for any lab setups, most plumbing supply stores should be able to help with spare caps.
 
Stefan VK4CSD
----- Original Message -----
From: G0FCU
Sent: Saturday, May 07, 2022 3:35 AM
Subject: [UKMicrowaves] 13cm filter

I built a pipe cap filter for 13cm but it has an insertion loss of 12dB when measured. Possibly this is down to my lack of sub-mm accuracy in construction. Does anyone have suggestions for a design that is reproducible, ideally that I could build before Sunday. I couldn't find pipe caps locally so bought from eBay but stupidly only bought one.

Thanks
Simon
G0FCU.
Stefan
 


here in AU they are sold as 40mm or 1-1/2 inch copper end cap , I checked screwfix too and they dont stock it.
Maybe in the UK they dont used that size copper pipe
 
 

----- Original Message -----
From: G0FCU
Sent: Saturday, May 07, 2022 7:49 AM
Subject: Re: [UKMicrowaves] 13cm filter

Hi Dave, Ben and Stefan,

Thanks for the inputs, I've just re-read Paul's paper but now have a much better understanding. I'll try lengthening the probes by a few mm tomorrow.

I've searched for pipe caps on the Screwfix website (and they sell everything for tradesmen) but can't find any or at least any of the needed size hence resorting to eBay.

73 Simon
G0FCU.

On Fri, 6 May 2022, 22:38 Stefan, <comlab@...> wrote:
Hi Simon and the group
 
From all my personal experience Pipecap filters are unfortunately a bit lossy specially when you want them narrow band.
 
I have build many and have stepped away from copper cap filters due being too lossy and also they are poor in stopband rejection,
while they are great in multiplier chains, they in general are unsuitable for input filtering.
 
But dont let that deter you they are fun to learn and simple to use for any lab setups, most plumbing supply stores should be able to help with spare caps.
 
Stefan VK4CSD
----- Original Message -----
From: G0FCU
Sent: Saturday, May 07, 2022 3:35 AM
Subject: [UKMicrowaves] 13cm filter

I built a pipe cap filter for 13cm but it has an insertion loss of 12dB when measured. Possibly this is down to my lack of sub-mm accuracy in construction. Does anyone have suggestions for a design that is reproducible, ideally that I could build before Sunday. I couldn't find pipe caps locally so bought from eBay but stupidly only bought one.

Thanks
Simon
G0FCU.
Gerhard_DK4XP
 

Don't forget that they are just a single resonator filter.

I have made some measurements on them.
More as a note to my selfes, not an official publication:

<  http://www.hoffmann-hochfrequenz.de/downloads/PipeCapFilters.pdf   >

~10 Meg pdf because of the many pictures.


Sorry. My web site is a mess. Bound to be rewritten RSN.

Gerhard


Am 06.05.22 um 23:38 schrieb Stefan:

Hi Simon and the group
 
From all my personal experience Pipecap filters are unfortunately a bit lossy specially when you want them narrow band.
 
I have build many and have stepped away from copper cap filters due being too lossy and also they are poor in stopband rejection,
while they are great in multiplier chains, they in general are unsuitable for input filtering.
 
But dont let that deter you they are fun to learn and simple to use for any lab setups, most plumbing supply stores should be able to help with spare caps.
 
Stefan VK4CSD
----- Original Message -----
From: G0FCU
Sent: Saturday, May 07, 2022 3:35 AM
Subject: [UKMicrowaves] 13cm filter

I built a pipe cap filter for 13cm but it has an insertion loss of 12dB when measured. Possibly this is down to my lack of sub-mm accuracy in construction. Does anyone have suggestions for a design
You don't need sub-mm precision. With the screw it can be tuned to your frequency.
And the probe length can be adjusted with wire cutter precision.

that is reproducible, ideally that I could build before Sunday. I couldn't find pipe caps locally so bought from eBay but stupidly only bought one.

They are in the local hardware store where the blue collar people are.


Thanks
Simon
G0FCU.
G0FCU
 

You're a star Alan, those are the magic words!
Thanks.

On Fri, 6 May 2022, 23:47 Alan Melia via groups.io, <Alan.Melia=btinternet.com@groups.io> wrote:
Try search ''end feed pipefittings'' (pg 473 in my paper cat)  part# for 15mm 90441   ''flowmasta''
 
Alan
G3NY
----- Original Message -----
From: G0FCU
Sent: Friday, May 06, 2022 10:49 PM
Subject: Re: [UKMicrowaves] 13cm filter

Hi Dave, Ben and Stefan,

Thanks for the inputs, I've just re-read Paul's paper but now have a much better understanding. I'll try lengthening the probes by a few mm tomorrow.

I've searched for pipe caps on the Screwfix website (and they sell everything for tradesmen) but can't find any or at least any of the needed size hence resorting to eBay.

73 Simon
G0FCU.

On Fri, 6 May 2022, 22:38 Stefan, <comlab@...> wrote:
Hi Simon and the group
 
From all my personal experience Pipecap filters are unfortunately a bit lossy specially when you want them narrow band.
 
I have build many and have stepped away from copper cap filters due being too lossy and also they are poor in stopband rejection,
while they are great in multiplier chains, they in general are unsuitable for input filtering.
 
But dont let that deter you they are fun to learn and simple to use for any lab setups, most plumbing supply stores should be able to help with spare caps.
 
Stefan VK4CSD
----- Original Message -----
From: G0FCU
Sent: Saturday, May 07, 2022 3:35 AM
Subject: [UKMicrowaves] 13cm filter

I built a pipe cap filter for 13cm but it has an insertion loss of 12dB when measured. Possibly this is down to my lack of sub-mm accuracy in construction. Does anyone have suggestions for a design that is reproducible, ideally that I could build before Sunday. I couldn't find pipe caps locally so bought from eBay but stupidly only bought one.

Thanks
Simon
G0FCU.
Michael Scott
 

They are called "Stop ends" in the UK

73, Mike G3LYP

On 06/05/2022 22:49, G0FCU wrote:
Hi Dave, Ben and Stefan,

Thanks for the inputs, I've just re-read Paul's paper but now have a much better understanding. I'll try lengthening the probes by a few mm tomorrow.

I've searched for pipe caps on the Screwfix website (and they sell everything for tradesmen) but can't find any or at least any of the needed size hence resorting to eBay.

73 Simon
G0FCU.

On Fri, 6 May 2022, 22:38 Stefan, <comlab@...> wrote:
Hi Simon and the group
 
From all my personal experience Pipecap filters are unfortunately a bit lossy specially when you want them narrow band.
 
I have build many and have stepped away from copper cap filters due being too lossy and also they are poor in stopband rejection,
while they are great in multiplier chains, they in general are unsuitable for input filtering.
 
But dont let that deter you they are fun to learn and simple to use for any lab setups, most plumbing supply stores should be able to help with spare caps.
 
Stefan VK4CSD
----- Original Message -----
From: G0FCU
Sent: Saturday, May 07, 2022 3:35 AM
Subject: [UKMicrowaves] 13cm filter

I built a pipe cap filter for 13cm but it has an insertion loss of 12dB when measured. Possibly this is down to my lack of sub-mm accuracy in construction. Does anyone have suggestions for a design that is reproducible, ideally that I could build before Sunday. I couldn't find pipe caps locally so bought from eBay but stupidly only bought one.

Thanks
Simon
G0FCU.
Alan Melia
 


Hi Simon, as a geriatric I find paper often is much easier to search than a web site :-))
 
Hope they have a suitable size
 
Alan
G3NYK

----- Original Message -----
From: G0FCU
Sent: Saturday, May 07, 2022 7:02 AM
Subject: Re: [UKMicrowaves] 13cm filter

You're a star Alan, those are the magic words!
Thanks.

On Fri, 6 May 2022, 23:47 Alan Melia via groups.io, <Alan.Melia=btinternet.com@groups.io> wrote:
Try search ''end feed pipefittings'' (pg 473 in my paper cat)  part# for 15mm 90441   ''flowmasta''
 
Alan
G3NY
----- Original Message -----
From: G0FCU
Sent: Friday, May 06, 2022 10:49 PM
Subject: Re: [UKMicrowaves] 13cm filter

Hi Dave, Ben and Stefan,

Thanks for the inputs, I've just re-read Paul's paper but now have a much better understanding. I'll try lengthening the probes by a few mm tomorrow.

I've searched for pipe caps on the Screwfix website (and they sell everything for tradesmen) but can't find any or at least any of the needed size hence resorting to eBay.

73 Simon
G0FCU.

On Fri, 6 May 2022, 22:38 Stefan, <comlab@...> wrote:
Hi Simon and the group
 
From all my personal experience Pipecap filters are unfortunately a bit lossy specially when you want them narrow band.
 
I have build many and have stepped away from copper cap filters due being too lossy and also they are poor in stopband rejection,
while they are great in multiplier chains, they in general are unsuitable for input filtering.
 
But dont let that deter you they are fun to learn and simple to use for any lab setups, most plumbing supply stores should be able to help with spare caps.
 
Stefan VK4CSD
----- Original Message -----
From: G0FCU
Sent: Saturday, May 07, 2022 3:35 AM
Subject: [UKMicrowaves] 13cm filter

I built a pipe cap filter for 13cm but it has an insertion loss of 12dB when measured. Possibly this is down to my lack of sub-mm accuracy in construction. Does anyone have suggestions for a design that is reproducible, ideally that I could build before Sunday. I couldn't find pipe caps locally so bought from eBay but stupidly only bought one.

Thanks
Simon
G0FCU.
geoffrey pike
 

There are some dimensions here and the losses are no where near  12dB !


cheers
Geoff
GI0GDP

On Friday, 6 May 2022, 18:36:02 BST, G0FCU <simon@...> wrote:


I built a pipe cap filter for 13cm but it has an insertion loss of 12dB when measured. Possibly this is down to my lack of sub-mm accuracy in construction. Does anyone have suggestions for a design that is reproducible, ideally that I could build before Sunday. I couldn't find pipe caps locally so bought from eBay but stupidly only bought one.

Thanks
Simon
G0FCU.
G0FCU
 

Thanks for all the input on my question. Sometimes I wonder if it wouldn't be easier just to buy kit off the shelf but I'd probably get bored and certainly not learn anything.
I've plotted the insertion loss and it's in the attached graph.
image.png
Best is at 2324-2326 MHz so not far off but with a minimum loss of 8dB so still a long way from good.
I am using a 28mm end cap which is 21mm tall with probes 17mm apart. The screw has to be most of the way in to get these figures. The probes I lengthened to 13.5mm to get these results which are better than when they were shorter. I wasn't able to keep the dielectric on the coax (.086 Belden) so I know from W1GHZ's paper that this will mean the probes need to be slightly longer.

Now I know that I can get stop ends from B&Q and Screwfix I think the next step will be to make another filter although I'm unclear if the height of the stop end should be 21mm, 26mm or it doesn't matter. 

Simon
G0FCU.

On Sat, 7 May 2022 at 18:05, geoffrey pike via groups.io <gi0gdp=yahoo.co.uk@groups.io> wrote:
There are some dimensions here and the losses are no where near  12dB !


cheers
Geoff
GI0GDP
On Friday, 6 May 2022, 18:36:02 BST, G0FCU <simon@...> wrote:


I built a pipe cap filter for 13cm but it has an insertion loss of 12dB when measured. Possibly this is down to my lack of sub-mm accuracy in construction. Does anyone have suggestions for a design that is reproducible, ideally that I could build before Sunday. I couldn't find pipe caps locally so bought from eBay but stupidly only bought one.

Thanks
Simon
G0FCU.
geoffrey pike
 

I used 26mm tall end stops and got acceptable results
Geoff
GI0GDP

On Saturday, 7 May 2022, 18:55:37 BST, G0FCU <simon@...> wrote:


Thanks for all the input on my question. Sometimes I wonder if it wouldn't be easier just to buy kit off the shelf but I'd probably get bored and certainly not learn anything.
I've plotted the insertion loss and it's in the attached graph.
image.png
Best is at 2324-2326 MHz so not far off but with a minimum loss of 8dB so still a long way from good.
I am using a 28mm end cap which is 21mm tall with probes 17mm apart. The screw has to be most of the way in to get these figures. The probes I lengthened to 13.5mm to get these results which are better than when they were shorter. I wasn't able to keep the dielectric on the coax (.086 Belden) so I know from W1GHZ's paper that this will mean the probes need to be slightly longer.

Now I know that I can get stop ends from B&Q and Screwfix I think the next step will be to make another filter although I'm unclear if the height of the stop end should be 21mm, 26mm or it doesn't matter. 

Simon
G0FCU.

On Sat, 7 May 2022 at 18:05, geoffrey pike via groups.io <gi0gdp=yahoo.co.uk@groups.io> wrote:
There are some dimensions here and the losses are no where near  12dB !


cheers
Geoff
GI0GDP
On Friday, 6 May 2022, 18:36:02 BST, G0FCU <simon@...> wrote:


I built a pipe cap filter for 13cm but it has an insertion loss of 12dB when measured. Possibly this is down to my lack of sub-mm accuracy in construction. Does anyone have suggestions for a design that is reproducible, ideally that I could build before Sunday. I couldn't find pipe caps locally so bought from eBay but stupidly only bought one.

Thanks
Simon
G0FCU.
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