Topics

PE1RKI 23 Cm Low loss filter responce

simonchettle
 

Hi All
 
I am thinking of using a 28 Mhz to 1296 transverter as part of a Station re-build ( after poor result on VHD NFD!).
 
However I do not know the passband  rejection of the above filter at  1268 Mhz.  I have mailed Bert and he has replied the loss / rejection is 0.99 dB – I think he slightly misunderstood  my question to him.
 
Has anybody measured the rejection at 1268 of one of his filters?  His current web site does not appear to display the filter response and I am sure it used to.
 
Cheers
Simon G8ATB
 

Phil Guttridge G3TCU
 

Hi Simon,

I bought a 23cm filter from Bert earlier this year and he sent me this
link. It doesn't show a lot of detail on the spectrum axis but it might
be some guide.

https://www.flickr.com/photos/pe1rki/23099962502/in/album-72157658763409636/

73, Phil G3TCU

On 11/07/2019 18:33, simonchettle via Groups.Io wrote:
Hi All
I am thinking of using a 28 Mhz to 1296 transverter as part of a
Station re-build ( after poor result on VHD NFD!).
However I do not know the passband  rejection of the above filter at 
1268 Mhz.  I have mailed Bert and he has replied the loss / rejection
is 0.99 dB – I think he slightly misunderstood  my question to him.
Has anybody measured the rejection at 1268 of one of his filters?  His
current web site does not appear to display the filter response and I
am sure it used to.
Cheers
Simon G8ATB

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Pete - GM4BYF
 

From Phils picture, I think Bert did understand your question. Guestimating from the grid there appears to be very little roll off between 1268 and 1296.

I wonder what your problems were on field day ? Transmit or receive or both?

73
Pete GM4BYF

On 11/07/19 19:12, Phil Guttridge G3TCU wrote:
Hi Simon,

I bought a 23cm filter from Bert earlier this year and he sent me this
link. It doesn't show a lot of detail on the spectrum axis but it might
be some guide.

https://www.flickr.com/photos/pe1rki/23099962502/in/album-72157658763409636/

73, Phil G3TCU

On 11/07/2019 18:33, simonchettle via Groups.Io wrote:
Hi All
I am thinking of using a 28 Mhz to 1296 transverter as part of a
Station re-build ( after poor result on VHD NFD!).
However I do not know the passband  rejection of the above filter at
1268 Mhz.  I have mailed Bert and he has replied the loss / rejection
is 0.99 dB – I think he slightly misunderstood  my question to him.
Has anybody measured the rejection at 1268 of one of his filters?  His
current web site does not appear to display the filter response and I
am sure it used to.
Cheers
Simon G8ATB

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--
vry 73
Pete GM4BYF

simonchettle
 

Pete

After a fair bit of re-build of the station (pre nfd) we became a bit of an a alligator based on the reports we were receiving and were giving. so a rebuild of the station is being considered. the use of 28 Mhz IF is to avoid the 2M and 70 Cm contest stations as they run a lot of power.s Also the 23 cm pre-amp measured 1.5 db nf (including relays and connectors) when tested but something may have failed on trip to site -tests to performed this week end.

73s and thanks for the replies

simon

-----Original Message-----
From: Pete - GM4BYF via Groups.Io
Sent: Thursday, July 11, 2019 7:51 PM
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] PE1RKI 23 Cm Low loss filter responce

From Phils picture, I think Bert did understand your question.
Guestimating from the grid there appears to be very little roll off
between 1268 and 1296.

I wonder what your problems were on field day ? Transmit or receive or both?

73
Pete GM4BYF

On 11/07/19 19:12, Phil Guttridge G3TCU wrote:
Hi Simon,

I bought a 23cm filter from Bert earlier this year and he sent me this
link. It doesn't show a lot of detail on the spectrum axis but it might
be some guide.

https://www.flickr.com/photos/pe1rki/23099962502/in/album-72157658763409636/

73, Phil G3TCU

On 11/07/2019 18:33, simonchettle via Groups.Io wrote:
Hi All
I am thinking of using a 28 Mhz to 1296 transverter as part of a
Station re-build ( after poor result on VHD NFD!).
However I do not know the passband rejection of the above filter at
1268 Mhz. I have mailed Bert and he has replied the loss / rejection
is 0.99 dB – I think he slightly misunderstood my question to him.
Has anybody measured the rejection at 1268 of one of his filters? His
current web site does not appear to display the filter response and I
am sure it used to.
Cheers
Simon G8ATB

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--
vry 73
Pete GM4BYF

Pete - GM4BYF
 

I was running the 23cm station of GM3HAM/P. On the receive side I would recommend Kevin G3AAF's high pass filter. Keeps out all the nasties on 2m and 70cm.  On the transmit side best to use a 1 Mhz offset on either 145 or 433 Hope that helps. Wonder which nfd station you were.

On 12/07/19 00:31, simonchettle wrote:
Pete

After a fair bit of re-build of the station (pre nfd) we became a bit of an a alligator  based on the reports we were receiving and were giving.  so a rebuild of the station is being considered. the use of 28 Mhz IF is to avoid the 2M and 70 Cm contest stations as they run a lot of power.s Also the 23 cm pre-amp measured 1.5 db nf (including relays and connectors) when tested but something may have failed on trip to site -tests to performed this week end.

73s and thanks for the replies

simon

-----Original Message-----
From: Pete - GM4BYF via Groups.Io
Sent: Thursday, July 11, 2019 7:51 PM
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] PE1RKI 23 Cm Low loss filter responce

From Phils picture, I think Bert did understand your question.
Guestimating from the grid there appears to be very little roll off
between 1268 and 1296.

I wonder what your problems were on field day ? Transmit or receive or both?

73
Pete GM4BYF

On 11/07/19 19:12, Phil Guttridge G3TCU wrote:
Hi Simon,

I bought a 23cm filter from Bert earlier this year and he sent me this
link. It doesn't show a lot of detail on the spectrum axis but it might
be some guide.

https://www.flickr.com/photos/pe1rki/23099962502/in/album-72157658763409636/

73, Phil G3TCU

On 11/07/2019 18:33, simonchettle via Groups.Io wrote:
Hi All
I am thinking of using a 28 Mhz to 1296 transverter as part of a
Station re-build ( after poor result on VHD NFD!).
However I do not know the passband  rejection of the above filter at
1268 Mhz.  I have mailed Bert and he has replied the loss / rejection
is 0.99 dB – I think he slightly misunderstood  my question to him.
Has anybody measured the rejection at 1268 of one of his filters?  His
current web site does not appear to display the filter response and I
am sure it used to.
Cheers
Simon G8ATB

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--
vry 73
Pete GM4BYF

Bob_G1ZJP
 

Hi Simon / All

You might like to consider this filter / source of filters too.

http://aerial-parts.co.uk/epages/626ba059-121d-45c5-8692-ea58514eb29c.sf/en_GB/?ObjectPath=/Shops/626ba059-121d-45c5-8692-ea58514eb29c/Categories/Filters 
description here - 
http://aerial-parts.co.uk/WebRoot/Store25/Shops/626ba059-121d-45c5-8692-ea58514eb29c/55DD/D0E9/2089/F94E/3C1E/0A48/355F/69B3/Aerial_Parts_of_Colchester_1296_filter.pdf 

I have no connection with the company but have known John for many years and have bought various products from him.  John produces quality products, knows his limitations and won't supply where he feels he can't produce to a commercial, repeatable specification and he's generally competitive in price.  His deliveries are realistic and reasonable time scales too!  Above all he's a UK supplier and well worthy of your consideration.

73
Bob
G1ZJP

alwyn.seeds1
 

Dear All,

Bert’s low loss filter is NOT the one to use for a 28 MHz IF. It is intended to remove out of band interference and is essentially flat response from 1.21GHz to 1.31GHz-see attachment.

However, Bert made a very nice LO and image reject filter for me, which I use for 1296 MHz with 28 MHz IF. Loss, of course is slightly higher.

DB6NT also sell a suitable filter.

Hope that helps.

At G5LK/P we had a different problem in VHF NFD- yet another blown pre-amp on the Sunday morning, currently attributed to 4m getting into the control circuit. Sorry to those we could not hear in consequence, though we did manage an OK without it, with a bit of aircraft assistance.

Regards,

Alwyn  G8DOH




_____________________________________________________

Alwyn Seeds, Director
SynOptika Ltd.,
114 Beaufort Street,
London,
SW3 6BU,
England.

Tel.: +44 (0) 20 7376 4110


SynOptika Ltd., Registered in England and Wales: No. 04606737
Registered Office: 114 Beaufort Street, London, SW3 6BU, United Kingdom.
_____________________________________________________

Bo, OZ2M
 

Hello

Another idea might be to use 50 MHz as IF. The reason for using 28 MHz as IF is probably rather classic and because this was the highest band on HF rigs. But these days most have 50 MHz. Perhaps this can move the issues from the top or knee to the slope of the filter?

I have had the use of 50 MHz IF for a 23 cms/s transverter in mind for years but to many projects have kept me from giving it a go.

Bo

Andy G4JNT
 

If more use was made of quadrature mixers, image cancelling, there's another 20dB at least to add to the image rejection - which can make the filtering somewhat easier.



On Sat, 13 Jul 2019 at 09:30, Bo, OZ2M <groups.io@...> wrote:
Hello

Another idea might be to use 50 MHz as IF. The reason for using 28 MHz as IF is probably rather classic and because this was the highest band on HF rigs. But these days most have 50 MHz. Perhaps this can move the issues from the top or knee to the slope of the filter?

I have had the use of 50 MHz IF for a 23 cms/s transverter in mind for years but to many projects have kept me from giving it a go.

Bo



John E. Beech
 

When I last took part in VHF NFD as a "proper" entrant we used a 29 MHz IF ( simple LO xtal change from 28 MHz IF) to avoid problems when there was 28 MHz activity ( like there was last night) - quite common in July.
50 MHz is NOT a good choice either because that was also "open" last night and again commonly in July
A better choice might be to use 70 MHz IF (as long as your 4m Rx isn't transverting). Perhaps you could transvert to 146/147 MHz, but I don't don't know how much QRM you would get from digital modes ( I suspect that part of the band is under used. ) Or you could use something like "Soft jump" to open up an FT-817 and use something like 35 MHz IF - you would need to re-engineer your LO/mixer and filters of course, but you may bea ble to tweak your existing ones.

de John G8SEQ

-------Original Message-------
From: Bo, OZ2M <@OZ2M>
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] PE1RKI 23 Cm Low loss filter responce
Sent: Jul 13 '19 09:30

Hello

Another idea might be to use 50 MHz as IF. The reason for using 28 MHz as IF is probably rather classic and because this was the highest band on HF rigs. But these days most have 50 MHz. Perhaps this can move the issues from the top or knee to the slope of the filter?

I have had the use of 50 MHz IF for a 23 cms/s transverter in mind for years but to many projects have kept me from giving it a go.

Bo



Andy G4JNT
 

Neither 50MHz nor the 70MHz  band is a good choice of IF if used in VHF NFD

Nothing wrong with 28MHz as an IF for 1296, or even higher bands - you just have to grit your teeth and make a proper filter

Even the old JVL design was designed with a 28MHz IF In mind.  That's why the LO filter was designed with such a narrow bandwidth - just 20MHz wide at 10GHz.



On Sat, 13 Jul 2019 at 09:51, John E. Beech <john@...> wrote:
         When I last took part in VHF NFD as a "proper" entrant we used a 29 MHz IF ( simple LO xtal change from 28 MHz IF) to avoid problems when there was 28 MHz activity ( like there was last night) - quite common in July.
         50 MHz is NOT a good choice either because that was also "open" last night and again commonly in July
A better choice might be to use 70 MHz IF (as long as your 4m Rx isn't transverting). Perhaps you could transvert to 146/147  MHz, but I don't don't know how much QRM you would get from digital modes  ( I suspect that part of the band is under used. ) Or you could use something like "Soft jump" to open up an FT-817 and use something like 35 MHz IF - you would need to re-engineer your LO/mixer and filters of course, but you may bea ble to tweak your existing ones.

de John G8SEQ

>  -------Original Message-------
>  From: Bo, OZ2M <groups.io@...>
>  To: UKMicrowaves@groups.io
>  Subject: Re: [UKMicrowaves] PE1RKI 23 Cm Low loss filter responce
>  Sent: Jul 13 '19 09:30

>  Hello

>  Another idea might be to use 50 MHz as IF. The reason for using 28 MHz as IF is probably rather classic and because this was the highest band on HF rigs. But these days most have 50 MHz. Perhaps this can move the issues from the top or knee to the slope of the filter?

>  I have had the use of 50 MHz IF for a 23 cms/s transverter in mind for years but to many projects have kept me from giving it a go.

>  Bo







ian hope (2E0IJH)
 

Our masthead set up is based on a SG labs unit running with a 146mhz IF, not had any issues with it yet.
 
Ian
2E0IJH

 
Sent: Saturday, July 13, 2019 at 9:51 AM
From: "John E. Beech" <john@...>
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] PE1RKI 23 Cm Low loss filter responce
When I last took part in VHF NFD as a "proper" entrant we used a 29 MHz IF ( simple LO xtal change from 28 MHz IF) to avoid problems when there was 28 MHz activity ( like there was last night) - quite common in July.
50 MHz is NOT a good choice either because that was also "open" last night and again commonly in July
A better choice might be to use 70 MHz IF (as long as your 4m Rx isn't transverting). Perhaps you could transvert to 146/147 MHz, but I don't don't know how much QRM you would get from digital modes ( I suspect that part of the band is under used. ) Or you could use something like "Soft jump" to open up an FT-817 and use something like 35 MHz IF - you would need to re-engineer your LO/mixer and filters of course, but you may bea ble to tweak your existing ones.

de John G8SEQ

> -------Original Message-------
> From: Bo, OZ2M <groups.io@...>
> To: UKMicrowaves@groups.io
> Subject: Re: [UKMicrowaves] PE1RKI 23 Cm Low loss filter responce
> Sent: Jul 13 '19 09:30
>
> Hello
>
> Another idea might be to use 50 MHz as IF. The reason for using 28 MHz as IF is probably rather classic and because this was the highest band on HF rigs. But these days most have 50 MHz. Perhaps this can move the issues from the top or knee to the slope of the filter?
>
> I have had the use of 50 MHz IF for a 23 cms/s transverter in mind for years but to many projects have kept me from giving it a go.
>
> Bo
>
>
>
>