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Dunstar Filters

 

These are the bandpass filters that have been used for years. Don't know if you can find them anymore. They are coupled resonator type filters using air core inductors. If you really want, you can make your own. See attached.


OIP (1).jpg
OIP.jpg
300-21_thumbnail (9).jpg

 

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Dave,

Do you have any data in re how sharp/effective this filter is? I'd like to try building one (or more for other bands besides 21MHz).

Hiroki AH6CY

On Oct 7, 2024, at 11:34 AM, David W Crocker via <dwcae@...> wrote:

These are the bandpass filters that have been used for years. Don't know if you can find them anymore. They are coupled resonator type filters using air core inductors. If you really want, you can make your own. See attached.


<OIP (1).jpg><OIP.jpg><300-21_thumbnail (9).jpg>
 

The values can be scaled by the ratio of the frequencies. ie: 21/28 for the multiplier for the inductors and capacitors to scale to 10 meters. if you want to see the response of various filters, use a program like Elsie. Take a look at the filters used by Rick and Joanna which are the one used by PAARA at Field Day and Pacificon.










Dave W6VYC



On Monday, October 7, 2024 at 11:43:22 AM PDT, Hiroki Kato <hiroki@...> wrote:


Dave,

Do you have any data in re how sharp/effective this filter is? I'd like to try building one (or more for other bands besides 21MHz).

Hiroki AH6CY

On Oct 7, 2024, at 11:34 AM, David W Crocker via <dwcae@...> wrote:

These are the bandpass filters that have been used for years. Don't know if you can find them anymore. They are coupled resonator type filters using air core inductors. If you really want, you can make your own. See attached.


<OIP (1).jpg><OIP.jpg><300-21_thumbnail (9).jpg>
 

If you have one built, let's put it in a VNA.? Either a nanoVNA, or my Rigol.? Cliff


On October 7, 2024 12:38:27 PM PDT, "David W Crocker via groups.io" <dwcae@...> wrote:
The values can be scaled by the ratio of the frequencies. ie: 21/28 for the multiplier for the inductors and capacitors to scale to 10 meters. if you want to see the response of various filters, use a program like Elsie. Take a look at the filters used by Rick and Joanna which are the one used by PAARA at Field Day and Pacificon.










Dave W6VYC



On Monday, October 7, 2024 at 11:43:22 AM PDT, Hiroki Kato <hiroki@...> wrote:


Dave,

Do you have any data in re how sharp/effective this filter is? I'd like to try building one (or more for other bands besides 21MHz).

Hiroki AH6CY

On Oct 7, 2024, at 11:34 AM, David W Crocker via <dwcae@...> wrote:

These are the bandpass filters that have been used for years. Don't know if you can find them anymore. They are coupled resonator type filters using air core inductors. If you really want, you can make your own. See attached.


<OIP (1).jpg><OIP.jpg><300-21_thumbnail (9).jpg>
 

We (AB6RF and me) have been pretty happy with K6WX's filters and diplexers at Pacificon.? ? We rarely run more than 500W on any station (due to AC power limitations).? They run cool; we have never plugged in the fans.

VA6AM also has some good designs as well.? ? We have used some of these too at the station.



73 de AI6KG




On Mon, Oct 7, 2024 at 11:35?AM David W Crocker via <dwcae=[email protected]> wrote:
These are the bandpass filters that have been used for years. Don't know if you can find them anymore. They are coupled resonator type filters using air core inductors. If you really want, you can make your own. See attached.
 

Christopher,

Nice looking products with very good adjacent band rejection. The low power toroid versions are reasonably priced.

Dave W6VYC

On Monday, October 7, 2024 at 01:47:12 PM PDT, Christopher AI6KG <ch@...> wrote:


We (AB6RF and me) have been pretty happy with K6WX's filters and diplexers at Pacificon.? ? We rarely run more than 500W on any station (due to AC power limitations).? They run cool; we have never plugged in the fans.

VA6AM also has some good designs as well.? ? We have used some of these too at the station.



73 de AI6KG




On Mon, Oct 7, 2024 at 11:35?AM David W Crocker via <dwcae=[email protected]> wrote:
These are the bandpass filters that have been used for years. Don't know if you can find them anymore. They are coupled resonator type filters using air core inductors. If you really want, you can make your own. See attached.

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