EMRFD Message Archive 382

Message Date From Subject
382 2007-01-27 20:37:10 Jim Miller Helical Filter?
Anyone had experience with Toko helical filters?

They appear to be tunable. Can one which is nominally 515Mhz be tuned down
to 500Mhz?

73

jim ab3cv
383 2007-01-28 02:23:13 Lasse Re: Helical Filter?
Yes!
I would be really surprised if you coudn't make it to 500! It's less than 5%
Was using a 550MHz Toko Helical filter to 560 with no degradation and
excellent passband and stopband!

/Lasse SM5GLC

At 05:36 2007-01-28, you wrote:
>Anyone had experience with Toko helical filters?
>
>They appear to be tunable. Can one which is nominally 515Mhz be tuned down
>to 500Mhz?
>
>73
>
>jim ab3cv
>
384 2007-01-28 06:10:32 Jim Miller Re: Helical Filter?
thanks!

i'll give it a go.

jim ab3cv
385 2007-01-28 08:15:05 Dan Rae Re: Helical Filter?
Jim Miller wrote:

>Anyone had experience with Toko helical filters?
>
>They appear to be tunable. Can one which is nominally 515Mhz be tuned down
>to 500Mhz?
>
>73
>
>jim ab3cv
>
>
>
Jim if you look at the list on the Toko web site you will find that
within each series they go in steps the size of which depends on the
bandwidth, whether they are 2 or 3 section. So, yes, within the ranges
that each type covers you can get continuous coverage by choosing the
nearest specified center frequency. So the answer to your specific
question is yes, assuming that the nominal 515 filter is the nearest to
your target frequency in that series. *But* if you are using the 5HT
triple tuned filter, then I'd go for the 495 nominal one, not the 515 to
be sure.

I just made a 400 MHz DDS clock source using a nominal 395 MHz 3 section
filter in the 5CHT series which tuned up easily. There is a nominal
510 MHz filter in that series also.

73
Dan
ac6ao / g3ncr
386 2007-01-28 08:32:17 Jim Miller Re: Helical Filter?
Hi Dan

I saw the 495Mhz CF 5HT at the Toko site but I couldn't find any place to
buy one. Digikey only has the 515 selection.

Any ideas on other folks who carry Toko in the US?

73

jim ab3cv