Hi Rick there is a problem building a sharp ladder filter with 500 or 455
kHz resonators. I have played with a number. the difficulty seems to stem
from the fact that to get a narow filter you have to design for a filter
impedance of around 250 to 300ohms. then when you conside the ESR of the
resonators of say 40 to 70 ohms and 5 in series you have a lot of loss
through the filter. The best I managed at 455khz was about 800Hz pass band,
but a lot of insertion loss. I think a more promising format is to use the
resonators in shunt (parrallel resonance) with top coupling. I think the
late Jan Noedling LA2AK had some information on his web pages which I
believe are still available. I have not tried that yet.
Rapid Electronics does wire ended ceramic resonators for between 10p and 20p
(exVAT)each in singles and discounts lots of 25 by a further 10% or more.
No Min order but £3 postage on oders less that £30
www.rapidonline.com
Best Wishes
Alan G3NYK
----- Original Message -----
From: "Rik Strobbe" <[email protected]>
To: <[email protected]>
Sent: Monday, June 15, 2009 2:10 PM
Subject: Re: LF: 500 kHz resonators at nedis.com
> Pedro,
>
> I have a VXO with a 4MHz ceramic resonator. That signal is divided by
> 8. Range is 500.5 - 506kHz.
> see
> http://wireless.org.uk/500k_tx.gif
> http://wireless.org.uk/qtx.htm
>
> 4MHz cer. resonators are available at less than 1 Euro in almost
> every electronic shop.
>
> 500kHz cer. resonators however could be interesting to build a sharp
> RX-input filter (cfr xtal ladder filter)
>
> 73, Rik ON7YD - OR7T
>
>
> At 14:50 15/06/2009, you wrote:
> >Hello group,
> >
> >I just discovered that the European grossist for electronic parts has
> >500 kc ceramic resonators in their range for less than half a Euro.
> >this is a great building block for a tunable 500 kHz transmitter. I
> >ordered some for test purposes to see how far they can e pulled.
> >Unfortunately they don't sell direct to customers, only to retailers.
> >
> >
> >Pedro
> >
> >www.nedis.com
>
>
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