Roger, this depends on the bandwith or Q that you want to have. You could build band filters that are much smaller than the band! But this is maybe not necessary in your case.

Something between 1...10mH is suited for a band filter on 137 kHz and a high µ pot core could be used. Like those 3 parts (just to get the idea):

http://www.reichelt.de/?;ACTION="">

http://www.reichelt.de/?;ACTION="">

http://www.reichelt.de/?;ACTION="">


73, Stefan


Am 25.07.2010 21:53, schrieb Roger Lapthorn:

All,

Thanks for the good advice already regarding LPF toroids for 136kHz. Sounds like a T68-2 or T157-2 (or something in between) should fit my requirements well. Mal, et al, my ERP is unlikely to exceed a few milliwatts on 136kHz, so don't worry about me putting out too much power :-)

Any suggestions on what inductor type to use for receiver input tuned circuit on 136kHz please?

73s
Roger G3XBM

On 25 July 2010 19:39, Gary - G4WGT <[email protected]> wrote:

Hi Mal,

You wrote :-

The aim on this band is for at least 1W erp

The maximum allowed ERP for this band (136kHz) is 1 watt ERP.

73

Gary - G4WGT.

On 25 July 2010 19:19, mal hamilton <[email protected]> wrote:

Roger

A T- 200 is ideal but maybe too large for u. Except you have a large antenna 20w is not enough on 137 for any serious impact.

The aim on this band is for at least 1W erp

de mal/g3kev

 

----- Original Message -----

From: Roger Lapthorn

To: [email protected]

Sent: Sunday, July 25, 2010 6:58 PM

Subject: LF: 136kHz LPF toroids?

Some advice please....

1. I'm about to construct a 136kHz transverter with an output power up to 20W. What's the best choice of toroid for the TX output low pass filter inductors for this sort of power level?  Around 54uH is required and this is rather too much for a T50 (red) toroid that I used on 500kHz. I don't want anything too physically large if I can avoid it.
2. Also, are there any readily available canned inductors (or toroids) suitable for use as the input tuned circuit on RX? Something like the KANK3333 inductors from Toko? Again, nothing too big unless this is a necessity for large signal handling.

Thanks in advance for inputs.

73s
Roger G3XBM

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G3XBM    GQRP 1678      ISWL G11088

--
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
G3XBM    GQRP 1678      ISWL G11088