CQ250 bandpass filter
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This forum is run by the BATC (British Amateur Television Club), it is service made freely available to all interested parties, please do not abuse this privilege.
Thank you
Re: CQ250 bandpass filter
Wouldn't a slot be a more controllable method? That or a coupling probe. I suppose it doesn't matter as long as you have the means to adjust the coupling, but it might be more repeatable.
Mike
https://www.wirelessdesignmag.com/artic ... ter-design
Mike
https://www.wirelessdesignmag.com/artic ... ter-design
Re: CQ250 bandpass filter
My Atlas LCD meter is not coping sub 2pF! It's very out of calibration. 25mm lengths of coax inner to outer are coming out -6 to -8pF. RG316 and RG402. I'm making the lid and hoping for CAT17 magic.....
Re: CQ250 bandpass filter
As long as you know the capacitance per metre you can at least make an estimate - cut it long in case you need to shorten it. Lengthening it, once cut is hard. UT141 for example is about 29pF per foot which is about 1pF per cm.M0YDH wrote:My Atlas LCD meter is not coping sub 2pF! It's very out of calibration. 25mm lengths of coax inner to outer are coming out -6 to -8pF. RG316 and RG402. I'm making the lid and hoping for CAT17 magic.....
Mike
Re: CQ250 bandpass filter
I made the lid and sides - the coupling can wait till CAT17 workshop session. Then I made a 432MHz comb line filter per the W1GHZ recipe on the club wiki. It looks like a piece of witch craft
I hope the club wizards can get it tuned on Saturday......
See you
David M0YDH
I hope the club wizards can get it tuned on Saturday......
See you
David M0YDH
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- M0YDH 1st comb line filter.jpg (584.78 KiB) Viewed 4961 times
Re: CQ250 bandpass filter
i built the w1ghz 432 filter a while ago and it tuned up "as advertised"
dave
g4fre
dave
g4fre
Re: CQ250 bandpass filter
Can anyone recommend a UK supplier for the UT-141 hardline to construct one of these filters?
73 Dave
73 Dave
...are you sure I can't use a pair of 813's?...
Re: CQ250 bandpass filter
Have a look at http://uk.farnell.com/pro-power/rg402/c ... hnicalDOCS
It may be similar
It may be similar
Re: CQ250 bandpass filter
Buying it new tends to be expensive. There is usually a lot of it available used at rallies.
Mike
Mike
Re: CQ250 bandpass filter
Thanks for the info, unfortunately working 3 weekends out of 4 limit the number of rallies I can get to, I think the next chance will be the Red Rose Winter rally.
73 Dave.
73 Dave.
...are you sure I can't use a pair of 813's?...