[CQ-Contest] Re: Bandpass Filtering

Christian Pidancier cpidanci at nortelnetworks.com
Fri Feb 19 14:36:32 EST 1999

	High power through BP filter may be ok but SWR has to be maintain at
a low level (voltage or current may be infinite in case of infinite SWR...).

	I'm using SEMCO capacitors, number of pole is choosed to avoid extra
losses and heating of the filter parts (40dB is not useful in my station,
the antennas are away from each other). 

	SEMCO web page is http://www.semco-usa.com/index.html 

	The problem is the same for ferrite cores, I try to use air coils
(with 2mm OD silvered wires) as often as possible (on the lowest freq to).

	73 de F6HLC, Christian 

> -----Message d'origine-----
> De:	i4jmy at kb9byq.ampr.org [SMTP:i4jmy at kb9byq.ampr.org]
> Date:	vendredi 19 février 1999 14:57
> À:	cq-contest at contesting.com
> Cc:	topband at contesting.com
> Objet:	[CQ-Contest] Re: Bandpass Filtering
> Building filters able to handle a consistent amount of power is not
> expecially difficult, unless a couple of parameters has to be taken
> in account.
> The first one is that components (mainly capacitors) has to be that
> type able to manage high currents and high voltages and not to change
> substantially their value because of heating.
> The second is that insertion loss could be significant in term of
> heathing. 
> This last drives to the need of low insertion loss design (typ -.5db)
> to prevent excessive heating, currents and voltages and critical 
> component values (i.e. too small inductances)
> Of course this goes in contrast with filter sharpness and building
> semplicity and tells, when possible, to use filters on receiving
> section only expecially on higher HF bands.
> About practical approaches, it's a number of years that Arrl HANDBOOK
> gives a full set of normalized values and calculating examples about
> filters.
> Concerning how to split one antenna to a couple of receivers, the
> easiest way is to use an inductive directional coupler that gives
> two outputs of typically -4db but with some 30-50db isolation
> between ports.
> 73, 
> Mauri, I4JMY (one of IR4T) 
> -----Original Message-----
> From: owner-cq-contest at contesting.com
> [mailto:owner-cq-contest at contesting.com]On Behalf Of Peter
> Sent: Thursday, February 18, 1999 8:22 AM
> To: CQ-Contest at contesting.com
> Cc: topband at contesting.com
> Subject: [CQ-Contest] Bandpass filtering
> Hi,
> Has anybody out there some experience with homemade band pass filters
> for the 200 watt level?
> yes I kwon there are dunstarr and ice filters, but howebrew is still my
> favourite way!
> Second are there any drawings for the use of 1 berverage and two rigs
> e.g. 80 and 160?
> How does the group handle this?
> Peter
> --
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