That filter has pretty much the same attenuation at 50 MHz as my homebrew one, so yes, it should work fine. Mine has better match at 28 MHz, at the expense of not as good match at lower frequencies. I ended up with the following, after some tweaking....
My filter is a two section low-pass pi-network. The two inductors are both 7 turns #22 AWG enamelled wire on T30-6 cores. The capacitors to ground at the input and output are both 166 pf (91 pF and 75 pF dipped silver-mica caps in parallel). The capacitor to ground at the junction of the two coils is 309 pF (270 pF and 39 pf dipped silver-mica caps in parallel). Measured > 30 dB return loss and < 0.5 dB insertion loss over 27-30 MHz (mind you my measurement setup probably isn't really accurate enough to reliably measure 30 dB return losses). Also > 30 dB attenuation at 50 MHz. When I try modelling the filter with SPICE I get only a fair agreement with measurements. I think the lead length and other strays are not insignificant. So if anyone else builds one, be prepared for some tweaking if you want best performance. The K2/K60XV now (after tweaking) likes the impedance it's seeing and can provide full 1 mW output with the filter mounted right at the output of the K60XV and a few feet of 50 ohm cable to the transverter. 73, Steve VE3SMA --- On Thu, 2/12/09, wayne burdick <n...@elecraft.com> wrote: > Minicircuits makes a 30 MHz in-line (BNC) low-pass filter > that should do just as well, for those who don't want to > roll their own: their model #BLP-30+. See: > > > http://www.minicircuits.com/cgi-bin/modelsearch?search_type=info&model=BLP-30%2B > > I would recommend this filter if anyone has similar RFI > problems with any transverter, used with either a K2 or K3. > > 73, > Wayne > N6KR __________________________________________________________________ Looking for the perfect gift? Give the gift of Flickr! http://www.flickr.com/gift/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
