I do have another bandpass cavity that has 55dB attenuation. Rather than use the 24dB preamp I can always use the one with less gain because I too was concerned with overloading the front-end.
The Hamtronics is a preselector helical resonator preamp, so doesn't it already do what the extra cavity does by way of the helical resonator? I'm not stuck on Hamtronics. I just want the best solution. --- In [email protected], "Ralph S. Turk" <w7...@...> wrote: > > Hi Bob > All duplexers have very poor out of band attenuation. The extra cavity is to narrow the bandwidth. > Cavity should have 2-3db of insertion loss (equates to sharp slopes). > Preamp gain is adjusted by use of a step attenuator. Determine how much attn is needed to just raise > the limiter by about 10% max. This way you make up for loss of system plus about 10%. Too much gain will > just lead to overload of the front end of the RX. > Ralph > ----- Original Message ----- > From: "Bob Ricci" <b...@...> > To: [email protected] > Sent: Wednesday, February 4, 2009 3:25:14 PM GMT -07:00 U.S. Mountain Time (Arizona) > Subject: [Repeater-Builder] Re: Hamtronics Helical Resonator Preamp or Advanced Research Preamp > > > > > > > The WA-COM 642 duplexer are Bp/Br cavities. The bandwidth is already > limited. Are you saying a 7th cavity adding further loss? And why > limit the gain? I remain teachable. > > "Those that don't know, ask..." > > --- In [email protected] , "Ralph S. Turk" <w7hsg@> > wrote: > > > > You would still need a pass cavity in front of the Preamp. Unless > the Helical is similar > > to the old Motorola vintage L, H or M receivers the cavity is still > needed to limit the bandwidth > > going to the preamp. You might also need an attenuator after the > preamp to limit the gain. > > Ralph > > ----- Original Message ----- > > From: "Bob Ricci " <bob@> > > To: Repeater-Builder@ yahoogroups .com > > Sent: Wednesday, February 4, 2009 2:08:14 PM GMT -07:00 U.S. > Mountain Time (Arizona) > > Subject: [Repeater-Builder] Hamtronics Helical Resonator Preamp or > Advanced Research Preamp > > > > > > > > > > > > > > Hamtronics has a preamp with a helical resonator with a 18dB > preamp. I > > am at a high elevation with noise all around me. Advanced R3esearch > has > > a 24dB preamp with a low NF and 1dB compression point. Either would > be > > behind a WACOM 642 6 cavity duplxer . > > > > Which would be the better approach? The ultimate goal is to improve > > reception of handhelds in a mountainous region. > > > > > > __ ._,_. __ _ > > Messages in this topic ( 1 ) Reply (via web post) | Start a new > topic > > Messages | Files | Photos | Links | Members > > > > > > > > Yahoo! Groups > > Change settings via the Web (Yahoo! ID required) > > Change settings via email: Switch delivery to Daily Digest | Switch > format to Traditional > > Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe > > > > > > > > Recent Activity > > > > ââ¬Â¢ > > 15 > > New Members > > ââ¬Â¢ > > 1 > > New Links > > ââ¬Â¢ > > 1 > > New Files > > Visit Your Group > > > > > > > > Sell Online > > > > Start selling with > > > > our award-winning > > > > e-commerce tools. > > > > Group Charity > > > > Be the Change > > > > A citizen movement > > > > to change the world > > > > Special K Group > > > > on Yahoo! Groups > > > > Join the challenge > > > > and lose weight. > > . > > > > __ ,_._, __ _ > > >
