Re: Simrex - GLB Pre-Selector Pre-Amplifier The Simrex (aka GLB) units are actually amplified pre-selector assemblies, not just plain wide-band Receive Pre-Amplifiers.
There's a reason why these units offer/spec 8dB Gain versus the others "un-protected" preamps. The less obvious gain when compared to traditional GasFet and BiPolar RF Preamplifiers is due to the internal integrated pre and post filtering. What does it all mean... If you have some types of IMD "grunge problems" when trying a regular GasFet/BiPolar Preamplifier, chances are your results using the Simrex/GLB pre-selector might be better. The pre and post filtering inside the Pre-Selector is a big deal. s. > Jack Chomley <ra...@...> wrote: > > This unit looks like the answer for me......I think! > I am in the process of building 2 repeaters on 70cm for possible emergency > use by our Amateur Radio Club. Both will be very portable, I have Vertex > VX-2200 radios for one, Hamtronics T304/R306 boards for the other. In > keeping the units very portable, I am using these filters > > http://www.polarelectronicindustries.com/model.php/model_id/983/ > > These filters are being used due to portability, but I have reservations > about performance IF my systems end up sited close to other equipment. > Would the Simrex unit offer advantages when used with my filters? I would > look to getting the higher selectivity spec, in preference to gain. > > 73, > > Jack. VK4JRC > > Sent from my Apple iPad Tablet PC > > > On Jul 30, 2010, at 6:20 AM, "Steven M Hodell" <st...@...> wrote: > > > More great info from Frank @ SIMREX. > > > > Steve ~ KA1RCI > > > > ----- Original Message ----- > > From: Frank Neuperger > > To: fr...@... > > Cc: Steven M Hodell ; maqui >> Mike Aquilino ; sa...@... > > Sent: Thursday, July 29, 2010 4:15 PM > > Subject: Re: [Repeater-Builder] Fw: TKR750 -Preamp > > > > Steve, > > > > That did not post to the list because I don't have membership. I would > > appreciate if you would forward to the list on my behalf. > > > > Regards > > Frank > > > > On 7/29/2010 3:58 PM, Frank Neuperger wrote: > >> > >> Steven, > >> > >> Thanks for the vote of confidence. We sell them to Hams (Ham > >> frequencies) for $275($25 less than 2-way dealers) as a gesture to Gil > >> Boelke (silenet key) who developed the preselector and founded GLB (now > >> owned by SIMREX). > >> > >> Note that the standalone preselector is still made in house by staff that > >> were trained by Gil and on tooling built by Gil. > >> It is also the front end of every SNRDS-II radio. Same radios that are > >> part of many FAA and other Federal systems. > >> > >> Standard gain is 8 db > >> > >> For +$25, you can order it with ~4 dB gain and steeper skirts on the > >> filter or > >> ~11 dB gain and gentler slope on the filter skirts. > >> > >> For extreeme interference, one usage of the preselector has been to > >> place a coax stub notch filter between the antenna and the preselector. I > >> have done ~3MHz spacing of the notches of the comb for a marine radio > >> BASE application using ~ 35?? feet of LMR 400 for my stub. One of the > >> notches was placed directly onto the frequency of collocated marine base > >> station giving us an extra 22dB of suppression at that frequency. > >> Using excessive length of coax resulting in a comb allows the > >> overallbandwidth to repeak steeply and with minimal loss between the > >> notches of the comb. A single notch approach (not a comb) when placed > >> close to your desired carrier will often have unacceptable insertional > >> loss at your desired frequency. The comb notch filter is just extra > >> coax and minimizes the insertion loss close to the notch. . The calcs for > >> length are not too difficult. > >> > >> Warmest Regards > >> Frank Neuperger > >> Simrex Corporation > >> VE3FNZ > >> > > > > ----- Original Message ----- > > From: Steven M Hodell > > To: Repeater-Builder@yahoogroups.com > > Cc: sa...@... > > Sent: Thursday, July 29, 2010 2:34 PM > > Subject: Re: [Repeater-Builder] Fw: TKR750 -Preamp > > > > > > Another very good choice for this application is the GLB Preselector / > > Preamp from Simrex Corp. > > > > I have several of these deployed on 144 / 220 / 440 Amateur repeaters and > > they all perform very well. They can be tuned to maximize gain or > > selectivity per your requirements and their support is outstanding. > > > > http://www.simrex.com/site/products/special.htm > > > > PRESELECTOR PREAMPLIFER > > > > Low cost solution to interference, intermodulation and desensitization > > problems. > > Helical Resonator Design. > > Preselector Specifications (pdf 63k) > > Preselector Example Diagram (pdf 10k) > > > > >
