skip I opened up My 2 meter GLB preamp preselector. it is an MRF-901. Years ago there was an article in one of the Ham radio handbooks that showed a 4 element UHF preamp/preselector that I built for ATV use. and it too was based on an MRF-901. It worked great. GaSfets I feel have too much gain, and introduce too much noise for repeater use. If Im not mistaken the Kendercom receivers use 2 MRF-901's in the Front end. Other than Commercial Gear(motorola/GE) I felt the Kendercoms were the best receivers out there. the newer Maggiorees are not bad either. Depentds on what eles is on your site that can create havic. Neal
--- On Sat, 1/10/09, skipp025 <[email protected]> wrote: > From: skipp025 <[email protected]> > Subject: [Repeater-Builder] GLB Preamplifier - Preamp Device (transistor) > Information > To: [email protected] > Date: Saturday, January 10, 2009, 2:24 PM > Re: GLB Preamplifier - Preamp Device (transistor) > Information > > Hello again Sailors! > > The smoking lamp is now lit... "smok'em if you > got'em" > (just a trip down memory lane if you get the above circa > 1940-1945 reference). > > **** > > Anyway... per my previous post requesting anyone who wanted > > to part with (sell or trade) a GLB Receiver Preamplifier > unit > (any band, any condition)... I did actually receive an > original > GLB and an Aria-GLB (Simrex?) unit to reverse engineer. > > Dealing with part one... it appears the GLB preamplifier > active device in the original unmodified unit I have here > is > actually a Dual Gate Mosfet. The Mosfet has only > "UG" printed > on one side of the device but the circuit is an interesting > > take on a Mosfet layout and I was able to pretty much > confirm > the device in the circuit I have here is a DG Mosfet. > Credit > where it's due... the original GLB design I'm > currently working > on appears to be a well thought out and practically > engineered > product. > > Going back through the group archives... I see some posts > that > suggest and/or confirm the device in their preamp was > reported > to be an MRF-901 (mrf901) device. I tried to review the GLB > > Pictures in the photos section of the group... but they > dont' > appear to load/show up. Joe, if you still have those > photos, > would you please resend them direct to me. I should be able > to > confirm the circuit is different or the same to the > original > GLB Preamp I have here. > > So... drum roll please... I suspect the original Dual > Gate > Mosfet device to be similar to or the actual BF981 Mosfet, > which of course is no longer in production. > > I have found a substitute device (in current production) > with > greatly improved IMD performance... so a "next > step" of this > project would be to figure out the best practical retrofit. > > > More to follow... If anyone has copies of the original GLB > Preamp photos I don't seem to be able to view or > download > from the group... please send them to me at my regular > email > address below. I'd like to sort out the MRF-901 device > being > actually used in some pre-amplifiers or just an educated > guess. > > thanks a mucho... > > cheers, > skipp > > skipp025 at yahoo.com > > > ------------------------------------ > > > > Yahoo! Groups Links > > >
