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
