At 7/29/2010 14:59, you wrote: >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.
Yes, but the NF is unpublished & unknown. I therefore assume it's poor, maybe 3 dB? A Chip Angle GaAsFET @ UHF has 0.5 dB NF. Put a 1/4 wave pass cavity with 0.5 dB loops in front of it & you have a narrow 1 dB NF front-end. I'll take 1 dB NF over 3 dB NF any day. The Simrex unit makes a nice solution if you don't have the physical space for a 1/4 wave bottle. Then again, I know someone who just ordered an even smaller MtronPTI front-end crystal filter to solve a front-end overload problem from a TX over 1 MHz away from his RX. Not the best solution (higher loss, can't be retuned if he ever has to change freq.), but I guess it works for him. Bob NO6B
