I have three of these preamps in service on GE Mastr II 440 repeaters. "The tuned circuit in front of the transistor will help a bit
with out of band signals." I build a shield from galvanized flashing and put it around the two turn front end coil. I use these preamps installed in the normal spot for the stock GE preamp, and I was concerned about hanging the front end coil out in the breeze in a repeater. "> Gain is typically 16 to 20 dB and noise figure is 1 dB @ > 2 Meters, 1.2 dB @ 220MHz, and 1.4 dB @ 440 MHz. Which is about what we would expect although the gain value appears a bit optimistic. But who knows... measuring one will tell the real story." I had too much gain on two of my installs and I reduce the gain by placing a 47 Ohm 1/4 watt resistor across the untuned output. I have had no instability from these preamps, even operated wide open for gain. If there is another 440 system in the area though, they are prone to overload and if you have any desense in a repeater, the receiver sensitivity actually will go down with the preamp installation. I have tried the two meter version in a GE Mastr II repeater and was not able to tame the desense increase, although the 440 preamps work fine. The two meter version already has a shielded coil on the front end, by the way. 73 - Jim W5ZIT --- On Sun, 1/11/09, skipp025 <[email protected]> wrote: From: skipp025 <[email protected]> Subject: [Repeater-Builder] Ramsey Preamplifier Kits... To: [email protected] Date: Sunday, January 11, 2009, 12:36 PM re: Ramsey Rx Preamplifier Kits. > Kevin Custer <kug...@...> wrote: > Great for sites that don't require pre-selection ahead of > the preamp. > Kevin http://www.ramseyel ectronics. com/cgi-bin/ commerce. exe?preadd= action&key= PR-SERIES **** Excellente' lead... Couldn't ask for a more practical low cost kit of this type. The advertisement spouts a little smoke and mirrors but the circuit is pretty straight forward. You can also download the manual before you buy it to have a look at the circuit. The tuned circuit in front of the transistor will help a bit with out of band signals. [pasted ad text] > "Fully protected against overload and designed for low > current and stable operation they employ high Q tuned > circuits which restrict out-of-band signals which can > cause intermod blanking and over load of your radio's > front-end." I doubt the "fully protected against overload" claim. (Please review the "no free lunch rule") The single stage tuned circuit is very nice... but shouldn't be trusted as any type of cure all. Nor is it really comparable against the GLB multi-stage tuned preamp with much higher circuit Q. > "Don't be misled by GaAs FET claims! The cheap dual-gate > FETs (manufactured for TV tuner usage!) used by others just > don't come close to the performance of these preamps designed > with NEC microwave transistor devices". Smoke... mirrors... pay no attention to the man behind the curtain. > Gain is typically 16 to 20 dB and noise figure is 1 dB @ > 2 Meters, 1.2 dB @ 220MHz, and 1.4 dB @ 440 MHz. Which is about what we would expect although the gain value appears a bit optimistic. But who knows... measuring one will tell the real story. > $14.95 Pretty much says it all if you want a low cost preamp kit. cheers, s. _._,___
