Jerry - Preamps at the antenna help. They help a lot if you have a setup that is limited by receiver performance and/or feedline loss. They won't help if you are limited by the noise environment. They usually help a lot for satellite operation as there is usually not much external noise when the antenna is pointed to empty space rather than to your neighbor's lamp dimmer.

For two meters a grounded gate preamplifier based on the U310 is a good choice:

< http://www.ham-radio.com/n6ca/50MHz/50appnotes/U310.html >

Unfortunately, the TO-52 style U310 has gotten pretty expensive; I think they are $11 a piece from Mouser! Still this is a tried and true design that is stable and easy to build. You might try the more widely available and cheaper J310, which is the same part in a plastic package.

MOSFETs also make a good preamp. Here are a couple using the BF981:

< http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=9247 >

< http://www.geocities.com/icdx_australia/bf981preamp.html >

There are lots of other designs out there. The old ARRL handbooks from the 90s had some nice designs for both dual gate MOSFETs and GaAs FETs. If you use the same feed line and antenna for transmit, you will need to add relays to switch around the preamp when you transmit.

Advanced Receiver Research, ARR, is a source of commercial preamplifiers, and there are some models that have built in RF switching.

There are other vendors, with higher prices.

A preamp is a good investment to upgrade your station, but it is not a cure all, particularly if you are dominated by terrestrial noise source. - DUffey

On Apr 12, 2009, at 6:22 AM, Jerry Felts wrote:

I've seen Preamps mentioned several times now so Who? What? Where? I have not seen them in the AES catalog I got the other day. Can you build one? Need info on them!!

Jerry - NR5A

-- Jerry - NR5A - South Dakota www.freewebs.com/nr5a http://groups.yahoo.com/group/Minimalist_QRP_Transceivers/ http://www.cakewalkblogs.com/nr5asminimalradio/index.aspx http://nr5abeaconblog.blogspot.com/ _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb

-- KK6MC James Duffey Cedar Crest NM