[amsat-bb] Re: preamps
kd0ar at sbcglobal.net
Sun Aug 31 11:11:42 PDT 2008
I use it on both radios. Improves both radios very nicely. I can even hear the birds when they go behind the trees, where I couldnt make out the audio before. Worked all 3 FM birds on it now, and there is a day and night difference on either radio I use. Just be careful you dont transmit on 435 mhz. I did, and the transistor will pop instantly.
I put my preamp between the 435 feed and the diplexer. Its safe with up to 20 watts TX on 145, no burnouts... I worked the last pass running that much, I havent tried it with more. No filtering on the input, used an arrow-like HB antenna. Pretty rugged, if its not mistreated (ie. transmitting on 435).
Also, I am working on an eggbeater for use on the SSB birds. Going to start testing the 435 version after I send this email off. Because I'm not switching the preamp, I have to go this route with seperate TX/RX antennas for these birds.
----- Original Message ----
From: Doug Faunt N6TQS +1-510-655-8604 <faunt at panix.com>
To: kd0ar at sbcglobal.net
Sent: Sunday, August 31, 2008 1:37:14 PM
Subject: Re: [amsat-bb] preamps
Does it improve the FT817? Mine seems to work well, but for $20....
I use the 817 for RX, and an ICOM IC706MKIIG or IC7000 for TX.
Date: Sun, 31 Aug 2008 09:59:33 -0700 (PDT)
From: Michael Heim <kd0ar at sbcglobal.net>
A recent post mentioned the need for a preamp. This reminded me of something I want to share with the group.
Station here consists of an FT-817ND and an FT-857D. The 817 is pretty sensitive on UHF, but the 857 is a little lacking in comparison.
I was looking for a preamp online that would help, especially with the 857. I went and ordered a Ramsey PR40. I figured for $15 I couldnt go wrong. Although its not a GaAs device, (its a bipolar), it works pretty well. I actually didnt want a GaAs because I was afraid of blowing the device anyway, being I'm running a homebrew "Arrow style" antenna on a fixed elevation mast, and the 144 MHz leakage getting into the preamp would probably blow the device the first time I keyed.
I am not using any TR switching on the preamp. (I only work the FM birds at this time).
After building the kit, I put it up, worked a pass on AO-27, then goofed and sent 432 TX energy up the line, blew the amp. I ordered replacement transistors from MCM for $.52 each!
Although I cannot measure noise figure, it specs at 1dB, 15 dB gain. I know it makes a HUGE difference on my end. Satellites that were noisy before are now full quieting and armchair copy
I have found this item a very cost effective solution. I wanted to share this experience with the group. I'm just pleased with the preamp and of course, receive no personal gain by recommending this product.
Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
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