Amplifier Plans Wanted

[zonian149]

Does anyone have DIY plans (schematic) for an antenna mount pre-amplifier or suggestions for an inexpensive one? I need one for monitoring 137mhz and 900mhz if that makes a difference. I have been googling, but haven't found anything yet.--Gary

 

[gewecke]

It would probably be wiser to invest the money in your antenna system. Low loss feedline,log periodic vhf/uhf beam maybe,but preamps are rarely worth the investment unless they're of the GAAS-FET type.
n9zas

 

[kb0nly]

A cheap wideband amp that covers 10-1000Mhz is worth the investment...

I use a cheap $20 drop amp for my scanners, improvement was great, didn't bring up the noise floor much, and above all it was cheap!!

 

[byndhlptom]

Amplifier

1- You will find some amplifier schematics on the ARRL web site, look for VHF/UHF amps. If you do not add the tuned elements, they will be reasonably broadbanded.

2- Look at the data sheets for low noise transistors (MRF-901) for one. They usually have basic amplifier circuits in thier data sheets

3- search both the Monitoring Times and Popular Communications sites. They have had articles over the years on preamps.....

4- Do a Google search on low noise wideband amplifiers. You should find a few days worth of reading......

have fun

tom

 

[byndhlptom]

Amplifiers

forgot....

5- Ramsey and others do have some wideband amplifier kits, add that word (kit) to your google search

6- Radio Shack used to have both a 10db and a 20db remote amplifier for TV applications, they can work reasonably well for VHF/UHF (esp the 10db one). Other TV amplifiers can be used, but be aware that they are optimized for the TV spectrum, which can cause more problems than they are worth.....

good luck

tom

 

[zz0468]

Check Mini-Circuits. They sell both both ready-made amplifiers that will do what you want, and sell the MMIC devices to build your own. Their application notes include sample designs. MMIC's are super easy to work with, because they have internal circuitry to match the active device to 50 ohm inputs and outputs, and are quite broadband.

Edit: LOL@myself for digging up an old dead thread. Oh well. *shrug*