[amsat-bb] AMSAT Broadband Preamp
zmetzing at pobox.com
Wed Sep 14 20:07:24 UTC 2016
On 09/13/16 19:45, David Mennerich wrote:
> Has anyone here used this before? Perhaps this would help me 'hear' a
> little better with my Arrow antenna, and I could use it for V/U and U/V
> modes. For those of you that operate with an Arrow, do you use this preamp
> or some other preamp? It appears there are other preamps out there that
> are more expensive, but require one per band (V or U). This one will cover
> both - seems like a good option, just wanted to get your thoughts.
You may have missed my previous post, due to no subject in the title.
If you're looking for a shoestring-budget LNA for 2m, the U310 JFET
preamp has been a good performer for me.
I've constructed one in a spare project box, and the gain (12dB) is
right on the predicted value. I have not verified the NF, but it is
claimed to be near 1.0dB. I built in in one evening, with some extra
evenings diagnosing a capacitor issue. Use a multi-turn piston trimmer
for the 1-10pF drain capacitor, as the output tuning is very sharp.
I've changed the layout a bit, but here's an early picture of the unit:
The air-core inductors are not difficult to wind on a 1/4" drill bit.
Not as fancy as a GaAsFET or pHEMT device, but it works just fine to
hear AO-85 and AO-7 with a non-ideal satellite antenna (folded
horizontal dipole) at 10 degrees above the horizon.
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