Hi John,
This would indeed be interesting.
I would assume that one would like to have shielded boxes for these.
Cheers,
Magnus
On 03/27/2016 04:33 AM, John Ackermann N8UR wrote:
In light of this discussion, I'm taking a deep gulp to mention a project
that's finished but has been on my back burner for a while.
A few years ago I laid out a high isolation, low noise buffer amp based
on one of Bruce's cascaded-transistor designs. Isolation was measured
in excess of 100dB with PN floor around -170dBc/Hz. The frequency range
is 1 MHz to 30 MHz and gain can be set from -10 to +7 dB. It's designed
for 18VDC input but will work at 13.8, with less headroom. At 18V it
can put out close to +20dBm. It's a 1.75 x 3.75 inch board using SMT
parts (nothing tiny, but *lots* of passives -- about 80 parts total).
The board is ready to go, but I wasn't sure if there would be enough
interest to justify production. Given the tedious surface mount
assembly, I assumed that there wouldn't be much interest in a kit, and
an assembly run requires at least 50, and preferably 100, units to get a
reasonable price. At 100 units, I hope the price for an assembled board
could be below $100, but no guarantees.
If there is enough interest, TAPR could consider doing a production run.
If not, I'll release the design package including Gerbers.
I'll try to get some better documentation put together in the next week
or two, and figure out a way to create a sign-up list for people who are
interested. We'd have to have a minimum number of committed orders
before kicking things off.
John
----
On 03/26/2016 08:24 PM, jimlux wrote:
On 3/26/16 4:14 PM, Richard (Rick) Karlquist wrote:
Nothing has come to my attention in the last
35 years that is superior for buffer amplifiers
to the simple cascade of grounded base transistors
as described by numerous NBS/NIST papers.
The chain usually starts with a common emitter
(with emitter degeneration resistor), which
is an even older NBS classic.
I realize you asked for an OTS connectorized
version. Unfortunately, I have never seen
one of these offered in said 35 years.
Yeah, i've spent a while looking through various catalogs..
Odd that nobody sells one: sure, it's probably a limited market, but
there's plenty of companies that sell limited market widgets (e.g. I'm
surprised Wenzel doesn't sell one.. in the online catalog info, they
don't even give S12 data of any kind)
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