DC in a transformer raises the low frequency corner a bit. Obviously not
a problem in your case.
I should point out that every active device Lankford puts in the signal
chain adds noise since the amp is really just a buffer, not an
amplifier. You really want front end gain so that devices after the gain
stage do not add as much to the noise floor. It is input referred noise
that is significant, and Lankford's design is terrible in this respect.
Oops, I almost started that pissing contest. ;-)
On 3/18/2012 11:44 AM, Poul-Henning Kamp wrote:
In message<[email protected]>, Attila Kinali w
rites:
On Sun, 18 Mar 2012 13:25:54 +0000
Not in my implementation, I have eliminated the input capacitor because
the active element is 3cm from the PCB,
Could you explain how the distance of the antenna to the PCB is related
to a DC block capacitor? And how do you block current flowing from the
input stage of your amplifier into the antenna?
The input to the amplifier is just a piece of metal, there is no need
for a capacitor in series with it.
The output from the amplifier goes to a transformer which drives a piece
of "twin-ax" cable back to my lab.
The reason for the transformer is that to go really deep in frequency
the usual choke to separate the DC supply from RF signal doesn't work.
I the 'cable-side' of the transformer, in both ends, is centertapped
and that's how I provide power to the antenna.
I have successfully received the Russian "Omega-like" system at
9-15 kHz and I have detected but not demodulated the 86Hz submarine
transmission.
That's DC enough for me :-)
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