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LF: SV: Jan-Martin's Preamp circuit

To: [email protected]
Subject: LF: SV: Jan-Martin's Preamp circuit
From: [email protected]
Date: Tue, 21 Jan 2003 15:42:03 +0100
Reply-to: [email protected]
Sender: <[email protected]>
Thread-index: AcLBWGTa58y2IkWYTLGMVPSMFV1hdgAAoJEQ
Thread-topic: Jan-Martin's Preamp circuit
TNX
This was constructed in times where we listened to BBC2 and no lower 
frequencies, so the capacitors are probably small.
Perhaps a resistor in series with the 10nF capacitor to adjust the positive 
feedback... hi
73
Jan-Martin
---
J M Nøding, Datakvalitet, TTS, Kristiansand
Telefon 0047-9077-7126



-----Opprinnelig melding-----
Fra: Hugh M0WYE [mailto:[email protected]]
Sendt: 21. januar 2003 15:11
Til: [email protected]
Emne: LF: Jan-Martin's Preamp circuit


Hi Jan-Martin and LF group,
I was going to ask if your preamp could be posted on the Reflector ...
Being the "some-other" Here it is ...
73
Hugh M0WYE

----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: Tuesday, January 21, 2003 1:10 PM
Subject: LF: Re: Re: Notch for DCF39/Spectrograms/Luxembourg effect


Hi,
I don't see the point in using NPN devices (PNP are better for this
purpose),
you would probably not have more than 0.5x voltage gain
A source follower has incredible low gain - even when driving high
impedance,
that's the reason I discard such constructions, but using a PNP instead of
NPN
you may achieve over unity gain. A BJT emitter follower has in the region
of
0.8-0.95x voltage gain.
You set the feedback to adjust the gain, and add some postive feedback to
the input and achieve very high input impedance.

Unfortunately I forgot to forward the circuit from home, but sent it to
Alan
and some other. Too high gain is of course a problem and may cause some
IMD,
will try to remember to pass the circuit later (I am in Stavanger at the
moment).
Passed the spectrogram as a separate mail

73 Jan-Martin
LA8AK




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