[Milsurplus] [Boatanchors] Programmable Osc Setback

[Peter Gottlieb]

The mosfet has a bunch of gate capacitance, perhaps that can be taken advantage 
of as part of a filter.  The computer oscillators are trying to put out a square 
wave so there is a lot of odd harmonics.  A few poles of LC filtering should 
help a lot.  As for drive, there are plenty of simple amp circuits out there.  
This is far from a dead end.

Peter

On 11/15/2014 1:16 PM, W2HX wrote:
> Dave, about the noise issue. Have you tried to see how the noise changes if you temporarily eliminate the DC-DC converted and put in a clean supply there? And what about swapping the mosfet with a bipolar with lower input impedance.  Just shooting from the hip here.
>
> 73 Eugene W2HX
>
>
> -----Original Message-----
> From: Boatanchors [mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of David Stinson
> Sent: Saturday, November 15, 2014 10:42 AM
> To: milsurplus at mailman.qth.net; boatanchors at mailman.qth.net
> Subject: [Boatanchors] Programmable Osc Setback
>
> OK, you fellas can "I told ya so."   I won't complain.
> On the receiver side, the tiny output of the programmable oscillators work fine and I hear no problem with increased noise floor.
>
> Not so on the transmit side, were the osc needs considerable "boost" to drive the 6L6 grid.
> My attempt to keep the TX Xtal-replacement circuit ultra-simple just isn't up to the job.
> The output is noisy and has unacceptable spurs.
> Not about to give up on it- I have high hopes it can be made to work in the BC-375.
>
> A reminder of the over-simple circuit as it is now:
> http://home.netcom.com/~arc5/oscbrd.jpg
> And the goal: use several of these oscillators on a satellite board to replace very expensive crystals
> (aside:  Bry's crystals work well in many circuits including the RX side of this rig, but do not oscillate in this transmitter circuit).
>
> There's a couple of ways we might go from here.
> The input impedance of the MOSFET gate is quite high, so a Hi-Q tuned circuit between the OSC and Gate might bring the nastys down to something workable.
> Might also turn the FET into a oscillator itself, so a tuned buffer as has been suggested might be in order.
> Can you neutralize a MOSFET?
> Operating the MOSFET linear might also help.
>
> Ideas?
>
> 73 Dave AB5S
>
> ______________________________________________________________
> Boatanchors mailing list
> Home: http://mailman.qth.net/mailman/listinfo/boatanchors
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Boatanchors at mailman.qth.net
> Message delivered to w2hx at w2hx.com
>
> List Administrator: Duane Fischer, W8DBF
> ** For Assistance: dfischer at usol.com **
>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
> ______________________________________________________________
> Milsurplus mailing list
> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Milsurplus at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>