The joke for today folks!

Here is a picture of my pile of parts.? I am somewhat embarrassed to show my shoddy workmanship.The BFO is to the left, off the main board. In this picture the crystal filter output is not connected to the mixer (I was troubleshooting).

On Sat, Sep 3, 2022, 12:46 AM Ashhar Farhan <farhanbox@...> wrote:

It could be oscillations as well. Can you post a picture of your build?

On Sat, Sep 3, 2022, 9:41 AM barry halterman <kthreebo@...> wrote:

Josh, with the input to the mixer disconnected and the BFO quenched, there is no noise. Ashhar pointed out that what I am hearing is phase noise from the BFO. If I am experiencing phase noise, that phase noise is above all but the strongest received signal.

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Barry

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Sent from for Windows

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From: Chris Mannon via groups.io
Sent: Friday, September 2, 2022 8:16 PM
To: [email protected]; Joshua Blanton
Subject: Re: [BITX20] Daylight again mixer noise

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Hello I would like to start building this rig . But don't have a 3d printer . Is there anyone that is making the pto form and cores ? I would like to get a few sets thanks .

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On Fri, Sep 2, 2022 at 4:02 PM, Joshua Blanton

<jtblanton@...> wrote:

Hi Barry,

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The basic design of the mixer should be very quiet - many low-noise VHF receivers use similar constructs in their front-ends.? Are you certain that your noise isn't coming in from somewhere else (a noisy power supply rail, bad bypass caps/poor power bypassing, or a bad part)?? If you don't have *any* input into the mixer (no BFO and no IF) it should be quite silent - but you might need to terminate both inputs with caps to ground.? It seems possible that this circuit could oscillate, depending upon the layout - is that a possibility that you've considered?? I have read many warnings about J310 oscillations at VHF, which can be hard to find with slower oscilloscopes.? Long leads are not your friend with this particular piece of the circuit.

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I haven't built this mixer yet, so I'm speaking theoretically - but it looks like a textbook cascode mixer circuit.

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Good luck!

Josh, KB8NYP

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On Fri, Sep 2, 2022 at 10:38 AM barry halterman <kthreebo@...> wrote:

I am curious as to how much mixer noise I should be hearing from the second mixer. Should the noise (hiss) be stronger than normal band noise? I might be looking into something that is not fixable and the nature of the beast.

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Chris Mannon

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