Yes, high frequency AC current doesn't usually result in flicker noise.
Bruce
life speed wrote:
Why would flicker noise be a concern if there is no dc current flowing
in the switches?
Bruce
Hi Bruce,
Does it matter if the current is DC or AC? I expect to see +/-20 mA current
due to the signal level.
Clay
From: Bob Camp<li...@rtty.us>
Subject: Re: [time-nuts] 10 MHz reference switching
Hi
Or put another way:
If you have a structure that uses series resistors and shunt diodes:
The diodes are reverse biased when the switch is "on".
The diodes are forward biassed when the switch is "off".
No current when on = no noise.
Bob
Hi Bob,
I had not considered pin diode switches. I guess in my mind they are "RF", and
10 MHz is not. No reason not to think about them. However, I think to get any sort of
useable isolation at 10 MHz series-shunt or pi configuration is required, which will have
current flowing in one of the paths at all times.
Clay
From: paul swed<paulsw...@gmail.com>
Subject: Re: [time-nuts] 10 MHz reference switching
rf relay would work
Hi Paul,
Sorry, no relays for a high-reliability application. Not enough room or
current either.
Clay
From: Bob Camp<li...@rtty.us>
Subject: Re: [time-nuts] 10 MHz reference switching
Hi
Assuming you are switching between an external reference and the internal OCXO:
The "bleed through" of the OCXO is going to show up as a discrete spur close to the external
reference carrier. Unless you have a very> unusual architecture, it will be inside the loop for
everything you are doing. Attenuating it to a "suitable" level may be quite difficult.
Bob
Good point. I could power down the internal oscillator based on a detected
external reference. Just more circuits to add . . .
Thanks to all who replied, you raised some good points. Locking the internal
to external sounds better all the time, it's just kind of expensive.
Clay
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