> 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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