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Input attenuator on xtal fixture

Jon EA2SN
 

Folks,
it seems that the designed attenuator (-5.4 dB) is a bit short when used with the
PHSNA, outputting 0 dBm or more.
Is there a recommendation for a newly built fixture? Suggested values?
Thanks
jon, ea2sn

Gary Tennyson <gtennys@...>
 

As I recall, 30 Ohms in the series legs, and 27 Ohms in the shunt leg yield a value close to 12 dB.

I've ordered these values in 1% tolerance, so I hope they're right. You should probably check it anyway.

Gary Tennyson
KO4CY

On 2/4/2016 4:44 AM, Jon Iza jon.iza@... [PHSNA] wrote:
 
Folks,
it seems that the designed attenuator (-5.4 dB) is a bit short when used with the
PHSNA, outputting 0 dBm or more.
Is there a recommendation for a newly built fixture? Suggested values?
Thanks
jon, ea2sn

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N5IB
 

There's no pressing need to change the fixture's attenuator, provided you have access to an external attenuator of 6 dB or so. I find the roughly 0 dBm output of one of my PHSNA to be convenient when testing things other than crystals or crystal filters. For those I have a couple of MiniCircuits units (6 dB and 10 dB) to insert in the line.

The higher output is especially nice for use with the return loss bridge.

If you decide to change the crystal test fixture, it looks like you'd need it to be about a 10 or 12 dB pad if your PHSNA is at roughly 0 dBm. That would make the resistor set on the input side 27 for the series elements and 33 for the shunt - that would theoretically yield 10.5 dB with a 50.1 ohm characteristic impedance.

Jim, N5IB






---In PHSNA@..., <jon.iza@...> wrote :

Folks,
it seems that the designed attenuator (-5.4 dB) is a bit short when used with the
PHSNA, outputting 0 dBm or more.
Is there a recommendation for a newly built fixture? Suggested values?
Thanks
jon, ea2sn