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RF out with RF OFF: Clock feed through

Clifford Heath
 

On 11 Jul 2017, at 10:41 PM, 'ambrogio.riboli@...' ambrogio.riboli@... [PHSNA] <PHSNA@...> wrote:
is the Coilcraft WB1015 suitable for this application in place of the T1-1T from Minicircuit ?
No, you need a centre tap to ground, and take the ends to IOUT/IOUTB.
The WB2010 should be fine. You'll get a lot more output, should be +6dB.

On 12 Jul 2017, at 12:34 AM, EB4APL eb4apl@... [PHSNA] <PHSNA@...> wrote:
I don't think so. The transformer reduce it a lot, as per Clifford explanations, but a suitable filter works also.
Yes. The problem is probably low-quality components in the filter; inductance
in the capacitors and capacitance (low SRF) in the inductors. It could also
be direct coupling, bypassing the filter.

The transformer is the only way to reduce 30MHz without adding a notch.

On 12 Jul 2017, at 1:17 AM, Nick Kennedy kennnick@... [PHSNA] <PHSNA@...> wrote:
A filter with a steeper slop ought to help. The transformer hasn't yet been shown to remove the clock signal.
I'm not familiar with the filter on the DDS-60 (and the server is down at present),
but on the AD9851 modules, the slope is quite steep enough. It's the quality of
the filter that's the issue.

Clifford Heath.

Ambro_IW2FVO
 

thanks for helping,
73. iw2fvo


On Wednesday, July 12, 2017 2:13 AM, "Clifford Heath clifford.heath@... [PHSNA]" wrote:


 
On 11 Jul 2017, at 10:41 PM, 'ambrogio.riboli@...' ambrogio.riboli@... [PHSNA] wrote:
> is the Coilcraft WB1015 suitable for this application in place of the T1-1T from Minicircuit ?

No, you need a centre tap to ground, and take the ends to IOUT/IOUTB.
The WB2010 should be fine. You'll get a lot more output, should be +6dB.

> On 12 Jul 2017, at 12:34 AM, EB4APL eb4apl@... [PHSNA] wrote:
> I don't think so. The transformer reduce it a lot, as per Clifford explanations, but a suitable filter works also.

Yes. The problem is probably low-quality components in the filter; inductance
in the capacitors and capacitance (low SRF) in the inductors. It could also
be direct coupling, bypassing the filter.

The transformer is the only way to reduce 30MHz without adding a notch.

> On 12 Jul 2017, at 1:17 AM, Nick Kennedy kennnick@... [PHSNA] wrote:
> A filter with a steeper slop ought to help. The transformer hasn't yet been shown to remove the clock signal.

I'm not familiar with the filter on the DDS-60 (and the server is down at present),
but on the AD9851 modules, the slope is quite steep enough. It's the quality of
the filter that's the issue.

Clifford Heath.