[time-nuts] Re: Phase noise of HP8663A 640 MHz reference?

[ghf at hoffmann-hochfrequenz.de]

If you start at 100 MHz, there is a good 400 MHz SAW filter
<   
https://www.digikey.de/de/products/detail/qualcomm-rf-front-end-rffe-filters/B39401B3742H110/1858962?s=N4IgTCBcDaIEYGYDsAWCBdAvkA 
  >

for spurious cleanup at $2 per pop. With 250 KHz BW it cannot do much
against close-in phase noise but 2 of them back-to-back deliver
quite clean a carrier at 400 MHz. Even if you just dump a 100 MHz 5V
LVCMOS signal into it. (2*74LVC1G125 etc buffers).
That delivers abt. -6 dBm @400.

Picture: R7, R8 can be smaller, MMIC can be SKY65014 with less gain.
Tested with an ECOC2522 100 MHz oven whose PN plots I passed on here
some months ago.

Mr. Fourier nags that *4 is not so fortunate with a  ~ 1:1 hi/low 
source,
but there is enough left. Diode doublers with their 10 dB loss each
are also not the bee's knees.

<  
https://www.digikey.de/de/products/detail/ecs-inc/ECOC-2522-100-000-5HS/6579018 
 >

That's a nice clock source for a LMX2594 15 GHz synthesizer
in integer mode or for a DDS, or for a 432-> 32 MHz down converter for 
SDR.
The filters may be driven with 10 dBm and feature abt. 2 dB loss.

There are also GPS filters at 1600 MHz that include 4*400 MHz.
I saw "usable BW = 2 MHz" on the DS cover page, but the VNA revealed
more like 35 MHz. The data sheets of both Qualcom an Taiyu Yuden
are quite a mess.
Nevertheless these filters are an option for multiplier chains.
Soldering them is not for the faint of heart with 5 pads on 1 mm**2.
The 400 MHz filter is harmless in this respect.

Using them in a box that also contains GPS is probably not
a lucky design.
I wished there was sth. for 300 MHz (LMX2594 in fractional mode)

Cheers, Gerhard



Am 2022-08-21 23:52, schrieb ed breya via time-nuts:
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