[time-nuts] Frequency distribution isolation transformers YCL20F001n arrived
kb8tq at n1k.org
Sun Dec 14 14:15:40 EST 2014
They are pretty fancy little gizmos if you want to do twisted pair. Volume counts here in terms of making them cheap.
Twisted pair is *good* stuff for isolation at low frequencies. It’s not so hot for microwaves. There is an item called STP (shielded twisted pair) that addresses the microwave part pretty well.
Will it beat some $1K / foot quartz filled uber coax for delay dispersion .. of course not. If you have those sort of needs (and credit card) go for the fancy coax. Plugging twisted pair into the back of a HP 5334 is a bit awkward as well. If you are running < 6 feet from distribution point to instrument, don’t bother with any of this stuff. Same goes if everything is already very solidly bonded to a common ground. Yes if you are in the middle of a DMTD or a phase noise tester other rules may apply.
Have a GPSDO buried in a 100’ deep dry hole in the back yard, 400’ from your house, running on it’s own isolated nuclear generator? These are pretty good gizmos to think about.
> On Dec 14, 2014, at 1:41 PM, paul swed <paulswedb at gmail.com> wrote:
> Well with zero effort the spec sheet. Bob indeed there are common mode
> chokes in them. Jeeze a lot in 1 package along with center taps.
> On Sun, Dec 14, 2014 at 12:22 PM, Bob Camp <kb8tq at n1k.org> wrote:
>> If you get the whole magnetics package (and not just a transformer) it
>> probably will have a pretty good common mode choke in it. If you go back to
>> the days of coax ethernet, the choke was more the “magic” that let them go
>> to twisted pair than the transformer.
>> Why does this matter?
>> Well … we seem to still be stuck back in the “coax ethernet” era when it
>> comes to standard distribution. Every time somebody brings up a need to go
>> hundreds of feet, coax becomes a second choice sort of solution. That’s
>> even more true for a pps. Don’t toss out the rest of the magnetics when you
>> salvage one of these old beasts …
>> Why mention pps? There are more than one isolated pair on those
>> connectors. You would need to modulate the pps onto something at one end
>> and demodulate it at the other end. There are a lot of cheap ways to do
>> that, very much so if you are generating the pps yourself in something on
>> the transmitting end.
>>> On Dec 14, 2014, at 11:59 AM, Alan Melia <alan.melia at btinternet.com>
>>> Hi Paul I confirm the 17MHz LPF response I didn't measure them for
>> flatness :-)) The source I used was surplus 16way 10BaseT switches which
>> were junked some time back but may still be lying in the back of store-room
>> cupboards.....you get a lot on one board that way.
>>> ----- Original Message ----- From: "paul swed" <paulswedb at gmail.com>
>>> To: "Time-nuts" <time-nuts at febo.com>
>>> Sent: Sunday, December 14, 2014 4:18 PM
>>> Subject: [time-nuts] Frequency distribution isolation transformers
>> YCL20F001n arrived
>>>> Another Time-nut suggested the use of 10 baseT ethernet transformers
>> for 10
>>>> MHz isolation that he pulls from old ethernet boards. The 20F001n. These
>>>> are available from UTSource on ebay at 90 cents each NOS. Ordered 20.
>>>> Well I have to say as a BPF or something for 10 Mhz they are lousy. BUT
>>>> then how could they be when they are a pretty flat transformer from 40
>>>> to 17 MHz! Take that Mini-Circuits. (Only in jest) Yes there are some
>>>> and bumps in that pass band But not large maybe 1-1.3db I need to get
>>>> more accurate. But now I have a nice transformer that can work at WWVB
>>>> Khz as well as with frequency distribution.
>>>> They come in a dip foot print and 2 X to a package.
>>>> I have more to check because to good to be true almost always is. At
>>>> for me.
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