[time-nuts] Distribution amp - Use a video amp unit ?

Mon Mar 26 16:02:28 UTC 2012

It would be interesting if the FTS-1050A curves were also plotted.

Joe

From:	John Ackermann N8UR <jra at febo.com>
To:	Discussion of precise time and frequency measurement
            <time-nuts at febo.com>
Date:	03/25/2012 03:54 PM
Subject:	Re: [time-nuts] Distribution amp - Use a video amp unit ?
Sent by:	time-nuts-bounces at febo.com

I haven't measured the video amps, but here are plots of an HP 5087A,
TADD-1, and Spectracom 8140 tap unit for a baseline:

http://febo.com/pages/amplifier_phase_noise/

John
----

Tom Knox said the following on 03/25/2012 03:48 PM:
>
> Has anyone measured Phase Noise on any of these distribution amps? By
looking at how widely the PN specs vary on the application specific
Symmetricom and HP DA's it would be interesting to see how well these video
da's perform in comparison.
> Thomas Knox
>
>
>
>> Date: Sun, 25 Mar 2012 12:28:56 -0700
>> From: pete at petelancashire.com
>> To: time-nuts at febo.com
>> Subject: Re: [time-nuts] Distribution amp - Use a video amp unit ?
>>
>> Sounds like Paul and I have similar DA's or will soon when a Leitch gets
to the
>> front porch next week. Its bandwidth is spec'd at 30 MHz.
>>
>> The only question I have on using DA's is the effect of them being
designed to
>> work in a 75 ohm environment.
>>
>> One thing to watch out for is what cards they have in them.
>>
>> -pete
>>
>>
>>
>> On Sun, Mar 25, 2012 at 11:39 AM, paul swed<paulswedb at gmail.com>  wrote:
>>> Well the easy answer.
>>> The older 1984 video amps would roll off above 6 MC or so.
>>> However as the IC technology took over they easily could do 30 Mhz.
>>> I have used Grass valley 8500 series for at least 10-15 years and the
work
>>> very well.
>>> I also have sets of Leitch DAs that are fine.
>>> Picked up the whole tray for some silly amount of $ 20 I think.
>>> I prefer the simple 8601 DAs but have 8604 delay days and they can all
be
>>> made into simple DAs with a few jumpers that are on the boards.
>>> I have also used a rgb da 6 output for each channel. No issue at all.
>>> One comment you would want to insure the amps are ac coupled and
clamping
>>> turned off since there is no sync signal to establish the clamp level.
>>> Regards
>>> Paul
>>> WB8TSL
>>>
>>> On Sun, Mar 25, 2012 at 2:14 PM, Bruce
Griffiths<bruce.griffiths at xtra.co.nz
>>>> wrote:
>>>
>>>> cfo wrote:
>>>>
>>>>> I need a distribution amp for my Tbolt , with 6..8+ outputs
>>>>>
>>>>> The TAPR-1 is NA , and the successor status is ???.
>>>>>
>>>>> I need it for distributing 10Mhz ref-clock to Counters
>>>>> (HP,Racal,Phillips), a Rigol Sig-gen&   maybe Oscilloscopes etc.
>>>>>
>>>>>
>>>>> It's for "better than ocxo/hobby use" , and not Tnut (ps accuracy).
>>>>>
>>>>> I have seen suggestions for using a video distributiution unit.
>>>>> But in my part of the world (EU) , there isn't a lot on "eby".
>>>>> I have seen some RGB amps , and was wondering if i could use those ?
>>>>>
>>>>> Could i use a 1:6 RGB unit for : Tbolt on R , FEI-5680A on G  -
and ?? on
>>>>> B ?
>>>>>
>>>>> I'm not experienced (yet) in the analog domain.
>>>>>
>>>>> If i go (simple diy) Would this one work  (also wo. the trafo's) ?
>>>>> http://www.oz9fw.dk/PDF%**20files/rubidium.pdf<
http://www.oz9fw.dk/PDF%20files/rubidium.pdf>
>>>>>
>>>>> I do have some trafo's on an old 10Mhz 8-chan Hub , that i might be
able
>>>>> to salvage if needed.
>>>>>
>>>>> Thanx for any input/hints
>>>>>
>>>>> CFo - T-Nut beginner Denmark.
>>>>>
>>>>>
>>>>>
>>>>> ______________________________**_________________
>>>>> time-nuts mailing list -- time-nuts at febo.com
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>>>>> and follow the instructions there.
>>>>>
>>>>>
>>>>>
>>>> Winding your own transformers isnt particularly difficult if you have
>>>> suitable (binocular) cores.
>>>> The discrete amplifier shown has a class AB output stage, lower
distortion
>>>> is possible if a class A output stage is used (requires an extra
resistor
>>>> between the output stage emitters and an additional diode in series
with
>>>> the LED).
>>>> With a Class A output stage the 39 ohm resistors should be replaced by
a a
>>>> pair of 100 ohm resistors to match the load.
>>>> Significantly lower distortion is possible if feedback from the output
to
>>>> the input stage is used.
>>>> If the feedback gain is unity (or less) at dc higher AC gains won't
>>>> significantly degrade the close in phase noise.
>>>> A different amplifier topology using the same number of transistors
will
>>>> allow a higher reverse isolation to be achieved.
>>>>
>>>> One problem with video distribution units (aside from the relatively
high
>>>> phase noise floor) is the limited output drive available. For some
purposes
>>>> 16-20dBm outputs are desirable.
>>>>
>>>> Bruce
>>>>
>>>>
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