what's the performance of the distribution amplifier like?

On Wed, Aug 7, 2013 at 9:12 AM, Steve G8EBM steve@g8ebm.com wrote:

--
--Eric

Eric Garner

Seems they are rated to 5MHz according to the manufacturer..
They ebay item number is 161081736069.

--marki

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Eric Garner
Sent: Thursday, 8 August 2013 5:57 AM
To: Steve G8EBM; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Rb video

what's the performance of the distribution amplifier like?

On Wed, Aug 7, 2013 at 9:12 AM, Steve G8EBM steve@g8ebm.com wrote:

--
--Eric

Eric Garner

time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Five (5) MHz is what normal NTSC video needs at a minimum. Most of those VDA
units are good to 20 MHz, HD units sometimes go the 100's of MHz.

They all seem to handle a 10 MHz house clock just fine. But to satisfy any
doubts, look up the data sheet for the op amps used.

Regards,
Tom

----- Original Message -----
From: "Mark C. Stephens" marks@non-stop.com.au
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com; "Steve G8EBM" steve@g8ebm.com
Sent: Wednesday, August 07, 2013 9:39 PM
Subject: Re: [time-nuts] Rb video

Seems they are rated to 5MHz according to the manufacturer..
They ebay item number is 161081736069.

--marki

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Eric Garner
Sent: Thursday, 8 August 2013 5:57 AM
To: Steve G8EBM; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Rb video

what's the performance of the distribution amplifier like?

On Wed, Aug 7, 2013 at 9:12 AM, Steve G8EBM steve@g8ebm.com wrote:

--
--Eric

Eric Garner

time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

Hi Mark:

These only ship to the UK.
"Does not ship to the US"

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html

Mark C. Stephens wrote:

Yup, Seller just emailed me.
Something about antipodeans and convicts ;)

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Brooke Clarke
Sent: Thursday, 8 August 2013 1:10 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Rb video

Hi Mark:

These only ship to the UK.
"Does not ship to the US"

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html

Mark C. Stephens wrote:

time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

On 8 August 2013 04:10, Brooke Clarke brooke@pacific.net wrote:

I've bought one. On the "message to seller" I have asked if he will
ship outside the UK.

I've had a couple of those rubidiums a few years, but have never
actually got around to fixing it up.  Perhaps that removes an excuse!

Dave

Sells to France if asked.  I mentioned there might be interest from the US.
Mike

Le 8 août 2013 à 11:19, Mark C. Stephens a écrit :

On 6 August 2013 09:37, Raj vu2zap@gmail.com wrote:

Interesting video. I decided to but one of the distribution amps. I
already have the rubidium. There were a few things that struck me in
the video.

1. Having a PIC to control an LED seems a bit OTT. Personally I'd just
   stick a second LED - one as a power indicator, the other as a lock
   indicator, rather than make it flash when warming up, and solid when
   locked.

2. If one does have a flashing LED, it would be better if it is
   slower, in case there are any epilepitcs about. As someone who suffers
   from photosensitive epilepsy, I would not want it flashing any faster
   than 1 Hz. He should just about be ok, but I'd feel a bit happier if
   it was slower.

3. I'm not really convinced there is a need to change the output
   impedance from 75 to 50 Ohms. The impedance mis-match is pretty small.

4. More concerning to me would be the fact the output connectors are
   75 Ohm, and so would be damaged with the larger male pin of a 50 Ohm
   connector. I guess one might get away with it given one is not going
   to be disconnecting this a lot, but I think I'd buy 75 Ohm BNC plugs
   to put on one end of the cable, and 50 Ohm BNC plugs on the other end,
   sticking a bit of heatshrink on the 75 Ohm end of the cable so I know
   they are not standard BNC cables.

5. I wondered if there is enough cooling air there? What size heatsink
   would be optimal? I think unlike most electronics, one does not want
   to cool the rubidiums too much, so "bigger is better" might not apply
   here.

6. Is the use of a SMPS a good idea? I thought the Rb oscillators
   should be powered from a linear supply. I don;t suppose it is possible
   to get a linear power supply in there.

7. He scrapped the BNCs configured as digital lines. I would have
   thought it worthwhile bringing out a 1 pps output, which I think those
   Rb oscillators have.

8. I wonder if one could fit a GPS locking module in that box and
   antenna connector on the box.

9. It will look very odd to have the heatsink as the front panel !!
   But I guess that is a small price to pay for getting a reasonably
   sized box and

10. I suspect the box will be hard to keep in place, since with a
    dozen or so BNCs on the rear, that is going to go where the cables
    tell it to go, rather than the other way around. Perhaps a heavy
    heatsink will mittigate that.

11. If I recall correctly, there is a way of adjusting the freqency of
    those rubidiums, though I guess for the intended application, a Rb is
    plenty good enough. I know it is for me, but perhaps not for a
    dedicated time-nut.

Dave, G8WRB

None left from that batch.  Hope you got yours.

Points taken, but cheap enough to  experiment with.

Le 8 août 2013 à 13:08, Dr. David Kirkby a écrit :

On 8 August 2013 14:49, mc235960 mc235960@gmail.com wrote:

I suspect he has a lot. He originally listed 10, and all them have
gone, so he has listed another 10

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=161082475549

Dave

The number on the front panel shows "53" on the current picture...
That gives hope to those who still think about it... :-)

Volker

Am 08.08.2013 16:05, schrieb Dr. David Kirkby:

I bought one of these DA's from the same seller and according to the
user's guide the BW is 300 MHz, fully loaded.  I didn't measured it but
it works very well at 10 MHz.

Regards,
Ignacio EB4APL

On 08/08/2013 3:39, Mark C. Stephens wrote:

Hi Dave,
The "old" thin pin 75R BNC sockets are rare these days. Most equipment now uses intermateable sockets that use the same size contact as 50R but with reduced diameter dielectric to maintain the impedance match. Fully compatible with 50R without damage. The only small drawback is that the old thin pin plugs (if you have any) may not make good contact.

HTH,
Robert G8RPI.

From: Dr. David Kirkby drkirkby@gmail.com
To: Discussion of precise time and frequency measurement time-nuts@febo.com
Sent: Thursday, 8 August 2013, 12:08
Subject: Re: [time-nuts] Rb video

On 6 August 2013 09:37, Raj vu2zap@gmail.com wrote:

Interesting video. I decided to but one of the distribution amps. I
already have the rubidium. There were a few things that struck me in
the video.

1. Having a PIC to control an LED seems a bit OTT. Personally I'd just
   stick a second LED - one as a power indicator, the other as a lock
   indicator, rather than make it flash when warming up, and solid when
   locked.

2. If one does have a flashing LED, it would be better if it is
   slower, in case there are any epilepitcs about. As someone who suffers
   from photosensitive epilepsy, I would not want it flashing any faster
   than 1 Hz. He should just about be ok, but I'd feel a bit happier if
   it was slower.

3. I'm not really convinced there is a need to change the output
   impedance from 75 to 50 Ohms. The impedance mis-match is pretty small.

4. More concerning to me would be the fact the output connectors are
   75 Ohm, and so would be damaged with the larger male pin of a 50 Ohm
   connector. I guess one might get away with it given one is not going
   to be disconnecting this a lot, but I think I'd buy 75 Ohm BNC plugs
   to put on one end of the cable, and 50 Ohm BNC plugs on the other end,
   sticking a bit of heatshrink on the 75 Ohm end of the cable so I know
   they are not standard BNC cables.

Hi

Bigger is indeed better when it comes to heat sinking these Rb's. Unlike an OCXO, they run quite a bit longer if you cool them well. If you want to get fancy, you can run a speed controlled fan on the heat sink to regulate the temperature. You still want to pick a temp that's as low as you can practically get it for your control point.

I've fried a lot of Rb's over the years…..

Bob

On Aug 8, 2013, at 7:08 AM, Dr. David Kirkby drkirkby@gmail.com wrote: