DD
Dr. David Kirkby
Thu, Aug 8, 2013 11:08 AM
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
I wonder if one could fit a GPS locking module in that box and
antenna connector on the box.
-
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
-
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.
-
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
On 6 August 2013 09:37, Raj <vu2zap@gmail.com> wrote:
> Found this on Hack-a-day
>
> http://www.youtube.com/watch?v=chrzrod3tQY
>
> Cheers
>
> --
> Raj, VU2ZAP
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
M
mc235960
Thu, Aug 8, 2013 1:49 PM
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 :
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
I wonder if one could fit a GPS locking module in that box and
antenna connector on the box.
-
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
-
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.
-
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
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.
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 6 August 2013 09:37, Raj <vu2zap@gmail.com> wrote:
>> Found this on Hack-a-day
>>
>> http://www.youtube.com/watch?v=chrzrod3tQY
>>
>> Cheers
>>
>> --
>> Raj, VU2ZAP
>
> 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
> _______________________________________________
> 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.
DD
Dr. David Kirkby
Thu, Aug 8, 2013 2:05 PM
None left from that batch. Hope you got yours.
On 8 August 2013 14:49, mc235960 <mc235960@gmail.com> wrote:
> None left from that batch. Hope you got yours.
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
VE
Volker Esper
Thu, Aug 8, 2013 2:21 PM
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:
None left from that batch. Hope you got yours.
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:
> On 8 August 2013 14:49, mc235960<mc235960@gmail.com> wrote:
>
>> None left from that batch. Hope you got yours.
>>
> 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
> _______________________________________________
> 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.
>
>
>
E
EB4APL
Thu, Aug 8, 2013 3:19 PM
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:
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:
Great video. The distribution units are still available on eBay. I
bought two today.
Regards
Steve G8EBM
-----Original Message----- From: David J Taylor
Sent: Tuesday, August 06, 2013 11:30 AM
To: Time Nuts
Subject: Re: [time-nuts] Rb video
Found this on Hack-a-day
http://www.youtube.com/watch?**v=chrzrod3tQY<http://www.youtube.com/wa
tch?v=chrzrod3tQY>
Cheers
Raj, VU2ZAP
Bangalore, India.
==============================**=========
Thanks for the pointer - I enjoyed that, particularly the PIC programming!
73,
David GM8ARV
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
_____________**
time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
https://www.febo.com/cgi-bin/**
mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listin
fo/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<https://www.febo.com/cgi-bin/mailman/listin
fo/time-nuts>
and follow the instructions there.
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:
> 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:
>
>> Great video. The distribution units are still available on eBay. I
>> bought two today.
>>
>> Regards
>>
>> Steve G8EBM
>>
>> -----Original Message----- From: David J Taylor
>> Sent: Tuesday, August 06, 2013 11:30 AM
>> To: Time Nuts
>> Subject: Re: [time-nuts] Rb video
>>
>> Found this on Hack-a-day
>>
>> http://www.youtube.com/watch?**v=chrzrod3tQY<http://www.youtube.com/wa
>> tch?v=chrzrod3tQY>
>>
>> Cheers
>>
>> Raj, VU2ZAP
>> Bangalore, India.
>> ==============================**=========
>>
>> Thanks for the pointer - I enjoyed that, particularly the PIC programming!
>>
>> 73,
>> David GM8ARV
>> --
>> SatSignal Software - Quality software written to your requirements
>> Web: http://www.satsignal.eu
>> Email: david-taylor@blueyonder.co.uk
>> ______________________________**_________________
>> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
>> https://www.febo.com/cgi-bin/**
>> mailman/listinfo/time-nuts<https://www.febo.com/cgi-bin/mailman/listin
>> fo/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<https://www.febo.com/cgi-bin/mailman/listin
>> fo/time-nuts>
>> and follow the instructions there.
>>
>
>
> --
> --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.
>
RA
Robert Atkinson
Thu, Aug 8, 2013 4:40 PM
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.
-
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.
-
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.
-
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.
-
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 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:
> Found this on Hack-a-day
>
> http://www.youtube.com/watch?v=chrzrod3tQY
>
> Cheers
>
> --
> Raj, VU2ZAP
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.
BC
Bob Camp
Thu, Aug 8, 2013 10:05 PM
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:
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
I wonder if one could fit a GPS locking module in that box and
antenna connector on the box.
-
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
-
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.
-
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
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
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:
> On 6 August 2013 09:37, Raj <vu2zap@gmail.com> wrote:
>> Found this on Hack-a-day
>>
>> http://www.youtube.com/watch?v=chrzrod3tQY
>>
>> Cheers
>>
>> --
>> Raj, VU2ZAP
>
> 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
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