Re: [time-nuts] buffer amp transformers...
I think I'm a time-nut; as symptoms I include (1) a lot of Mini-Circuits parts on my bench, (2) searches on eBay for Mini-Circuits goodies, and (3) the desire to know how my LPRO, 10811, and Thunderbolt are different, and how much better a Thunderbolt would be with a 10811 double-oven in it... Anyway, here's an eBay auction for 25 T-626 1:1:1 transformers -- item number: 220544907085 http://cgi.ebay.com/25-Mini-Circuits-T-626-RF-Transformers-0-01-10-MHz-/220544907085?cmd=ViewItempt=LH_DefaultDomain_0hash=item335980374d which look like just the thing for this amp... 73 de bob k6rtm in silicon valley - Message: 4 Date: Thu, 05 Aug 2010 10:05:39 +1200 From: Bruce Griffiths bruce.griffi...@xtra.co.nz Subject: Re: [time-nuts] Buffer / distribution amplifier for TCXO To: Discussion of precise time and frequency measurement time-nuts@febo.com Message-ID: 4c59e433.6000...@xtra.co.nz Content-Type: text/plain; charset=iso-8859-1; Format=flowed Bruce Griffiths wrote: In which case a linear distribution amplifier is probably required. With only a ~3V supply available, options for the distribution amplifier topology are somewhat limited. In principle you could use an emitter follower driving 4 other emitter followers with a resistor in series with the emitters of the output devices and the AC coupled loads to match the source to the interconnecting cable impedance to minimise reflections without requiring excessive dissipation in the emitter followers. With the low voltage supply available, using an RF choke is series with the emitter follower's emitter to ground resistor will also be useful in achieving the required dynamic range. Bruce A more efficient buffer amplifier circuit schematic is attached. The series transformer feedback stage has high input impedance and an output impedance matched to the transmission line (yes it works well with long transmission lines as well). However a trifilar wound RF transformer is required. In principle the various GPS receivers could be connected to taps along an end terminated transmission line using feedthrough connections with compensation for the tap shunt capacitance if necessary. A lower impedance line (eg 50 ohms) could also be driven at the expense of a higher collector current. In this case the value of R3 would need to be reduced to around 100 ohms or so. Bruce -- next part -- A non-text attachment was scrubbed... Name: TCXO_BUFFER.gif Type: image/gif Size: 7990 bytes Desc: not available URL: http://www.febo.com/pipermail/time-nuts/attachments/20100805/091e6a74/attachment.gif -- ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts End of time-nuts Digest, Vol 73, Issue 12 * ___ 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.
Re: [time-nuts] buffer amp transformers...
The spec sheet lists them as being good to 10MHz; would they be ok at 16MHz with a little more loss, or should I worry about resonances with parasitic capacitance? 73 de Henry M0HMH in Santa Cruz On Wed, Aug 4, 2010 at 9:14 PM, k6...@comcast.net wrote: I think I'm a time-nut; as symptoms I include (1) a lot of Mini-Circuits parts on my bench, (2) searches on eBay for Mini-Circuits goodies, and (3) the desire to know how my LPRO, 10811, and Thunderbolt are different, and how much better a Thunderbolt would be with a 10811 double-oven in it... Anyway, here's an eBay auction for 25 T-626 1:1:1 transformers -- item number: 220544907085 http://cgi.ebay.com/25-Mini-Circuits-T-626-RF-Transformers-0-01-10-MHz-/220544907085?cmd=ViewItempt=LH_DefaultDomain_0hash=item335980374d which look like just the thing for this amp... 73 de bob k6rtm in silicon valley - Message: 4 Date: Thu, 05 Aug 2010 10:05:39 +1200 From: Bruce Griffiths bruce.griffi...@xtra.co.nz Subject: Re: [time-nuts] Buffer / distribution amplifier for TCXO To: Discussion of precise time and frequency measurement time-nuts@febo.com Message-ID: 4c59e433.6000...@xtra.co.nz Content-Type: text/plain; charset=iso-8859-1; Format=flowed Bruce Griffiths wrote: In which case a linear distribution amplifier is probably required. With only a ~3V supply available, options for the distribution amplifier topology are somewhat limited. In principle you could use an emitter follower driving 4 other emitter followers with a resistor in series with the emitters of the output devices and the AC coupled loads to match the source to the interconnecting cable impedance to minimise reflections without requiring excessive dissipation in the emitter followers. With the low voltage supply available, using an RF choke is series with the emitter follower's emitter to ground resistor will also be useful in achieving the required dynamic range. Bruce A more efficient buffer amplifier circuit schematic is attached. The series transformer feedback stage has high input impedance and an output impedance matched to the transmission line (yes it works well with long transmission lines as well). However a trifilar wound RF transformer is required. In principle the various GPS receivers could be connected to taps along an end terminated transmission line using feedthrough connections with compensation for the tap shunt capacitance if necessary. A lower impedance line (eg 50 ohms) could also be driven at the expense of a higher collector current. In this case the value of R3 would need to be reduced to around 100 ohms or so. Bruce -- next part -- A non-text attachment was scrubbed... Name: TCXO_BUFFER.gif Type: image/gif Size: 7990 bytes Desc: not available URL: http://www.febo.com/pipermail/time-nuts/attachments/20100805/091e6a74/attachment.gif -- ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts End of time-nuts Digest, Vol 73, Issue 12 * ___ 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. -- Henry Hallam Sent from my Laptop ___ 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.
Re: [time-nuts] buffer amp transformers...
For this application you'll need a bandwidth of somewhat more than 10MHz to preserve the clock slew rate. Those transformers are better suited to sinewave operation at 5 or 10MHz. If one uses a pair of transformers (one for the feedback and one to isolate the output) then wider bandwidth 1:1 transformers can be used. Or one could just elect to capacitively couple the load. Alternatively one can just wind one's own trifilar transformer using a suitable binocular ferrite core. Bruce Henry Hallam wrote: The spec sheet lists them as being good to 10MHz; would they be ok at 16MHz with a little more loss, or should I worry about resonances with parasitic capacitance? 73 de Henry M0HMH in Santa Cruz On Wed, Aug 4, 2010 at 9:14 PM,k6...@comcast.net wrote: I think I'm a time-nut; as symptoms I include (1) a lot of Mini-Circuits parts on my bench, (2) searches on eBay for Mini-Circuits goodies, and (3) the desire to know how my LPRO, 10811, and Thunderbolt are different, and how much better a Thunderbolt would be with a 10811 double-oven in it... Anyway, here's an eBay auction for 25 T-626 1:1:1 transformers -- item number: 220544907085 http://cgi.ebay.com/25-Mini-Circuits-T-626-RF-Transformers-0-01-10-MHz-/220544907085?cmd=ViewItempt=LH_DefaultDomain_0hash=item335980374d which look like just the thing for this amp... 73 de bob k6rtm in silicon valley - Message: 4 Date: Thu, 05 Aug 2010 10:05:39 +1200 From: Bruce Griffithsbruce.griffi...@xtra.co.nz Subject: Re: [time-nuts] Buffer / distribution amplifier for TCXO To: Discussion of precise time and frequency measurement time-nuts@febo.com Message-ID:4c59e433.6000...@xtra.co.nz Content-Type: text/plain; charset=iso-8859-1; Format=flowed Bruce Griffiths wrote: In which case a linear distribution amplifier is probably required. With only a ~3V supply available, options for the distribution amplifier topology are somewhat limited. In principle you could use an emitter follower driving 4 other emitter followers with a resistor in series with the emitters of the output devices and the AC coupled loads to match the source to the interconnecting cable impedance to minimise reflections without requiring excessive dissipation in the emitter followers. With the low voltage supply available, using an RF choke is series with the emitter follower's emitter to ground resistor will also be useful in achieving the required dynamic range. Bruce A more efficient buffer amplifier circuit schematic is attached. The series transformer feedback stage has high input impedance and an output impedance matched to the transmission line (yes it works well with long transmission lines as well). However a trifilar wound RF transformer is required. In principle the various GPS receivers could be connected to taps along an end terminated transmission line using feedthrough connections with compensation for the tap shunt capacitance if necessary. A lower impedance line (eg 50 ohms) could also be driven at the expense of a higher collector current. In this case the value of R3 would need to be reduced to around 100 ohms or so. Bruce -- next part -- A non-text attachment was scrubbed... Name: TCXO_BUFFER.gif Type: image/gif Size: 7990 bytes Desc: not available URL:http://www.febo.com/pipermail/time-nuts/attachments/20100805/091e6a74/attachment.gif -- ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts End of time-nuts Digest, Vol 73, Issue 12 * ___ 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.
