Hi, A new 10mhz distribution amplifier is available at amateur prices. Jerry N7EME is producing them. His website is at http://jwmeng.com/model_RDA-6.html Doug K6JEY

Doug Millar wrote: > Hi, > A new 10mhz distribution amplifier is available at amateur prices. > Jerry N7EME is producing them. His website is at > http://jwmeng.com/model_RDA-6.html > Doug K6JEY > > > There's a few specifications missing: 1) input impedance and return loss. 2) output impedance and return loss 3) phase noise These are essential if one is to make a rational decision on the suitability of the distribution amplifier. The outputs and inputs appear to share a common ground. This would preclude its use in some setups without external means of providing the required isolation. The other question is does the device use AGC to set the output level? If it does the phase noise floor will almost inevitably be relatively high compared to the state of the art. Bruce

Additional specs to consider: The return loss should be low for 10 MHz and the first 8 harmonics. The harmonic distortion should be low. The isolation between outputs should be high. The phase drift vs temperature should be low. The short term stability at 1 second should be good. The magnetic field susceptibility should be low. Line sidebands should be low. Compare, for example, the HP5087, a so-so design, to the output amplifier design in the 5071A cesium, as documented in my FCS paper in 1992. Huge difference in specs. The 5071A has 120 dB isolation between outputs. Rick Karlquist N6RK Bruce Griffiths wrote: > Doug Millar wrote: >> Hi, >> A new 10mhz distribution amplifier is available at amateur prices. >> Jerry N7EME is producing them. His website is at >> http://jwmeng.com/model_RDA-6.html >> Doug K6JEY >> >> >> > There's a few specifications missing: > > 1) input impedance and return loss. > > 2) output impedance and return loss > > 3) phase noise > > These are essential if one is to make a rational decision on the > suitability of the distribution amplifier. > > The outputs and inputs appear to share a common ground. > This would preclude its use in some setups without external means of > providing the required isolation. > > The other question is does the device use AGC to set the output level? > If it does the phase noise floor will almost inevitably be relatively > high compared to the state of the art. > > Bruce > > _______________________________________________ > 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. > >

Rick Karlquist wrote: > Additional specs to consider: > > The return loss should be low for 10 MHz and the first 8 harmonics. > The harmonic distortion should be low. > The isolation between outputs should be high. > The phase drift vs temperature should be low. > The short term stability at 1 second should be good. > The magnetic field susceptibility should be low. > Line sidebands should be low. > > Compare, for example, the HP5087, a so-so design, to the > output amplifier design in the 5071A cesium, as documented > in my FCS paper in 1992. Huge difference in specs. The > 5071A has 120 dB isolation between outputs. > > Rick Karlquist N6RK > > > Rick Did you mean a high return loss or equivalently low reflection coefficient? The layout of the board in the picture is perhaps preliminary the input signal track to 3 of the output sections is a little too close to another track. Its hard to tell from the low res image but have thick film resistors been used? These can have excessive flicker noise thus increasing the close in phase noise above that possible with thin film resistors. Bruce

I should have said the return loss should be "high" or "good" :-) Bruce Griffiths wrote: > Rick Karlquist wrote: >> Additional specs to consider: >> >> The return loss should be low for 10 MHz and the first 8 harmonics. >> The harmonic distortion should be low. >> The isolation between outputs should be high. >> The phase drift vs temperature should be low. >> The short term stability at 1 second should be good. >> The magnetic field susceptibility should be low. >> Line sidebands should be low. >> >> Compare, for example, the HP5087, a so-so design, to the >> output amplifier design in the 5071A cesium, as documented >> in my FCS paper in 1992. Huge difference in specs. The >> 5071A has 120 dB isolation between outputs. >> >> Rick Karlquist N6RK >> >> >> > Rick > > Did you mean a high return loss or equivalently low reflection > coefficient? > > The layout of the board in the picture is perhaps preliminary the input > signal track to 3 of the output sections is a little too close to > another track. > > Its hard to tell from the low res image but have thick film resistors > been used? > These can have excessive flicker noise thus increasing the close in > phase noise above that possible with thin film resistors. > > Bruce > >

Rick Karlquist wrote: > I should have said the return loss should be "high" or "good" :-) "high" works, "good" depends on the application. :-) I would look at the return loss curve in general. Cheers, Magnus

Rick, > Compare, for example, the HP5087, a so-so design, to the > output amplifier design in the 5071A cesium, as documented > in my FCS paper in 1992. Huge difference in specs. The > 5071A has 120 dB isolation between outputs. If I look at your FCS92 paper and specially to figures 5 and 6: Do I understand you correct in the sense that you are proposing a less analogue and more digital styled distribution amplifier with a near-sine construction from an digital clock and analogue output filtering for every output or are you just refering alone to the triangle amplifier building blocks to be seen in figure 5? 73s Ulrich, DF6JB > -----Ursprungliche Nachricht----- > Von: time-nuts-bounces@febo.com > [mailto:time-nuts-bounces@febo.com] Im Auftrag von Rick Karlquist > Gesendet: Freitag, 15. August 2008 00:37 > An: Discussion of precise time and frequency measurement > Betreff: Re: [time-nuts] New 10mhz Distribution Amplifier > > > Additional specs to consider: > > The return loss should be low for 10 MHz and the first 8 > harmonics. The harmonic distortion should be low. The > isolation between outputs should be high. The phase drift vs > temperature should be low. The short term stability at 1 > second should be good. The magnetic field susceptibility > should be low. Line sidebands should be low. > > Compare, for example, the HP5087, a so-so design, to the > output amplifier design in the 5071A cesium, as documented > in my FCS paper in 1992. Huge difference in specs. The > 5071A has 120 dB isolation between outputs. > > Rick Karlquist N6RK > > > Bruce Griffiths wrote: > > Doug Millar wrote: > >> Hi, > >> A new 10mhz distribution amplifier is available at > amateur prices. > >> Jerry N7EME is producing them. His website is at > >> http://jwmeng.com/model_RDA-6.html > >> Doug K6JEY > >> > >> > >> > > There's a few specifications missing: > > > > 1) input impedance and return loss. > > > > 2) output impedance and return loss > > > > 3) phase noise > > > > These are essential if one is to make a rational decision on the > > suitability of the distribution amplifier. > > > > The outputs and inputs appear to share a common ground. > > This would preclude its use in some setups without external > means of > > providing the required isolation. > > > > The other question is does the device use AGC to set the > output level? > > If it does the phase noise floor will almost inevitably be > relatively > > high compared to the state of the art. > > > > Bruce > > > > _______________________________________________ > > 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. >