Economical option for precision frequency reference?

[f1rmb]

Hi,

Great to read that. I guess I'll click the button ;-)

Oh yes, hopefully you won't have any trouble. They are sold as working after all. But it's well worth it even if you have the hassle I had.

Did you connect the power supply (on the first step, before DC/DC troubles) like on the Trimble:
http://www.ebay.com/itm/Trimble-GPS-Receiver-GPSDO-10MHz-1PPS-GPS-Disciplined-Clock-/181777773438

Yes. I started at 5V at the fuse and current limiting going up in steps to 12V, also down to 3.3V. I just had bad switching noise and the input circuit clamping my PSU voltage really low. Even with 12V it never got above 4V at the fuse. Boost converter eventually totally failed. (Not at 12V I might add - I had it running at 5.5-6V all this time to supply enough current to prevent reported OCXO failure, but it should really run at 5V alone)

Also, do you have some documentation for this board (tried a quick google search without real success until now).

Cheers.
---
Daniel

I'm looking but can't find anything specific. It does appear this board is a direct replacement for the Trimble though.

   Did you measured the output signal level ? I'm looking to add an output buffer.

Cheers.
---
Daniel

[Macbeth]

~1.5V p-p, 50 ohms IIRC when I had 12V going to it. I have it put aside for now waiting for the replacement.

[f1rmb]

Hi,

~1.5V p-p, 50 ohms IIRC when I had 12V going to it. I have it put aside for now waiting for the replacement.

Excellent. Thanks again for everything. Can't wait to receive mine and start playing with.

Cheers.
---
Daniel

[Gandalf_Sr]

OK, I'm looking to jump in on this bandwagon.  So here what I think my options are..

1. If I buy this Trimble system for $119, I just need a box and GPS antenna or
2. If I buy this Symmetricon unit for $49, I'll also need a PSU and the pigtails.

Is the Trimble the better buy? Or has someone got a better suggestion?

Thanks

[TheSteve]

OK, I'm looking to jump in on this bandwagon.  So here what I think my options are..

1. If I buy this Trimble system for $119, I just need a box and GPS antenna or
2. If I buy this Symmetricon unit for $49, I'll also need a PSU and the pigtails.

Is the Trimble the better buy? Or has someone got a better suggestion?

Thanks

What will be your ultimate use for the device? If you are only interested in 10 MHz I'd recommend looking for a Nortel NTBW50AA - it has a cleaner 10 MHz with less phase noise and works with Lady Heather. It is much bigger though.

[Shock]

FYI the LUCENT/SYMMETRICOM Z3810AS, KS24361 has gone up to $200 now. 9 left.

Last one is up for sale.

[Shock]

I have been touring ebay for a distribution amplifier after reading that several people have used video amplifiers for the job. Decided on a Link Electronics video distribution amplifier .

This is what mine looks like, Extron ADA 6 300 MX HV, bit excessive but hey. I was originally going to get it for a Frequency Electronics Inc FE-5680A Rubidium standard, happy with my LUCENT/SYMMETRICOM Z3810AS, KS24361 RFTG/GPSDO instead.

[TheSteve]

I have been touring ebay for a distribution amplifier after reading that several people have used video amplifiers for the job. Decided on a Link Electronics video distribution amplifier .

This is what mine looks like, Extron ADA 6 300 MX HV, bit excessive but hey. I was originally going to get it for a Frequency Electronics Inc FE-5680A Rubidium standard, happy with my LUCENT/SYMMETRICOM Z3810AS, KS24361 RFTG/GPSDO instead.

Very nice - you're going to need a lot of equipment to connect to all those ports.

btw, have you checked to see how clean the signal coming out is versus what is going in? With mine I can't see too much on my spectrum analyzer however when I feed the 10 MHz into some devices I can see that the output isn't as clean(but its always bang on frequency!). I can generally see a small difference with and without the amplifier. The devices I have experimented with are an HP8714C network analyzer and an HP 8921A service monitor.
I can also see small differences between my cheapie Trimble GPSDO and the Nortel unit - the Nortel is cleaner.

The one device I need to keep experimenting with is my N1996A spectrum analyzer. The noise floor specs are only specified for its internal oscillator and are generally not as good with an external reference(it claims anyway). However instead of using 10 MHz in it will also accept 1 PPS. I can't help but wonder if possibly 1 PPS might end up cleaner.

[Shock]

This is what mine looks like, Extron ADA 6 300 MX HV, bit excessive but hey. I was originally going to get it for a Frequency Electronics Inc FE-5680A Rubidium standard, happy with my LUCENT/SYMMETRICOM Z3810AS, KS24361 RFTG/GPSDO instead.

Very nice - you're going to need a lot of equipment to connect to all those ports. btw, have you checked to see how clean the signal coming out is versus what is going in?

I have 5/10/15Mhz references and about half a dozen devices with 10Mhz external reference inputs, haven't done anything yet with it, but I believe the op amps are fairly high bandwidth and should give good results. This model is the more expensive version, though I only paid about $10 for the unit.

Here is a great video by Gerry Sweeney showing the unit. My source signals are very clean, incomparable to what he is using, also I don't have to gut the power supply in my situation. I was thinking of other ideas like on some of the outputs increasing the gain or making some attenuated.

I don't have a SA suitable just FFT on the 100MHz oscilloscope and a low frequency SA. I can't seeing it being too much of a problem though but I'll guess I will find out eventually.

[SoundTech-LG]

I have been touring ebay for a distribution amplifier after reading that several people have used video amplifiers for the job. Decided on a Link Electronics video distribution amplifier .

This is what mine looks like, Extron ADA 6 300 MX HV, bit excessive but hey. I was originally going to get it for a Frequency Electronics Inc FE-5680A Rubidium standard, happy with my LUCENT/SYMMETRICOM Z3810AS, KS24361 RFTG/GPSDO instead.

Are you planning to mod that for 50 ohm in/out? Lots of work. I haven't used, or modded mine yet...

[Shock]

Are you planning to mod that for 50 ohm in/out? Lots of work. I haven't used, or modded mine yet...

Yeah that is the plan to initially convert it to impedance match as shown in the video, I'll look at gain at the same time. I don't think there is too much work involved, it just depends how far I take it. Makes for a nice project box either way.

In case you weren't aware there is some specs on it here.
http://www.extron.com/product/product.aspx?id=ada6300mxhv#spec

[Gandalf_Sr]

What will be your ultimate use for the device? If you are only interested in 10 MHz I'd recommend looking for a Nortel NTBW50AA - it has a cleaner 10 MHz with less phase noise and works with Lady Heather. It is much bigger though.

Steve, I took your advice and ordered a Nortel NTBW50AA from eBay, it needs a 24-48 volt power supply which gets up to 75 Watts when the heater is on full.  I found this power supply but it would be running at 100% at 75 Watts which seems a bit tight, I'll keep looking but any suggestions are welcome.

[carpelux]

Are you planning to mod that for 50 ohm in/out? Lots of work. I haven't used, or modded mine yet...

It isn't really that much work. I have one, and if I remember correctly it's replacement of only 15 resistors.

[Shock]

Are you planning to mod that for 50 ohm in/out? Lots of work. I haven't used, or modded mine yet...

It isn't really that much work. I have one, and if I remember correctly it's replacement of only 15 resistors.

Just saw w2aew did a distribution amp video yesterday some might find interesting.

[TheSteve]

What will be your ultimate use for the device? If you are only interested in 10 MHz I'd recommend looking for a Nortel NTBW50AA - it has a cleaner 10 MHz with less phase noise and works with Lady Heather. It is much bigger though.

Steve, I took your advice and ordered a Nortel NTBW50AA from eBay, it needs a 24-48 volt power supply which gets up to 75 Watts when the heater is on full.  I found this power supply but it would be running at 100% at 75 Watts which seems a bit tight, I'll keep looking but any suggestions are welcome.

When they wrote that spec they were talking about some worst case in rush current I am sure. When I tested mine it used 12 watts when warming up and about 9 watts after that. I use a good quality 24 vdc 0.5 amp wall adapter. That is what I had on hand but if buying new I would get one with a slightly higher current rating so it wasn't operating at 100% capacity when the OCXO is warming up. Absolutely no problems at all and it has been running for months and turned on/off many times. I also added a small rubber o-ring to one of the existing holes in the back of the unit and ran a power cord through it which leads to a 2.1mm connector. The wall adapter has the mating connector which keeps things nice and simple.

[SoundTech-LG]

Are you planning to mod that for 50 ohm in/out? Lots of work. I haven't used, or modded mine yet...

Yeah that is the plan to initially convert it to impedance match as shown in the video, I'll look at gain at the same time. I don't think there is too much work involved, it just depends how far I take it. Makes for a nice project box either way.

In case you weren't aware there is some specs on it here.
http://www.extron.com/product/product.aspx?id=ada6300mxhv#spec

I was aware, but still nice to see the 300, or 400mHz bandwidth. Getting the boards out/in seems to be most of the work for swapping out the terminating/source resistors.

[N8AUM]

Are you planning to mod that for 50 ohm in/out? Lots of work. I haven't used, or modded mine yet...

Yeah that is the plan to initially convert it to impedance match as shown in the video, I'll look at gain at the same time. I don't think there is too much work involved, it just depends how far I take it. Makes for a nice project box either way.

In case you weren't aware there is some specs on it here.
http://www.extron.com/product/product.aspx?id=ada6300mxhv#spec

This might be a dumb question but why the high bandwidth ? Don't most instruments add low pass filtering on their "REF" inputs ?
I picked up an el cheapo chinese video distribution amp from fle-bay, ya it's 75 ohms but so far none of my HP gear seem to mind the slight impedance mismatch. 

[bson]

Heads-up: there's a pile of 8 (7 now ) Spectracom 8140 distribution amplifiers on eBay right now:
http://www.ebay.com/itm/Spectracom-8140-Frequency-Distribution-Amplifier-10Mhz-Input-Eight-Available-/221943556149?hash=item33acdde835:g:HRYAAOSwdvpWDWDb

One input, five outputs - four rear and one front.

[Shock]

This might be a dumb question but why the high bandwidth ? Don't most instruments add low pass filtering on their "REF" inputs ? I picked up an el cheapo chinese video distribution amp from fle-bay, ya it's 75 ohms but so far none of my HP gear seem to mind the slight impedance mismatch.

You mean the bandwidth of the CLC409 op amp in the Extron in particular? Well I'm no expert but it's a good indicator that signal fidelity issues at 10MHz will be non existent, if compared to say an op amp which has a lower bandwidth than the input signal, gain will be affected and since it's operating outside it's parameters it's going to exceed it's noise specifications. I can't tell you if this would make it totally unusable plugged into a reference input (as they aren't that fussy on signals) but if you want to use your distribution amp for higher frequencies you're going to hit a wall sooner or later.

About the impedance, well RF commonly uses 50 Ohm cabling and termination so we are just matching that. Mismatched impedance is going to affect the gain and unterminated it can cause reflections/superstitions of the source signal. Will it matter for a 10MHz ref input? Well guess it depends how clean your source and how fussy your ref input is.

[SoundTech-LG]

Heads-up: there's a pile of 8 (7 now ) Spectracom 8140 distribution amplifiers on eBay right now:
http://www.ebay.com/itm/Spectracom-8140-Frequency-Distribution-Amplifier-10Mhz-Input-Eight-Available-/221943556149?hash=item33acdde835:g:HRYAAOSwdvpWDWDb

One input, five outputs - four rear and one front.

but, don't forget, you'll need the Spectracom Line Taps, and/or the Versa Taps to fully utilize the system. as intended...  you can also modify it to remove the +12 Volts DC riding on the rear panel outputs.
http://spectracom.com/documents/instruction-manual-model-8140/attachment

[bson]

Good catch!  Wouldn't have noticed until I checked the output...  Bought a couple of taps to go with it.

[Gandalf_Sr]

Got my NTBW50AA now and have ordered a PSU; thinking I'll copy the mods that Steve has done for 1 pps etc.  One question though, is the RS232 'real' RS232 (i.e. does it need + and - signals) or is it TTL?  It says it complies with the RS232-E standard but that seems to be something to do with rise times and noise.  I can already do TTL RS232 but I'll need to buy a cable to do 'real' RS232.

[moya034]

If you want to put your frequency standard(s) and measurement ability to the test, the ARRL regularly sponsors a frequency measuring contest. http://www.arrl.org/frequency-measuring-test

[TheSteve]

The Nortel unit is real, old school RS232 from the DB9 on the front.

[bson]

Received the Spectracom 8140 and a couple of line taps, and it works perfectly.  My Thunderbolt outputs sinusoidal AC while the taps output sinusoidal DC.  The front BNC outputs a DC square wave that can be divided using the front buttons.  I'll be putting this to good use.