[time-nuts] 10MHz LTE-Lite

[Bob Camp]

HI

At a 1 second gate, your 5335 is good to about 1 ppb. (1x10^-9). A TCXO based GPSDO should be good to 10X that level. An OCXO based unit should be good to 100X that level.  If you extend the counter’s gate time, the 5335 will overflow fairly quickly. Up to the point it does, it’s accuracy will improve directly with the gate time. Once it overflows, you can correct the result, but it is messy. 

Bob

> On Dec 8, 2014, at 2:07 PM, Byron Hayes Jr <bhayes at earthlink.net> wrote:
> 
> Time-Nuts Group,
> 
> I thought some of you might be interested in my experience with the 10MHz LTE-Lite.
> 
> The 10MHz LTE-Lite arrived about a week ago.  I was not ready to make a permanent installation, I wanted it portable and I wanted to get started quickly.  I am hobbyist interested mainly in the HF spectrum.  So I decided to operate the LTE-Lite inside the Priority Mail box, which was pretty much intact.  I cut a 5" X 8" piece of corrugated cardboard, mounted the unit on it with two doublestick pads, and put the cardboard with the unit into the Priority Mail box.  I cut a hole in the top of the box so I could see the LEDs, and cut three small holes in the side, one for the USB cable, one for the antenna wire and one for the 10 MHz output.  I attached the USB cable, antenna wire and 10 MHz output cable to the unit and ran them out of the box through the holes.  I had an operating Lenovo X220 Windows 7 computer near to the box, so I plugged the USB cable into the computer (I did not try to get or use any software on the computer to decipher any messages from the LTE-Lite).  I was in an upstairs North facing bedroom (in the Los Angeles area) so I put the antenna on a nearby windowsill.  I hooked the 10MHz output to the channel 1 (Hi Z) input of my Tektronix 222A osciloscope, with the trigger on channel 1.
> 
> When power was applied through the USB line, the LEDs seemed to light normally.  Within a couple of hours the lock LED was on, but the oscilloscope was showing noise, not a meaningful output.  I let the whole thing sit overnight, and the next day an apparent 10 MHz trace was on the screen.  It was not a sine wave, and not a square wave, but something in between.
> 
> I had a small Rb unit, an Efratom 10 MHz FRS-C built into a TM-500 plug-in.  I set that up and let it warm up and lock.  I connected the Rb output to channel 2 of the 222A and got that trace on the screen.  It was a sine wave basically in lock step with the LTE-Lite trace.  Over a few hours one could see slight relative movement, but very slight.  What next?
> 
> I had a couple of HP 5300 series frequency counters, one a 5300B display with Option 1 (Hi-Stability time base) and a 5308B lower unit, and the other a plain 5300B display with a 5303B Option 1 (Hi-Stability time base) lower unit.  I give both time to warm up.  I put a "T" in the LTE-Lite output line and another "T" in the Rb output line, and connected coax from the Ts to the HiZ input of each frequency counter.  After they settled down, the counter connected to the LTE-Lite read 10000008 and the counter connected to the Rb read 10000002.  So, after a while, I reversed the leads to the counters, and the counter connected to the LTE-Lite read 10000002 and the one conntected to the Rb read 10000008.  Those readings have been consistent for several days.  That indicated to me that the LTE-Lite and the Rb were both outputing essentially the same frequency, but the counters were a bit off (I had never calibrated these counters, since I wasn't sure of the accuracy of the Rb unit).  But, I felt like the proverbial man with two watches.
> 
> So, I brought out "Big Gonzo", a HP 5335A counter with Option 010 (Hi-Stability time base) I purchased on eBay about six months ago but had never fired up.  It came up OK and I hooked it to the LTE-Lite output.  It initially read 10000028, but I gave it a couple of hours to warm up the oscillator oven and stabilize.  By then, the reading had settled to 10 000 000.  Now I switched cables and hooked the Rb to the 5335A, and it read 10 000 000.  I hooked the LTE-Lite to channel A of the 5335A and the Rb to channel B of the 5335A, and set the counter to "ratio".  When it settled, the counter read 1.000 000 indicating that the two outputs were the same frequency, at least to six decimals.  Apparently the 5335A is "right on".
> 
> I conclude that both the LTE-Lite and the Rb are outputting a 10000000 MHz signal.  I'm not sure of the accuracy beyond that.  They are probably both accurate enough for my purposes for calibrating other test equipment, receivers and transmitters operating in the HF spectrum.
> 
> I would be interested in any comments or suggestions from other list members.
> 
> Byron WA6ATN  _______________________________________________
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