[time-nuts] 10MHz LTE-Lite

Byron Hayes Jr bhayes at earthlink.net
Mon Dec 8 14:07:59 EST 2014

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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