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Electronics => RF, Microwave, Ham Radio => Topic started by: CaptDon on May 31, 2020, 11:42:21 pm

Title: Strange beat note against WWV 5mhz and 10mhz
Post by: CaptDon on May 31, 2020, 11:42:21 pm
Anyone else got a signal about 20hz away from WWV
on their 5mhz and 10 mhz signals?? My 15mhz is clear
with no problem. The signal is not generated within my
household. I have three railroads close to me with all
kinds of wayside signalling gear. Haven't gone looking
yet, but perhaps something coming from them?
Title: Re: Strange beat note against WWV 5mhz and 10mhz
Post by: Wallace Gasiewicz on June 01, 2020, 11:21:58 am
Capt:

I do not see anything with 3 or 10 Hz resolution. 10 Hz per division. I looked at 5 and 10 MHz.
Nothing 20 Hz from the signals. Signals look pretty clear and are strong.
There are lots of RR lines and switching stuff near here also.

Wally
Title: Re: Strange beat note against WWV 5mhz and 10mhz
Post by: radiogeek381 on June 01, 2020, 05:07:50 pm
I see signals near WWV all the time.  Some come from 10MHz reference oscillators in the room.  Network adapters, appliances with crystal driven clocks.  One of the radios in the shack has a synthesizer whose coarse ref freq is 10MHz.  If I don't lock that one, it can beat with WWV.

What kind of radio are you using?

Title: Re: Strange beat note against WWV 5mhz and 10mhz
Post by: CaptDon on June 01, 2020, 08:57:01 pm
The receiver is a Kenwood TS-690S. I think the internal ref oscillator
is 4mhz. If I remember correctly, the guy I bought the radio from
paid a little extra to have the TCXO installed as opposed to the plain
vanilla oscillator in a can they normally ship with. When calibrating my
bench counters and AFG units I have been using beat notes against
the 15mhz WWV as there is no interfering signal near it and I receive
the 15mhz signal around S9 during the mid afternoon. I switch the receiver
to CW mode giving me a 700hz tone then zero beat against that tone
to calibrate my bench test gear. I do have a double oven military 10mhz
TCXO that is always on. The daily drift is about 1 cycle in ten seconds
or 1 part in 100,000,000. I could tweak the trimmer for less drift but
it is fine as is, close enough for what I need.
Title: Re: Strange beat note against WWV 5mhz and 10mhz
Post by: 0culus on June 02, 2020, 03:22:47 am
Bet you have a local source of 5 or 10 MHz from your equipment. I've had this happen in my lab due to using a poor quality coax to connect the GPSDO to the distribution amplifier. Replaced it and the stray 10 MHz tone went away.