WWVH?

[Phil Karn]

Has WWVH been affected by Hurricane Lowell? I heard it well on 10 MHz
late last night. The skip was long and I wasn't hearing WWV so I noticed
that WWVH's 10 MHz signal is a lot cleaner than WWV's. Were they on
their primary or backup transmitter?

From what I can find, WWVH's primary 10 MHz transmitter is a 10 kW
Elcom-Bauer model 710C, which uses the same high level plate modulation
used by the 5/10/15 MHz CCA primary transmitters at WWV that have a lot
of AM-to-PM conversion and intermodulation distortion between the
500/600 Hz audio tones and the 100 Hz timecode subcarrier. (This makes
it difficult to use the tone sidebands to isolate Doppler measurements
between them when both are being received, which is routine at night
here on the west coast.)

But WWVH is shown as using some old (1971) AEL LA-40KA transmitters as
backups. I can't find much information on them but they appear to use
linear amplifiers, like the 2.5, 20 and 25 MHz TMC transmitters at WWV
that are so much cleaner (but less powerful and efficient).

Phil

[Dana Whitlow]

Phil,

I would imagine that WWVH's signal would now be tending

somewhat towards circular polarization.  (That's a joke, son)

I have very often seen simultaneous signals from WWV

and WWVH, and end up looking at the tone sideband

frequencies as a means of distinguishing between the

H and non-H signals.  My QTH is Kerrville, TX, about

70 miles NW of San Antonio.

Dana Whitlow

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[Phil Karn]

On 9/9/26 14:37, Dana Whitlow wrote:

>
> I have very often seen simultaneous signals from WWV
> and WWVH, and end up looking at the tone sideband
> frequencies as a means of distinguishing between the
> H and non-H signals.  My QTH is Kerrville, TX, about
> 70 miles NW of San Antonio.
>

Then as you've probably noticed, the AM-PM conversion in WWV's
transmitters generates a lot of intermodulation between the 100 Hz time
code subcarrier and the 500/600 Hz audio tones. I had thought of using
those tones in place of the carriers to distinguish between WWV and WWVH
when both are audible, but 500+100 = 600 and 600-100 = 500, so they
basically QRM each other during the first part of each second while the
subcarrier is on.

I don't observe this on WWV's 2.5, 20 or 25 MHz transmitters, which use
linear RF amplifiers so my not seeing intermod on WWVH's 10 MHz signal
last night made me wonder if they were on their backup transmitter,
which also uses a linear amplifier. If it was their primary, then it
must be possible to null out the intermod on a plate-modulated AM
transmitter, probably with neutralization of the final amplifier. Both
WWV and WWVH use 4CX15000As in the final RF stages of their primary 5,
10 and 15 MHz transmitters.

Phil