[time-nuts] Re: HP 10509A antenna specifications?

[paul swed]

Great to hear on the vlf117 Matt.
I have 2 of the units that I had to repair also. Fortunately no leaking
caps.
The urge is to add new tubes and then tweak the coils. Don't. They are
fragile.
However the fact that you need -80 dbm does seem a bit low.
Assuming the preamp in the antenna is about 10 db or so.
Believe there were 2 antenna versions. One used 2 X nuvistors and as I
recall the other 2 X transistors.
Coax sends 30 VDC.
The antenna is a loop antenna and does look like a piece of conduit. But
there is a break in the conduit so it
does not form a shorted turn. Typically the loop is a piece of 25 pair
phone cable. The ends solder together turn by turn to make 1 wire.
Then a resonating cap for 60 KHz.

Now the bad news.
Even if you get the vlf117 working. It can no longer track the wwvb carrier
because phase shift keying was introduced some 10 years ago. This obsoletes
all of the old tracking receivers. You need some adapter to get rid of the
keying.
Several have been made. One thats been very effective is the d-psk-r.
Search time nuts archives. But these adapters are a whole additional layer
of complexity.
Without them you have a nice heater.
Good luck Matt.
Paul
WB8TSL



On Tue, Feb 28, 2023 at 5:48 PM Matt Krick via time-nuts <
time-nuts at lists.febo.com> wrote:

> I am refurbishing a HP117A VLF comparator and would like to recreate the
> outdoor antenna.
>
> I've cleaned up the A1 module where all of the 4.0uF at 60V caps leaked
> electrolyte damaging the wiring and ate holes in the ground plane on the
> PCB.
>
> I've also made most of the updates to bring the unit up to serial prefix
> 832 from a 512. Can't seem to find a human part number for the 1853-0009
> transistors though.
>
> I've also got new Nuvistors coming for module A1.
>
> So far my ferrite stick antenna doesn't have enough signal strength to make
> the meter twitch. But using a function generator it takes about a -80dBm to
> get the signal strength meter to come to the 10 mark.
>
> For the antenna It looks like the outer structure is just conduit and a
> couple of junction boxes but I would like to know if anyone has more
> detailed specifications of the loops inside the conduit. Such as number of
> turns and gauge of wire that was used in the original.
>
> Thank you!
> --Matt
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