[time-nuts] Adret 4101A, the DCF77 and a good antenna
Alan Melia
alan.melia at btinternet.com
Thu Oct 22 16:23:30 UTC 2009
Hi Bert oh well commiserations I don't have that problem. With LF you don't
actually need a clear sight and takeoff. like at higher frequencies. The
wavelength of 60kHz it so big is goes round buildings without any trouble.
(It will actually penetrate seawater to some extent though not as well as
NAA on 24kHz) The loop should work just as well in your back lot. and you
can probably get better spacing from the domestic noise sources?? Also
height is not too important either though they are better at least a few
feet off the ground to reduce the coupling to the lossy ground.
Alan G3NYK
----- Original Message -----
From: <EWKehren at aol.com>
To: <time-nuts at febo.com>
Sent: Thursday, October 22, 2009 4:10 PM
Subject: Re: [time-nuts] Adret 4101A, the DCF77 and a good antenna
> Alan, my problem is it has to look half way decent and be acceptable to
the
> neighbors, one time I had to take down a HP Loop for 60 KHz. Did not fit
> the esthetics of the home fronts and only the front faces Boulder. I once
> tried forming plastic pipe by heating it with a heat gun while wrapping
it
> around an oil barrel. Still not perfect.
> Bert
>
>
> In a message dated 10/21/2009 8:03:07 P.M. Eastern Daylight Time,
> alan.melia at btinternet.com writes:
>
> Hi Bert yes it makes a good "former" if you have it. I bent some stiff
> wire
> (fence wire ?) into a loop of the right size, insulated the ends so it
> didnt
> form a "shorted turn" and tiewrapped the multiway cable to that.......not
a
> s neat as your method. The point I was making is that the (Faraday)
> screening doesnt buy you much, if anything, at these very low
frequencies.
> It is a very different story higher up the spectrum.
>
> I looked at 1in. white water pipe but it is not easy to form into a loop
> :-)) For smaller loops I used hoola hoops from Toys R Us....there is a
> plug
> holding them together which is easily removed then I jouned the ends with
a
> 1in "T" piece and glued that into a plastic box (lots of hot melt to
> water-proof it ......I hope!) where I made the connections to form itinto
a
> mutiturn loop.
>
> Best wishes
> Alan G3NYK
> ----- Original Message -----
> From: <EWKehren at aol.com>
> To: <time-nuts at febo.com>
> Sent: Wednesday, October 21, 2009 1:53 PM
> Subject: Re: [time-nuts] Adret 4101A, the DCF77 and a good antenna
>
>
> > Alan,
> > I used a copper pipe because it is the easiest way to make a round
> loop.
> > I have also used PVC but it always ended up rectangular. If you have a
> > better idea please let me know, because I am considering to fire up my
> old
> > Tracor 599 receiver that I modified to work up to 80 KHz. Used it a
long
> time on
> > 60 KHz.
> > Bert Kehren WB5MZJ
> >
> >
> > In a message dated 10/21/2009 5:19:28 A.M. Eastern Daylight Time,
> > alan.melia at btinternet.com writes:
> >
> > Hi Magnus I was not sure whether the 4101A would go up that far. I had
> not
> > noticed the news about HBG. That is a disappointment, particularly
with
> > the
> > number of "radio clocks" around in "domestic" use, and from the "Land
of
> > Clocks" too.
> >
> > Someone mentioned a screened loop in copper pipe. Screening loops at
> this
> > frequency gives little advantage and the extra stray capacitance can
> > degrade
> > the performance. An open loop works just as well (and is much easier
to
> > build for a trial) the problem usually comes from common mode pick-up
on
> > the
> > feeder to the receiver. This is often best combatted by careful
> balancing,
> > or transformer isolation.
> >
> > Alan G3NYK
> >
> > ----- Original Message -----
> > From: "Magnus Danielson" <magnus at rubidium.dyndns.org>
> > To: "Discussion of precise time and frequency measurement"
> > <time-nuts at febo.com>
> > Sent: Wednesday, October 21, 2009 1:30 AM
> > Subject: Re: [time-nuts] Adret 4101A, the DCF77 and a good antenna
> >
> >
> > > Alan Melia wrote:
> > > > Marco, have you considered that HBG on 75.0kHz might be stronger
> with
> > you
> > > > from Switzerland??. In a lab or other complex quite often with
> off-air
> > > > standards the problem is local noise. I have a friend in Porto who
> used
> > to
> > > > be able to lock to MSF when it was at Rugby a few years
ago.......I
> > havent
> > > > asked since it moved north to Anthorn but I suspect he uses GPS
now.
> If
> > the
> > > > noise is not a problem these receiver will often work well on a
> > resonable
> > > > wire antenna which is fairly easy to rig. Or see the PA0RDT
> MiniWhip
> > design
> > > > for a very simple active low frequency antenna. This is used all
> round
> > the
> > > > world for receiving weak amateur signals on 136kHz ....it is
> broadband
> > up to
> > > > about 500kHz, and down to 40kHz Japanese frequency standard
> > transmissions.
> > > > It is so small you can experiment to find the best quiet position.
> At
> > LF
> > the
> > > > secret is the higher the better.
> > >
> > > The TDF 162 kHz is a 2 MW transmitter which is even closer...
> > >
> > > A bit tricker to retriev the timing signal thought, but this is
> assuming
> > > the signal can be freely selected.
> > >
> > > The HBG transmitter is going off-air (for good) in a not to distant
> > future.
> > >
> > > Cheers,
> > > Magnus
> > >
> > > _______________________________________________
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