[ARC5] NDB IDs

[don davis]

DC resistance might be 2 MOhm, but impedance is mostly reactive and a
function of frequency, no?  

-----Original Message-----
From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On
Behalf Of Kenneth G. Gordon
Sent: Wednesday, October 31, 2012 9:14 AM
To: Dennis Monticelli
Cc: Arc5 at mailman.qth.net
Subject: Re: [ARC5] NDB IDs

On 30 Oct 2012 at 20:09, Dennis Monticelli wrote:

> Yes, MOG is here in California.  After I restored my BC-453-B several 
> years ago I started logging beacons with it using the 160M wire. Being 
> in an urban location on a city lot I usually had to wait until the 
> neighbors were in bed to DX the NDB's.  I have logged almost 100 
> different ones from as far away as Puerto Rico and Hawaii as well as a 
> Siberian AM broadcast station on this completely stock receiver.  Once 
> I took it into the mountains to escape the city noise.  With 12V 
> batteries for the filaments and a short stack of 9V (60V worth) it is 
> more portable than one thinks.

Thanks, Dennis. I had thought of doing this too, and may do that yet.

And thanks to everyone here who have posted ideas and information on input
impedance and matching.

Robert Downs has essentially confirmed the same input impedance I had
thought might be the case from my very peremptory view of the input
circuitry: 2 megohms.

Brians's ideas will be put into effect as soon as possible. I am going to
mount one of my very high-quality Stoddart 3 foot-diameter loops on its
tripod and on the roof and run twin-ax to my shack. All I have to do now is
to built the UN-BAL to match. I may also build a solid-state preamp for the
loop. In fact, I think that will be necessary very soon. I'll also have to
figure out a way to rotate the loop remotely.

As far as the noise here is concerned, it is very frequency-specific, not
generalized, across-the-band noise. Some of it is very weird sounding and
VERY loud. Although there is, of course, some across-the-band noise, it is
not particularly loud, nor does it really interfere with signals.

The addition of a simple diode or dual-diode noise limiter will help that.

We have three computers running in our home constantly, and a wireless
network, so I, of course, suspect those of being the source of some of the
noise.

The noise is not coming from the switching supplies, as I have cured an
especially bad case of that with one of my 7.62 X 54R Mosin-Nagants at 50
yards some time ago. (Boy! Was THAT fun!)

In the past, I know that the computer monitors (screens), especially,
whether LCD or tube-based, output noise in the 500 KHz range.

I have also discovered that our computer-controlled clothes-washing machine,
a Fisher and Paykell, outputs noise when it is running, on almost exactly
500 KHz, so noise sources are very variable and unusual.

I also suspect the curly-light bulbs of outputting very frequency-specific
noise, but have not yet confirmed that.

In any case, my NDB DX so far is YE in Fort Nelson BC, way up north, and at
least 1100 to 1200 miles from here.

There is also some sort of National Weather Service reporting station in
Lewiston, Idaho, about 35 miles south of here, that is copyable 24/7 here.
Its output is AM, BUT, with the BFO on, it sounds like SSB or DSB, and tunes
exactly like a side-band signal would. It is much more clear with the BFO on
than with it off.

Also, there are two AM radio stations down quite low, both are in Canada I
suspect, one at around 535 KHz, the other a bit higher, about 555 KHz. The
station at 555 Khz was broadcasting a news program from the BBC last night.

The reason I am not very definite about frequencies is that I have not yet
attempted to calibrate the dial, but even after 70+ years, it is still
pretty close.

Those of you in the eastern half of the U.S. might listen for the various
members of the 600 Meter Research Group and affiliates who are actively
transmitting in the 600 meter band. If you would like me to list specific
frequencies and modes, let me know and I will attempt to do so. There are
about 40 stations on the air from that group at this writing, some on CW,
others on various experimental digital modes.

I will repeat once more for emphasis: in my opinion, the "ARC-5" receivers
are the very finest single-band receivers ever built.

Ken W7EKB
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