40M, noise and the HW-8 from P.R.


From: rohre (rohre@arlut.utexas.edu)
Date: Mon May 01 1995 - 19:39:03 EDT

Pablo laments his lack of success on 40M from WP4 land.

Perhaps it is not just the sometimes poor propagation we have had re the lack of
sunspots; but also the use of the HW-8 receiver. Pablo, as you may know, a
direct conversion receiver such as this has a number of limits. It will pick up
a signal both sides of zero beat, thus, you have to be careful you are always
tuning from the same or know direction, so you get the "right" signal centered
in the receiver, and then you will have the right offset to work the other
station you call.

Also, the HW 8 and other direct conversion receivers have such high audio gain,
they may pick up electrical noise from the power lines. Pablo, do you still
have noise problems at the times you like to operate if you temporarily power
the rig on a battery, with no connection to AC mains? That includes keeping all
of the HW 8 wiring away from AC operated things for this test.

Now it is good that you mention the times you have been operating. I am unsure
how many hours your local time is off GMT, but I think you may be within an hour
of Eastern U.S. time. It is possible that you are operating at times 40 has
skip changing, and going out. Also, it may be times that more electrical noise
is around your location, from folks using lighting, and appliances in the
evening. Perhaps this is a clue, for you say you have better luck early in the
morning, which I took to mean after sunrise. Good DX may be found around local
sunrise and sunset.

40 has been very good in the mid evening hours to about midnight in the Central
U. S. time zone, which is now on daylight time, 5 hours earlier to GMT, Zulu
time. But that is only when we have had decent sunspot numbers. Last midnight
was extremely poor, as the solar forcast is low on sunspots now. Mid May should
be better than this first week. There are more Solar disruptions and storms
lately with few sunspots. If you can get WWV on 10 Mhz, you could check the
propagation forcasts at 18 minutes after each hour. The explanation of the
numbers they give are in articles on propagation in Handbooks such as the ARRL
Handbook, and various operating and DX manuals. Maybe a local library at a
college would have books that go into more detail on propagation forcasting.
But the main point is that we are all having difficulty for the next year or so
until the sunspot cycle goes back up.

Finally, is your antenna parallel to any power lines? You must not be at the
same height as the power wires, or you will have much difficulty with noise
pickup. If you can manage to put up a high enough support (45 ft.), like
sections of PVC water pipe glued together, you might try a half wave vertical
dipole, with one half truly vertical, and the other horizontal, or sloping.
This would work to see if your noise is coming in on the polarization of antenna
you were using before. You might go all the way to using a magnetic full wave
wire loop in triangle, square, or any way you can hang it to lower the pickup of
electric field noise in the neighborhood, and it would give you some gain over
the dipole, if you have the space. As a triangle, it would of course take up
43.3 ft. on a side,( and that might be most of ones yard, in my case.) Again,
you might be lucky and have a friendly tall palm or pole you could hang it on.
Well, there are some ideas on first finding out if it is your receiver, and then
things around your location, or antenna pickup of extra noise, so let us hear
what your experiments show!--Stuart K5KVH

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