Topband: LU5OM update (29 day reception report, plus more)

Don Kirk wd8dsb at
Fri Aug 11 08:55:25 EDT 2017

This is a follow up to my post about a month ago regarding how well I heard
Manuel (LU5OM) when he was using a dipole (mounted as an inverted vee) on
160 meters.  Since then I have made a point of getting up everyday
(typically 5 am EDT) to listen for Manuel, and to spot him if and when I
hear him.

The main reason for this post is to say how amazed I/we have been that out
of the last 29 days, I have been able to hear Manuel each day with a few
exceptions (25 days I could copy him, 1 day he was faint but not really
able to copy him and on the remaining 2 days I did not try to copy him
because one day he was not on, and the other day I had a bad lightning
storm).  It's like clock work that I turn the radio on, and there he is but
sometimes faint (I would have never thought this possible).  Also I might
mention that my RX antenna (pennant that's 51.6% the size of a full size
pennant) is nothing to brag about, but it's definitely better than my TX
antenna (my RX antenna typically has an approximate 2dB signal to noise
level advantage for this long haul stuff).

The main point I would like to make with this post is that during the 29
day period it has not been like a open or closed propagation situation, but
rather slightly better or poorer propagation regarding signal strength each
day.  (Note: 5am EDT (0900 UTC) was about 1.5 hours before my sunrise, and
just as long if not longer before Manuels sunrise).

Also very early on during this 29 day period Manuel changed his feedline
over to open wire feedline which allows him to switch his TX antenna from
the inverted vee configuration to basically a top loaded vertical (what he
has been calling a Marconi Tee).  Same antenna with the two feeder wires
tied together at the output of his antenna tuner.

In all honestly the dipole has almost always been as good if not better
than the Marconi Tee configuration (often very similar results and with
static crashes very hard to put firm signal strength numbers on each for an
exact comparison).

The dipole (inverted vee) also provides a lower receive noise level for
Manuel, and therefore this is typically his configuration of choice.  I did
some quick modeling, and the inverted vee configuration definitely does not
hear well at low elevation angles, and this might be why the RX noise level
is lower than when this antenna is in the Marconi Tee configuration when
exposed to Manuels high noise level environment.

Note: Modeling suggests that above an approximate elevation angle of 35
degrees Manuels dipole (inv-vee) would have a gain advantage over his
Marconi Tee configuration whereas below 35 degrees the Marconi Tee
configuration should be better (I modeled his Marconi Tee using 4 full size
elevated sloping radials to keep things simple, whereas Manuel is using
buried ground radials).

Note: Manuel runs 500 watts output power.

Manuel apologizes for not hearing as well as he can be heard, and he is
currently working on some different RX antenna configurations with hopes of
improving his receive performance.

Just FYI, and 73.
Don (wd8dsb)

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