[3830] TBDC K1LT Single Op LP

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                    Stew Perry Topband Challenge - Summer

Call: K1LT
Operator(s): K1LT
Station: K1LT

Class: Single Op LP
QTH: Ohio EM89ps
Operating Time (hrs): 5:38
Radios: SO2R

Summary:
Total:  QSOs = 134  Total Score = 506

Club: Mad River Radio Club

Comments:

I've been mostly ignoring my radio station except when radio is an
excuse to go do something outside.  Last year I spent too much time
inside sitting, both for work and for play.  Earlier this year, my
energy level was at an all time low, so I made a point of making
reasons to go outside and do stuff.

One of the useful things to do outside is to build another short
vertical phased array that I can use to finish the new phased array
receiving system hardware and software.  So I found a spot in the
"front" woods where I could erect a couple of 23-foot short verticals
with the 4 top hat / guy wires without removing too many trees.  A
side effect of this effort is an investigation into how much effect do
trees have on antenna performance.

The 23-foot short vertical with 16 23-foot radials and 4 23-foot top
hat wires sloping at 45 degrees can be made to match 75 ohm feedline
with a 33 uH base loading inductor and a series 68 ohm resistor.  The
inductor resonates the antenna and the resistor matches the impedance.
For receiving, we don't care about loss or efficiency, just repeatable
behavior.  The resistor broadens the SWR curve and lossy short
verticals can be used in close proximity without concern for mutual
coupling.

When the 23-foot short vertical is put in the woods, the resistive
component of the feed point impedance goes up, sometimes a lot (30
ohms, for example) and resonance is shifted lower suggesting extra
loading.  I have found that the trees contribute in the following
ways: a vertical tree trunk a few feet from the antenna vertical wire,
numerous leafy branches essentially touching the top hat wires, and
any part of the tree close to the ends of the top hat wires.  I
suspect that tree trunks look like lossy wires that couple to the high
current (low impedance) conductors while leafy branches look like
lossy capacitors that couple to the high impedance (low current but
high voltage) top hat wires.  Capacitive coupling at the ends of the
hat wires is particularly apparent.  I spent many pleasant evenings
gradually removing tree parts selectively from near the short
verticals while watching the feed point impedance.

What does any of this have to do with the summer Stew?  While messing
with new short verticals, I figured that some careful maintenance of
the existing short verticals might restore some lost performance.
Just before the contest I did some tree pruning around the short
verticals that showed the greatest deviation from ideal impedance and
replaced some water logged coax.  I also found one end-fire switching
box wherein 2 of the 3 transformers had exploded into tiny shards of
ferrite.  There were no scorch marks but I figure a nearby lightning
strike must have created a pulse that thoroughly overloaded those
transformers.  One transformer inverts the signal polarity to be added
to the other signal to form the end-fire array from 2 adjacent short
verticals; the second transformer does not invert but keeps the signal
paths balanced, and the third transformer proves a 2:1 impedance
transform.

I always use low power for the summer Stew because then I don't get
called by numerous stations that I cannot hear through the static.
Also, not having to listen to the amplifier roar makes the static
slightly more tolerable.  Activity during the hour before and after
sunset seemed higher than normal but my total number of contacts is
only slightly increased over previous summer tests.  The static was
not as bad as it could be, especially since I was surrounded by
thunderstorms although I didn't hear any thunder.  But propagation was
not a good as normal.  No Europeans heard at all, and very few west
coast stations were heard.  I made only 2 contacts in the DN grid and
two others were aborted because the 7 could not hear my EM89 exchange.

I got up an hour before sunrise and worked both new stations but I did
not call CQ and I went back to bed after a few minutes.

Best DX was KV4FZ and NP2J.  I had to abort a QSO in WQ5L because he
faded while giving his exchange.  KG7CW could not hear my EM89 and
N7GP could not hear my call well enough.  Sorry!  I'll build a full
sized transmit antenna soon.

Here is the year by year propagation and participation analysis:

            raw     raw    points
    year    QSOs   score  per QSO   power   weather
    2011     86     223     2.59     high  noisy west
    2012     81     224     2.77     low     noisy
    2013     72     141     1.95     low   noisy west
    2014     77     142     1.84     low   not noted
    2015     64     136     2.13     low     noisy
    2016    119     241     2.03     low     quiet
    2017     86     169     1.97     low     noisy
    2018    122     286     2.38     low   noisy then not
    2019    134     253     1.89     low   not as noisy

Note the raw score does not include the power multiplier.  Even though
I made more QSOs than ever, points per QSO were very low.  Maybe more
nearby people, but I couldn't reach distance people.

Equipment: K3S/P3 at 100 watts for the main radio, K3/P3 for the RX
pounce radio, 65-foot "tee" vertical transmit antenna, 16 short
verticals configured as 3 different phased arrays for receiving along
with custom direct conversion hardware and SDR software.


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