Although I basically agree with most of the points below, those of us
who live on city lots, or small suburban lots, somehow continue to
radiate reasonably decent signals on the bands without the benefit of a
tower. or other "sky hook." Reality is always different than "what we'd
like to do, or have," as it's often directly related to HOAs,
incompatible lots, structures, or simply being a good neighbor by
keeping one's avocation in perspective. Installing a 75 ft. tower on a
small city lot within falling distance of a neighbor's home, power
lines, etc. is simply not good engineering practice, and begs for a
possible liability suit.
For many city or suburban hams today, ham radio operation has become a
very serious challenge, not only for antenna installations, but
sometimes even more importantly, locally-generated RFI levels. I
remember when I first got my ticket back in 1961, and living on a small
city lot in a very small town in Indiana, my noise level due to
RFI-related issues was typically an S1 or lower. Today on my small
suburban lot, my noise level can be as high as S7 to S8 due to the
plethora of RFI generators in the neighborhood... power line noise,
neighbor's plasma TVs, SMPS wall warts, utilities' smart meters,
non-ballast florescent lighting, LED lighting... The list goes on and
on. Personally, a high-dynamic range receiver with great blocking and
two-tone DR specs is less important than one that offers a well-designed
and functional noise blanker - having a rotatable loop receiving antenna
and phasing networks are also sometimes required.
If entry-level hams took the well-written, and intended, points below as
sacrosanct for ham radio operation, they would be well-advised to take
up another hobby.
73
Don W9CW
On 1/13/2015 6:03 AM, Jim Thomson wrote:
## This pdf is very well done..and a real eye opener. It also assumes you
are in the middle of a wheat field in Kansas. Your typ back yard in suburbia
is not like that at all. You are crowded by other homes, 40 ft tall utility
poles,
metal fences, metal cars, aluminum window frames, miles of house wiring,
utility drop wires etc. Stucco homes have miles of well grounded chicken mesh
beneath their surface. Toss in street lights and also freestanding 30 ft tall
aluminum street lamps.
## Your backyard ground mounted 40m full size vertical, even with lots
of ground mounted radials does not fare too well. Its radiating into all this
junk, rendering it semi useless at best. Inverted L verts on 160 + 80m
are in the same boat. How are you going to get radials laid out 360 degs,
with a home and garage in the way ? Trying to elevate radials on 160 +80m
in a typ small backyard is unobtanium. 30 ft high dipoles and yagis on the
upper 20-10m bands still does not put the ant into the clear. You are still
10’ below the utility lines, and still radiating into your neighbours homes.
## Dipoles that dont rotate.... you just lost 14 db off the sides. A rotary
dipole is a huge
improvement over a fixed dipole. When you increase the height from 30 ft to
50+ feet, the difference is almost staggering. The ant is now in the clear.
## trying to shunt feed a tower on a city lot, with less than optimum length
radials..and
only across 180 degs usually amounts to an exercise in futility. Trying to
get any type of RX ant
away from the TX ant is another exercise in frustration. A quarter wave
sloper or loaded
loaded quarter wave sloper at least puts the feedpoint at the top of the tower,
with less
reliance on radials.
## Even a 50 ft tower is only clearing the HV utility lines by 10 feet.
Trying to guy a tower on a
small city lot is usually dangerous at best..and makes for any install or
removal of ants very
difficult. What does work on a city lot is the tallest, freestanding tower
you can install.
Then you have something to work with. Not everyone is blessed with tall trees,
suitably located
on their property. The pdf is superb though. In the clear and ...higher is
better. 70-75 feet
is a good compromise between a 50 ft tower and a 100 ft tower...when on 20m.
For folks with
crank up towers, dial in the correct height for whatever band you are on,
factoring everything else in.
Jim VE7RF
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