[TowerTalk] Inverted v vs dipole at different heights

[K4SAV]

Wow, and inverted vee for 80 meters at 1/2 wavelength height is a very 
good antenna.  Maybe you meant 1/4 wavelength.  To answer the question 
you asked, an inverted vee at 140 feet will beat the heck out of a flat 
top dipole at 70 feet.

An 80 meter inverted vee with an included angle of 120 degrees with the 
apex at 70 feet, for gain purposes, is very close to a flat top dipole 
at 55 ft height. This also scales to 40 meters, an inverted vee at 35 ft 
is very close to a dipole at 27 ft on 40 meters.

Your noise levels seem to be excessively high. There are a couple of 
possibilities. You live in an area of very high local noise, or since 
your are not using a baluns, there is a possibility that some of that 
noise is originating from your station ground. Think of it this way. You 
know a feedline will radiate when feeding a dipole with coax and no 
balun. This may not be a problem for transmit unless you have RFI in the 
shack. The opposite condition happens on receive. The feedline can pick 
up signals either from out of the air or coupled onto the feedline from 
the end where it is attached (station ground). When these signals reach 
the antenna, they are converted from common mode to differential and you 
will hear them. A good balun can prevent this.

So my recommendation would be add baluns to your inverted vees and 
dipoles. This probably will not fix all your noise problems, but it may 
help.

Your S5 noise on 20 and S9 on 40 is very high.  Last night my noise 
level on 20 was S0 and maybe S2 on 40. Is this noise present at all 
times of the day? After adding baluns, I would try to identify the 
source. It must be from something local, being that high. Most AC line 
noise is related to 60 Hz and harmonics. You can verify this 
relationship by looking at the noise with the waterfall display of a 
PSK31 program. You may have to determine if it is from something within 
your house or your neighbors house. Of course it could be the combined 
noise of many sources from all the houses around you. A horizontal 
antenna with a balun might offer a little improvement if the noise is 
from a fairly distance source and from primarily only one direction, but 
don't expect miracles.  If the noise source is close to your antenna, it 
probably won't make any difference at all.

If you can't find the source, it may be time for a receive only antenna, 
K9AY, EWE, flag, pendant, beverage, etc.

Jerry, K4SAV

Jim Miller WB5OXQ wrote:

>It seems that from the discussion about v's vs flattop that the flattop may be quieter.  However when height of support structures becomes an issue is it better to use an inverted v with an apex at least a 1/2 wave above the ground or a flattop an half that height.  I understand that antennas that are too low can be cloud warmers so is it feasible to use a flattop that is too low for a receive antenna and an inverted v at proper height for a transmit antenna?  I have 1 tower at 60' in the center of my lot and 2 others at 25' at either side of the lot for end supports.  The 25' towers are limited in height due to power line clearance.  The dipole wires lay 150 degrees by 340 degrees.  I have 2 separate dipoles 2 feet apart fed by separate coax feeds with no baluns or chokes for 80 and 40 meters.  My noise level usually runs around s 5 on 20 using a beam at 60' and s9 on 40 on the dipole and s9+10 on 75. the sweep display looks like a pocket comb on 75 and not much better on 40
> . No weak signals worked here.
>
>      Jim & Ella Miller 
>WB5OXQ & KA5EPM
>     Abby & Sparky
>Dalmatian Furbabies
>        Waco, TX
>_______________________________________________
>
>
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk at contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
>
>  
>