TopBand: inv-L vs dip/EWE info (long)

[Steve Ireland]

Dear all,

I got this great e-mail from Earl, K6SE, with another view of the
inverted-L/dipole discussions and some great info about EWEs and the VP9/VK6
path.  His part of the e-mail should be read first and is more interesting
than my reply.  Enjoy!

73,

Steve, VK6VZ 

Dear Earl,

Many thanks for the terrific e-mail.  It was most interesting - I printed it
for further reference.  I have wanted to try a EWE for a long time and
lacked the data, particularly for poor VK-type soil.  At the end of our
summer (February - March) we have a lot of trouble from QRN from the north
and a directional Rx antenna can help substantially.

Most of the time, 160 is relatively quiet and VK SSBers chatting in the CW
DX window are more of a problem than noise here.

I checked my log for the last month or so and until the 4th October, I was
still using my inverted-U dipole, so when you heard me I was probably using
this rather than the inverted-L (which went up on the 3rd October).  Right
through September, I was working a lot of west and mid-west USA stations -
worked Ralph W1ZK in VT for a new state a day or so before the equinox.

It is very interesting to hear comparisons between me and Mike VK6HD.
Usually we are about on a par, but some nights/mornings one of us will seem
to have the edge.  One of the reasons I gave up (at least for now) on
inverted-L antennas (3/8 and 1/4 wave) was that I was nearly always 2 'S'
points down on Mike on Tx into the USA (rather than 2 'S' points up as I was
on the dipole that night when you heard me!)  Into EU it was even worse,
with Mike hearing and working stuff I couldn't hear/work at all.

The crunch came when on one of the first mornings FH/DJ2BW was on, Mike
could hear Herman RST559.  I left the inverted-L up throughout Herman's stay
and although I could tell he was there, I never heard him well enough to
copy, despite a relatively low noise level on a couple of occasions.  On the
dipole, I had previously worked D68DV and heard FH/DF2SS at 559 (although I
could not work him through the EU pile-up), and my feeling was having the
inverted-L rather than the dipole cost me a new country (what would have
been my 98th).

I have limitations in both height, space available for radials and poor
soil.  If I had a couple of acres rather than the 0.5acre here, I would put
up a 80 - 90' vertical, top loaded with 50 - 100 full sized radials, which
even with my poor soil I am sure would kill the dipole on Tx (and Rx when
the band was quiet).

With my site size and soil limitations, it is very, very hard to make an
inverted-L with a 66' vertical and 50 short radials (the northerly ones
running up toward the grey line are only some 30' long) work better than a
inverted-U dipole at 50 - 60' high.  My feeling is that there are a number
of other 160m 'little pistols' in a similar situation.

Kind Regards,

Many 73,

Steve, VK6VZ 

(97/At 03:03 AM 10/22/97 EDT, you wrote:
>Hello, Steve,
>At 03:03 AM 10/22/97 EDT, you wrote:
>Hello, Steve,
>
>Don't sell your inverted-L too short.  A month or so ago, I heard both
>you and VK6HD on the band at the same time.  Mike was 559 and you were
>579.  I don't know whether you were using the inv-L at the time, but
>whatever, you were a couple of s-points stronger.
>
>Perhaps to enhance your receive capabilty you can try a directional rx
>antenna.  If no room for a Beverage, then a short Ewe antenna might do.
>
>BTW, in my modeling,  I came up with a variation the Ewe -- a 30' piece
>of wire supported in the middle by a 10' pole, both ends of the wire at
>ground level (looks like a very low 20m inverted vee).   Feed one end of
>the wire against ground (about a 9:1 impedance xfmr to match 50 or 75-ohm
>line) and terminate the other end with about 2100 ohms to ground.
>
>The pattern is cardioid-shaped with an azimuth beamwidth of about 140
>degrees.
>Front-to-back is about 49 dB.  The front lobe is max at an elevation
>angle of 32 degrees, and down 3 dB at about 9 and 75 degrees.  All this
>is for "average" ground (5 millmhos/meter).
>
>For "poor" ground (2 millmhos/meter) , the optimum wire length is 26 feet
>(supported in the center at 10' high).  Termination resistance is 3300
>ohms, F/B is 40 dB, elevation angle of max signal is 36 degrees.  Azimuth
>beamwidth the same as before.
>
>For "very poor" ground, (1 millimho/meter), the optimum wire length is
>only 20', supported in the center at 10' high.  Termination resistor is
>4300 ohms.  F/B ratio is 35 dB, max sig elevation angle is 38 degrees,
>and azimuth beamwidth again the same.
>
>All three configurations have a gain about 30 dB below an isotropic
>antenna, with max signal in the direction of the feedline end of the
>wire.  To ensure this "gain", you might want to insert some inductance in
>series with the fed end of the wire.  The 30' wire requires about 71 uH,
>the 26' wire about 93 uH, and the 20' wire needs about 113 uH to resonate
>the antenna at 1825 kHz.  In any case, use of a preamplifier seems
>appropriate.
>
>If you have the room, you can erect another Ewe for the same direction to
>the side of the first one and feed them in phase to narrow the azimuth
>beamwidth.  About 300' separation will yield the greatest enhancement. 
>I'd say that 100' would be the minimum worthwhile separation.  Two more
>modified Ewes added 90 degrees to the "front" of the original two and fed
>90 degrees lagging from the "rear" Ewes (with a broadside spacing of
>300') has a pattern superior to an 1100' Beverage!  I'm amazed at what
>such a small amount of wire can be made to do for receive on 160m, hi.
>
>I haven't tried an Ewe here in the Mojave Desert (poor soil conductivity)
>because my 2-el phased vertical array seems to have good enough
>directivity to get reasonable signal-to-noise ratio on receive (although
>not as good as the 1100' Beverage I used to have for VK years ago --
>population growth has forced me to limit antennas to my 330' x 330' lot)
>-- but because of the "modified" Ewe's simplicity, I may just try one
>some day, maybe even a 4-el Ewe.
>
>BTW, regarding the VK6HD/VP9AD QSO in January 1996.  Because it was not
>during the equinox, that almost assures the the path was east-west or
>more northerly up to directly over the north pole.  The time of day
>(1124Z) would be close to the VP9's sunrise and probably near your
>sunset, so the signal could've been going easterly from VK6 across the
>USA.   At the antipodes, any path is possible as long as it doesn't go
>through daylight. 
>
>My computer says the short path beam heading from Perth (31deg 56min S,
>115deg 50min E) to VP9 (32deg 20min N, 64deg 45min W) is 356.2 degrees,
>or just about over the north pole, a distance of 19930.4 km.  Long path
>(20069.6 km) would have to be over the south pole (176.2 degree heading),
>which doesn't seem possible in January while the south polar region is in
>daylight.  Move 70 or more km south of Perth and then long path would be
>over the north pole -- I'm not sure of Mike's (and your) QTH.
>
>The VP9 must've fallen off his chair when he heard Mike calling him, hi.
>
>73 es DX, de Earl, K6SE
>
>


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