[TenTec] New and Improved Terminology (NVIS origins)

Wed Jan 5 17:42:26 PST 2011

At my last 3 home QTH's, I have put up both a horizontal antenna fed with
open wire, and a vertical dipole (also fed with openwire), for reasons Gary
just stated.

It's horses for courses.
The horizontal dipole works best for NVIS, the vertical dipole works best
for DX.

I have used the vertical dipole instead of the classical vertical because of
my despise for radials.

In several emails we have been arguing if the number of radials affects the
angle of radiation, the efficiency of the antenna, or both.

WELL I DON'T REALLY CARE. I run a vertical dipole, which is INDEPENDENT of
radials and I don't have to worry about all that BS.  My ground losses are
determined by my ground, but I can't change that, unless I  move.

Due to the shortening of the antenna, I lose a percentage of a single dB of
power (not more), but due to the efficiency compared to a normal trap
vertical with just a couple of radials, I gain several dB.  It's a win
situation.

I still stand by my challenge for anyone to come up with a simple cheap
antenna that will out-perform the simple vertical dipole.  I know of
nothing, and I've been at this game for a long time.

Beams will beat them. Quads will beat them.  No contest on that point.  What
else?

73
Rick

-----Original Message-----
From: tentec-bounces at contesting.com [mailto:tentec-bounces at contesting.com]
On Behalf Of CSM(r) Gary Huber
Sent: Wednesday, January 05, 2011 6:37 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] New and Improved Terminology (NVIS origins)

I am NOT taking sides on this thread, but reporting my twenty five year 
experience with NVIS and vertical antennas at my location.

My conditions are a rural subdivision one acre lot, with several feet of 
glacial moraine black soil over water bearing clay at 3 to 5 feet. The NVIS 
antenna is an all-band doublet some 130 feet overall in a inverted VEE 
configuration, apex at 12' fed with 450 Ohm window line. The vertical is an 
old Butternut HV-2 (80-40) top loaded with four 12 foot wire umbrella to 
cord guys. The 160m base loading kit is usually in place. The vertical is 
mounted on a 12 foot mast which was was "water hose driven" 10 feet into the

ground.  Twenty four radials are made from surplus telephone central office 
jumper wire (# 20 -# 22 ?), each approximately 65 feet in length, laid on 
top of close cut grass over the septic leach field. The feed line is direct 
burial RG-8 laid on the ground.

The NVIS performs as expected out to about 500 miles. The vertical has 
performed better than expected for DX, consistently getting through on 
gray-line, and breaking pile-ups. Local DXers returned from DX-peditions in 
report the signals from my vertical is usually stronger than those from 
stations in the region.

I do not use low dipoles other than the NVIS because of my focus on HF DX. 
I do have a sloper but find the vertical produces a stronger signal for DX. 
I have used a low wire Beverage style RX antenna with excellent results.

73 es DX,

Gary - AB9M

-----Original Message----- 
From: Steve Hunt
Sent: Wednesday, January 05, 2011 4:38 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] New and Improved Terminology (NVIS origins)

There are two distinct and different issues here. Take a look at how the
ARRL Antenna Book tackles them quite separately.

1. Antenna efficiency: directly affected by the ground conductivity in
the Reactive Near Field. This is the parameter we are usually improving
by laying down a good ground radial system

2. Elevation angle pattern: determined by soil characteristics in the
Far Field where ground reflections are taking place. Do some simple
geometry and you'll see that at really low elevation angles - 5 degrees
say - the ground reflections from an 80m quarter-wave vertical will
extend out to at least 750ft from the base of the vertical. A typical
ground radial system will do nothing about the conductivity there.

You can check this using EZNECs ability to have two different ground
media. Set up Media 1 as salt water extending for about 50ft around the
vertical, and Media 2 as rocky soil beyond. Look at the elevation
patterns - they will be those which pertain to poor ground. Now
gradually extend Media 1 outwards until you get the elevation pattern to
match that over salt water - that will tell you how far out the
reflections are taking place and how extensive your radial system would
need to be.

Please note - I'm not saying a good ground system doesn't help. I'm
saying that the usual ground radial system predominantly affects antenna
efficiency and not elevation pattern.

Please also note that nothing I have said conflicts with the Exam
Question answers.

73,
Steve G3TXQ

On 05/01/2011 21:44, Richards wrote:
> Er... ah...   No joke.   Do you doubt the proposition that a
> good ground plane lowers radiation take off angle?  If so,
> I would be curious as to your reasons.   (Seriously, and with
> no intention to flame or cause an argument, as I have
> made quite an investment in time and resources in vertical
> developing a reasonably decent vertical antenna system
> for my small, suburban back yard.   Any info would be
> greatly appreciated. )
>
> FYI ---
>
> ------ Extra Class Exam Questions of interest -----
>
> Question E9A12  - and the answer is that the efficiency
> of a quarter wave grounded vertical antenna can be improved by
> installing a good radial system.
>
> Question E9A13 - answer is - soil conductivity is the most important
> factor in determining ground losses for a ground-mounted vertical
> antenna operating in the 3-30 MHz range.
>
> Question E9C13 - answer is - When a vertically polarized antenna
> is mounted over seawater versus rocky ground, the far-field
> elevation pattern low-angle radiation increases.
>
> Question E9C17 - answer - The main effect of placing a vertical
> antenna over an imperfect ground is that it reduces low-angle
> radiation.
>
> Also, on the audio study guide, Gordo makes some stray comments
> about using 3 inch copper strap for radials on his roof, and
> mentions improving the ground field increases low angle
> radiation  - he goes on to say it does not increase signal strength,
> of course, but only that it increases the amount of signal that
> has low take off angle.
>
> This information is consistent with all that I have read on verticals
> in the ARRL Antenna Handbook, and I did LOTS of research before
> installing a large vertical monopole in the back yard.
>
> A huge ground pane does lower take off angle (as NEC modeling
> shows) and also improves antenna efficiency -- I stopped at 65 radials
> but I wish had installed even more just to be sure.    Also, my back yard
> soil is very conductive and remains moist even through the summer, so
> the soil, itself, helps me considerably.   Rob Sherwood and I exchanged
> some nice email at the time I was doing this homework, and I believe
> he lives over a more dry, rocky soil, and that is much harder to work
> over.   I also corresponded with the infamous  Rudy Severns N6LF
> and his findings are consistent with this conclusion.    NEC modeling
> produces consistent results.
>
> N'est ce pas?       Happy trails OM.
>
> ===============  JHR  ============================
>
>
>
> I had
>
> On 1/5/2011 1:01 PM, Steve Hunt wrote:
>> I presume the "wink" indicates that is a joke !
>>
>> The only thing that would improve the elevation pattern would be
>> improved ground conditions in the Fresnel Zone where the ground
>> reflections are taking place. That would take some awfully long radials
>> - certainly well beyond my property boundary - and an awful lot of them
>> to achieve a copper density that would affect the conductivity so far 
>> out.
>>
>> 73,
>> Steve G3TXQ
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