[HCARC] 10 Meter Net

Thu Aug 9 14:51:45 EDT 2012

Bill,

I realize that NVIS at 10 meters is not a reality, and only mentioned NVIS 
and the loop antenna at 40 meters and above - that part I have down pat.  I 
was just wondering if a loop antenna might work at 10 meters, since nothing 
anyone else is trying at 10 meters is working for local coms.  When Center 
Point can't hear Kerrville, which is line of sight for many places, it is a 
fair bet that 10 meters isn't going to work.  Maybe it would work if someone 
took two 10 meter beams and pointed them directly at each other and pumped a 
KW through them.

http://www.sanantoniohams.org/nets/index.htm    This group operates numerous 
nets across the area including one on 6 meters at 50.130 mhz.  Since they 
apparently are successful with this Freq, maybe it's something we should try 
on a different night from their net.

Gary J
N5"BAA"

----- Original Message ----- 
From: "Bill Tynan" <billandmattie at windstream.net>
To: "Gary and Arlene Johnson" <qltfnish at omniglobal.net>
Sent: Thursday, August 09, 2012 1:24 PM
Subject: Re: [HCARC] 10 Meter Net

Gary:

You cannot use NVIS at 10 meters because 28 MHz is ALWAYS above F0 (the
Critical Frequency) - that frequency (wavelength) which is returned back to
Earth from directly above the transmitting antenna. This technique can be
used on 160, 80, 60 and even 40 meters, but on none of them all the time.

On 30, 20, 17, 15, 12, 10 and shorter wavelengths (higher frequencies),
signals impacting the ionosphere at any angles except very small ones, are
not refracted enough by the ionosphere to be returned to Earth and are
passed through to space. Thus on 10 meters, signals are NEVER reflected back
directly form above - hence no NVIS. The fact that signals are NOT reflected
straight back down causes the so-called "skip zone" which can be anywhere
from a few hundred miles to thousands of miles, depending on the ionized
state of the ionosphere and the wavelength (frequency). In the skip zone,
generally no signal is heard. For various reasons, sometimes, a very weak
signal can be heard. One of these reasons is backscatter (the transmitted
signal is refracted back to Earth in the ionosphere and then reflected by
the Earth back to the ionosphere and then refracted back to Earth again. But
at 10 meters, that effect will NEVER occur at distances less that a few
hundred miles. So called "short skip occurs when the E region of the
ionosphere (about 60 miles above Earth) becomes very heavily ionized. This
is called Sporadic E and can also affect 6 meter (50 MHz) signals and even 2
meter (144 MHz) signals. I got in on one of these rare 2 meter openings two
weeks ago, working stations in New York State, Ontario and Ohio. But, even
during the summer months, when Sporadic E is most prevalent, it does not
occur all the time. That's why it is called "sporadic." And it NEVER returns
10 meter signals directly back to Earth (NVIS). About the highest frequency
that Sporadic E will return directly back to Earth is roughly 10 MHz (30
meters).

The reason that Sporadic E, or any ionosphere layer, will return signals
back to Earth is because of the lower angle which the signals hit the layer.
You can see this in water. If you look directly up through the water, you
don't see a reflection, You see what is above the water, generally the sky.
But if you look at a smaller angle, you can see reflections from the surface
of the water.

There is nothing wrong with full wave loops, but unless erected in an
inverted V type configuration, they require four supports instead of just
two. The principal advantage of full wave loops is that they don't exhibit
extremely high voltages. Half wave dipoles exhibit a curve with the voltage
(impedance) low at the center and very high at the ends, simply because the
ends are open and there is no place for current to flow.

One of the first uses of the full wave loop was at short wave station, HCJB,
at Quito Ecuador. Because of the high altitude and high power of the
transmitters, corona discharges were often experienced off the ends of the
antennas. An engineer at the station, concluded that the problem could be
alleviated by closing the ends with another halfwave length of wire., Thus
the was born the "cubical quad" antenna. Many UHF and microwave antennas
employ this principal - the so-called "loop Yagi". I have several loop
Yagis, including a 73 element monster for 2304 MHz still not up. My 902,
1296 and 3456 MHz antennas are all loop Yagis (full wavelength elements).

I hope this responds to your suggestion for employing NVIS for the HCARC 10
meter net and gives you a little incite into HF and VHF propagation and full
wave loops.

73,

Bill, W3XO/5

----- Original Message ----- 
From: "Gary and Arlene Johnson" <qltfnish at omniglobal.net>
To: "Bill Tynan" <billandmattie at windstream.net>
Sent: Thursday, August 09, 2012 10:38 AM
Subject: Re: [HCARC] 10 Meter Net

> Bill,
>
> I have been reading about local HF nets and one of the antennas they 
> recommend (on 40 meters) is a full wave loop as they say full wave loops 
> are inherently quieter and more effective at NVIS.  I wonder if a full 
> wave loop would work at 10 meters.  I have enough wire to donate (80 
> feet - enough for 2 loops) for two people to find out if they can hear one 
> another.  I guess the other side of the question is what have we got to 
> lose, since nothing else we have been trying seems to work.  At approx 9 
> feet per side they could be hung vertically and connected to be either 
> Horizontally or Vertically polarized.
>
> Gary J
> N5"BAA"
> ----- Original Message ----- 
> From: "Bill Tynan" <billandmattie at windstream.net>
> To: <galeheise at windstream.net>; "HCARC Reflector" <HCARC at mailman.qth.net>
> Sent: Thursday, August 09, 2012 10:26 AM
> Subject: Re: [HCARC] 10 Meter Net
>
>
>>I listened - no 10 meter antenna.
>>
>> I heard most of the stations with my 6 meter beam, some quite weak. K5XA 
>> was
>> by far the strongest.
>>
>> 73,
>>
>> Bill, W3XO/5
>> ----- Original Message ----- 
>> From: <galeheise at windstream.net>
>> To: "HCARC Reflector" <HCARC at mailman.qth.net>
>> Sent: Wednesday, August 08, 2012 9:35 PM
>> Subject: [HCARC] 10 Meter Net
>>
>>
>>> To All-
>>>
>>>  Thanks to the following hams who checked into the 10 meter net tonight
>>> and provided excellent encouragement to the hams who spoke from the Club
>>> Station.
>>>
>>> K5HV - Harvey
>>> KF5NHK - Terry
>>> W0LPD – Fred
>>> K5XA – John
>>> WD5ENH – Steve
>>> K5YB – Bob
>>> AF5AO – Charlie
>>> AD5UZ – Curtis
>>> KK5IA - Frank
>>> N4YPT - Jeff
>>> AC4CA – John
>>> W5QXX – Andy
>>>
>>>  We also had three Club Members visit the Club Station this evening.
>>> KF5QXN, Joe Vaughn, K5AFC, Alan Cone and KF5NHP, Mike Connor.  While
>>> meeting at the Club Station provided a centralized meeting place, it 
>>> wasn’t
>>> the best location for net control.  Although there were 12 stations that
>>> checked into the net I had either difficult or no copy on 6 of these
>>> stations.
>>>
>>>  I’m certainly open to any suggestions as to how we can increase the
>>> coverage and provide encouragement to those interested in HF operations.
>>>
>>> Gale
>>> KM4DR
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