Richard
The data is indisputable but I think for the average ham about a dozen 45
degree radials will produce about 3 DB less than theoretical. That is less than
an S unit. The other difference is that all this information is based on ground
wave propagation. There is nothing that addresses
Static drain chokes and ground rods should be SOP. The chokes drain
static build up which usually prevents direct hits. The chokes are
available from various broadcast suppliers.
On 7/30/12 11:40 AM, DAVID CUTHBERT wrote:
Bob, do you have ground rods for lightning?
The stub should be ok for
A one or two inch form and #12 wire.
On 7/30/12 12:23 PM, Jim Hoge wrote:
Then what would you recommend for homebrewing a choke?
Tnx,
Jim W5QM
*From:* W2XJ w...@nyc.rr.com
*To:* topband@contesting.com
*Sent
A while back on another list there was a discussion about a robust amp
can not be built in a table top size. I believe this applies to solid
state amps as well. The key to building a gutsy solid state amp is the
use of multiple devices and distributing the heat over a larger area.
All solid
There is no single solution for detuning an antenna it depends on
electrical length. For verticals a quarter wavelength or less it is
common to have a contactor between the network and the radiating element
and open the connection to float that element. This is the practice in
commercial
Sensitivity is not always important. Small loops in general receive less
noise and the real exercise is balancing the internal noise floor
against the actual signal received. In some cases a loss up to 20 db can
be acceptable the numbers are easy enough to run.
On 6/16/12 8:17 PM, Brian Miller
EZNEC is your friend.
On 6/16/12 9:35 PM, Tom W2MN wrote:
A couple of us in the radio club were discussing the possibility of
installing a full wave horizontal loop antenna (for Rx and Tx) on top of a
building we have access to. The loop would be about 20ft above the building
roof, making it
Probably part has to do with the fact that your vertical is 1/8
wavelength and rule of thumb is 1/8 wavelength or less do no have a
significant influence unless extremely close.
On 6/17/12 5:34 PM, Bill and Liz wrote:
I have been following the thread with interest. I have a K9AY and a DO loop
You really do not need stranded wire. Bare solid wire is typically used
for grounds. and while the standard of 120 radials spaced 3 degress is a
well known standard for ground systems, it is very rare in amateur
radio. Anything beyond 12 1/8
One has to be careful with 5/8 wavelength verticals. A radiator that is
physically 5/8 wavelength is already electrically too tall. That is why
a 300 foot BC tower would not work well at low angles on 160. There are
too things to considers one is that towers have velocity factor just
like
I think Carl may have his time line backwards. In the 20s and early 30s
many stations used various forms of wire antennae including dipoles and
various cage designs. During the 30s Dr Brown and colleagues studied and
tested various vertical radiators and ground systems. The result of that
work
Subject:
Date:
From:
Reply-To:
To:
Having worked in the business over 54 years with LW MW and SW
transmission systems up to 2 megawatts and having built numerous MW
arrays to 12 towers I would respectfully suggest a quick check of
fundamental broadcast history. Google
The sign up procedure fails. There seems to be a problem with the
majordomo address.
On 2/22/12 1:17 AM, Mike Waters wrote:
Thanks. That must be it. http://www.500kc.com/Maillists.htm
On Tue, Feb 21, 2012 at 9:59 PM, Tod Olsont...@k0to.us wrote:
http://www.500kc.com/
all
about what makes it easier for them to administrate.
On 2/21/12 7:36 PM, Joe Subich, W4TV wrote:
On 2/21/2012 4:17 PM, W2XJ wrote:
In broadcast work the antenna impedance is first determined by
calculation (now modeling) then the actual impedance are measured
when the station is tuned up
for the skywave to exceed the groundwave, the
monopole needs to be longer than half wave (somewhere in the area
exceeding 0.64 wave).
73,
... Joe, W4TV
On 2/21/2012 8:58 PM, Rick Karlquist wrote:
W2XJ wrote:
If you can find a used FIM 22 it goes from 200 KHz to 550 KHz. That said
I
the measurements are matched to the best
fit ground conductivity curve the variations in signal strength above
and below the theoretical can be significant in many cases.
On 2/21/12 8:58 PM, Rick Karlquist wrote:
W2XJ wrote:
If you can find a used FIM 22 it goes from 200 KHz to 550 KHz
The link provided below shows how to calculate EIRP. I think each
administration will spell out the requirements of how to legally
calculate EIRP. To me it is fairly straight forward. 60M in the US is an
example. While there is an EIRP limitation, the FCC simplified the
determination by
The Potomac Analog FIM is no longer available, nor are the parts to
repair them and calibration service is no longer available. The new
meters are expensive digital units. But in broadcast we do not use them
to determine power but rather coverage usually when directional systems
are tuned.
On
As I posted earlier field measurement is not an accurate method of
determining power. I seriously doubt an administration permit such a
technique unless it was very dumbed down and produced very 'safe'
results or in other words less power than could otherwise be achieved.
On 2/21/12 2:54 PM, Tod
, W2XJ wrote:
The Potomac Analog FIM is no longer available, nor are the parts to
repair them and calibration service is no longer available. The new
meters are expensive digital units. But in broadcast we do not use them
to determine power but rather coverage usually when directional systems
They have stray radiation that the FCC's computer can not model.
On 2/10/12 5:43 PM, Guy Olinger K2AV wrote:
Off top my head, it would seem the slant wire would work to create a
directional effect of one sort or other, depending on the specifics, but I
have no clue why the FCC dissed that one.
Here is a link to that paper. It is easy see what field a radiator of X
height will produce with varying number of radials from 2 to 113. From
the graphs 15 radials and a 45 deg tower gets reasonably close to the
ideal. It also shows a 45 deg tower with 113 radials is almost as good
as a 90
Vertical antennas have been shunt fed for over 70 years. There is no
magic involved. Very few MW verticals are ever resonant and resonance is
irrelevant. The only important thing is to match the TX so it is happy.
The easiest way to deal with matching is to first model on EZNEC which
will
For most of us a precise model is not possible. EZNEC will give you an
approximation. The tower is represented as a cylinder equal to the cross
section of the real tower. You could measure the existing R and J and
then in EZNEC just keep adding loading until EZNEC agrees with your
The best way to handle the problem is to assume the new antenna made an
impact on the match. The first step would be to measure the actual
resistance and if it is not 50 ohms, reset the tap for 50 ohms. Then
measure the J again and you can easily calculate the amount of C
required to cancel
This is quite true although some patterns will be closer to theory than
others. In a commercial phasor as is used for broadcast there are
several elements that must be taken into account. The first is the
matching at each vertical element. It must take the actual drive
impedance of the
That would be a function of a number of things unrelated to array
topology. It could reflect difference in electrical tower height or how
the array is phased. A properly designed vertical array will always have
maximum vertical angle gain near zero degrees elevation. Theoretically
the maximum
A wide spaced array offers many benefits when possible. In general the
is less coupling between the elements results in better less mutual
impedance interdependence. When enough space is available a simple Ham
array would be 1/2 wave spaced elements fed from the center point with
open wire.
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