I have installed a FAA approved NDB beacon here at our private
airport located in Manchester,TN .

The Beacon is transmitting on 529 KHZ Carrier power is 50 watts the
facility Id is : LYQ

I have shunt feed a 120 foot high Rhon 25G tower. The tap wire (3/8
dia aluminum 'power line' cable) is at the 90 foot level runs down
the face of the tower with 24 inch spacing to the matching network.

I am using the 'Gamma' match network : the SWR is down to 1.2 or so.

The top of the tower has 4 ten foot radials

The base of the tower has 8 200 foot 3/ 8 inch aluminum cable
radials we plan to add more.

The tower has a 3/8 'power line' type cable from the top to the base
to ensure bonding of each section.

When I fly the Company's Jetstar from 1000 to 41,000 feet, I get
solid points on the RMI indicator:

when I pass right over the beacon tower the RMI needle swings to the
tail indicating positive station passage.

The problem is the range of the LYQ beacon it seems to work 10 miles
or less??? The airplane has dual ADF systems that work perfect.

As an aside, 10 miles away, is another ADF beacon on 332 KHZ 25
watts! using the traditional three strand 'flat top' suspended
between two telephone poles. The vertical radiator for this beacon is
less than 60 feet high : I can track the beacon out to 70 miles or so!

Is a shunt feed tower lossy??? poor radiator??? comments???

I am a Ham op WA4SZE : by the way, we will QSL the beacon when we
get it commissioned.

Thanks!!

wrote:
I have installed a FAA approved NDB beacon here at our private
airport located in Manchester,TN .

The Beacon is transmitting on 529 KHZ Carrier power is 50 watts the
facility Id is : LYQ

I have shunt feed a 120 foot high Rhon 25G tower. The tap wire (3/8
dia aluminum 'power line' cable) is at the 90 foot level runs down
the face of the tower with 24 inch spacing to the matching network.

I am using the 'Gamma' match network : the SWR is down to 1.2 or so.

The top of the tower has 4 ten foot radials

The base of the tower has 8 200 foot 3/ 8 inch aluminum cable
radials we plan to add more.

The tower has a 3/8 'power line' type cable from the top to the base
to ensure bonding of each section.

When I fly the Company's Jetstar from 1000 to 41,000 feet, I get
solid points on the RMI indicator:

when I pass right over the beacon tower the RMI needle swings to the
tail indicating positive station passage.

The problem is the range of the LYQ beacon it seems to work 10 miles
or less??? The airplane has dual ADF systems that work perfect.

As an aside, 10 miles away, is another ADF beacon on 332 KHZ 25
watts! using the traditional three strand 'flat top' suspended
between two telephone poles. The vertical radiator for this beacon is
less than 60 feet high : I can track the beacon out to 70 miles or so!

Is a shunt feed tower lossy??? poor radiator??? comments???

I am a Ham op WA4SZE : by the way, we will QSL the beacon when we
get it commissioned.

Thanks!!

More radials certainly won't hurt, especially since at this freq 200
feet is short.

What's the ground around it like?

--
Jim Pennino

Remove .spam.sux to reply.

On Jul 4, 8:45 pm, wrote:
wrote:
I have installed a FAA approved NDBbeaconhere at our private
airport located in Manchester,TN .
TheBeaconis transmitting on 529 KHZ Carrier power is 50 watts the
facility Id is : LYQ
I have shunt feed a 120 foot high Rhon 25G tower. The tap wire (3/8
dia aluminum 'power line' cable) is at the 90 foot level runs down
the face of the tower with 24 inch spacing to the matching network.
I am using the 'Gamma' match network : the SWR is down to 1.2 or so.
The top of the tower has 4 ten foot radials
The base of the tower has 8 200 foot 3/ 8 inch aluminum cable
radials we plan to add more.
The tower has a 3/8 'power line' type cable from the top to the base
to ensure bonding of each section.
When I fly the Company's Jetstar from 1000 to 41,000 feet, I get
solid points on the RMI indicator:
when I pass right over thebeacontower the RMI needle swings to the
tail indicating positive station passage.
The problem is the range of the LYQ beaconit seems to work 10 miles
or less??? The airplane has dual ADF systems that work perfect.
As an aside, 10 miles away, is another ADFbeaconon 332 KHZ 25
watts! using the traditional three strand 'flat top' suspended
between two telephone poles. The vertical radiator for thisbeaconis
less than 60 feet high : I can track thebeaconout to 70 miles or so!
Is a shunt feed tower lossy??? poor radiator??? comments???
I am a Ham op WA4SZE : by the way, we will QSL thebeaconwhen we
get it commissioned.
Thanks!!

More radials certainly won't hurt, especially since at this freq 200
feet is short.

What's the ground around it like?

--
Jim Pennino

Remove .spam.sux to reply.

open land flat, somewhat damp covered with grass the radials lay on
top of the ground The beacon is on air right now going to leave it
on tonight for reception reports do you think a shunt feed tower is
not good?? I could jack up the tower and insulate from ground it
then series feed do you think that would be better??? lots of work
but might be worth the effort!

On Jul 4, 8:59 pm, wrote:
On Jul 4, 8:45 pm, wrote:



wrote:
I have installed a FAA approved NDBbeaconhere at our private
airport located in Manchester,TN .
TheBeaconis transmitting on 529 KHZ Carrier power is 50 watts the
facility Id is : LYQ
I have shunt feed a 120 foot high Rhon 25G tower. The tap wire (3/8
dia aluminum 'power line' cable) is at the 90 foot level runs down
the face of the tower with 24 inch spacing to the matching network.
I am using the 'Gamma' match network : the SWR is down to 1.2 or so.
The top of the tower has 4 ten foot radials
The base of the tower has 8 200 foot 3/ 8 inch aluminum cable
radials we plan to add more.
The tower has a 3/8 'power line' type cable from the top to the base
to ensure bonding of each section.
When I fly the Company's Jetstar from 1000 to 41,000 feet, I get
solid points on the RMI indicator:
when I pass right over thebeacontower the RMI needle swings to the
tail indicating positive station passage.
The problem is the range of the LYQ beaconit seems to work 10 miles
or less??? The airplane has dual ADF systems that work perfect.
As an aside, 10 miles away, is another ADFbeaconon 332 KHZ 25
watts! using the traditional three strand 'flat top' suspended
between two telephone poles. The vertical radiator for thisbeaconis
less than 60 feet high : I can track thebeaconout to 70 miles or so!
Is a shunt feed tower lossy??? poor radiator??? comments???
I am a Ham op WA4SZE : by the way, we will QSL thebeaconwhen we
get it commissioned.
Thanks!!

More radials certainly won't hurt, especially since at this freq 200
feet is short.

What's the ground around it like?

--
Jim Pennino

Remove .spam.sux to reply.

open land flat, somewhat damp covered with grass the radials lay on
top of the ground Thebeaconis on air right now going to leave it
on tonight for reception reports do you think a shunt feed tower is
not good?? I could jack up the tower and insulate from ground it
then series feed do you think that would be better??? lots of work
but might be worth the effort!

As an aside, I wonder if this is proof that a shunt feed tower is no
good??? I can SEE the tower (runway) over the nose of the airplane
at 15 miles out! yet the RMI indicator is wandering! The beacon
ID is in the noise!

I get a good match but the band width is NARROW! this indicates to
me that the Q is high just as it should be? the RF amp meter is
showing current thru the vertical run up the tower face if your
careless around the 2300 pf vac cap you get a nice RF burn.

By the way, I made a mistake, I am using an omega match the values of
the caps:

C-1 500 pf ( from 50 ohm coax center conductor to 2300 PF Vac Var
cap )

C-2 2300 pf vertical wire run thru C-2 2300 pf cap then ground


thanks!!!!

As an aside, I wonder if this is proof that a shunt feed tower is no
good??? I can SEE the tower (runway) over the nose of the airplane
at 15 miles out! yet the RMI indicator is wandering! The beacon
ID is in the noise!

I get a good match but the band width is NARROW! this indicates to
me that the Q is high just as it should be? the RF amp meter is
showing current thru the vertical run up the tower face if your
careless around the 2300 pf vac cap you get a nice RF burn.

By the way, I made a mistake, I am using an omega match the values of
the caps:

C-1 500 pf ( from 50 ohm coax center conductor to 2300 PF Vac Var
cap )

C-2 2300 pf vertical wire run thru C-2 2300 pf cap then ground


thanks!!!!

I have just run a preliminary NEC model. I am showing a gain of
-9 dBi at an elevation angle of 10 deg. at 530 kHz. Directly overhead the
gain is about -26 dBi. A typical matching network should
have a loss of about 4 dB, for a TRP of around 1 W or so.
The input impedance will be about 0.2+j176. You should have about
10 A RMS in the base of the gamma match vertical wire and, 1.7 kV RMS ,
assuming a 4 dB loss in the matching network.

My model needs some refinement, but should give a ball
park idea of what to expect. I did not understand exactly how you
are using two capacitors to match the antenna.

Regards,

Frank (VE6CB)

On Jul 4, 5:56 pm, wrote:


Is a shunt feed tower lossy??? poor radiator??? comments???

I am a Ham op WA4SZE : by the way, we will QSL the beacon when we
get it commissioned.

Thanks!!

The tower would not be the most efficient thing, being a 1/4 wave at
that
freq is about 442 ft. The four 10 ft radials, which I assume are a top
hat,
will be fairly useless at that freq. Too short to really do any good.
How long is the top horizontal wire is the "T" they are using at the
other
airport? I bet it's pretty long across.
What I would do if possible, is lengthen the top hat wires to be as
long
as you can. There does not really have to be four.. Two is enough, as
you can see from the other station. I don't know what the current
distribution
is with that setup, but it would seem that max current is at your
matching
device. The longer you can make that tower look electrically, the
better.
I'm not sure what the norm is for the usual NDB antenna systems..
I would basically use the same measures I would running a short mobile
whip.. Longer top hat wires would greatly help current distribution if
they
are long enough. To resonate the tower at that freq with no coil
loading, you would need wires about 315 ft... :/
But you could use shorter, and compromise a bit.
The ground is pretty important, but I think the current distribution
across
the tower equally so. I think all your current is huddled up around
your
matching device, and ground area.. Not really where you want it.
MK

WA4SZEwrote
I have installed a FAA approved NDB beacon here at our private
airport located in Manchester,TN .... Is a shunt feed tower lossy???
poor radiator??? comments???
_____________

Other things equal, a shunt fed MW vertical monopole can produce
essentially the same radiation pattern shape and gain as when series fed.

The link below leads to an analysis of what might be expected for either
case for the system you described.

Assumptions made in the analysis:

1) The four top-hat radials added 10 feet to the electrical height of the
tower

2) The ground radials described have a net r-f resistance of 25 ohms at the
operating frequency.

The analysis shows that for 50 watts of available power, this system could
generate an inverse-distance groundwave field strength of better than 700
µV/m at a radius of about 15 miles.

Of course, earth losses along the groundwave path will reduce that value,
but even with 6 dB of additional loss the field should still be better than
350 µV/m, and higher than that for higher elevations above the earth at that
distance (as would be true for airborne receive systems).

The performance you are describing indicates that the antenna is not
radiating much of the available power, which may point to problems with the
feed system.

http://i62.photobucket.com/albums/h8...alRadiator.gif

RF

WA4SZE wrote:
"I have shunt fed a 120 foot high Rohn 25G tower."

The Rohn has a 1-ft face, so the h/d is about 120. That`s OK. What`s
wacko is a 23-degree tower over (8) 200-ft radials at 529 KHz. Ground
connection resistance is high and eating up all the signal.

Shunt - feeding is OK. Bill Orr and Stu Cowan give feed capacitors for
scalimg in "All About Vertical Antennas".

Brown, Lewis and Epstein would be disappointed with your radials. Shoot
for the broadcast practice of (120) evenly distributed around from the
tower base.

A short tower radiates almost as well as a 1/4-wave. but it has a very
low radiation resistance so can`t tolerate any loss resistance.

Kraus gives advice for Electrically Small Antennas in the 3rd edition of
"Antennas". Page 710 says:
"To increase the radiation efficiency requires an increase in the
radiation resistance Rr or a decrease in the loss resistance Rl or both.

The SWR of a dummy load usually looks fine, but radiation is just
incidental.

Best regards, Richard Harrison, KB5WZI

"Richard Harrison" wrote
Brown, Lewis and Epstein would be disappointed with your radials. Shoot
for the broadcast practice of (120) evenly distributed around from the
tower base.
_________

BL&E's 1937 measurements show (Fig 30) that a vertical monopole of 25 to 90
electrical degrees used with 113 buried radials each of 0.412 wavelength
produced a measured groundwave field within a few percent of the theoretical
maximum for such radiators over a perfect ground (notwithstanding that the
conductivity at their test site was around 4 mS/m).

In Fig 32 of that paper it can be seen that if the 113 radials are only
0.274-wavelengths long, then at the 25-degree electrical height of this Rohn
tower, the measured field was about 79% of theoretical field over a perfect
ground.
..
So it's not just the number of radials that is important, but also their
length.

The referenced figures are linked below, under the "fair use" provisions of
copyright law.

http://s62.photobucket.com/albums/h8...BLERadials.gif

RF

Here is the correct link to BL&E Figs 30 and 32.

http://i62.photobucket.com/albums/h8...ndERadials.gif