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!!!!

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

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)

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

On Jul 5, 7:57 am, "Richard Fry" wrote:
Apologies, the link in my first post was an analysis
for 25 watts instead of 50 watts.

Here is the correct one:

http://i62.photobucket.com/albums/h8...rticalRadiator...

RF

You need a flat top to pull the current node higher from the ground...
Our NDB at KHYX is less than 100 feet tall, has a series fed vertical
wire with a long, multiwire flat top and is easily copied from 80
miles away at night and 40 miles in the day...

denny

"Frank" wrote
At 1000 m, between a height of zero meters, and 1000 m
the field strength is in the range of 5 mV/m peak. (i.e. including
ground wave). Not sure why the calculation does not agree
with Richard Fry's analysis, but may be due to the fact that
NEC computes ground losses for the surface wave.
_____________

Below is a development of my earlier analysis, now based on the worst-case
ground conductivivity for a site in Tennessee, per the FCC's "M3" map of
same for the contintental US.

The field strength values below are referenced to the MW propagation charts
of the FCC for the power, radiator efficiency and presumed groundwave path
conductivity in this situation. These values are traceable to measured
data.

This approach shows an inverse distance field strength at 1 mile to be 11.2
mV/m. At 1 km the inverse distance field would be about 1.61 X that much,
or about 18 mV/m (which agrees with the analysis I posted earlier in this
thread).

Groundwave path loss at 1 km for 529 kHz is very small regardless of earth
conductivity, so the measured field at that distance should be almost the
same as the calculated inverse distance field (18.5 mV/m).

Using "real" earth conductivity shows (below) less field at about 15 miles
than in my first analysis. But there I just picked an arbitrary value of 6
dB for ground loss at that distance.

As a side note, the FCC permits shunt-fed monopoles for use by some
non-directional AM broadcast stations, and they must (and do) produce the
same minimum allowable field strength for 1 kW at 1 km as if they were
series-fed.

+ + + +

FCC Approach

Frequency = 529 kHz
Power = 0.05 kW
Inverse Distance Field at 1 mile = 11.2 mV/m
Groundwave Path Conductivity = 2.0 mS/m

Radius to a Given Field Strength:

Field Strength Radius
0.500 mV/m 10.3 miles
0.250 mV/m 15.5 miles

RF

"Richard Fry" wrote in message
...
Apologies, the link in my first post was an analysis
for 25 watts instead of 50 watts.

Here is the correct one:

http://i62.photobucket.com/albums/h8...Radiator-1.gif

RF

The antenna fed with a gamma match appears to be just a very narrow loop,
with very high copper losses.

Eliminating the gamma match, and base feeding the tower
I noticed in my previous analysis that I had read the wrong E-field column.
With
50 W input the peak E-field at 1000 m is 62.9 mV/m (44.5 mV/m RMS). At
24 km the E-field is 2.2 mV/m (1.5 mV/m RMS), at ground level, and 2.0 mV/m
(1.4 mV/m RMS) at 10,000 m elevation. These results appear to be very close
to Richard Fry's analysis, though not sure why there is a 6 dB difference.

Frank

CM 523 kHz NDB Antenna
CE
GW 1 1 0 0 0 0 2 -0.25 0.03125
GW 2 99 0 2 -0.25 0 200 -0.25 0.03125
GR 1 8
GW 12 60 0 0 0 0 0 120 0.03125
ce GW 13 5 0 0 90 0 2 90 0.03125
ce GW 14 45 0 2 90 0 2 2 0.03125
ce GW 15 5 0 2 2 0 0 2 0.03125
GS 0 0 0.304800
GE -1 -1 0
GN 2 0 0 0 4.0000 0.0100
EX 0 12 1 0 5173.59784 0.00000
FR 0 1 0 0 0.53 0.01
LD 5 0 0 0 5.8001E7
RP 1 1001 1 0000 0 90 1 1 1000
NE 0 1 1 11 0 1000 0.0 1.0 1.0 10
NE 0 1 1 11 0 24000 0.0 1.0 1.0 1000
EN