"Wes Stewart" wrote in message
...
On Sat, 19 Mar 2005 23:23:30 GMT, "Frank"
wrote:

[snip]

The following code produces Zin = 0.117 - j2717 ohms at 1.9 MHz. What did
I do wrong? Note the high segmentation to place the feed-point near the
base of the antenna.

Frank

CM 9 ft monopole
CE
GW 1 108 0 0 0 0 0 108 0.25
GS 0 0 0.025400
GE 1
GN 1
EX 0 1 1 00 1 0
LD 5 1 1 108 5.8001E7
FR 0 9 0 0 1.8 0.025
RP 0 181 1 1000 -90 0 1.00000 1.00000
EN

My bad. I hate it when that happens. A typo on the length on my
part. 101 instead of 108.

It's more like 0.12 -j2890 in EZNEC. I'm not real fluent in NEC decks
but I think you are using too many segments.

A more realistic analysis than above, with the following structure, produces
some interesting results:
9ft monopole, segmented in 12" lengths, mounted above a 6' x 6' wire grid
model, also 12" segments, (All wires # 10 AWG). 5 ft above a
Sommerfeld/Norton average ground (Er = 13, Sigma = 5 mS/m). Frequency 1.9
MHz.

Zin = 1.23 - j3059, max gain = -8.3 dBi at 25 deg. elevation. (surface
wave not computed). Structure
efficiency 98.7%.

A suitable matching network, assuming an inductor Q of 300, consists of a
shunt "L" (161uH) followed by a
series C (16.2 pF). The network loss is 11.5 dB and 28 kV RMS at the base
with 1.5 kW in.

With an inductor Q of 1000, the component values become: L = 193.5 uH, and C
= 8.88 pF.
Loss = 6.3 dB, and 51 kV RMS.

Frank

Edited code follows:

CM 9 ft monopole above 6ft X 6ft wire grid gp
CE
GW 1 9 0 0 14 0 0 5 0.0509449
GW 2 1 -3 -3 5 -2 -3 5 0.0509449
|
|
GW 85 1 3 2 5 3 3 5 0.0509449
GS 0 0 0.304800
GE 1
GN 2 0 0 0 13.0000 0.0050
EX 0 1 9 0 1 0
LD 5 1 1 9 5.8001E7
LD 5 2 1 1 5.8001E7
|
|
LD 5 85 1 1 5.8001E7
FR 0 9 0 0 1.8 0.025
RP 0 181 1 1000 -90 0 1 1
EN

Gary:

First, you are off by a decade, the Texas DPS moved from 1658 kcps. to 42.9 Mc. in 1949. Prior to the move, they used
(very successfully, I might add) a earlier version of Reg's antenna, which was a 10 foot bamboo pole helically wound
with waxed cotton insulated bell wire. IIRC, the winding was spaced about 1 to 1½ wire diameters apart . The
transmitter was directly connected to the base of the antenna with a short piece of 8 gauge wire, so there was no SWR to
worry about, and final tuning of the antenna was done in the transmitter output pi-network. Black '41 and '48 Fords
with 10 foot cane poles on the rear bumper brackets, brings back memories.

--
Crazy George
The attglobal.net address is a SPAM trap. Please change that part to: attdotbiz properly formatted.
wrote in message ups.com...

snippety

I read somewhere that in the 50's, law
enforcement 2-way radios operated close to our 160m ham band. Wonder
what kind of antennas they used on the police cars. Of course the
distances they were interested in are different from hams.
Gary N4AST

Crazy George wrote:
Gary:

First, you are off by a decade, the Texas DPS moved from 1658 kcps.
to 42.9 Mc. in 1949. Prior to the move, they used
(very successfully, I might add) a earlier version of Reg's antenna,
which was a 10 foot bamboo pole helically wound
with waxed cotton insulated bell wire. IIRC, the winding was spaced
about 1 to 1=BD wire diameters apart . The
transmitter was directly connected to the base of the antenna with a
short piece of 8 gauge wire, so there was no SWR to
worry about, and final tuning of the antenna was done in the
transmitter output pi-network. Black '41 and '48 Fords
with 10 foot cane poles on the rear bumper brackets, brings back
memories.

--
Crazy George
The attglobal.net address is a SPAM trap. Please change that part
to: attdotbiz properly formatted.
wrote in message
ups.com...

snippety

I read somewhere that in the 50's, law
enforcement 2-way radios operated close to our 160m ham band.
Wonder
what kind of antennas they used on the police cars. Of course the
distances they were interested in are different from hams.
Gary N4AST


Hi C. George, Thanks for the interesting info. I certainly did not
know the 160m radios dated to the 40's. My memories of 1950's law
enforcement are "Highway Patrol" starring Broderick Crawford on the BW
TV. I remember watching him standing outside his police car and saying
"10-4" into the mike. Then, he would sometimes put the mike to his
ear, as if it were a speaker.
At the time I didn't wonder about the antenna on his car. I would
expect from your post it would be 43mhz. I don't remember if that show
was any good or not?
Gary N4AST

Chicago once dispatched their cars on a frequency of about 1700 kHz. Used
to listen with a Wilcox-Gay receiver (made in Charlotte, Michigan) that had
a knob used to switch from broadcast band to the MF police band. Long time
ago!
I was of the opinion that the Chicago system was one way. Does anyone
remember?
Some of the police HF frequencies were used on CW into at least the
mid-60s. They were not allowed to use RTTY as it was thought to compete too
much with The telephone company. I visited the main HF site for Ohio in the
early 60s - the site was controlled from Columbus with a microwave link.
The engineer liked to call it the longest IF in the world.

73, Mac N8TT

--
J. Mc Laughlin; Michigan U.S.A.
Home:

My dad was a policeman in the 40s, right after the war, his operated 40
something mHz. About 8 yrs old and an interest in radio helped me to
remember radio things, many other things didn't have sticking power,
like english and such :o)

KF5DE

wrote:
Crazy George wrote:

Gary:

First, you are off by a decade, the Texas DPS moved from 1658 kcps.

to 42.9 Mc. in 1949. Prior to the move, they used

(very successfully, I might add) a earlier version of Reg's antenna,

which was a 10 foot bamboo pole helically wound

with waxed cotton insulated bell wire. IIRC, the winding was spaced

about 1 to 1½ wire diameters apart . The

transmitter was directly connected to the base of the antenna with a

short piece of 8 gauge wire, so there was no SWR to

worry about, and final tuning of the antenna was done in the

transmitter output pi-network. Black '41 and '48 Fords

with 10 foot cane poles on the rear bumper brackets, brings back

memories.

--
Crazy George
The attglobal.net address is a SPAM trap. Please change that part

to: attdotbiz properly formatted.

wrote in message

ups.com...

snippety

I read somewhere that in the 50's, law
enforcement 2-way radios operated close to our 160m ham band.

Wonder

what kind of antennas they used on the police cars. Of course the
distances they were interested in are different from hams.
Gary N4AST



Hi C. George, Thanks for the interesting info. I certainly did not
know the 160m radios dated to the 40's. My memories of 1950's law
enforcement are "Highway Patrol" starring Broderick Crawford on the BW
TV. I remember watching him standing outside his police car and saying
"10-4" into the mike. Then, he would sometimes put the mike to his
ear, as if it were a speaker.
At the time I didn't wonder about the antenna on his car. I would
expect from your post it would be 43mhz. I don't remember if that show
was any good or not?
Gary N4AST