Re: NEC-LIST: Question on "vertical folded monopoles"

To: J. Belrose

Dear John,

I'm a designer for RAI RADIOTELEVISIONE ITALIANA for MW antennas. I
simulated several times folded unipoles (we use only this type of
antennas) 75m and 175m for 50, 100kW until 1.2 MW. I use NEC-2; I
simulate the cage as you describe with only one source centered in a
horizontal wire that connects all the other thin wires of the cage but
I found sometimes discrepancies with the real measurements of the feed
point impedence after the erection. Discrepancies that went lower if I
changed the high of the tower (closer to the reality).

I read in your answer that with NEC 4 you had to increase the high of
the tower due to the fact that you set the end of the tower foot 5m
below gnd level.

My question is: is a problem of NEC2 solved by NEC4 or what else? I
send you one of the test I made for a 4 wire cage folded unipole
antenna; can you check the validity and can you tell me if I have to
switch to NEC 4 (but I know that I have to request it through US
embassy in Italy as it is forbidden to import outside of US)

Thank you for your help and my very best regards

Dr. Ing. A. FASSIO PhD Turin Politech Italy

CM Antenna a dipolo ripiegato
CM altezza 75m - gabbia a 4 fili - 1 punto di alimentazione
CM palo metallico 2m dia. - perfect ground
CE
GW 1,10, 0,-5,2, 5,0,2, 0.05 ! raccordo corda 4-1
GW 2,100, 3,0,75,5,0,2,0.05 ! corda 1
GW 3,10,0,0,75, 3,0,75, 0.5 ! sbraccio 1
GW 4,10, 0,5,2,5,0,2, 0.05 ! raccordo corda 1-2
GW 5 100 0 3 75 0 5 2 0.05 ! corda 2
GW 6 10 0 0 75 0 3 75 0.5 ! sbraccio 2
GW 7 10 -5 0 2 0 5 2 0.05 ! raccordo corda 2-3
GW 8 100 -3 0 75 -5 0 2 0.05 ! corda 3
GW 9 10 0 0 75 -3 0 75 0.5 ! sbraccio 3
GW 10 10 -5 0 2 0 -5 2 0.05 ! raccordo corda 3-4
GW 11 100 0 -3 75 0 -5 2 0.05 ! corda 4
GW 12 10 0 0 75 0 -3 75 0.5 ! sbraccio 4
GW 13 100 0 0 0 0 0 75 1 ! palo in acciaio 75m dia. 2m
GW 14,1, -5,0,2, -5,0,0, 0.05 !alimentazione
GS 0 0 1
GE 1
GN 0 0 0 0 13 .005
EK 0
EX 0 14 1 00 1000.00000 0.00000
CM FR 0 6 0 0 0.512 0.2
FR 0 1 0 0 0.846 1
RP 4 1801 1 1000 -90 0 0.1 1 1000
CM RP 0 90 1 1000 0 0 1 1
CM NE 0 100 1 1 2 0 0 0.5 1 1
XQ 0
EN
Received on Thu Apr 23 1998 - 12:35:45 EDT