shunt inductor for 1/4 wave ground plane
 

Hi all...
I have converted an old cb antenna to an elevated 1/4 wave ground plane cut
for 20 meters. I know I can use a 5 watt 100,000 ohm resistor to shut static
discharges to ground. How many turns of no 14 enamel wire around a T200 core
would it take to do the same job?
thanks in advance, de Denton WB7TDG

"denton" wrote in message
...
Hi all...
I have converted an old cb antenna to an elevated 1/4 wave ground plane
cut
for 20 meters. I know I can use a 5 watt 100,000 ohm resistor to shut
static
discharges to ground. How many turns of no 14 enamel wire around a T200
core
would it take to do the same job?
thanks in advance, de Denton WB7TDG


Depends on the core material. T200-WHAT?. Generally, you would want the coil
impedance to be at least 10 times the antenna impedance. So, for a 37 Ohm
antenna, 370 Ohms. The coil impedance X(L) at 14 MHz is:

X(L) = 6.28 * 14E6 * L

or L = 370/(6.28 * 14E6)

If you ignore the E6, the answer will be in microhenries. So, L=370/(6.28 *
14) = 4.2uH. You will have to look at the chart for your core to see how
many turns that takes. For the common T200-2 core, it will be 19 turns,
which might not fit. So, use #18 wire - there's very little current flowing
through it.

Tam/WB2TT

Just fill up the core with 20 awg.

I settled for 40 some odd turns of no 14 enamelled wire on the core...as
many turns as I could get on it....swr reads the same as before but the
signal to noise level is a lot better.
this will do until I homebrew a matching network...remotely controlled
variable cap and tapped inductor in parallel at feedpoint...to use the
antenna on 20 thru 10 meters. Unless someone else has a better idea.
In the past, I attached 10 and 15 meter radiators and radials on the same
antenna and it did fairly well on 10 and 15, but I think the gain and
radiation pattern will be a tad better if I go the matching network route.
"denton" wrote in message
...
Hi all...
I have converted an old cb antenna to an elevated 1/4 wave ground plane
cut for 20 meters. I know I can use a 5 watt 100,000 ohm resistor to shut
static discharges to ground. How many turns of no 14 enamel wire around a
T200 core would it take to do the same job?
thanks in advance, de Denton WB7TDG

On Sat, 28 Aug 2004 12:20:26 -0700, "denton"
wrote:
In the past, I attached 10 and 15 meter radiators and radials on the same
antenna and it did fairly well on 10 and 15, but I think the gain and
radiation pattern will be a tad better if I go the matching network route.
KISS