It all depends upon how much survivability you want, nothing will survive a
direct hit. Any 1.5 to 2.5 mH choke will suffice, just look at the safety
choke in a commercial amp for the smallest choice.
The big ones are often found in scrapped BCB transmitters and tuning units
as well as show
I need to construct a heavy-duty choke to be installed from the feed point
of my 160 meter vertical to ground, for static drain and for lightning
protection. How large does the wire, form, and inductance need to be?
Phil,
This is like any shunt or series choke problem. The choke needs to be
20 uH should be sufficient at the base of a 1/4 wave length vertical.
#4 copper wire is used to connect towers to ground for direct strikes.
Such an inductor can be close-wound with insulated #4 wire, diameter 8, 8
turns.
It should survive intact except for the insulation.
Dave WX7G
On Jul
I need to construct a heavy-duty choke to be installed from the feed point
of my 160 meter vertical to ground, for static drain and for lightning
protection. How large does the wire, form, and inductance need to be?
Phil,
One method of dealing with this problem, particularly if one is
That is only 226 Ohms at 1.8MHz and at 1500W will be dissipating about 30W in a
50 Ohm system but Phil didnt say how he is feeding his tower which is resonant
well below 160M.
Yes it will work as well as survive a lot of energy at 35-50 Ohms compared to a
larger inductance 1A choke.
Carl
KM1H
30 watts is correct for 1500 watts in a 50 ohm system and a coil Q of 226.
The power loss is 0.1 dB and the coil temp rise is around 20 deg C.
WX7G
On Jul 26, 2012 3:20 PM, ZR z...@jeremy.mv.com wrote:
**
That is only 226 Ohms at 1.8MHz and at 1500W will be dissipating about 30W
in a 50 Ohm
That is only 226 Ohms at 1.8MHz and at 1500W will be dissipating about 30W
in a 50 Ohm system but Phil didnt say how he is feeding his tower which is
resonant well below 160M.
That choke is probably too small and will change SWR, but thankfully
reactance in reactances does not dissipate
70 turns 2 diameter over 4 length would be 100 uH, and with an air core
and #16 magnet wire would have a Q of about 200 or so. That's 1000 ohms
impedance, a few hundred thousand ohms parallel resistance, and the
dissipation would be less than 1 watt at 1500.
Or 38 turns over 4 inches on a 4
30 watts is correct for 1500 watts in a 50 ohm system and a coil Q of 226.
The power loss is 0.1 dB and the coil temp rise is around 20 deg C.
No, it isn't.
1500 watts is 273 volts into 50 ohms.
If Q is 226, and reactance 226 ohms, Rp is 51,077 ohms. 273 volts is 1.46
watts heat.
To get 30
My Mistake:
To get 30 watts of heat with 226 ohms reactance, Q would have down near
unity. No one makes a coil that bad.
I misplaced a decimal. Q would have to be near ten in the coil with 226 ohms
reactance and 1500 watts to make 30W heat, not near 1.
The other numbers are correct. A Q of
My mistake.
Now then, for lighting we don't really want much inductance between the
antenna and ground.
For a 100 kA strike rising in 2 us 1 MV is developed across 20 uH.
Instead we want a sturdy spark gap of 1/32 inch connected directly from the
feedpoint to the ground system.
WX7G
On Jul 26,
Hi Phil
I'm no expert but plan to use a quarter wave shorted stub of RG6 at the feed
point of my verticals for static drain and harmonic reduction, along with a
spark gap in the event of a close strike.
73 Bob
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