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,
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
> 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
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 i
> 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 p
m:* DAVID CUTHBERT
> *To:* ZR
> *Cc:* philcleme...@centurylink.net ; topband@contesting.com
> *Sent:* Thursday, July 26, 2012 4:35 PM
> *Subject:* Re: Topband: Choke Construction Info Needed
>
> 20 uH should be sufficient at the base of a 1/4 wave length vertical.
>
> #4 copper
- Original Message -
From: DAVID CUTHBERT
To: ZR
Cc: philcleme...@centurylink.net ; topband@contesting.com
Sent: Thursday, July 26, 2012 4:35 PM
Subject: Re: Topband: Choke Construction Info Needed
20 uH should be sufficient at the base of a 1/4 wave length vertical
>
> >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
d in scrapped BCB transmitters and tuning units
> as well as show up at hamfests and on Fleabay as old military gear had
> various candidates.
>
> Carl
> KM1H
>
>
> - Original Message -
> From: "Phil Clements"
> To:
> Sent: Thursday, July 26, 2012
>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
up at hamfests and on Fleabay as old military gear had
various candidates.
Carl
KM1H
- Original Message -
From: "Phil Clements"
To:
Sent: Thursday, July 26, 2012 3:03 PM
Subject: Topband: Choke Construction Info Needed
>I need to construct a heavy-duty choke to be insta
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?
Thanks in advance for your expertize!
(((73)))
Phil, K5PC
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