Glenn;
Remember that adding length to the inverted L will help, but most
important is that the vertical portion be as long as possible. All you'll be
doing by adding length to the horizontal portion is making a bigger cap.
hat. Good luck, Mark AJ1X
>>> N7EX <n0dh@iea.com> 01/08/97 01:36pm >>>
Swanson, Glenn, KB1GW wrote:
> > Greetings,
> > Okay, so I'm thinking about extending my 1/4-wavelength
"inverted-L"
> out to 170 feet (+/-) and putting a (air-variable) capacitor at the
> feedpoint.
> I know I'll need something like a 500 to 1000 pf cap. However, what
> voltage rating? And, if you have a brand/catalog number, that'd be
> great.
> > Enjoying the TopBand chatter (well, most of it, anyway) and look
> forward
> to any replies to the above question(s). Have fun on the gentlemen's
> band.
> > 73, Glenn, KB1GW
>
Glenn
Since the cap is in series with a "current" point on the antenna. HV
ratting is not as important as current ratting. a 2KV cap should be plenty.
In fact If you can build a suitable enclosure then even Air variables work
quite well. I use a 150pf air variable shunted with several of the old
surplus 100pf transmitting micas (the brown ones abt
2" square). For example to 500pf TV style doorknobs wont work
because they cant handle the current (they get warm even with 100
watts) even though they are rated 15kvto 20kv. At 1KW the current can
be on the order of almost 6 amps (more on on peaks). If you plan on
using the antenna on other bands (say with a tuner) then be careful you
can end up at "voltage" node on another band and blow the caps!I that
case the vaccumn variable is more likely a better bet. I have had the best
luck finding vacumn varibles at HAM fests I have paid anywhere from
$35 to
$80 for them.
Dave
N7EX
PS: I have two L's in this configuration fed in phase...good luck
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