[MRCA] Moose Net Tuesday

[Al Klase]

Hi Alex,

The idea is to put a small capacitance in series with a random-wire 
antenna to move it's impedance to a place that make the tuner in the rig 
happier.

For example, a rig designed to tune a short whip if always going to be 
looking for a capacitive load, as the antenna is usually less than a 
quarter wavelength, and thus look like a capacitor in series with the 
antenna's radiation resistance.
.
If the wire in use is longer than a quarter wave say by 20 or 30% it 
will look inductive.  Putting a cap in series can make the total 
impedance capacitive, and allow the rig to tune it.

I was hoping I could find my box for a photo op, but no.  It's a small 
plastic box with three 5-way binding posts and a 100 pf and 50 pF 
high-voltage "doorknob" inside in series.  You can easily choose 50, 
100, or 150 (in parallel) or 33 pF (in series).  Caps should be HV types 
as the RF voltage can get pretty astronomical even with 20 watts.

The long-wire adapter for the PRC-1099 is just such a device, not 
variable however.

This is a matter of cut and try for most of us.  For possible 
enlightenment Google "conguate match" and "smith chart."   Imaginary 
numbers give me nightmares, however.

Regards,
Al

On 9/10/2013 2:55 PM, Alex J Rokowetz wrote:
> Breck,
>
> I am not afraid to admit when I do not know something and I will 
> readily admit that I know way less than most of folks on this email 
> reflector.
>
> Would you be so kind as to briefly outline what I would do with these 
> capacitors or point me to a online or print resource to help me learn 
> more.  I searched online but did not find something useful.
>
> Thanks,
> Alex
> K2AJR
>
> P.S. Thanks for the signal report about KW2K's transmission!  She was 
> operating the TW7000F with the remote autotuner and a 65' wire up into 
> the tree.
>
> ------------------------------------------------------------------------
> *From:* B. Smith <smithab11 at comcast.net>
> *To:* mrca at mailman.qth.net
> *Sent:* Tuesday, September 10, 2013 12:57 PM
> *Subject:* [MRCA] Moose Net Tuesday
>
> Interesting band  conditions, Heard all stations, copied Yuki KW2K
> louder than I have before. Fun watching Al on video trying to get that
> PRC-104 to tune.
>
> K4CHE antenna hint for the day: Put several fixed caps(25, 50, 100 pf or
> a variable) in your antenna bag and use them either in series or in
> parallel for that random wire antenna.
>
> Z
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-- 
Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/

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