[AMRadio] new antenna and matchbox a bust.


John Lawson jpl15 at panix.com
Mon Jan 29 13:00:04 EST 2007



On Mon, 29 Jan 2007, Brett gazdzinski wrote:

>
>>     Probably. W/out going into a lot of math - 50' is quite
>> short, and not
>> near a multiple or fraction, of the bands you mention.
>
> 50 feet is all I got...
> If I let some dangle, it will be inside the trees...
>

   Ok - this is not the major problem






>
>>
>>     "Fed with open wire line": Fed in the center?  What Z is
>> the feedline?
>> What Z is the feedPOINT of the antenna at the height and ground
>> conditions?
>
> Home made #14 about 4 inches apart.

     What is it's characteristic impedance?  What is the exact spread of 
the wires?

   Basically it's best for the feedLINE impedance to match the feedPOINT 
impedance at the frequency of interest.




>
>
>>
>>   Then you mention RG214 - how does the balanced(?) 'open
>> wire line' make
>> the transition to the coax? if the feedline is 450 ohms, you
>> need a 4:1
>> Balun at that point in your System.
>>
>>     Oooh, wait - do you mean you ran *two parallel runs of coax*
>> side-by-side, "with the shields tied together at the ends"...?
>>
>>     Umm - that just won't work at all, I don't theenk.....
>
> That is what wa1hlr told me to try.

    no comment....



> Not sure if that was the problem or not.

   guaranteed it was 80% of it....


> Brick house, antenna tuner in a 6 foot rack cabinet
> in the center of the basement. No easy way to get the
> open wire line into the tuner...
>

   drill two 3/16" holes thru the brick (with a masonry bit) spaced the 
width of your feedline apart. Get a couple of #8 through-bolts (or 
all-thread) long enough to allow connecting the wires on the outside and 
inside of the shack.  Glob on a bit of RTV or bathtub caulk to seal stuff 
up.  If you ever move it, then RTV or caulk the two holes, with something 
the color of the brick - done.



> As a G5RV type antenna into the heathkit tuner, it
> seems to work real well for what it is.
>

   As long as it works - problem over.  HOWEVER: does it work 'well'?  are 
you getting 600 watts worth of signal out? Is the antenna as 'quiet' as it 
can be on recieve?


Cheers
John
KB6SCO




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