[AMRadio] Re: new antenna and matchbox a bust.


Geoff/W5OMR ars.w5omr at gmail.com
Wed Jan 31 11:27:02 EST 2007


Brett gazdzinski wrote:
> My lot looks exactly like a piece of pizza. 
> The street is the crust and the power/phone/cable runs along the crust (on poles).

I know I keep harping on this 'loop' idea, but if your lot is triangle 
shaped, you could use the 'point' and then come out to each corner of 
the 'crust', and toss up as much wire as you possibly can, then use your 
open-wire line/450-ohm ladder line to feed the antenna. 

If you've got 100' of wire up now, from the 'tip' of the pizza slice, 
then from that same point, in the other direction, run another 100', and 
then whatever it takes to close off the 'crust'/street end of your 
property.  And, there's trees out there?  Natural Antenna Supports.  
However, with the power/phone/cable lines running along the 'wide' end 
of the property, I, too, would worry about RF being induced into the 
lines.  But, there's an alternative ;-)  Read on....

> I doubt I could put up a tower even if I had the money, a tall mast might be possible but the wife would likely have to go before that happened.
>   

4 20' 2x4's, or 3 20' joints of 1 1/4" ID EMT.  They're threaded and 
tapped on each end, and they're roughly around $10~$15 per.

> The loop idea is very interesting, but it would be hard
> to do if I want to keep away from all the power/phone lines.
>   

Well, that depends on if you install the loop in a horizontal plane, or 
a vertical plane.  Installed in a Vertical plane, you can still have 
horizontal polarization so don't let that stop you.  Given that, if you 
decide to put up a loop, you'd probably have to consider putting it in a 
vertical plane, because of the power/phone/cable lines on the street-side.

> I could change the length of the antenna if I run wire through the trees and down, instead of rope, but I don't want to start a fire in the trees.
>   

I recall seeing you said that the antenna wire you're using is insulated?

> While a resonant antenna is always best, short of that I heard the more wire you get up the better.
>   

Because there's more 'capture' effect.

Here's something to contemplate, Brett...

The formula for a Loop is:
L(ft) = 1005 / F(mc)

L = 1005 / 3.865

L = 260'.

I know, that looks like a -lot- of wire, for a small space, but think of 
this... you've got 100' of wire, stretched between two support points 
now.  Were you to take and add another length of wire, the same distance 
and some how 'elevate' it higher than the wire you have up now, you'd 
basically have twice the wire in the air, and hey... even if it's only 
220' of wire, it's -more- wire than you'll need for 75m.  Perhaps even 
make a 'diamond' out of 250 of wire (if that's possible).

Besides, here's the real numbers... if you've got a Delta Loop up (as I 
do, installed in a vertical plane) then you're only looking at about 
~85' per segment, using 3 segments.  Make it a diamond, and you're 
looking at around 240' /4, or ~60' per side.  Feed it either at the 
bottom of the diamond, or in the middle of the bottom segment (if using 
the Delta config).

Barring all that, in order to get up 'twice as much wire', consider 
using a 'folded dipole' in which you just run another length of wire 
along the same wire you have up now, spaced around an inch or two apart, 
and add it to your existing antenna.  Instant loop.  A Loop, as 
explained to me by John/WA5BXO, is merely a folded dipole, pulled apart.


> Last night I had an S6 electric motor hash for an hour (vacuum cleaner?).
>   

Jim/WD5JKO discovered at his -new- residence that the clock oscillator 
in a VCR generates and creates -MORE- noise when it's turned "off" than 
when it's on.  You might go around, checking your other electronic 
devices in the house.  If your place is clean, then it's probably in the 
neighborhood.

> 3880 has a TV horizontal sweep noise on it most of the time...
>   

We've all been through this before, and really, there's no need to 
re-open this can of worms, but we're not 'regulated' to staying on 
3.880kc/s.  We *can* (and should) search for and seek out new and 
different frequencies upon which to operate.

Ronnie/K5WLT, after the utter successful and complete restoration, and 
modification of a recently (> 1 year) acquired Johnson Viking Valiant, 
has taken to operating on 3855kc/s during the daylight hours (1pm ~ 4pm) 
with a 'potent' signal from near Seguin, TX (pronounced 'Seh'geen')

Of course, Ronnie always did well with his original novice rig, the 
Knight Kit T-50, with a homebrewed p-p 6L6 modulator. 
Funny story about that Modulator... it had a semi-microphonic 6L6... and 
a resonant metal cover.  He could rap the side of that 6L6 and it would 
'ring', like a tubular bell.

Somewhere, I have a recording of that...

--
73
-Geoff/W5OMR



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