Topband: 1/4, 1/2 or 5/8 vertical summery

[Richard Cariello]

Tom,
This information is great.
Just a couple of other questions to conclude.

The wire I use for my balloon held verticals is a Stainless Steel Wire Rope. 
The material is 302/304, Diameter 3/32" and is 1 at 17 strands. Again with six 
1/4 wave radials number 12 copper wire on a clay and rocky soil. With this 
information can you figure the loss for a 1/2 and 1/4 wave vertical system 
on 160 meters?

Final question. (Yes, here is comes)
If I phase a set of 1/2 wave wire verticals would the tank matching units 
cause any problems? I'm thinking phase shift. I would think not being that 
both antennas are being feed the same way and any phase shift would be the 
same on each antenna. The system would be as discribe in ON4UN's antenna 
book. 1/4 wave space between each vertical. 84 degree line length to each 
antenna, 71 degree phase line. But I really don't know. What do you think??

The bottom line is to keep the system symple. In my case putting down 60 1/4 
wave radials is out of the question. The parts to build the matching units 
are on hand. If I can come close to a 1/4 wave setup with a good radial 
system then I would be very happy. If I need to go through the extra 
building and longer antennas then thats what I'll simply have to do. After 
all isn't that what Ham Radio and Contesting is all about? (Turning in a big 
score is nice too)

The information you have provided has been a great help.
Thanks very much.
Rich AA2MF

P.S. Spotted your entry in the third edition of ON4UN's book. Very nice..



----- Original Message ----- 
From: "Tom Rauch" <w8ji at contesting.com>
To: "Richard Cariello" <rcariello at si.rr.com>; <Topband at contesting.com>
Sent: Friday, January 13, 2006 6:41 AM
Subject: Re: Topband: 1/4, 1/2 or 5/8 vertical summery


>> I would have thought that the 1/2 wave vertical would have
> come in first with the lack of a good ground radial system I
> alway thought the 1/4 wave and 5/8 wave performance was very
> dependent on the radial system.
>
> Rich,
>
> Any vertical is ground dependent, although some more than
> others. The 5/8th is an automatic no sale. Even the AM
> broadcasters learned they are no good and quickly quit using
> them.
>
> A half wave spreads the fields around and does reduce loss
> considerably when you don't have a ground system. I disagree
> that feeding it is difficult, but it certainly isn't as easy
> as with a 1/4 wl or 3/8th wave.
>
> You need a matching circuit that matches maybe 4000 ohms to
> 50 ohms. With a normal L/C network that roughly requires a Q
> of the square root of the impedance ratio, or sqrt of 80
> around Q=9. The cap would then have about 4000/9 or about
> 450 ohms reactance. That's about 200pF.
>
> At 1500W with a typical air wound good construction coil
> (silver plate is meaningless) you have:
>
> 3500 volts peak on the cap
> 5.4 amperes RMS through the cap and coil
> 43 watts of heat in a coil with a Q of 300
> 97% power transfer, 3% heat.
> .6 amperes flowing to ground at the network.
>
> You should be able to move about 25kHz or so. This does not
> include antenna losses. So you see, it is workable if you
> have a 4.5kV 400pF variable cap and a 40uH or so inductor
> that can handle 3.5kV at 5.5 amperes.
>
> You have to decide if building that network is cheaper and
> easier than laying down 50 1/4 wl radials, because either
> way your signal will be the same. There is no free lunch.
>
> 73 Tom
>
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