[Fwd: LF: SV: How long is a piece of wire?]
Fri, 01 May 1998 21:44:06 -0400
The HamRadio magazine issue mentioned below (September 1982) is one of the very
few I do not have.
Does anyone have that issue, and if so, could he contact me? I'd like a xerox
copy of that article.
Peter Bobek wrote:
> Hi John (SM6LKM), hi all,
> in the article I mentioned the author did not specify "what is optimum top
> loading". IMHO I would guess "optimum" toploading is represented by a
> "disc" on top of the the vertical structure to reso-
> nate it without any other means. Since this is impractical/impossible in
> most cases on LF the disc
> will be replaced with as many wires as necessary and as horizontal as
> possible (not sloping down!) and connected at the ends to come close to the
> dimensions of the required disc. The top-hat of the 77.5 kHz transmit
> antenna of DCF77 is built that way. This, however, requires additional
> masts of the same height as the transmit aerial (and will create a lot of
> other problems)!
> BTW: DCF77´s antenna is 200m high and the transmitter output power (not:
> ERP) is 50 kW.
> The signals you can hear on129 kHz and around 124 kHz (broadband stuff) are
> coming from the
> same transmitter site (about 30 km east of Frankfurt) - using 100/125 kW -
> while the signal on 139 kHz
> is coming from Burg (near Magdeburg) SW of Berlin.
> Re: UMBRELLA-antennas...
> John Belrose/VE2CV published a 6-page article "Folded umbrella top loaded
> vertical antenna"
> in HAMRADIO 9/1982 containing a lot of theory adaptable to any band. In the
> references-list at
> the end he mentions two other publications (which I do not have):
> 1. A.F. Gangi, et al, "The characteristics of electrically short, umbrella
> top-loaded antennas",
> IEEE Transactions on antennas and propagation, AP-13, November 1965, pages
> 2. C.E. Smith and E.R. Graf, "Increased capacity for VLF umbrella antennas
> using multi-wire
> rib construction", IEEE Transactions on antennas and propagation, November
> 1968, pages
> Peter/DJ8WL (DA0LF on LF)