[TenTec] Re. [Ten Tec] Grounds and balanced fed verticals

[Steve Hunt]

Hi Joel,

Nice to hear from you!

The ladderline loss figures quoted in the Antenna Book - which I believe 
are also repeated in TLW - are out by a factor 2. It's very easy to 
demonstrate that with a simple I^2R loss calculation. I'm happy to show 
the sums if you need convincing.

Tenths of a dB differences may not matter of themselves. However, they 
*do* matter when the losses you are trying to measure are of the same 
order. In your article you said that the measurements on dry line agreed 
with TLW predictions "within a few tenths of a dB in each case". Given 
that the TLW loss figure for ladderline is 0.05dB at 3.7Mhz, measuring 
something "within a few tenths of a dB" of that figure could represent a 
*gross* difference.

Also, we need to remember that in many (if not most) Ham applications 
ladderline is operating at a high VSWR, so what might seem to be 
negligible differences in *matched* loss figures become much more 
significant in real life applications.

I think the most puzzling result you reported was the substantial 
increase in loss (3dB to 10dB) when you set the line on dry ground, 
whereas there was virtually no increase in loss when you set the line on 
wet ground. When (or is it if) our UK weather improves, I intend to try 
some measurements myself.

73,
Steve G3TXQ





On 27/01/2012 02:44, Joel Hallas wrote:
> Steve,
>
> Well, I'm not sure if TLW is exactly on or not, but I'm pretty comfortable
> with our technique. When we're talking differences of 0.1 dB, not sure if
> the exact value is too critical for the usual HF amateur.
>
> Bob and I took careful data, rematched with every new set of data to
> compensate for any Zo differences and used good, commercially calibrated
> gear to take the data.
>
> Regards, Joel Hallas, W1ZR, BSEE, MSEE
> Westport, CT
>