[AMRadio] 160 noise floor or a new view on antennas?


Rob Atkinson ranchorobbo at gmail.com
Sun Nov 3 16:06:49 EST 2013


Antennas as snake oil and self deception methods providing an illusion
of good performance is a whole topical section unto itself.

I like to think AMers have better antenna knowledge than the run of
the mill ham because an extremely good (efficient) antenna system is
vital to satisfactory AM operating due to the wider rx passband and
the tx signal bandwidth among other things.

But I'm willing to believe the DX Eng. guy given the on-going quest I
observe among hams looking for a single do-everything tuner for
example.

The problem with the 43 foot vertical on 160 is that it is extremely
short -- around 30 degrees -- so it is going to be pretty inefficient.
 I wouldn't be surprised if the impedance is in the single digits in
ohms.   Clamping a wire to the top to make it an inverted L might help
quite a bit.   If that pulls at the top of the antenna, you could try
turning it into a T so the tension on the top is equalized by wires in
two opposite directions.

73

rob
k5uj

On Sun, Nov 3, 2013 at 11:02 AM, CL in NC <mjcal77 at yahoo.com> wrote:
> When it comes to 100 watts being barely adequate for 160 as some have suggested, could it be the modern scenario as explained to me by the folks at DX Engineering at Dayton a couple years ago?  I have had a 43 foot vertical for over 40 years, and old commercial model made in the 1930's.  I have a good counterpoise underneath it along with a home made remote tuner at the base.   When I inquired about the sudden popularity of the 43ft vertical, and the fact no mention was made about matching or just the use of a 'special' balun at the base, I was enlightened by the DXE guy.  His experience was that a whole crop of hams today, don't care what is going on from the rigs output to the antenna as long as their antenna tuner will match the load.  If they can hear something or work one or two, they are apparently happy.  A 20:1 SWR on the feedline is inconsequential to them as long as their meter says 1:1 and the power out is 100 watts to the tuner.  So, your 100
>  watts to a well fed antenna may not be the Achilles Heel you think it is, it very well could be the other ends problem.  This applies to all the bands also, where antenna bragging comments along the lines of  "I work everything I hear", really means they may not be hearing much.
>
> Charlie, W4MEC in 9 land at the moment
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