Topband: Beverage ground rod substitute
zr at jeremy.mv.com
Sun Jan 23 19:05:34 PST 2011
After rereading I caught a little boo boo.
A single wire Beverage can still use a 9:1 transformer, its the termination
resistor that must be reduced to compensate for ground resistance so you
wind up with the 450-500 Ohms mentioned in the books..
Sorry for the confusion.
----- Original Message -----
From: "ZR" <zr at jeremy.mv.com>
To: "Thomas" <ac7a at cox.net>; <topband at contesting.com>
Sent: Sunday, January 23, 2011 11:18 AM
Subject: Re: Topband: Beverage ground rod substitute
> The object is to establish a stable RF ground and not necessarily a very
> ohmic one. Drive three 4-8' rods (use a rented rotary hammer drill) will
> for starters with say 3 20-30' radials at each one. Radials can be under
> Beverage 20' or so from the termination, double back on themselves or any
> convenient path. I use cheap hamfest #20-22 insulated hookup wire just
> laying on leaves and pine needles.
> My granite hilltop with only 4-24" of soil cover measures 200 Ohms with 3
> 4' rods driven at an angle and 3 20-30' radials each, at both ends. The
> end of one also terminates at a point that I cant use any in-front radials
> so one is at the termination, another to one side (a stone wall is at the
> other side) and the last is back under the antenna about 10'.
> The transformer designs for a 2 wire reversible or single wire will have
> be designed to subtract the RF ground loss. This is easiest with a
> MFJ-259/269 and a single wire at first with a carbon pot termination. The
> transmission line mode impedance doesnt change. So for my 4 700-900'
> reversibles Im using 270 Ohms for the ground dependent windings and either
> 175 or 93 Ohms for the transmission line calculations. Using the very high
> 8500 Al BN73-202 binocular cores it is not possible usually to get a
> precise match when only 4-6 turns are involved and contrary to the ON4UN
> description you can wind at odd turns also; ie.a 5T winding can be center
> tapped on turn # 2 1/2 which will be at the other end of the core....its
> still balanced. Ive found F/B to exceed 20dB most of the time and be
> or worse sometimes. I use an external switchable attenuator to calibrate
> TS-950SD S meter so the results are accurate enough for this project.
> ----- Original Message -----
> From: "Thomas" <ac7a at cox.net>
> To: <topband at contesting.com>
> Sent: Sunday, January 23, 2011 8:46 AM
> Subject: Topband: Beverage ground rod substitute
>> All of this talk about a short Beverage antenna has me thinking I just
>> might be able to install one 250-280' E-W wire. One issue would be the
>> ground rod. The earth here is Caliche which is quite similar in
>> properties to concrete, so I can't drive a ground rod into it. I've
>> thought about using short buried radials like I do with my K9AY, but the
>> Beverage termination points will be in the extreme corners of my lot.
>> Any ideas what could be substituted and might work as well as the simple
>> ground rod earth? It is funny I find myself attempting to make the
>> proverbial silk purse from the sow's ear!
>> Tnx, Thomas - AC7A (Tucson)
>> UR RST IS ... ... ..9 QSB QSB - hw? BK
> UR RST IS ... ... ..9 QSB QSB - hw? BK
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