Topband: K2AV 160m Folded Counterpoise - Questions ?

[Guy Olinger K2AV]

Looking at this in the afternoon light, need some corrections in places:

On Sat, Dec 10, 2011 at 4:02 AM, Guy Olinger K2AV <olinger at bellsouth.net>wrote:

> The orientation of the FCP relative to the L's horizontal wire doesn't
> matter.  It's folds are designed to self-cancel fields.  This works both
> ways.  The induction from an L horizontal into the 5/16 FCP is more than
> ten dB down from the horizontal's induction into 1/4 wave radials.
>
> Smaller can be a killer for QRP.  PORTABLE may need smaller, but QRP does
> NOT.  Particularly at QRP you need the least amount of loss possible
> anywhere and everywhere.  An extra bit of loss not perceptible at all on a
> QRO signal, may drop a QRP signal into the noise and no copy.
>
> That PARTICULAR toroid is chosen because:
>
> a) The low mu and powdered iron means it will not saturate with QRO.
> b) The loss is low enough with that material that it will run QRO
> brick-on-key and stay cold (have checked).
> c) The loss is low to support QRP
> d) The larger size of the (low mu) toroid helps provide the high degree of
> coupling needed between the windings.
> e) The form factor provides enough winding space for 20 bifilar turns of
> low loss #14 wire with teflon sleeving for QRO.
> f)  The residual inductance from the transformer is close to being the
> conjugate for the FCP's reactance.  That means that the two together are
> close to self resonant on the low end of 160.
>
>  g) This in turn means that the simple use of FCP, isolation transformer
> and "pruned-to-resonance" wire, delivers a wire length that is close to a
> quarter wave, and with the total wire involved (9/16 wave outside the
> transformer) the feed Z comes closer to a convenient 50 ohms. A shorter
> pruned-to-length wire means more current in the FCP, and more loss in the
> ground.
>
> Mess with the toroid choice and the winding turn count on the toroid, and
> you screw up all that convenient convergence of advantages for the rock
> bottom simple configuration.  Pay the $14 bux for the toroid and deal with
> it.  That's cheaper than a family meal at McDonald's.
>
> You need the 228 Al value of this toroid and the room to wind. You could
> get similar Al of 250 with a T200-1, of number one material, but the inside
> diameter goes down to 1.25 inches from 1.94, and now you can't wind with
> teflon sleeved or insulated #14, and you have to use insulated #18.  You
> are now getting into loss, the evil enemy of QRP.  But you DID save $7 on
> the toroid :>).
>
> I already saved you $26.  I can for sure do the BEST job using a T400A-2
> toroid made of the same # 2 powdered iron, that costs $40.  Jerry Sevick
> settled on this expensive toroid as the best core for a 160-10 voltage
> balun for the output of a QRO tuner, one that actually delivered the same
> performance on 160 as 10.  You can find the details on that in his balun
> book.  ("Understanding, building, and using Baluns and Ununs" Jerry Sevick,
> 2003, CQ Communications, pp 60, 61)
>
> People are going try anything I guess, but I am telling them methods and
> components that we have TESTED, made contest scores with for over a year,
> and KNOW WORK, have low loss for QRP, and handle power.  I will not be able
> to vouch for or troubleshoot alternate methodology.  Roll your own methods
> and you're walking away from what we're familiar with.  The first question
> I am forced to ask is what components you used.
>
> 73, Guy.
>
> On Fri, Dec 9, 2011 at 11:15 AM, Jim F. <j_fitton at yahoo.com> wrote:
>
>> Great reflector !
>>
>> I am a new list member, condo dweller, Top Band lover, QRPer, and
>> contester.
>> And strangely enough these present a challenge for others and maximum
>> enjoyment for me :-)
>>
>> 1.  Is the FCP shown in the diagram in a line with the inverted L wire ?
>>
>> 2. Do you think a smaller T200-2  transformer would work  (QRP levels)  ?
>>
>> Profuse thanks,
>>
>> jim / W1FMR
>> _______________________________________________
>> UR RST IS ... ... ..9 QSB QSB - hw? BK
>>
>
>