[Elecraft] Verticals

[Joe Subich, W4TV]

> Well, the toroid in my R5 was anything but "large" (I don't even
> think it was 1.5 inch diameter) and there was no way that network
> was efficient.

I happen to have an R5 network board (need to drill a new case since
the old one failed).  I haven't dragged it out to measure the toroids
but from memory they appeared to be 2 inch.  One can see pictures of
the network here: http://www.iol.ie/~bravo/r7_vertical.htm, here: 
http://pa0fri.home.xs4all.nl/Ant/R5/onhr5eng.htm and here: 
http://www.mrs.bt.co.uk/mrs/r5/

The R5/R6000/R7/R7000/R8, etc. are all off center fed vertical dipoles - 
one toroid is an auto-transformer (~4.5:1) and the other a common
mode choke (balun).  Both re quire efficient when operated within their
design limits.

> I might also point out that, generally speaking, it is often extreme
> overheating (usually voltage overstress) that causes a toroid to
> fracture into several pieces.

With the OCF verticals it is typically using a tuner to load the
antenna on a band for which it is not designed (e.g. 30 meters with an
R5/R6000) or using to use an R7/R7000/R8 at high power on the "other
end of the band" - beyond the 2:1 SWR limits - that causes failure of
the ~4.5:1 transformer and common mode choke.  The common mode choke
does not have sufficient choking impedance where the feedline is an
odd multiple of 1/4 wavelength and the stress on the core can be very
significant with high power on those bands.

73,

    ... Joe, W4TV


On 2014-09-12 10:27 AM, David Gilbert wrote:
>
> Well, the toroid in my R5 was anything but "large" (I don't even think
> it was 1.5 inch diameter) and there was no way that network was
> efficient.  I might also point out that, generally speaking, it is often
> extreme overheating (usually voltage overstress) that causes a toroid to
> fracture into several pieces.
>
> As I say, the reality is that simple vertical elements (I made one for
> 20m and a separate one for 15m, later replaced with a 40m vertical for
> 40m/15m) fed against a haywire collection of ground plane wires
> stretched across the roof significantly outperformed the R5 in the exact
> same location.
>
> 73,
> Dave   AB7E
>
>
>
> On 9/11/2014 9:22 PM, Dave Heil wrote:
>> There was nothing really wrong with the R-5.  I used one for almost
>> all of my 12 and 17m operating as 9L1US in the 1990-91 time frame.
>> Maybe all you needed to do would have been to mount it on a steel
>> railing atop a three story building on a 400 ft. hill overlooking the
>> Atlantic. :-)
>>
>> The large toroid in the matching network in the plastic box fractured
>> into several pieces by the time I was 5H3US.  Cushcraft wanted to sell
>> me the entire box full of components only at a very high price and I
>> got rid of the rest of the thing.
>>
>> I keep a Hustler 6BTV with 25 radials here in case I lose a wire
>> antenna or have a rotator problem.
>>
>> 73,
>>
>> Dave K8MN
>>
>> On 9/11/2014 21 51, David Gilbert wrote:
>>>
>>> Not to heap coals on the fire, but I also owned an early R5 and it was a
>>> terrible performer.  I had it over a year and when I finally got rid of
>>> it and put up a simple 20m vertical in the exact same spot on the roof
>>> and fed it against random length wires as a "ground plane", the
>>> improvement was astounding.  I don't think the basic concept was so bad,
>>> but the implementation was horrible.  I realized what I had as soon as I
>>> opened up that little box at the base and saw what some clueless person
>>> thought could act like a matching network.
>>>
>>> In general, though, I think it is a mistake to characterize all
>>> verticals a poor performers.  It's all a function of efficiency
>>> (avoiding losses) and location.  Check out the ground conductivity
>>> charts across the U.S. and you'll see huge differences, with some areas
>>> essentially acting as terrestrial dummy loads.  Nearby structures that
>>> can absorb energy or distort patterns represent other possible culprits
>>> for bad results with verticals.  I used nothing but verticals for most
>>> of three decades, but mine were always on a flat roof and well in the
>>> clear of anything nearby.
>>>
>>> 73,
>>> Dave   AB7E
>>
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