Topband
[Top] [All Lists]

Re: Topband: Best small space antennas

To: Bill Aycock <billaycock@centurytel.net>
Subject: Re: Topband: Best small space antennas
From: Guy Olinger K2AV <olinger@bellsouth.net>
Date: Thu, 8 Dec 2011 02:56:49 -0500
List-post: <topband@contesting.com">mailto:topband@contesting.com>
Bill,

Instructions for creating a drawing of the basic configuration: 160 only,
no tuning inductors or capacitors. Tuning after construction by adjusting
the length of the top of the L.

Start in the center of a blank piece of paper.  Draw a transformer with a
completely separate primary and secondary.  Draw the core bars vertical so
all of one winding is on the left and all of the other winding is on the
right.

On the left side of the tranformer connect the upper end of the winding to
the inverted L.

On the left side of the transformer connect the lower end of the winding to
the folded counterpoise.

On the right side of the transformer connect the upper end of the winding
to the feed coax center conductor.

On the right side of the transformer connect the lower end of the winding
to the feed coax shield.  Do not ground the coax shield until 30-50 feet
away from the transformer.

That's the wiring diagram.

Length of the inverted L is adjusted to prune to resonance at your choice
of center frequency.  This appears to be centering in the vicinity of
130-140 feet, **IF** you are using an isolation transformer built to our
specs, but we will know more when there are 100 of these up in the air and
reporting.

The transformer is wound on an Amidon T300A-2 #2 material powdered iron
toroid.  Twenty bifilar turns of #14 double polyimide insulated, sleeved
with AWG12 teflon standard wall no shrink sleeving.  Requires 15 feet of
wire and 15 feet of teflon sleeve, cut in half to make the two winding
wires.

73, Guy.

On Wed, Dec 7, 2011 at 11:33 PM, Bill Aycock <billaycock@centurytel.net>wrote:

> Guy--(and others who may contribute)
> I have been following your posts, and have some questions, brought on by a
> view at the W0UCE diagrams, at:
> http://www.w0uce.net/**K2AVantennas.html<http://www.w0uce.net/K2AVantennas.html>
> The top figure seems to match what I understood from your post, but the
> figure that includes the Inv "L" confuses me, particularly with regard to
> the connections. I need a more simplistic description, including the
> connections to the transformer
> Thanks- Bill--W4BSG
>
>
> ----- Original Message ----- From: "Guy Olinger K2AV" <
> olinger@bellsouth.net>
> To: "Jim Miller Waco Texas WB5OXQ" <wb5oxq_1@grandecom.net>
> Cc: <topband@contesting.com>
> Sent: Wednesday, December 07, 2011 7:57 PM
>
> Subject: Re: Topband: Best small space antennas
>
>
>  Note: the following is not a theoretical or untested antenna.  There
>> are working antennas in the field using the folded counterpoise
>> described below, scoring well in contests**, in use up to a year and
>> more.  Contest scores of the sort attained are not made using antennas
>> with significant deficiencies or fundamental flaws.
>>
>> A miscellaneous end-fed inverted L or end-fed inverted U over an
>> elevated 5/16 wave single wire folded counterpoise (FCP) will have
>> good radiation from a small lot, with the ability to put out a strong
>> signal not usually associated with small lots.  In the simple
>> implementation of this antenna (160 only), the length of the L or U is
>> adjusted for zero reactance, usually resulting in a 50-60 ohm feed Z
>> at resonance.
>>
>> There are NO radials.  The main design point of the antenna is to
>> minimize lossy currents induced in the dirt and confine TX signal
>> current to the FCP and the radiating wire.  This is a real, and lossy
>> issue for a few short or miscellaneous radials.  Enough of an issue to
>> kill 15 dB.
>>
>> The radiating wire first goes up as much vertical as you can manage,
>> then out as far as manageable, and then down if length is still needed
>> to prune to resonance.  The main point is to pick a feed point on the
>> property that has your best vertical rise and then get the rest of the
>> length for resonance however you can. For some properties this has
>> meant putting extra angles in the up+over+down radiator.  Some
>> properties will not need the "down" part.
>>
>> The antenna uses a REQUIRED isolation transformer at the feed point
>> because the counterpoise is NOT resonant, and the feed would really
>> rather use the much lower Z but hugely lossy coax shield current as a
>> counterpoise.  The folds in the FCP are designed to maximally reduce
>> counterpoise fields at the ground, reducing lossy currents in the
>> dirt.
>>
>> The isolation transformer's leftover inductive reactance, a
>> disadvantage in many applications, in this case helps to tune out the
>> capacitive reactance of the FCP and reduces the length of the
>> radiating wire needed to achieve simple resonance for the antenna.
>>
>> The counterpoise extends plus and minus 33 feet from the feed point,
>> 167 feet folded into 66 linear feet occupied on the property. The
>> middle 20 feet of the 66 should be straight, but either end can be
>> bent away from the straight line to accommodate the property.  Up 8
>> feet or higher is recommended.  Lowering the counterpoise increases
>> the coupling to dirt, increasing losses.
>>
>> The isolation transformer uses the same physical components as a
>> balun, but the unlike the balun there is NO connection of any kind
>> between the primary and secondary windings.  This is accomplished with
>> twenty bifilar turns of double polyimide insulated #14 with teflon
>> sleeving wound on an Amidon T300A-2  #2 material powdered iron toroid.
>> One wire is the primary, and the other is the secondary.  The low MU
>> powdered iron toroid was picked over time to avoid heating, still
>> provide required coupling, with other choices sometimes failing in
>> spectacular fashion.  We have no information of our currently-used
>> winding method on the Amidon T300A-2 ever failing for any cause,
>> though we would not expect it to survive a direct lightning strike.
>>
>> With the isolation transformer, the antenna and FCP is entirely above
>> ground and not connected to anything else. We use a 5 megohm resistor,
>> in parallel with a non-resistor lawn mower spark plug, from the FCP to
>> ground as a static drain. The gap drains lightning induced voltage to
>> protect the resistor, the resistor drains wind, snow, rain static.
>> The resistor and gap protect the winding from a voltage puncture that
>> will grow into a carbon track to ground.
>>
>> 73, Guy.
>>
>> **  As reported in Dec 2011 CQ, Jan 2011 CW160CW contest, USA low
>> power unassisted, the 29 scores over 100K out of 335 scored logs in
>> class:
>>
>> Station, state, score, QSO, ST+PROV, DX
>>
>> K9AY   WI  259,346 991 58 36
>> W0UO   TX  250,716 882 58 44
>> K1EP   MA  232,750 909 56 39
>> K2AV   NC  223,908 907 57 37 << No radials, 5/16 FCP
>> K8BL   OH  203,328 819 58 38
>>
>> KU1CW  KS  197,885 795 58 37
>> N2WN   TN  191,090 640 55 42
>> WB8JUI OH  190,372 852 58 38
>> N7IR   AZ  183,855 856 58 27
>> W2TZ   NY  178,633 723 56 35
>>
>>
>> NA8V   MI  177,030 793 59 31
>> W4AA   FL  173,619 494 56 45
>> K1HTV  VA  172,956 733 55 32
>> W1WBB  RI  161,550 654 55 35
>> KU8E   GA  152,613 615 58 35
>>
>> W7RH   AZ  135,369 500 55 34
>> K4WI   AL  128,520 509 55 30
>> N9NCK  WI  126,162 516 55 31
>> KV8Q   OH  125,741 674 57 20
>> N9AUG  OH  125,330 608 55 28
>>
>>
>> W2TX   FL  121,800 504 52 35
>> K9QVB  IL  120,120 641 56 21
>> WW3S   PA  119,848 706 55 16
>> K2UF   NY  119,392 541 53 29
>> K0PK   MN  118,400 678 58 16
>>
>> WF4U   UT  114,239 664 56 15
>> W1BYH  MA  106,444 404 54 35
>> W5WMU  LA  106,020 574 54 22
>> N4JF   AL  101,920 493 54 26
>>
>> ** 3830 claimed scores listing of Dec 2011 ARRL 160 contest, North
>> America low power unassisted, top 20 of 119 listed as of this writing:
>>
>> Station, state, score, QSO, ST/PROV, DX
>> 2011 ARRL 160 - 3830 Claimed Scores 06Dec2011
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~**~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> Call               QSOs   Sec Cntry   hr      Score Club
>> NA Single Op LP
>> K8FH               920    74    18    27    175,076 Medina 2 Meter Group
>> NE9U               978    75    14          172,927 MWA
>> K4FT               976    75     9    28    166,236 KCG
>> WB8JUI             940    71     9 21.32    152,560
>> K0TI               920    76     5    21    150,255 MWA
>> K0DI               875    75     8    28    146,495 Lincoln ARC
>> K2AV               788    65     9  21.5    119,066 PVRC    << No
>> radials, 5/16 FCP
>> W0DLE              725    74     3    21    112,343 Grand Mesa
>> K9MMS              653    74    10    16    112,224 SMC
>> K0PK               657    72     6    19    104,130 MWA
>>
>> K3PA               618    74     7          101,817 Kansas City DX Club
>> WA1FCN             645    68     7           99,864 ACG
>> K2ZR               695    64     4  20.0     90,112 Western NY DX Associ
>> K0AD               584    75     6    10     88,500 MWA
>> W0UO               519    71     9    14     85,680 NTCC
>> K0CN               478    73    11           83,076 MWA
>> N1IX               516    60    10    13     78,540 YCCC
>> VE3OSZ             442    68    15           77,854 CCO
>> W9ZRX              492    69     8  20.5     77,616 SMC
>> W7RH               437    72     8           76,869 Arizona Outlaws Cont
>>
>>
>>
>> On Sun, Dec 4, 2011 at 8:18 PM, Jim Miller Waco Texas WB5OXQ
>> <wb5oxq_1@grandecom.net> wrote:
>>
>>> With limited space what is the best antenna for 160? The only room
>>> available is a 130X50' area. Ground radials will be nearly impossable to
>>> put in large enough to be of much value. 1/4 wave antenna tried, very
>>> narrowband and interfeared with every receiving device in a block. I may
>>> just be out of luck. wb5oxq
>>> ______________________________**_________________
>>> UR RST IS ... ... ..9 QSB QSB - hw? BK
>>>
>> ______________________________**_________________
>> UR RST IS ... ... ..9 QSB QSB - hw? BK
>>
>>
>
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK

<Prev in Thread] Current Thread [Next in Thread>