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Re: [IRCA] â"Science Fiction PL-380"-- Pest Control Version



Fascinating discussion. 

Iâm now wondering if it would be possible to feed a short, stubby FSL with 50 Ohm coaxâperhaps through an isolatorâthen mount it outdoors on a rotor? If the FSL were mounted high above the rotor on PVC pipe, and supported by either wood or PVC, with the coax running at a right angle to the FSL, could this work? 

As a dedicated domestic DXâer, anything that will null local and semi-local pests is worth trying! 

73,

Les N1LF

Les Rayburn, director
High Noon Media Services
130 1st Avenue West
Alabaster, AL 35007-8536
205-621-7500
205-621-7505 FAX
205-253-4867 CELL
highnoonfilm.com

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> On Jan 23, 2016, at 6:37 PM, d1028gary@xxxxxxxxxxx wrote:
> 
> Hi Guy, 
>   
> Thanks for your comments. 
>   
> <<<   I'm still puzzled as to the best way to go for nulling of pests, regarding 
> diameter vs length proportions. Initially the "long and skinny" antennas 
> such as in the SRF-T615 were praised for their nulling, but now the 
> "stubby" FSLs appear to have the upper hand.    >>> 
>   
> Guy, there's no doubt that the stubby, hard-wired FSL's have really created a new level of nulling capability-- in an entirely different league than the loopsticks or long ferrite rods that preceded them. There are two primary reasons for this. The new hard-wired FSL's are completely isolated away from the radio circuitry, and they have no variable tuning capacitor to upset their RF symmetry. They present a completely symmetrical RF coil for reception purposes, which can null out pest stations under laboratory-perfect conditions every time. All of the preceding antenna designs were limited either by surrounding radio circuitry, a variable tuning capacitor to upset the RF symmetry, or both. 
>   
> <<<   I guess this is an unfair apples to oranges comparison (hollow FSL vs 
> traditional solid rod antenna). To compare FSL to FSL then, are you finding 
> better nulling the "stubbier" you make the antennas?   >>> 
>   
> Yes, there is now no doubt that the shorter and stubbier a hard-wired FSL coil becomes, the greater its nulling capability will be-- so long as the RF design is completely isolated , and completely symmetrical. 
>   
> <<<   Do you recall the large diameter, short rod FSLs that Kevin Schanilec built 
> inside of Christmas wreath containers? I wonder if those models were 
> excellent at nulling. I do remember that he did a lot of his testing 
> indoors, which can screw up nulls and reception completely. High 
> performance ferrite antennas CANNOT be reliably evaluated indoors!    >>> 
>   
> All traditional FSL's (including Kevin's designs) have a variable tuning capacitor-- which is a distraction from a perfectly symmetrical RF reception pattern. The larger and clunkier the variable capacitor, the worse and worse the nulling capability gets. Long hookup wires to a variable cap also upset the symmetrical RF reception pattern, further reducing nulling capability. The new hard-wired FSL's avoid both issues completely-- with perfect symmetry and no variable tuning capacitor.  
>   
> By the way, all of the local pests except for 1450-KSUH have been nulled down into the noise. My guess is that the over-modulated KSUH is broadcasting on more frequencies than its fundamental, making it tough to null each one :-) 
>   
> 73, Gary 
>   
>     
>   
>   
> 
> ----- Original Message -----
> 
> From: "Guy Atkins" <dx@xxxxxxxxxxxxx> 
> To: "Mailing list for the International Radio Club of America" <irca@xxxxxxxxxxxxxxxx> 
> Sent: Saturday, January 23, 2016 3:02:59 PM 
> Subject: Re: [IRCA]        â"Science Fiction PL-380"-- Pest Control Version 
> 
>> 
>> âGary, 
>> 
> 
> âI'm still puzzled as to the best way to go for nulling of pests, regarding 
> diameter vs length proportions. Initially the "long and skinny" antennas 
> such as in the SRF-T615 were praised for their nulling, but now the 
> "stubby" âFSLs appear to have the upper hand. 
> 
> Do you think the cylindrical (hollow) design of the FSLs changes the 
> response to a groundwave pest station so that a high diameter-to-length 
> ratio *FSL* nulls better than a *solid* rod with a high LENGTH-to-diameter 
> ratio? 
> 
> I guess this is an unfair apples to oranges comparison (hollow FSL vs 
> traditional solid rod antenna). To compare FSL to FSL then, are you finding 
> better nulling the "stubbier" you make the antennas? 
> 
> Do you recall the large diameter, short rod FSLs that Kevin Schanilec built 
> inside of Christmas wreath containers? I wonder if those models were 
> excellent at nulling. I do remember that he did a lot of his testing 
> indoors, which can screw up nulls and reception completely. High 
> performance ferrite antennas CANNOT be reliably evaluated indoors! 
> 
> 73, 
> 
> Guy Atkins 
> Puyallup, WA 
> 
>> â 
>> 
>> 
>> ---------- Forwarded message --------- 
>> From: d1028gary@xxxxxxxxxxx 
>> To: Mailing list for the International Radio Club of America < 
>> irca@xxxxxxxxxxxxxxxx> 
>> Cc: 
>> Date: Sat, 23 Jan 2016 13:40:28 +0000 (UTC) 
>> Subject: [IRCA] 
>> ââ 
>> "Science Fiction PL-380"-- Pest Control Version 
>> Hello All, 
>> 
>> The first of the new hard-wired FSL models specifically designed to have 
>> an unusually sharp nulling capability is now a reality. With a "short and 
>> stubby" FSL design that emphasizes symmetry, isolation and a tidy RF 
>> reception pattern, this model can put all of my semi-locals (Seattle and 
>> Tacoma) down in the noise-- and even receive a few competing stations on 
>> their fundamental frequencies. Using 22 of the commonly available Russian 
>> surplus 62mm x 12mm x 4mm bars, this model is one of the "spinoff" versions 
>> of the 3" Bar FSL PL-380 model (for which the 15-page "Heathkit-like" 
>> construction article was posted at 
>> http://www.mediafire.com/view/w0gcek56f6aq7kr/3_Inch_FSL_Tecsun_PL.doc 
>>  ), and has an FSL "sensitivity score" (coil diameter x ferrite length) of 
>> 264-- pretty close to the 300 point score of the article version (with 
>> 100mm ferrite bars). The advantage of this model is that there is a huge 
>> supply of the Russian surplus 62mm ferrite bars, currently sold on eBay by 
>> two different sellers. You can get 20 of them for $13-- including shipping 
>> from Lithuania. 
>> 
>> Construction of this model is identical to the article version, except for 
>> the FSL construction (which may be added as an addendum). All of the 
>> construction parts are readily available, also. Unless you live practically 
>> next door to a local pest, this "pest control" model should cut 
>> your offenders way down to size. A photo of the new model is posted at 
>> https://app.box.com/s/5r95oxc9v24vm9hbpe2w1g800lbt4d3b 
>> 
>> 73 and Good DX, 
>> Gary DeBock (in Puyallup, WA, USA) 
>> 
>> 
>> 
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