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

[d1028gary@xxxxxxxxxxx]

Hi Walt, 
 
<<<ÂÂ Fellas, I'm interested again with the removal of the variable tuning 
capacitor and use for broad spectrum Perseus SDR captures. ÂAs you recall, 
a number of these early large units were kindly built by Gary. ÂOne was 
sent my way (and I may have the same in Masset). ÂResults have been 
variable. ÂWould anything different be done with these units compared to 
what we know today?ÂÂ >>> 
 
Thanks for your comments. 
 
Although these hard-wired FSL antennas perform exceptionally well in the PL-380 model, they can do this only because the radio has a Silicon Labs' Si4734 DSP chip with an antenna-tuning function. Whenever the DXer changes frequency the DSP chip automatically responds by peaking sensitivityÂfor the new frequency, eliminating the need forÂthe DXer to peak a variable capacitor (asÂwith traditional FSL antennas). 
 
Since the Perseus-SDR and other spectrum capture receivers don't have thisÂcritical component, hard-wiringÂthose 7"ÂFSL antennas into their circuitry wouldn't really accomplish anything (except maybe melting down the Perseus' front end with an RF overload). The hard-wired FSL's do behave somewhat like broadbandÂantennas in the PL-380, but that's only because of the DSP chip's antenna tuning function. The combination essentially becomes single-optimized frequency reception from 531-1701 kHz, selectable by the DXer. 
 
73, Gary 
 
 

----- Original Message -----

From: "Walter Salmaniw" <canswl@xxxxxxxxx> 
To: "Mailing list for the International Radio Club of America" <irca@xxxxxxxxxxxxxxxx> 
Sent: Saturday, January 23, 2016 5:52:37 PM 
Subject: Re: [IRCA]ÂÂÂÂÂÂÂÂâ"Science Fiction PL-380"-- Pest Control Version 

Fellas, I'm interested again with the removal of the variable tuning 
capacitor and use for broad spectrum Perseus SDR captures. ÂAs you recall, 
a number of these early large units were kindly built by Gary. ÂOne was 
sent my way (and I may have the same in Masset). ÂResults have been 
variable. ÂWould anything different be done with these units compared to 
what we know today? Â 73,...Walt 

On Sun, Jan 24, 2016 at 12:37 AM, <d1028gary@xxxxxxxxxxx> wrote: 

> Hi Guy, 
> 
> Thanks for your comments. 
> 
> <<< Â 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. Â Â>>> 
> 
> 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. 
> 
> <<< Â 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? Â >>> 
> 
> 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. 
> 
> <<< Â 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! Â Â>>> 
> 
> 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 Â Â Ââ"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 
> > Â), 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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