Re: Backup 3" FSL Tecsun PL-380 Design (with 62mm ferrite bars)


Gary DeBock
 

<<<   Your observation of superior nulling ability with the stubby FSL antenna is very interesting Gary.   One of the most intriguing aspects of the old SRF-59 in my recollection was that in spite of its tiny size, it had very good nulling capability.   >>>
 
Thanks for your comment, Nick.
 
Yes, in the early days of the Ultralight boom many DXers (Canadians, especially) ran wild with the nulling capabilities of radios like the SRF-59, SRF-39FP and SRF-T615. I can still remember the excitement of Rob Ross, putting his Ontario pests way down in the noise. After performing about 45 alignments on the SRF-59, I can still see the short and stubby shape of the loopstick.
 
<<<   Is it a rule of thumb that a stubby antenna has better nulling capabilities?  (though a single rod hasn't much signal pickup overall)   >>>
 
Well, with stock loopsticks there is always a practical limit how short and stubby an antenna coil can get, since the ferrite rod needs to fit inside the radio (i.e. it can't be a very large a diameter, like the 3" diameter of these FSL's), and too short a rod will limit the radio's sensitivity. These externally mounted FSL's have no such limitation, and that's probably why this bizarre nulling capability first appeared. Of course, it's now easy to design external, hard-wired FSL's that go specifically in this "short and stubby" direction-- and possibly create the ultimate nulling monster!
 
When my local graveyard pest (1450-KSUH) finally gets nulled completely down into the noise, Nick, victory will be claimed :-)
 
73, Gary DeBock (in Puyallup, WA, USA)
 
 
 
      
    
 
 

-----Original Message-----
From: nhp@... [ultralightdx] <ultralightdx@...>
To: ultralightdx
Sent: Sun, Jan 17, 2016 8:19 am
Subject: [ultralightdx] Re: Backup 3" FSL Tecsun PL-380 Design (with 62mm ferrite bars)

 
Your observation of superior nulling ability with the stubby FSL antenna is very interesting Gary.   One of the most intriguing aspects of the old SRF-59 in my recollection was that in spite of its tiny size, it had very good nulling capability.

Is it a rule of thumb that a stubby antenna has better nulling capabilities?  (though a single rod hasn't much signal pickup overall)

best wishes,

Nick


---In ultralightdx@..., wrote :

.........
 
The design uses 15 of the smaller 62mm x 12mm x 4mm ferrite bars, and ends up being slightly more lightweight than the 100mm ferrite bar model (see photo). Like its larger 100mm bar FSL sibling the model seems to have an exceptional nulling capability, possibly because of the unusual, stubby shap e for a hard-wired antenna coil-- something which hasn't been tried in loopsticks since radios were created. This new model can put all of my Seattle semi-locals down in the noise, and most of the Tacoma semi-locals as well. Further experimentation in these short, stubby antenna coils may well breed a new class of portable radios with a breakthrough mission-- "pest control."
 

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