Re: SW degraded with 3" FSL PL-380


Gary DeBock
 

Hi Ryan,
 
<<<   I just finished building Gary's 3" FSL PL-380 and noticed when I hook up the FSL antenna to AM1 and AM2, the shortwave reception takes a nosedive. The shortwave reception is also affected by gently moving the litz wires from side to side. When I unsolder the antenna, the shortwave reception comes back. There are no solder bridges. I did test the radio beforehand and it was O.K.   >>>
 
I have checked the Shortwave reception on the three 3" FSL PL-380 test models here, and can confirm that the SW reception is degraded, as you discovered. This is an unintended side effect of the modification, which was not discovered at the time of initial testing. For those DXers who need to use their PL-380's for SW as well as MW reception, I do not recommend the FSL transplant modification. If any of the DXers who purchased the sets of 100mm ferrite bars from me are included in this category, I will be happy to not only refund their $25 purchase cost but also pay return postage for the 100mm bars to be shipped back to me.
 
<<<   The AM side works much better than the stock antenna but not noticeably better than my Skywave w/7.5" loopstick.   >>>
 
That is far less MW performance than the three test models here provide, Ryan. All three of the 3" FSL Tecsun PL-380 test models here greatly outperform the 7.5" loopstick CC Skywave model from 530-1700 kHz, to the extent that they are not even in the same league. Without checking your model I can't really be sure of the reason, but did you use the recommended 250/46 Litz wire? If not, that would certainly be a possible reason. Any substitutions in parts or materials can cause a degradation in performance. Also, the use of shielded Litz wire (as called for in the 4.25" "Pest Control" FSL model) is not recommended for this model. The 3" Bar FSL model's design is already fairly close to the maximum RF tolerance level of the Si4734 DSP chip, and the use of shielded Litz wire pushes the RF input level past the recommended limit.
 
73, Gary DeBock (in Puyallup, WA) 
 
     
 
 

-----Original Message-----
From: rmartin100@... [ultralightdx]
To: ultralightdx
Sent: Tue, Feb 16, 2016 6:49 pm
Subject: [ultralightdx] SW degraded with 3" FSL PL-380

 
I just finished building Gary's 3" FSL PL-380 and noticed when I hook up the FSL antenna to AM1 and AM2, the shortwave reception takes a nosedive. The shortwave reception is also affected by gently moving the litz wires from side to side. When I unsolder the antenna, the shortwave reception comes back. There are no solder bridges. I did test the radio beforehand and it was O.K. The AM side works much better than the stock antenna but not noticeably better than my Skywave w/7.5" loopstick.
Any ideas on what could be wrong?
Ryan 

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