Re: No Joy with Tecsun PL310 Antenna Mod

Gary DeBock

Hello Gregory,
Thanks for your interest in the external loopstick modification for the Tecsun models, and I hope that we can optimize the sensitivity of your PL-310 to obtain great sensitivity on all MW and LW frequencies.
In the experimentation here, identical material (7.5" type 61 ferrite bar wound with a single coil of 81 turns of 40/44 Litz wire starting 43 mm from one end of the bar) was used, except for the adhesive tape holding the Litz wire in place. With these experimental parameters, the loopstick transplant in the PL-310 did provide a very sizable performance boost on all LW and MW frequencies over the stock PL-310, although it did not provide the average 20 dBu MW boost observed in the PL-380 (it was more like 15 dBu in the PL-310, presumably because of the larger stock loopstick in the PL-310 which is naturally more sensitive than the PL-380 stock loopstick). 
By experience I know that the electrical insulating properties of the adhesive tape used to wrap a loopstick coil are critical to proper coil performance, and if the tape adhesive has a slight deviation from being a perfect insulator, it can really upset the coil performance. During the development of the E100 Slider models (explained at ) we did a lot of testing to eliminate a hand capacitance issue at the higher frequencies, and discovered that most of the masking tape commonly sold was useless for coils. The Johnson & Johnson 2" wide Waterproof tape (shown below in an E100 Slider coil construction photo) was found to be an ideal insulator, and is the tape used here for all experiments. It was obtained from two years ago, although they do require quite a sizable purchase as a minimum order. If you need some of this ideal tape to use in your loopstick experiments and have trouble tracking it down, I would be happy to send you a smaller amount sufficient to meet your needs.
73 and Good Luck,
In a message dated 12/28/2009 2:52:28 P.M. Pacific Standard Time, gmosherat@... writes:



Following your "Supercharging The Tecsun PL380" article I decided to do the same with my PL310.

I made a new 7.5 inch loopstick using the material in the article - Amidon #61 Ferrite bar and 40/44 Litz wire, 81 turns starting 43mm from one end. The total length of the colied witre on my verison is just over 1 11/16 inches long.

Tests show rather than the Avg 20dBu gain across the band I'm getting avg 18 dBu reduction (lower number)!

Since the chipset in the PL310 is the same as the PL380 I am assuming my results are due to something I did wrong?

I tried two methodologies for wrapping the coil, same results for each. First try I wrapped the ferrite bar with one layer of double sticky tape. I assumed this was a reasonable substitute for masking tape?

When results were not as expeced I removed everything and started over, this time wrapping the ferrite Bar with one layer of regular paper. For this second attempt I used the same type of wire but not the same piece I had used for the first attempt (just in case the first piece of wire was bad in some way).

Anyways, I get smae results for both versions and from what I see the instructions are pertty basic and clear.

Any idea what I might be doing wrong?

Gregory Mosher

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