Re: TECH: PL310 stock loopstick tested

Gary DeBock

Hi Steve,
Thanks very much for investigating the PL-310 stock loopstick Q readings, and it's great to have you back in ULR tinkering. Those are very interesting results on the LW frequencies, and may help to explain why the PL-310's LW performance is so much better than that of the PL-380.
I have ordered some type 33 Amidon 7.5" ferrite bars and 165/46 Litz wire for some experiments to create an LW-optimized 7.5" loopstick PL-380, and will be interested to find out the optimum coil inductance for maximum LW sensitivity. I'll probably need to construct a longer Slider coil than the 81-turn model used for the peak AM sensitivity tests, to allow shifting the coil inductance up past 1000 uh (judging from your PL-300WT optimum LW inductance tests).
The SWP 7.5" Slider models that you helped create (by designing the CFJ455K5 filter mod) have been outstanding DXpedition performers throughout the past year, but they may finally have some serious competition from the new 7.5" Amidon PL-380's (Kevin's term :-)
Welcome back, and have fun.
73, Gary

In a message dated 1/13/2010 7:08:37 P.M. Pacific Standard Time, steveratz@... writes:

I removed the Tecsun PL310 stock loopstick today and checked it on the
HP4342A Q meter. Since this model ULR is about the only one that will
receive anything on LF (my closest LF NDB is 20 miles away, on 296 kHz), I
was curious how the loopstick measured. Bottom line is this loopstick works
has very low Q at MW above about 1000 kHz and is optimized more for LF
I will have to check the loopstick in my PL380 next and see if it's similar,
though that model doesn't hear anything on LF even though the loopsticks
look the same visually.

The PL310 loopstick measured 322 uH at 796 kHz, with a Q of 86. (The Q meter
uses certain fixed frequencies on various ranges when measuring inductance;
a range is chosen to peak the Q for a given inductance being tested, then
the inductance is read off the dial.)

1500 kHz Q 20 (that's the highest frequency I could check Q at since the Q
meter's variable cap was at its minimum setting)
1300 kHz Q 31
900 kHz Q 71
700 kHz Q 106
530 kHz Q 160
500 kHz Q 172
400 kHz Q 203
300 kHz Q 228
200 kHz Q 229


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