Re: Ferrite rod quality- Question for Gary DeBock, and favouri...


Gary DeBock
 

Hello Laurie,
 
Greetings from western Washington, and we are certainly pleased to have another dedicated loopstick enthusiast in our Ultralightdx group! (especially one from Australia, the source of many fine AM signals that cooperated to make my recent Ultralight DXpedition so much fun :-)
 
Thanks also for your comments on the ferrite bar experimentation, which are much appreciated. Loopsticks are the natural antennas of Ultralight radios, and I'm very happy to work together with other enthusiasts to create some effective upgrade antennas, to replace the semi-deaf Chinese factory designs. Unlike the Japanese companies like Sony and Panasonic, Tecsun has no extended experience in making sensitive AM loopsticks, so they are certainly finding it a challenge to balance performance and cost.
 
Regarding the complaints that the current type 61 ferrite mix sold by Amidon in the 7.5" x .5" bars may be of lesser quality than in previous years, I have heard similar comments from enthusiasts here, Laurie. My own detailed experience with these Amidon bars started about two years ago, when the accidental development of the "Slider" loopstick (a single, shifting coil design of 40/44 Litz wire on the type 61 7.5" bar) was found to boost the AM sensitivity of the Eton E100 (Tecsun PL-200) model up to an extremely high level. At that time I made about 15 of these "Slider" loopstick E100 models for myself and others, using the Amidon type 61 bars, and found them all to be of uniformly high quality in providing the excellent sensitivity.
 
For the past two years many other loopstick antenna designs have been created and tested here using the Amidon type 61 bars, and I haven't noticed any quality drop off during this time. Recently the type 61 mix was changed by Amidon's Fair-Rite supplier to a type which has a significantly rougher surface appearance, making it a challenge to create new Slider loopsticks because of the increased friction. However the A/B signal tests have always confirmed that the AM sensitivity performance of the two type 61 mixes is the same.
 
As you may have noticed, there is an extremely great demand in our group for 7.5" upgrade loopstick antennas, especially those of the plug-in variety. It was my pleasure to create and send out over twenty 7.5" plug-in loopsticks for owners of the PL-360 model, many of whom should be enjoying DXing thrills this coming season. Current efforts are focused on adapting these plug-in loopsticks to the PL-380 and PL-310 model cabinets, and refining the current LW plug-in loopstick design (a 2000 uh center-wound coil of 40/44 Litz on the type 33 ferrite bar).
 
Welcome again, Laurie, and I can assure you that you have come to a group where your talents will be greatly appreciated!
 
73, Gary DeBock (N7EKX), in Puyallup, WA, USA                 
 
In a message dated 8/7/2010 10:18:28 P.M. Pacific Daylight Time, lmann98@... writes:

 

Hello Gary,

Greetings from Australia. I admire and applaud your loop stick transplants, and I was wondering if you had any comments on the quality of the current 61 mix as supplied in the Amidon (Bytemark) 1/2 x 7.5 inch rods ? There were reports a while back on other groups that the Q of some samples was not up to their historical standard (short cuts on annealing was speculated as a cause).

I have some 0.5 x 7.5 inch rods from Amidon that are about 15 years old and these are excellent for Q on LW and MW and on up through to MW X band but I haven't purchased any new ones since then to be able to get a comparison.

I would like to replicate my favourite external ferrite antenna which comprises four 0.5 x 7.5 inch rods bundled in a square giving a one inch square cross section for the wound coil. I'd estimate this performs about the same as two single 0.5 x 7.5 in rods joined end to end, as the four rod bundle has approx four times the area of a single rod but about half the effective rod permeability of a single rod, so about twice the signal gathering capacity overall of a single rod. I prefer this configuration as it is compact and fits nicely into neat ABS boxes, with a good quality poyvaricon cap, albeit at the cost and weight penalty of using four rods.

Being shy of buying new Amidon rods, I have been using the old trick of synthesising rods out of half inch or 3/4 in diameter type 61 ferrite toroids. Gluing with Supaglue works well and gives 'rods' that are on a par with my ref Amidon rods for Q. Cost per one of these synthetic rods is higher than the landed cost of a comparable whole rod into Australia so I am not keen on continuing this practice.

Anyway, keep up the great work on ferrite transplants; I always enjoy reading about your new creations.

Regards,
Laurie

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