Ferrite rod quality- Question for Gary DeBock, and favourite loop sticks.

Laurence Mann

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.


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