Re: Russian Surplus 140mm x 8mm Ferrite Rod Prices on eBay


Gary DeBock
 

Hi Guy,

Thanks for this interesting question, which I'm sure that other DXers
have also wondered about.

The shortest Russian surplus ferrite rods that I have actually tried
are the 140mm x 8mm ones, obtained from both "Alexer1" and "Sovtube."
These have proven to be very effective in compact antennas like the 7"
diameter medium-wave "Affordable" FSL model (the one you took to Oregon
during your vacation). Based on the excellent performance of these
140mm x 8mm rods (and the 160mm x 8mm and 200mm x 10mm ferrite rods of
the same 400 permeability that have excelled in other FSL's) I have no
doubt that the Russian surplus 100mm and 65mm-long rods would also give
great performance, at a significant cost advantage. The shorter length
may make it difficult to get enough turns of Litz wire to make a
Longwave FSL design without using a variable capacitor of more than 381
pf capacitance, but for a medium wave FSL design, that should not be an
issue. As always, the important factors for good DXing performance will
be the accuracy of the cylindrical ferrite sleeve (all the ferrite rods
should be lined up, and pointing exactly the same way), the use of
high-quality Litz wire (660/46 is recommended), and the use of a
high-quality variable capacitor to take maximum advantage of the high-Q
tuning system. A/B testing here has also shown that the FSL's DXing
performance can be enhanced simply by placing the antenna up[ on a 5'
high PVC stand.

The eBay ferrite sellers usually price their rods according to the
purchasing demand, and the current "hot item" seems to be the 140mm x
8mm size. The 160mm x 8 mm size was also a hot item back in the
spring-- until Kevin and I apparently cleaned out the sellers of that
particular size. The 200mm x 10mm size was ordered in serious quantity
around May and June, but the sellers were not able to make a price
increase stick (presumably because of a huge supply of these rods,
owned by multiple sellers). The smaller sizes haven't really had much attention at all, so they would probably be a great option for
experimentation, Guy.

73, Gary (from across town)

-----Original Message-----
From: thinkdx <dx@...>
To: ultralightdx <ultralightdx@...>
Sent: Thu, Sep 1, 2011 10:58 am
Subject: [ultralightdx] Re: Russian Surplus 140mm x 8mm Ferrite Rod
Prices on eBay




Hi Gary,

What do you think of the shorter rods as alternatives, such as the 65mm
or 100mm long versions? For the same general price you could get more
rods and make a larger diameter loop.

Which begs the question-- which is better: shorter ferrite rods with
bigger overall loop diameter, or longer ferrite rods but smaller loop
diameter?

73 from across town...

Guy Atkins
Puyallup, WA USA

--- In ultralightdx@..., D1028Gary@... wrote:

Hello All,

Yikes! The Russian ferrite sellers on eBay may be reading the
Ultralightdx messages, including the post that I sent this morning
regarding the price of the 140mm x 8mm rods used in the 7" diameter
"Affordable" FSL antenna design. The shipped price of these rods from
"Alexer1" has practically doubled, compared to his asking price this
morning
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItemRevisionDetails&_trksid=p4340.l2569&item=190570858315





The price of the same rods from "Sovtube" is still very reasonable,
though (at least at this moment). 70 of these rods (enough to build
the
63 rod FSL) can be obtained from him for $104 (US Dollars) including
air mail shipping to North America, according to his current listing
at
http://www.ebay.com/itm/Large-balun-ferrite-rods-8x140-mm-Lot-10-/400239422868?pt=LH_DefaultDomain_0&hash=item5d3020ed94



.

The supply and prices of these Russian surplus ferrite rods on eBay
have always been very unpredictable, and of course all of the sellers
try to make as many rubles of profit as possible (they seem to have
adapted to capitalism quite eagerly). My advice is to wait until you
see a listing of a very large number of ferrite rods (enough to build
your chosen FSL design) at a reasonable price, and then secure them
all
in one single purchase. The sellers will probably try to raise the
asking price after your order, but they have been doing that anyway
for
years.

73, Gary DeBock (in Puyallup, WA, USA)

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