That's interesting, Joe. I thought type 73 and type 77
were both lousy in terms of loss tangent. In fact, when
I looked up the tan(d)/ui numbers in my amidon catalog -
they appear to me to be very similar. What am I
missing?
Also it was interesting that last time I ordered beads
from Amidon, I asked for FB-77-5621 beads, but got
FB-31-5621 beads instead. When I inquired as to the
difference, Amidon said that the type 31 material was
a replacement for type 77. It has similar properties to
type 77 material (high ui, low resistivity), but in fact still
isn't listed in the Amidon catalog. It is however, listed
in the Fair-Rite products catalog, which I believe is
where Amidon buys all of their ferrite material.
73 de Mike, W4EF..................................
----- Original Message -----
From: "Joe Reisert" <W1JR@arrl.net>
> Hi Mike,
>
> In my opinion, the best material for sleeve baluns is type 73 material,
the
> same as recommended buy W2DU. The 77 material is like a resistor!
>
> BTW, the balun that WX0B sells I believe is a copy of the W1JR broad band
> toroid balun design as originally described in my Ham Radio Magazine,
> September 1978 article! Changing the core material to type 43 ferrite will
> probably extend it down to 160 meters.
>
> BTW #2, it is the balun used in the Cushcraft R5, R& etc. verticals so
it's
> had lots of use!
>
> 73,
>
> Joe W1JR
>
>
>
> At 06:30 PM 7/11/2003 -0700, Michael Tope wrote:
> >The type 77 material is notorious for having a poor loss
> >tangent, hence the 60 deg phase angle. Type 61 material
> >is much better, but the mu is much lower so you need
> >bocque beads to get the same series impedance as with
> >type 77. One design worth looking at is WX0B's 1:1 balun.
> >He winds RG-142 on a large torroid and puts it in a plastic
> >box. With this method you get a lot more inductance per
> >pound of ferrite as compared to the beads, so you can use
> >a lower mu material with better loss characteristics than
> >type 77. It would be interesting to measure the choking Z
> >of Jay's balun and compare it with one of those type 77
> >bead baluns.
> >
> >73 de Mike, W4EF............................
> >
> >----- Original Message -----
> >From: "Jim Lux" <jimlux@earthlink.net>
> >To: "Pete Smith" <n4zr@contesting.com>; <towertalk@contesting.com>
> >Sent: Friday, July 11, 2003 3:06 PM
> >Subject: Re: [TowerTalk] Balun filler
> >
> >
> > >
> > > The beads show a phase angle of 60 odd degrees, implying that the XL
is
> > > about 1.7 times the R.. .. from that you could calculate the heat
> > > dissipated, for a given amount of power incident in the choke. I
wonder
> > > why the Z is so high below 14 MHz.. Do you happen to know what
material it
> > > is? Maybe the mu starts to drop off above 14 MHz, so the inductance
> >starts
> > > to drop, making the resistive losses more significant?
> > >
> > >
> >
> >
> >
> >_______________________________________________
> >
> >See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
> >Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
> >any questions and ask for Sherman, W2FLA.
> >
> >_______________________________________________
> >TowerTalk mailing list
> >TowerTalk@contesting.com
> >http://lists.contesting.com/mailman/listinfo/towertalk
>
>
|