Date: Thu, 20 May 2010 07:24:35 -0700
From: Dan <n5ar@air-pipe.com>
Subject: Re: [TowerTalk] BN-86 Balun
Strong words, Jim but you are right on. Type 31 material is easily
available from Mouser (no minimum order size) and other electronic parts
houses. Poor baluns, even if they do not fail with legal power, allow
the coax outer shield to be part of your antenna. Who wants their coax
outer shield radiating part of your power and picking up noise when
receiving? The info on your web site about your tests takes some careful
reading to understand but is worth the effort.
Keep up the good work, Jim.
73, Dan, N5AR
### The Z measurements, I believe were done on a HP vector Z meter,
per Ken Hirchberg at Cal-Av labs. [ he also builds all the F-12 baluns]
The real acid test is to use a clamp on RF ammeter...and not the MFJ
clamp on RF ammeter that will only handle a max coax OD of .5"
You need a real commercial clamp on ammeter, to handle stuff
like LMR-600, LMR-1200, big heliax, etc.
That's the one thing that got eliminated with the EB-3 [or sliding
17 x large type 43 beads over 393/213 u ] and that's poor F/B,
RFI, etc. They don't heat up... and a Fluke 61 was pointed right at the
beads, from 4" away...and run up/down the length.
>> You can`t get water into em.. and you can`t blow them up. The EB1 and EB2
>> baluns are excellent as well.
>>
> "Excellent" is a wild exageration with respect to these so-called "baluns,"
> which are nothing more than simple-minded "string of beads" common mode
> chokes. True that you probably can't blow them up with the illegal power that
> you like to run, but they aren't very effective as common mode chokes either.
### How do you know that? A simple clamp on ammeter will tell you just abt
all you want to know. I also tried my lcr meter from end to end.. just out of
interest vs different types of beads... just out of curiosity. I don't see
any
RF spill over with 17 x beads on 40-6m. [38 uh] Nor 24 x beads on 80m..[58
uh]
.. nor 30 beads on 160m. [67 uh]
## when folks e-mail me or phone me.. and want to run XXX watts at
freq YYY.... there are only so many options. Besides... 1.5 kw RTTY
is the same as 7.5 kw pep out on ssb [same average power].
## another balun that works good is several wraps of 393 coax around
several type 61 cores.... [solenoid fashion]. Dunno if 31 material is better
than
61 material or not. If you get too many cores stacked on one side for the size
of nema box used... several cores can be stacked on the left side... and more
stacked
on the right side. And no, you won't blow these up either.
## we also tried RG-400 + RG-303 wound on 8 x type 43 cores. IF too many turns
used, you end up with parasitic arcing. Jay ar AS warned me abt that. Sure,
the Z goes up to the square of the turns... but only a few turns could be used,
till it arced badly, between the braids. Think that was abt 6-8 turns of
RG-400.
## I have also seen 61/43 material, [torroids] used as 'beads'... and slid over
7/8" + 1.25" heliax... and also LMR-1200.
> Manufacturer's published data is quite inferior to what any ham can make by
> winding multiple turns of RG8 or RG11 through #31 toroids and they are VERY
> conservatively rated for max legal ham power.
## will they handle 2.5 to 3 kw...with high SWR ??? After line loss,
I want to see at least 2250 w at the ant feed point.
## This 31 material.. with it's mu=1500 looks like something between
43 material.[mu=800] and 85 material. [mu=2000] It would be interesting
to try type 31 beads..since you can get em in 1" OD x .5" ID x 1.125" long.
I think a type 31 bead balun would present a higher Z... per their graphs.
Looking at their graphs, I don't think a type 31 bead balun will handle as
much power as type 43 beads ?
## I just read through your tutorial. What are we after here exactly?
Do we want high RES... or high XL.... or high Z..... or a combo ?
I'll opt for high Z. How high is high enough ?? Some 'experts' say
250 ohms..some say 500... some say 1000. You are advocating 5000 ohms.
Those baluns made from rg-8x... wound on 4.5" od pvc.. are only abt
1300 ohms on 80m, measured on a hp meter. The same balun is only 650 ohms
on 160m. You would require even more turns to get 1300 ohms on 160m.
## W8JI, and other's per your notes at end of tutorial, seem to think that
650 ohms is plenty on 160m.. and ditto with 1300 ohms on 80m.
[ which is what u get by using xl=2 x pi x f x l]. I think that inductive
reactance
formulae coming out with the same XL is just a coincidence. If the inductive
reactance formulae was accurate.. all these bead baluns would have sky high
Z on 10m..and they don't.
## Those solenoid coax solenoid /pvc pipe choke's will only work over
a 4-5 to 1 freq range... then they resonate on the upper freqs. The problem
with
those chokes is the same as a plate choke in an amplifier. C between turns
will
resonate with the coil.
## I also have a 17" long bead balun.. made from type 75 [ might be 77]
large beads [1" od x .5" id x .875" long beads] That balun is good down to
3.5 mhz.
I require 24" long..if using type 43....and want it work down to 3.5 mhz.
## OK, how abt this concept. Can large style type 75/31 beads be placed at
the tail
end of a string of type 43 beads ?? [To increase the total Z] IE: a string
of
type 43 beads.... followed by as bunch of large type 75/77 beads. The #43
beads
at the ant end of the string..... # 75/77/31 beads facing the ham shack.
There should be no heating of the # 75/31 beads .
## Do we really require 5 k choking Z ?? Has anybody actually toggled between
2 x identical yagi's .... one with 1 k of choke Z... and the other yagi with 5
K choke Z
..and then compared the f/b f/s and noise pick up ?? Or compared RFI,
etc ?
Detailed instructions and
> MEASURED data are on my website in http://audiosystemsgroup.com/RFI-Ham.pdf
>
> As to "hams are cheap" -- yes we are, but we are also stupid, buying into
> advertising claims, and buying inferior junk from companies run by salesmen
> that know nothing but advertise in QST for 40 years. The common mode chokes
> described in my tutorial (cited above) are fully documented, and the tutorial
> completely describes how they work. And I'm not selling anything! The cheap
> junk you buy from salesmen like Amidon, Palomar, and their ilk is completely
> undocumented and vastly inferior.
## we have arced amidon/palomar/palstar baluns . They were all insulation
breakdown
problems caused by minimal insulation of some connections. The baluns that
were tried
on the 50 ohm side of a T type tuner [ with open wire line on output side]
were all a disaster
The palstar cracked into 3 x pieces ! Even the hb one with 8 x #43 big
cores and rg-400
over heated... with only 2.5 kw of average power. We gave up with the concept
of using a
1:1 choke balun on the input side of a tuner. Several 4:1 baluns were then
tried on the
450 ohm output side.. and all bit the dust. The only ones that work good,
don't blow up,
were the 4:1 units made by AS. [ they came with a life time warranty]
Later... Jim VE7RF
They re-sell Fair-Rite parts at huge mark-
> ups (4-5X cost), but disguise that fact by creating their own new part
> numbers. That so-called technical data on their websites is next to useless!
>
> 73,
>
> Jim K9YC
>
>
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|