RF Inquiry HI-Q Filter CF5KV

I think these are typically a PVC pipe with uhf females on the ends, between 
them around 10 or 12 inches of small 50 ohm coax with teflon dielectric and 
beads strung on it.  they are aka 1:1 ununs, common mode filters, and line 
isolators.  they stuff foam into the pipe so the beads don't clack together 
and break.  that unfortunately also holds in heat.   so you can make one 
without too much trouble and i would leave off the foam and pvc, but it 
might wind up costing more to make it than to buy it (well, not the RF 
Inquiry ones).
The chief advantage to making one is you get to design it to do well, what 
you want it to do.
My experience with the mfrd. ones for example is their attenuation begins to 
rapidly fall off below 7 mhz.  they do not do all that well on 75 m. and are 
transparent at 160.  if you want one to work on 3.5 and 1.8 mhz you could 
make one with mix 77 beads but it might be cheaper to wind 20-30 turns of 
coax on a paint bucket or garbage can.

rob/k5uj

----- Original Message -----
From: Jim Lux 
To: 
Sent: Monday, February 21, 2005 7:35 AM
Subject: [TowerTalk] RF Inquiry HI-Q Filter CF5KV


> I think these are typically a PVC pipe with uhf females on the ends,
between
> them around 10 or 12 inches of small 50 ohm coax with teflon dielectric
and> beads strung on it.  they are aka 1:1 ununs, common mode filters, and line
> isolators.  they stuff foam into the pipe so the beads don't clacktogether> and break.  that unfortunately also holds in heat.   so you can make one
> without too much trouble and i would leave off the foam and pvc, but it
> might wind up costing more to make it than to buy it (well, not the RF
> Inquiry ones).
> The chief advantage to making one is you get to design it to do well, what
> you want it to do.
> My experience with the mfrd. ones for example is their attenuation beginsto
> rapidly fall off below 7 mhz.  they do not do all that well on 75 m. and
are> transparent at 160.  if you want one to work on 3.5 and 1.8 mhz you could
> make one with mix 77 beads but it might be cheaper to wind 20-30 turns of
> coax on a paint bucket or garbage can.Which brings up the interesting point... Is there a manufacturer of these
sorts of things that tells you what the innards are?  Or that will build to
order (at a low cost..)?  Then you get the advantage of making your own
evaluation of expected performance, but also the quantity purchase of
components and assembly by someone who does a lot of it.  I'd much rather
have connectors installed by someone who does it 200 times a day than
someone (like me) who does it every few months.  It IS a craft or art, and
regular daily practice helps a lot.

Is this a market niche that is not being addressed?

Jim, W6RMK
>

Cable Xperts advertises that they will build custom coax jumpers
to order. It wouldn't surprise me if you could arrange to send them
the beads and let them do the assembly. Might be a good thing
for a group buy. You can also just buy a pre-made RG-8X jumper
and wrap several turns around an FT-240-77 core if you need a
good common-mode choke for the lower HF bands (2 cores
in series with 6 turns each will give about 1100 ohms common-
mode impedance on 160 meters and 900 ohms on 80 meters).
You can easily get 5 or 6 turns through the core even with PL-259's
installed. Cost would be about $15.00 for the jumper and $10 for
the 2 cores.  If you need better suppression towards the middle of
the HF range, you can substitute FT-240-43 cores in place of the
-77 ones. The 43 cores will give an impedance peak around
12 MHz.

73 de Mike,
W4EF.................................................................> Which brings up the interesting point... Is there a manufacturer of these
> sorts of things that tells you what the innards are?  Or that will buildto> order (at a low cost..)?  Then you get the advantage of making your own
> evaluation of expected performance, but also the quantity purchase of
> components and assembly by someone who does a lot of it.  I'd much rather
> have connectors installed by someone who does it 200 times a day than
> someone (like me) who does it every few months.  It IS a craft or art, and
> regular daily practice helps a lot.
>
> Is this a market niche that is not being addressed?
>
> Jim, W6RMK
> >
>

----- Original Message -----
From: Jim Lux 
To: "Jim Lux" ; "Rob Atkinson, K5UJ"
; 
Sent: Monday, February 21, 2005 9:50 AM
Subject: Re: [TowerTalk] RF Inquiry HI-Q Filter CF5KV> Cable Xperts advertises that they will build custom coax jumpers
> to order. It wouldn't surprise me if you could arrange to send them
> the beads and let them do the assembly. Might be a good thing
> for a group buy.That's half way to a solution. If you're buying toroids in real quantity,
they get a LOT cheaper (from reduced shipping costs, if nothing else). I was
just thinking that there are several suppliers of bead baluns in a PVC pipe.
Would it affect their sales materially if they were to tell you what
material and how many beads of what size?  Probably not, and then you could
buy the product without worrying about what the performance might be.

I can understand that if there were some proprietary design that they didn't
want to have stolen, but I don't really think that's the case here.  The NRE
for this kind of product is very, very low, and the fraction of time spent
figuring out what beads to use is correspondingly low (assuming they don't
just copy the design out of a handbook).  Therefore, the only real
distinguishing feature between the various makes is the manufacturing cost
and quality, which is something that will be different for a competitor (not
necessarily better or worse, but just different).  For instance, a mfr might
get a real good price on beads that another didn't. (perhaps due to large
quantity, or physical location, or just better shopping around), but
ultimately, the beads are a commodity item.

You bring up an interesting idea, though.  Maybe CableXperts would be
willing to do all the steps, including procuring the ferrites.  Sometimes,
all it takes is an indication from the market that a product is needed.


 You can also just buy a pre-made RG-8X jumper> and wrap several turns around an FT-240-77 core if you need a
> good common-mode choke for the lower HF bands (2 cores
> in series with 6 turns each will give about 1100 ohms common-
> mode impedance on 160 meters and 900 ohms on 80 meters).
> You can easily get 5 or 6 turns through the core even with PL-259's
> installed. Cost would be about $15.00 for the jumper and $10 for
> the 2 cores.  If you need better suppression towards the middle of
> the HF range, you can substitute FT-240-43 cores in place of the
> -77 ones. The 43 cores will give an impedance peak around
> 12 MHz.
>
> 73 de Mike,
> W4EF.................................................................
>

Take a look at this site:  http://users.erols.com/rfc/Choke%20Kit.htm

This item is a 2 ft piece of RG-213 with a male and female UHF connector 
attached. I have one but it has not been tested.


Here is an excerpt from their page on this product:

Specifications
Frequency:  1.8 ? 60 MHz
Through-line impedance:  50 ohms (nominal)
Insertion loss: less than 0.2 dB at 60 MHz
Common mode inductance: 24 uH (nominal)
Power handling: 2kW continuous duty
Load mismatch tolerance:  greater than 5:1 VSWR at 2kw
Connectors:  PL-259 and SO-239
Ferrite material:  seven Fair-Rite P/N 2643102002 (850 Initial Perm, 2900 
gauss at 10 oersteds, nickel-zinc)


73
Jim W7RYAt 10:08 AM 2/21/2005, Jim Lux wrote:

>----- Original Message -----
>From: Jim W7RY 
>To: "Jim Lux" ; "Rob Atkinson, K5UJ"
><k5uj@hotmail.com>; 
>Sent: Monday, February 21, 2005 9:50 AM
>Subject: Re: [TowerTalk] RF Inquiry HI-Q Filter CF5KV
>
>
> > Cable Xperts advertises that they will build custom coax jumpers
> > to order. It wouldn't surprise me if you could arrange to send them
> > the beads and let them do the assembly. Might be a good thing
> > for a group buy.
>
>That's half way to a solution. If you're buying toroids in real quantity,
>they get a LOT cheaper (from reduced shipping costs, if nothing else). I was
>just thinking that there are several suppliers of bead baluns in a PVC pipe.
>Would it affect their sales materially if they were to tell you what
>material and how many beads of what size?  Probably not, and then you could
>buy the product without worrying about what the performance might be.
>
>I can understand that if there were some proprietary design that they didn't
>want to have stolen, but I don't really think that's the case here.  The NRE
>for this kind of product is very, very low, and the fraction of time spent
>figuring out what beads to use is correspondingly low (assuming they don't
>just copy the design out of a handbook).  Therefore, the only real
>distinguishing feature between the various makes is the manufacturing cost
>and quality, which is something that will be different for a competitor (not
>necessarily better or worse, but just different).  For instance, a mfr might
>get a real good price on beads that another didn't. (perhaps due to large
>quantity, or physical location, or just better shopping around), but
>ultimately, the beads are a commodity item.
>
>You bring up an interesting idea, though.  Maybe CableXperts would be
>willing to do all the steps, including procuring the ferrites.  Sometimes,
>all it takes is an indication from the market that a product is needed.
>
>
>  You can also just buy a pre-made RG-8X jumper
> > and wrap several turns around an FT-240-77 core if you need a
> > good common-mode choke for the lower HF bands (2 cores
> > in series with 6 turns each will give about 1100 ohms common-
> > mode impedance on 160 meters and 900 ohms on 80 meters).
> > You can easily get 5 or 6 turns through the core even with PL-259's
> > installed. Cost would be about $15.00 for the jumper and $10 for
> > the 2 cores.  If you need better suppression towards the middle of
> > the HF range, you can substitute FT-240-43 cores in place of the
> > -77 ones. The 43 cores will give an impedance peak around
> > 12 MHz.
> >
> > 73 de Mike,
> > W4EF.................................................................
> >
>
>_______________________________________________
>
>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 at contesting.com
>http://lists.contesting.com/mailman/listinfo/...

On Mon, 21 Feb 2005 11:19:19 -0800, Jim W7RY wrote:

>Here is an excerpt from their page on this product:
>Ferrite material:  seven Fair-Rite P/N 2643102002 (850 InitialPerm, 2900 

This core has a resonant frequency of about 400 MHz. Below that 
frequency, a single turn (that is, the coax going through it) will 
look inductive, and above it will look capacitive. It's going to 
have fairly low loss at HF, so there shouldn't be a lot of 
dissipation. 

I'm looking at a plot of the Z of one core, and the product you 
are citing uses seven. Their impedance adds in series. One core is 
roughly 85 ohms at 10 MHz, 170-180 at 30 MHz. The parallel 
equivalent R component is roughly 270 ohms at resonance, and I 
would guess it's in the same order of magnitude at HF. 

Another point -- any resistive component will cause heating with 
common mode current flow, while any reactance can resonate with 
the common mode length of a feedline (which is why Tom's 
applications note on baluns talks about feedline length). Now, 
let's say that the resonance is occuring -- now, the only thing 
limiting common mode current (that is, shield current) is the 
resistive component that the balun contributes! I would expect the 
resistive component to be pretty small on this balun. 

This product doesn't look like it would have enough Z to make a 
decent balun below 20 meters, but perhaps Tom can shed some light 
on this. Tom --what do you think the common mode Z of a balun 
ought to be?  And what do you think about the tradeoff between R 
and X (that is, dissipation vs: interaction with the feedline's 
lengh)?

If I were using these parts to make a balun, I would use at least 
twice as many of them. BTW -- I just measured the Palamar RG8 
balun kit -- it is a #31 part, but the same size, I think. They 
use six of them, and it doesn't have much Z below 10 MHz either!

Here's a tutorial I'm writing for sound contractors on ferrites 
that you might find helpful. It's in progress, and not complete. 
I'm still adding and revising it as i learn more. 

http://audiosystemsgroup.com/SAC0305Ferrites....

Jim Brown  K9YC

Thanks, I did not know about this. I looked for a price but did not find 
one.

The 213 is a step in the right direction with the higher breakdown voltage 
but including 160 in the coverage is a stretch.  I have a hunch the beads 
are 43.
Somewhere on there they say the Z on 160 is 270 ohms or in that ballpark.   
That's not really enough to do much good.  They say their chokes add up to 
the equivalent of 28 feet of feedline in 9 turns of coil.  As a coax choke 
that would be okay on say, 15 meters but I think on 1.8 mhz you need about 4 
times that much feed on a wider diameter form--I'd use 16 or 18 inches.

I'll give them this--they come forth with some helpful specs about their 
product, which is probably fine for higher frequencies.
As always, my opinions only.


Rob/K5UJ



<<<Take a look at this site:  http://users.erols.com/rfc/Choke%20Kit.htm

This item is a 2 ft piece of RG-213 with a male and female UHF connector
attached. I have one but it has not been tested.


Here is an excerpt from their page on this product:

Specifications
Frequency:  1.8 – 60 MHz
Through-line impedance:  50 ohms (nominal)
Insertion loss: less than 0.2 dB at 60 MHz
Common mode inductance: 24 uH (nominal)
Power handling: 2kW continuous duty
Load mismatch tolerance:  greater than 5:1 VSWR at 2kw
Connectors:  PL-259 and SO-239
Ferrite material:  seven Fair-Rite P/N 2643102002 (850 Initial Perm, 2900
gauss at 10 oersteds, nickel-zinc)>>>>

One more point I'd like to make I just thought of this morning is that if 
you decide to make your own line isolator with beads, it is very important 
that you buy from a vendor who can specify the mix.  I made the mistake of 
buying them from RF Parts.  They are a great vendor of a lot of good 
products but in the case of ferrite chokes, they do not specify the mix.  
This was my mistake -- buyer beware.  I wound up with chokes that measured 
low Xl at HF and almost nothing on 160.  I don't know what the mix was but 
it apparently wasn't 43 or 77.  but at the time they were about 50% the cost 
of other vendors.  This was another case of you get what you pay for.

Rob/K5UJ

<<<Which brings up the interesting point... Is there a manufacturer of these
sorts of things that tells you what the innards are?>>>

as far as i know, the pvc pipe guys don't say what's inside.  i have not cut 
one open to find out, however i have read about them getting fried and the 
owner finding remnants of charred foam.
the coax with beads on it guess seems to have a reasonable likelyhood of 
being correct to me.

There is one mfr that sells them as coax with uhf males, beads strung on the 
coax and covered with shrink wrap.  I like that assembly method better.

The coax I have seen used (in balanced tuners) is the teflon stuff (i think 
it is RG303) which is about the same diam. as 58 and I bet that is what is 
used in these pvc pipe isolators.  Why not use 213 you may ask.  Good 
question and in fact when i make one that's what i use.
I suspect 303 is used because it can handle ham limit power but is small 
enough to take small (cheaper) beads.  the resulting product is smaller, 
weighs less and is cheaper to ship.
But 213 handles much more voltage and is therefore more robust.  I find it 
is also easier to solder pl259s on it.  But it needs bigger heavier beads 
and the choke is going to wind up being larger and heavier.  If you make it 
for yourself this doesn't matter because you aren't shipping it to anyone 
for profit.
So you can still make your own bead balun or unun and you have a choice of 
coax and beads so you can make the mother of all isolators if you want to 
and use a mix that focuses on a range of frequencies or even have 43 and 77 
if you want to cover MW and SW as they aren't really hard to make.  why 
doesn't a business make them to order for hams?  the market.   custom 
isolators would not sell to cheap hams.  A kit maybe but not assembled.  
Custom work for hams is normally limited to things that are difficult to 
homebrew, are very expensive and the ham market for them is very very small. 
  Things that require expensive shop tools and parts that can't be purchased 
in small quantities for example.

rob/k5uj

BTW if you have trouble soldering connectors you can buy a made up jumper of 
a foot or more and clip split beads on it and still have your choice of 
length, coax, connectors and bead mix.
You can get a connector on one end and have the other end open for a 1:1 
balun.



  <<<Or that will build to
order (at a low cost..)?  Then you get the advantage of making your own
evaluation of expected performance, but also the quantity purchase of
components and assembly by someone who does a lot of it.  I'd much rather
have connectors installed by someone who does it 200 times a day than
someone (like me) who does it every few months.  It IS a craft or art, and
regular daily practice helps a lot.

Is this a market niche that is not being addressed?

Jim, W6RMK>>>