++++++++++++++++++++++++++++
Date: Sat, 26 May 2001 14:13:26 -0600
From: "Santa Fe" <kt5x at cnsp.com>
Subject: [Elecraft] Re: 9269 cable

Look.  Feedlines do NOT have to be matched.  You can use any wire length,
and feed it with virtually any coax and any HF frequency (well, I am over
simplifying).

IF

The coax is (relatively) short, and you use a tuner.  The word relatively
has to do mostly with the frequency.  The higher the frequency, the shorter
relatively short is, and...

That dadblamed Elecraft tuner is one heck of a tuner.

So, let's put it this way.

If you put up a non-resonate (prefered) dipole  (prefered to be non-resonate
because even multiples of half waves pose a theoretically infinite
impedance), may I humbly suggest either 44 feet for 10-40 or 88 feet for
10-80, and feed it with say 20 to 50 feet of thet thar coax, and use your
tuner, you are in business.

Will you have any losses?  Yes, but the loss will insignificant except on
ten meters where it won't be much.

BUT

you want a small balun on the antenna to keep the currents on the feedline
nice and balanced.  My balun is built into a piece of one inch PVC pipe and
weighs a few ounces.  Never found a commercial QRP balun and had to make it
myself.  Ask W1CG for advice.  He KNOWS baluns!  My baluns work thanks to
him.

Have fun!

FD
# 700
w5ya


> Well, here is another question for all you antenna guru's.
> Just pick up a large batch of Beldon 9269 coax at a local
> garage sale.
> Got it so cheap I couldn't pass it up.
> In checking the spec's on it, turns out its 93 ohm cable.
> Any suggestions as to how this could be used as feed
> line for portable setup!!
> It seems obvious that some type of matching network
> would have to be used.
> Currently building K1 #601 and will install the ATU.
> Tuner should handle this from the shack but I'm unclear
> as to what,  if anything,  would be needed to match it
> up to a dipole.
> Any suggestions?
>
> Thanks Jerry          N0JRN
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Date: Sat, 26 May 2001 16:13:10 -0400
From: "Don Wilhelm" <w3fpr at peoplepc.com>
Subject: Re: [Elecraft] 9269 cable

Jerry,
Useful stuff, it should match a quad loop rather nicely (single loop has
about 110 ohm feedpoint impedance)
Secondly, use two in parallel to create a 186 ohm shielded parallel
transmission line that you can run into the shack.
Yes, you could feed a dipole with it - the SWR should be about 2:1 on the
line.
73,
Don Wilhelm  -Chapel Hill, NC   W3FPR home page: http://www.qsl.net/w3fpr/
  QRP-L # 485   K2  SN 0020   mailto: w3fpr at arrl.net
++++++++++++++++++++++++++++++++++
Date: Sat, 26 May 2001 14:35:17 -0600
From: Larry East <w1hue at ida.net>
Subject: Re: [Elecraft] 9269 cable

At 01:37 PM 5/26/01 -0500, Jerry Ford wrote:
>Well, here is another question for all you antenna guru's.
>Just pick up a large batch of Beldon 9269 coax at a local
>garage sale.
>Got it so cheap I couldn't pass it up.
----snip----

Now you know why it was so cheap... :-)

Unless you are using several hundred feet of the stuff, there will be very 
little loss at HF resulting from the "mismatch". Anyway, the feed point of 
most antennas can vary from 40-90 ohms, so no big deal. But if you really 
feel the need to get closer to 50 Ohms, run two lengths of the coax in 
parallel! Yes, it works -- been there done that with RG-71 93 Ohm coax 
years ago that  I also got for next to nothing. I used BNC connectors and a 
"T" on each end to get the two pieces of coax in parallel. You can do the 
same with UHF T's.

72,
Larry W1HUE/7
++++++++++++++++++++++++++++++++++++++
Date: Sat, 26 May 2001 16:03:18 -0500
From: "George, W5YR" <w5yr at att.net>
Subject: Re: [Elecraft] 9269 cable

Probably the biggest problem you will have with the 93-ohm coax is that
your SWR meter is calibrated for a 50-ohm line, so it will not read
correctly on the 93-ohm line. You may see fairly large SWR *readings* but
this does not mean a large SWR and/or excessive losses. The meter in your
tuner is on the 50-ohm coax side so it will still read correctly even with
the 93-ohm coax on the output side to the antenna. But if you stick a
50-ohm meter directly in the 93-ohm line, expect some funny readings.

Use the coax, see if your rig can tolerate it - with or without a tuner -
and if  you, you got a good deal at the sale!   <:}

BTW,if you intend to use two lengths of the coax as a 186-ohm shielded
parallel-line affair, do NOT simply connect the coaxes in parallel. Connect
the shields together at the input end and to the tuner ground. Connect the
shields together but leave them unconnected at the antenna end. Connect
each inner conductor to the tuner output and to the feed points of the
antenna.

You end up with a shielded parallel line, but note that the coax cables are
not connected simply in parallel at each end. If you do connect them truly
in parallel, you will end up with a 46-ohm unbalanced coax cable. Take your
pick . . .

72/73, George  W5YR - the Yellow Rose of Texas QRP-L 1373 NETXQRP 6            
Fairview, TX   30 mi NE of Dallas in Collin county   EM13qe   
Amateur Radio W5YR, in the 55th year and it just keeps getting better!
Icom IC-756PRO #02121  Kachina #91900556  IC-765 #02437
+++++++++++++++++++++++++++++++
Date: Sun, 27 May 2001 13:53:06 -0700
From: "Ron D' Eau Claire" <rondec at easystreet.com>
Subject: RE: [Elecraft] Re: 9269 cable

There is also a nice little program available from a variety of free sites
that will let you put in the parameters for a dipole (feedline impedance,
length, radiator length, etc.) and will give you the feed point impedance at
the transmitter end, the efficiency of the antenna compared to an ideal
dipole, etc.

It works with radiators of any length, not just classic "dipoles" (1/2
wavelength radiators), and you can input the feedline specs you want.

It is a BASIC program and runs nicely in a basic window in my machines under
either Win 98 or Win ME. It was written by R.J. Edwards, G4FGOX. I did a
quick check with WebFerret and see that it is currently available at
http://www.mirror.ac.uk/sites/ftp.simtel.net/pub/simtelnet/msdos/hamradio/an
tenna.zip[peek]

Also, WebFerret appears to have found a visual basic version of the program
at:

http://www.tmiller.net/dipole.html

I haven't tried that one.

73,

Ron AC7AC
K2 # 1289
++++++++++++++++++++++++++++++++++++
Date: Sun, 27 May 2001 08:42:38 -0400
From: Charles Greene <cgreene at fctvplus.net>
Subject: Re: [Elecraft] Re: 9269 cable

At 09:04 AM 5/27/2001 -0400, baltimoremd at baltimoremd.com wrote:
>On Sun, 27 May 2001, Charles Greene wrote:
>
> > I submit that what you want to do is to make 1/2 the length of the dipole
> > plus the length of the feedline not be equal to 1/2 wavelength.  I wrote a
> > little Basic program to figure out the lengths feed line to use, with an
> > input of freq.  Unfortunately it only works on 1/2 wave dipoles.  I will
> > need to modify it for ;random length dipoles.
>
>Would love to have a copy of the program...either before or after the
>mods...sounds like it's something what would fit on the qrp web ring page,
>of course with your permission.

Let me modify it so that it will do any length of dipole.  Just needs a 
length of the dipole as an input instead of the frequency, as it calculated 
a 1/2 wave dipole from the frequency.  It also uses the velocity factor of 
the feed line instead of the type as an input.  I could modify it to input 
the feed line type, ie RG8 type, RG8X type, 9913 type and open wire types 
and it could use the four different values of velocity factor.  That just 
means I would have to look them up rather than each person.  I'll just 
includ the program in text instead of an attachment as some reflectors 
(like this one) are finicky about attachments.

Give me a few days as I have some other things to do.


73, Chas, W1CG
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