[50mhz] Re: 50mhz digest, Vol 1 #171 - 4 msgs
Larry Himes, Jr
[email protected]
Fri, 8 Nov 2002 23:31:46 -0500
Hello to N5WBI,
My callsign is KG9KV and I would like to suggest an antenna to you. It is a
copper "J" pole that KG9MB and myself built for 6 meters. You will need the
following parts:
one stick of 1/2" x 10' copper pipe
two sticks of 3/4" x 10' copper pipe
one 3/4" coupler
one 3/4" end cap
one 3/4" x 1/2" x 3/4" "T"
one 1/2" 90 degree elbow
one 1/2" end cap
one 3/4" ground clamp
one 1/2" ground clamp
twelve #6 x 1 1/4" Machine Screws
twelve #6 Nuts
twenty-four #6 lock washers
Cut four feet off of one of the 3/4" x 10' copper pipes and leave the other
3/4" x 10' pipe the full length. The four foot section of 3/4" pipe will be
coupled to the end of the 3/4" x 10' pipe to create the radiator. The six
feet that is left over from the 3/4" pipe can be cut to what ever length you
want for mounting the antenna. Next cut 56 inches from the end of the 1/2"
copper pipe, then cut a six inch length from what is left of the same 1/2"
pipe. There will be three sections of 1/2" pipe that are 6", 56" and 58".
The 58" section of the 1/2" pipe will be placed inside of the 3/4" pipe
radiator section for more support.
Now that all of the sections are cut you can start assembling it. The first
thing to do is to put the 1/2" x 6" section of pipe into the 1/2" port of
the "T" that is at a right angle to the body of the "T". The opposite ends
of the "T" are 3/4". Drill a small hole through the center of the 1/2"
sleeve of the "T" and put one of the #6 sheet metal screw through it. Place
a lock washer on the bolt before inserting it into the hole you just
drilled. Then place a #6 lock washer onto the open end of the sheet metal
screw and put a nut on the screw and tighten it down. You can solder the
junction if you wish. Use the method for holding the junctions of pipe as
was described earlier. Place the 90 degree elbow at the end of the 1/2"
pipe so that the open end of the elbow is in alignment with one end of the
"T". Bolt this junction with one of the #6 sheet metal screws. Place the
3/4" x 10' pipe in the end of the "T" that is aligned with the elbow and
bolt this junction. Next place the 1/2" x 58" pipe inside of the 3/4" x 10'
pipe so that 29" of the 1/2" pipe is exposed. Measure from the end of the
3/4" pipe down 18" and drill a hole through both pipes. Secure this
junction as described above with a #6 machine screw. Slide the 3/4" coupler
over the end of the 1/2" pipe that was just installed and onto the 3/4" x
10' pipe end. Drill a hole through the coupler wall and the end of the 3/4"
pipe then bolt the junction. Place the 3/4" x 4' section of pipe over the
1/2" pipe and into the coupler. Drill a hole in this end of the pipe and
the coupler then secure the junction with a screw, washers and nut. Measure
up 18" from the coupler and drill a hole through both pipes and secure the
junction with a screw. Place the end cap onto the end of the 3/4" x 4' pipe
and secure it with a screw. Next place the 1/2" x 56" pipe into the open
end of the elbow. Drill a hole through the sleeve of the elbow and the 1/2"
pipe then secure it with a machine screw. Place the 1/2" end cap onto the
open end of the 1/2" x 56" pipe and secure it. The last part for assembling
the antenna is to place what ever length of 3/4" pipe into the bottom end of
the "T" for mounting the antenna. The open end of the "T" will be opposite
from the two parallel elements of the antenna. The antenna assembly is now
complete.
Moving on to the matching of the antenna:
Place the 3/4" ground clamp onto the 3/4" pipe 7" above the 1/2" x 6"
separator pipe. Next place the 1/2" ground clamp 7" above the 1/2" x 6"
divider pipe. Tighten both clamps. Separate the braid and the center
conductor at one end of the coax you are using to feed the antenna enough so
that the outer braid is connected to the clamp on the 1/2" pipe and the
center conductor is connected to the clamp on the 3/4" pipe. This is the
best matching point that I have found. The SWR stays between 1.2:1 and
1.3:1 for the power input range of 10 watts to 800 watts between 50MHZ and
51MHZ. The SWR goes up to 1.5:1 at 54MHZ. The antenna gain is near 6dBd.
We have experimented with this antenna a while and have very good results
with it for DXing. It is also good for use with repeaters. We have no
problem getting into Indianapolis repeaters from Plymouth, Indiana. This is
approximately 160 miles with 10 watts output from the transmitter when the
band is open. These are FM repeaters and the AM, SSB and CW results are
much better.
I stated sheet metal screws earlier in the e-mail but I meant machine
screws. I apologize for that and I hope this e-mail helps you out. It
sound complex but when you start building the antenna it is not difficult.
Please let me know if you build it and what the results are. The antenna
cost us about $25.00 for all of the parts. The 1/2" pipe inside of the 3/4"
radiator at the coupler is needed because with out it the radiator has a
tendency to bend.
Larry KG9KV
----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: Friday, November 08, 2002 9:08 PM
Subject: 50mhz digest, Vol 1 #171 - 4 msgs
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> Today's Topics:
>
> 1. Home-Brewing a 50 MHz Dipole ([email protected])
> 2. RE: Home-Brewing a 50 MHz Dipole ([email protected])
> 3. Re: RE: Home-Brewing a 50 MHz Dipole (Sparks72)
> 4. Re: Home-Brewing a 50 MHz Dipole (Wayne)
>
> --__--__--
>
> Message: 1
> Date: Thu, 7 Nov 2002 10:41:48 -0600 (CST)
> To: [email protected];, [email protected];, [email protected]
> From: [email protected]
> Reply-To: [email protected]
> Subject: [50mhz] Home-Brewing a 50 MHz Dipole
>
> I have tried (at least twice now ...) to home-brew a dipole antenna cut to
the USB calling frequency of 50.125 MHz. The first one I built used "cheap"
stranded hook-up wire. The second one used heavier wire (solid). Both
failed miserably. The SWR's were off-scale, even though I had cut and
trimmed each of the dipole legs using the "standard" equation (468/F).
>
> Am I missing something here? Thankfully, all I've "lost" is a few feet of
wire and a couple of hours. I really don't want to pay the big bucks to buy
an antenna when I can home-brew one on the cheap.
>
> Thanks in advance for your help!
>
> 73,
>
> Steve N5WBI
> Houston TX EL29
>
> --__--__--
>
> Message: 2
> Date: Thu, 7 Nov 2002 15:07:42 -0600 (CST)
> To: [email protected];, [email protected]
> From: [email protected]
> Reply-To: [email protected]
> Subject: [50mhz] RE: Home-Brewing a 50 MHz Dipole
>
> Let's see ... Eight responses in less than 2 hours! Awesome!
>
> Thanks to everybody who replied! Here's a synopsis of the
> responses that I received.
>
> [1] Check your coax to make sure it and the connectors are
> in good shape. Coax and connectors degrade over time.
>
> [2] Make sure that the length of your coax feed line is
> ODD multiples of 1.4 wavelength.
>
> [3] Use 9913 flexible coax instead of the RG-XX type.
>
> [4] Cut the dipole legs too long to begin with, then trim
> as you tune. Use the "sweep" method (with proper ID's, of
> course) to check the SWR as you move up in frequency,
> starting at 50.000 MHz.
>
> [5] Adjust the cut length of each dipole leg for velocity
> factor (if you're using insulated wire). The velocity
> factor is around 0.9, so the equation becomes 468/F * 0.9
> Or, you could use the standard equation and trim for best
> SWR.
>
> Like I said, LOTS of good suggestions!
>
> Thanks, everybody! I'll let you know how all of this
> turns out.
>
> 73,
>
> Steve N5WBI
> Houston TX EL29
>
> --__--__--
>
> Message: 3
> Date: Thu, 07 Nov 2002 14:14:10 -0700
> From: Sparks72 <[email protected]>
> To: [email protected], [email protected]
> Subject: Re: [50mhz] RE: Home-Brewing a 50 MHz Dipole
>
> Regarding cutting a dipole:
> I use an MFJ-259B SWR VHF/HF SWR Analyzer and that is one of the best
> investments I have ever made. It tells you the resonant frequency of the
> antenna, impedance, and SWR and it is so easy, thast it takes all the
> work out of the trumming and cutting and the Biggie is: YOU DON'T HAVE
> TO TRANSMIT ON THE AIR, even though the band has been so dead from this
> area.
> My opinion, for what it is worth.
> 73's de Stan W5ZF (In the Black Hole)
> Albuqerque, New Mexico DM-65
>
>
> --__--__--
>
> Message: 4
> From: "Wayne" <[email protected]>
> To: <[email protected]>, <[email protected]>
> Subject: Re: [50mhz] Home-Brewing a 50 MHz Dipole
> Date: Thu, 7 Nov 2002 15:21:32 -0800
>
> Dipole should be simple and easy.
> Having built mine as a simple 40, then 40/20 (2 sets of wires, common
> center), and then adding W2AU 1:1 balun.
> I use the formula, 234/F for the length of each side, and then add a
foot,
> and trim downward.
> Check at lowest frequency you can, then highest.
> Allow a bit for wrap at insulator, and so on.
> the 468/F gives you the 1/2 wave dimension (aprox.), and each leg needs
to
> be half of that.
> Could it be you tried an actual full wave dipole (each leg 1/2 wave?
>
> Wayne WA2YNE
>
>
> ----- Original Message -----
> From: <[email protected]>
> To: <[email protected]>; <[email protected]>; <[email protected]>
> Sent: Thursday, November 07, 2002 8:41 AM
> Subject: [50mhz] Home-Brewing a 50 MHz Dipole
>
>
> > I have tried (at least twice now ...) to home-brew a dipole antenna cut
to
> the USB calling frequency of 50.125 MHz. The first one I built used
"cheap"
> stranded hook-up wire. The second one used heavier wire (solid). Both
> failed miserably. The SWR's were off-scale, even though I had cut and
> trimmed each of the dipole legs using the "standard" equation (468/F).
> >
> > Am I missing something here? Thankfully, all I've "lost" is a few feet
of
> wire and a couple of hours. I really don't want to pay the big bucks to
buy
> an antenna when I can home-brew one on the cheap.
> >
> > Thanks in advance for your help!
> >
> > 73,
> >
> > Steve N5WBI
> > Houston TX EL29
>
>
>
> --__--__--
>
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