<%@ Language=JavaScript %> JAMES JPOLE 2M 440 ROLL UP ANTENNA REVIEW

JAMES JPOLE 2M / 440 ROLL UP ANTENNA REVIEW BY JIM BAUDO

THE MAIN QUESTION WE HAVE RECEIVED ABOUT THE ANTENNA WAS THE POWER WATTAGE RATING. I EMAILED JIM AND HE RESPONDED WITH THE FOLLOWING. 
The 2 meter /440 roll up antenna can handle up to 500 watts, It is a good addition to any Emergency operator or Search and Rescue member also works fine for those that must travel and operate from the motel or hotel rooms...works great hanging in a window.
I WAS NEVER ABLE TO GET A SAMPLE ANTENNA FROM THE MANUFACTURE SO I DECIDED TO MAKE MY OWN. 2 METER ANTENNA, HERE ARE THE DETAILS
A 2-Meter 300 Ohm TV Twin-lead Roll-up J-pole.

The antenna that we are going to MAKE will be made from ordinary 300-Ohm TV Twin lead wire. This wire is available at RADIO SHACK, AND almost every hardware STORE, AND HAMFESTS.

SEE diagram below.

Now, on to the step by step ASSEMBLY.

Tools: DRILL AND 1/8" DRILL BIT, OR A SMALL PUNCH, Ruler, Wire strippers, Wire Cutters, SOLDER AND Soldering Iron.

  1. Measure 60" of 300-OHM Twin lead and CUT IT. If this is your first attempt at ANTENNA building, FOLLOWING THE STEP BY STEP DIRECTIONS ARE VERY IMPORTANT.
     
  2. Remove the center insulation from the bottom 1-inch of 300-OHM twin lead. Strip the insulation off of the bottom section of twin lead (only 1/2 " ON EACH SIDE). BEND AT 90 DEGREES TOWARD CENTER AND SOLDER THEM TOGETHER.
     
  3. From the splice you just made at the bottom, measure up about 1 1/4 " and remove 1/8 " of insulation from each conductor. This is where we will be attaching the coax.
     
  4. From the SOLDERED splice measure up one side 16 ½" . CHECK THE MEASUREMENT TWICE. Cut a gap on this side about ¼" wide. MAKE sure to remove the WIRE material from the notch.
     
    5.
  5. Attach some LIGHTWEIGHT coax to the opened area of the wire about 1 ¼" from the splice. SOLDER THE FEED POINT OF THE COAX CENTER CONDUCTOR TO THE LEFT, THE LONGER SIDE. The shield of the coax MUST connect to the notched, SHORTER side.
     
    6.
  6. DRILL OR PUNCH A HOLE IN THE TOP OF TWIN LEAD AND ATTACH A STRING TO THE TWIN LEAD AND ATTACH TO THE CEILING IF INDOORS, OR IF OUTDOORS TO A TREE BRANCH OR TO SOMETHING AT LEAST 60 INCHES AWAY FROM ANY METAL. THE FARTHER AWAY FROM OTHER METAL OBJECTS THE BETTER IT WILL PERFORM. IF YOU HAVE A SWR METER, YOU CAN CUT TO YOUR DESIRED CENTER FREQUENCY.
     
  7. TUNING TO YOUR FREQUENCY. APPLY POWER ON THE FREQUENCY YOU WISH AS A CENTER FREQUENCY, I LIKE TO USE 146.00 FOR FM AND 144.2000 FOR SSB. CUT 1" OFF THE TOP BETWEEN EACH SWR MEASUREMENT. AS THE SWR DROPS, CUT 1/2" OFF From the splice. WHEN THE SWR IS 2 TO 1 START CUTTING OFF 1/8 TO 1/4" TILL YOU GET IT DOWN TO 1.5 TO 1. I HAVE FOUND THAT MOST OF THE TIME IS  IT IS HARD TO GET IT BELOW 1.5 TO 1. IF YOU DO NOT HAVE A SWR METER Measure the total length to 54 " and trim the top. I HAVE FOUND 54' IS ABOUT RIGHT FOR FM.
     
  8. Attach a suitable connector on the end of the coax for your transmitter HAVE FUN. EMAIL ME WITH YOUR RESULTS AND COMMENTS.

Note: The antenna can be hung from almost anything using some string through a hole in the TWIN LEAD AT the top.

COMMENTS:
From: "KG4OHH@Cox" <KG4OHH@Cox.Net> 
To: JIMBAUDO@YAHOO.COM
Subject: From URL twin lead J-pole
Date: Thu, 30 Dec 2004 22:56:58 -0800
hello
just put together the twin lead J pole that I found on your web page
 
cut twin lead to 60 inch...
antenna was tested pined to all sheet rock wall wirh nothing on the other side and about 20 Ft of RG 58/U 50 ohm coax
 
works like a champ on 2 meters, had to make some Adjustment to the short stub side of the J-pole, had to cut 1 inch and a 1/4 to bring the SWR from when I first tested it out with your calculations, on
146.000 SWR= 2.3
144.000 SWR= 1.2
for what I can figger out, I started to trim off the top of the antenna 1/2 inch and SWR did not change at all, I took another 1/2 inch off the top and SWR on 146.000 went up to 2.5
 
I then took some out of the notched end (short stub) 1/2 inch at a time SWR started to come down from 2.5 to 2
I took another 1/4 inch off the shortened SWR went down from 2 to 1.8, did the same again, SWR went from 1.8 to 1.4 on 146.000 & on
144.000 SWR= 1.1
145.000 SWR=1.8
 
I can live with this
 
on 440.000 band
SWR 
420.000 SWR = 1.6  very good
425.000 SWR = 3.0 ???
430.000 SWR = 1.4  very good
435.000 SWR = 3.1 ???
440.000 SWR = 1.2 very good
445.000 SWR = 3.2 ???
450.000 SWR = 1.8 ok
 
I am no going to play with it, it is under 2.0 and seams to preformed well
I will however buy some PVC tubing tommrow and install it inside with end caps
and a hole at the bottom for the coax to come out.
when I have finished with the antenna I will email U a pic, this antenna is going to be mounted
out side on the chimney Brest at about 40 Ft off the ground
 
thanx for the info
job well worth doing 73
 
Changes i made
on the bottom of the twin lead, an soldered wires togeather, and go up to where the coax is joined insted of cutting th jacket off, I slid it down and oldered it on
makes it E-Z'er...
 
Thank You
   Mark
       K4EEZ
Ham Radio Community
Email: K4EEZ@Cox.Net
Www.Qrz.Com/K4eez

 
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