Tape Measure Antenna

The tape measure 2 meter antenna is a common, easy

project for amateur radio operators.  A great design is

online at http://home.att.net/~jleggio/projects/rdf/tape_bm.htm

or here.

This antenna uses schedule 40 PVC pipe.  The PVC frame

(with tees at both ends, not a cross at one end) weighs 152

grams (5.4 oz).

                                            a standard PVC antenna frame

Since this antenna is often used in backpacking, it would    

be nice to make this of 1/2" CPVC, a pipe material with smaller

mechanical dimensions and, thus, the possibility of lighter

weight.

This has been investigated by others, but apparently, no

CPVC crosses are manufactured.  (See

http://forums.qrz.com/showthread.php?t=145647, but

no real sources exist.  If you can find one, please let

me know!)

So, the trade-off seems to be that a 1/2" CPVC design

would require an extra tee and a non-linear design.

                                                                                                                                                             a standard PVC antenna with tape measure elements held by rubber bands

Two versions have been developed and built.  Their weights

are 128 grams and 127 grams (4.6 oz).  Thus, about 1 oz

can be saved with these designs.

For the designs, open this drawing.

The rest of the construction uses the instructions at

http://home.att.net/~jleggio/projects/rdf/tape_bm.htm or

here.

Note that at my local Ace Hardware, the CPVC tees

and 45º elbows for around 99 cents each.  As of May

2010, my local Ace reduce the price to 49 cents.  The local

Orchard Supply Hardware had the same for around

39 cents each, so shop around!  The farm supply

store also had these for 49 cents.  A nominal 10' piece of

CPVC 1/2" pipe is $3 to $4.  Home Depot doesn't

carry CPVC at all!

                                                     the 128 gram design

The PVC pipe is 0.84" in outside diameter, while the

CPVC pipe is 0.63" in diameter.  The PVC pipe has

a wall thickness of 0.06" and the CPVC has a wall

thickness of 0.08", so the CPVC is a stronger pipe. 

The original PVC model could be built using schedule

80 pipe instead of schedule 40, but that would add

additional weight.

                                                      the 127 gram design

It is possible to make the traditional, straight design using CPVC

by making a bushing so that a 1/2" PVC cross can be used.  Two

pieces of 1/2" schedule 80 PVC pipe will work.  The CPVC pipe

needs to be sanded to fit inside the schedule 80 bushings.  The weight

of this is also 127 grams.

One ham has taken a lathe and cut a PVC to make it a cross.  The total

weight of this assembly is 102 grams.  So, we've saved 50 grams, nearly

2 oz.  John Breckenridge will make these for fellow hams for $5 each.  If

you want one, email AD6YB@ARRL.net.

Comments and suggestions are welcome to AD6YB@ARRL.net.

Good building and 73s!

                                                                                                                                                                                                                   the design with the 1/2" PVC tee and two home-made bushings

          the design with a CPVC cross made from a CPVC tee

                            weight on the frame is 102 grams

www.winepi.com/tma.htm

last updated:  08/05/11 01:01:11 AM