|
|
|
|
From Shortwave Listener To Extra Class!
Here is my story and I'm sticking to it! I built a multiband dipole
as my first "HF" antenna for the ham bands. Actually it is a modification of
a dipole I had been using for SWL with an Icom R75.
I just got "a ham license" a few weeks ago. That's me with that big proud grin below!
Yes, this is an Extra call sign, AE5JU . . . I took and passed all three tests in one sitting, after just 3 weeks of cramming. My head still hurts! I took the tests... all of them... at a hamfest 10-11-08 in Pineville, a 3 hr drive, early on a Saturday morning. My wife drove while I reviewed study guides. I passed 35/35 on the Tech, 33/35 on the
General, and barely eeked by 38/50 on the Extra. Well, I
passed! And I cheated... I'm not new to electronics. I've been
playing with soldering irons since I was about 8 yrs old. I didn't
start from scratch on this, just had to learn regs and
such. I had gotten the Icom IC-R75 shortwave receiver early last spring and did what all newbies do. I stretched out a spool of hookup wire for a makeshift "random wire" antenna. Performance was so-so. I sought the advice of a friend from church who is a ham. He advised me to build an 80 meters dipole, and for SWL only, it would do well. He said, "Don't buy nuthin’. We (the ham club) are going to fix you up." One ham club member cut the
dipole center and end insulators from 1/4" plexiglass (seen below),
mounted an SO-239 socket in the middle, holes for the wire to tie onto,
and at the top to tie to a rope. Another gave me some RG-8/U and a
box of assorted fittings, and connectors. I had to buy only the mast
and brackets, rope, and some 14 ga insulated
wire.
I use a lot of heat shrink tubing . . .
I love the stuff. You can see in the picture
above
The mast is mounted to a wood
privacy fence on the side of my lot. I used regular TV type standoff
brackets, with two 10' sections of TV mast tubing. Through what was
to be the top end, I packed the end of the tubing about 4" deep with epoxy
putty to keep it from collapsing. I drilled through that and
inserted a piece of 3/8" all thread rod. Put a nylon insert lock nut
(aka "aircraft nut") on each side and snugged it up. The epoxy putty
kept it from egging on the end of the tube, and the nuts keep it
tight. Two more nuts held a little 2" marine type pulley in
place. I used some good 3/8" woven synthetic rope to go up over the
pulley, and down to tie to the top of the plexi center
insulator section. I can raise and lower that when needed, for
storms, repair, whatever.
The ends of the ropes from the end insulators are tied off to eyebolts in the top rail of the wood fence shown in the picture below. I later replaced the white rope in the pictures with black "550 parachute cord" (aka paracord) as the black wire and black paracord are practically invisible against most backgrounds, showing only if you get under it viewing it against the blue sky.
At first I had just the two 66'
legs for SWL. Great all the way down to 100 khz for beacons (ahh,
what great programming!) from 100-300 khz. The AM band comes in
great. 160 meters is almost useless, but on rare occasions I pick up
some hams on phone or CW. So, I got that all working well with the
R75.
The guys at the ham club and Steve K9ZW, a ham friend in another state, kept asking when I was going to get a ham license. Steve had gotten me the great deal on the NIB R75 from one of his ham friends. Steve’s a VE, too. And he has a popular ham blog that has quite a readership, reviews of new gear and other topical subjects. I had to take the original 80 meter
dipole down temporarily due to Extra legs were added to make this a multi band dipole similar to the one shown here on Hamuniverse. The original legs were for 80 meters, each leg cut to 66' (+ 2' folded back for tuning). I cut those for 3.55 mhz, not realizing at the time that was down in CW territory, and phone was higher. I later trimmed those back to 60' each side for 3.90 mhz for the phone portion of the band. 40 meters segments were added, each leg cut to 33' (+ 2' folded back for tuning). 20 meters segments were added, each leg cut to 16.5' (+ 1' folded back for tuning). All connections were soldered
and well insulated with heat shrink tubing and sealed with Scotch
Linerless Rubber Splice Tape 130C 3/4" wide. This is the butyl
rubber type tape that is soft and moldable, and commonly used for this
purpose. Now the modified dipole looked like
this:
Already I could tell that reception was better with the R75 on the 40 meter and 20 meter bands. Due to the emergency situation created by Hurricane Gustav, I decided I really needed to go on and get a ham license which you read about earlier. Steve sent me one of his "spare field radios", a Yaesu FT-897, complete with installed FP-30 110 vac power supply and LDG AT-897 tuner screwed on the side. It was a complete package except for an antenna. I had already modified
my SWL dipole for three bands, adding to the original 60' legs for 80
meters, a pair of 33' legs for 40 meters (which work for 15 meters, too),
and 16.5' legs for 20 meters. I did not know at that time about the
correction factors that make tuning faster in an update to
the multiband antenna
article here, or would have done it as
suggested.
A few more notes: I used plenty of "coax seal" (Scotch 130C) around the plugs/sockets of both antennas. I also added an "Ugly Balun" consisting of 17 turns of LMR-200 wrapped around a piece of 4" PVC pipe.
I had just gotten in some LMR-200. I ordered that as it is low loss coax, but is the same diameter as RG-58, to more easily wind a choke balun, aka "Ugly Balun", 17 turns on a piece of 4" pvc pipe. Home Depot sells little cut off pieces of PVC pipe so you don't have to buy 10' or anything like that. The wraps were held in place with Ty-Wraps through holes drilled in the pvc. Steve wrote this about me... http://k9zw.wordpress.com/2008/10/11/with-words-of-encouragement-newly-minted-ham-extra-class/ While at the hamfest I bought a B-Square Engineering 2m/70cm J-pole. It is stainless steel construction. Man, as much as I like DIY, I wouldn't fire up my torch to solder copper tubing at the price of the B-Square J-pole... just $40 in 2008 prices. While the antenna was lowered to add the balun I decided to take the mast down and attach the J-pole at the same time. The J-pole is attached to the top of the mast with two stainless radiator hose clamps. The RG-8/U I had previously attached to the dipole was moved over to the 2m antenna. OK, it is a little lossy at 70 cm, and not great at 2m, but better than the LMR-200 at that frequency. The LMR-200 is one continuous piece from the dipole center, around the pvc of the choke balun, and on down into my workshop/hamshack. The wood fence is 143' long, the eyebolts for the longest segments are about 2' from each end, and parachute cord tied from eyebolts to the end insulators. So that makes for a very shallow inverted Vee. The other two segments, 40 m and
20 m legs are tied to eyebolts further in toward the center mast, and form
slightly sharper inverted
Vees.
The white rope on the ends of the dipole elements in the
photos has been replaced with black 550 parachute cord. The black is
nearly invisible against most backgrounds. This is something to keep
in mind if you have HOA Nazis
lurking.
The droop in the wires looks bad from an end view above, but it is really not that bad. You just cannot pull the wire tight enough to get it perfectly straight. There is a huge difference in pull between almost straight and a little sag. Don't try to pull it straight. Just get it acceptable. There will be a lot less strain and less likely to break in windy conditions. Not mentioned before, GROUND. That metal building (my shop/ham shack) is on blocks on footings, and tied down on each corner to 6' long auger type anchors screwed into the ground. With the moist soil conditions here on the coast, and the large amount of area of the auger end of the anchors, they make good grounds. So my metal building is grounded on each corner, and I have additional ground wires from my transceiver and antenna tied to the nearest anchor as well. There are lots
of other ways to do this. So, how does it work? I was listed in the FCC ULS database late Thursday afternoon of 10-16-08. Friday morning (I work 14 on/14 off), I checked out everything one last time, no shorts in the coax. I plugged it all up, read the manual again. I turned power down to 5 w, found a freq that was not being used just below 3.900 mhz, listened for a few minutes, then keyed the mic, gave my call sign and asked if the frequency was in use, listened some more. Then I announced I would be doing a short antenna test. (OK, most hams don’t seem to do all that, they just tune. But it seemed the polite thing to do, and being a new ham, it couldn’t hurt.) I switched to FM, keyed the mic with the meter set to read SWR. Not bad, about 2:1, and no magic smoke came out of the radio. Hit the tune button on the tuner and it dropped down to 1.1:1. Wow! And that tuner is noisy... sounded like my printer that just went out. OK, that band will tune. I changed bands up to 40 meters, found a freq around 7.2 mhz, same procedure, listened, gave my call, etc. With the tuner bypassed SWR was a little higher, but it tuned right up. 20 meters, SWR started out at at 1.5:1 and went down from there as it tuned. I was able to tune 17 m, 15 m, 12 m, 10 m, and 6 m. 2 meters with the
J-pole: So, there you have it, two antennas, and the FT-897 with LDG AT-897 tuner that will cover from 80 m - 70 cm. So, how does it really work? The next morning, around 09:00, I made my very first QSO with my good friend and Elmer, Steve K9ZW way up in Wisconsin from my home in southern Louisiana, a distance of 1,016 miles, on 20 meters with that dipole and 100 w. http://k9zw.wordpress.com/2008/10/24/working-paul-ae5ju-for-his-first-hf-qso/ Later I worked guys all over Louisiana and a guy in Florida on 80 meters. I also worked a guy in Massachusetts on 17 meters. He was pegging my meter, and me his. I mean PEGGED. Like you could hear the needle click on the stop pegged. I also signed in on a net up in New Iberia (just south of Lafayette) 45 miles away on 2 meters with just 8 watts with that B-Square Engineering J-pole. So far no luck on 6 meters or 10 meters. Just no activity up there at this time, but those bands will tune up. Final Lengths and Testing Updates 11-16-08 I spent the afternoon checking SWR at several places on each band, trimming length. Here's what I started with: 120' total (60' each leg) for 75 meters 66' total (33' each leg) for 40 meters 33' total (16.5' each
leg) for 20 meters
SWR @ 60' 3.665mhz =
1.1 This showed that it was too long, resonance down around the lower end of the phone band. I wanted to get that higher, nearer to 3.9 mhz. I took 26" off each end = 57.83' each leg SWR @ 57.83' 3.665mhz =
2.6 This is VERY close to
the 96% adjustment for the lowest band segments from the
Multiband Dipole
page
at HamUniverse.com.
SWR @ 33' 7.165mhz =
2.0 I took 8" off each end = 32.33' each leg SWR @ 32.33' 7.165mhz =
1.1 Again, this ended up
VERY close to corrections from the Hamuniverse page. I could probably have
taken off another 1/2" or so, gotten the upper end down a fraction, but
why? That is close enough for me. SWR @ 16.5' 14.155mhz =
1.2 It is easy to see this section was a little too long. I took off 1" each end = 16.4' each leg SWR @ 16.4' 14.155mhz =
1.4 I went back and confirmed that 75 meters and 40 meters were still the same as before, had not changed as a result of tuning the 40 m and 20 m legs. ------------------------------------------------------- 17m 18.120mhz = 3.5 15m 21.205mhz = 3.0 12m 24.960mhz = 5.0 10m 29.000mhz = 2.0 6m 52.800mhz = 2.0 15 meters had been somewhat lower, around 1.2:1, before I tuned the 80m and 40m segments, but not too bad now. It is easy to see that shortening the 40 meters segments shifted the resonance for 15 meters up out of the band. But the tuner easily handles it. And 17 meters is about what it was before. Additional notes: All SWR readings above were obtained with the tuner bypassed, that is, the coax in from the antenna was plugged directly into the radio’s HF antenna socket. These bands all tune down to 1.1 using the tuner. I don't think I'm going to do any better than this. Everyone tells me to leave it alone now! Had I used the Stanford Research corrections as per the Hamuniverse Multiband Dipole page, I would have already been finished. Update - November, 2009 - ALTERNATE CENTER
INSULATOR USING COMMERCIAL INSULATOR: Water had gotten into the SO-239 socket also. I made
a new center hanger by bolting a Jetstream JTCE1 Dipole Center Insulator
to a piece of plastic kitchen cutting board. The holes for
attachment of the wire legs were chamfered by lightly touching the holes
with a larger diameter bit. The V shaped notch on bottom is to allow
easier wrapping of the coax connection with Coax Seal or Scotch 130C butyl
rubber tape.
I already had a new hanger fabricated from a Jetstream
JTCE1 Dipole Center Insulator and a piece of plastic kitchen cutting board. See photos
below:
The notch on the bottom of the backing piece is to make it
easier to wrap the coax connector with coax sealing tape (Scotch
130C).
It took only minutes to replace my original
center insulator with this new, more weather resistant
one. 73 Paul - AE5JU  Monitor police, fire, ham radio, rescue, ships and more!  Hamuniverse.com uses Green Geeks Web Hosting! |
