N5PUV s 4 Band Fan Dipole Experiment. Using the New SRI (Stanford Research Institute) Method

Transcription

1 N5PUV s 4 Band Fan Dipole Experiment Using the New SRI (Stanford Research Institute) Method

2 Goals of Experiment Develop a Multi-band Antenna that does NOT require a tuner Build using the new, easier tuning method SRI Use least expensive methods to build using leftover materials and few new hardware pieces Be easy to build and hang in less than a day or two Be easy to install by one or two people using existing structures (1 in this case) Be a good performer on chosen bands

3 Materials List PVC pipe 3 to 6 inches in diameter (left over) Caps to fit either end of that pipe Copper strip (left over) Brass Screws, washers and nuts (left over) Eye Bolts with nuts THNN House Wiring 220 feet (had this left over) 18 to 21 feet RG8X Coax (left over) SO-239 Connectors 2 10 foot ½ PVC pipe for spreaders Oh, and whatever tools you have to use on this.

4 Step 1: Prepare 2 buss bars Needed: 2 Strips of Copper at least 18 inches long. Drill 3 holes in each for brass screws every 5.5 Inches Here I used some brass Channel for Stained Glass I had lying around. You could use copper pipe strap or any stiff piece of copper strips

5 Step 2: Solder Brass Screws Here I soldered the Brass Screws to the copper strip This makes installation easier in a future step, but is not mandatory at all. If you are patient or have better tools you could omit this step

6 2 Identical Finished Copper Strips with Brass Screws Attached Here I made 4 screws spaced at 5.5 Inches Apart for a 4 element Fan Dipole. You can use 2 or 3 if you want

7 Step 3: Create Ugly Balun on bottom end of PVC pipe This is using 18 to 21 feet of RG8x, but any malleable coax will do for low power. Simply wind the coax around the 3-8 PVC tube as shown, drilling holes in the PVC for the start and ending ends. PVC size is not critical nor is number of turns, just the length.

8 Step 4: Drill Holes for the Copper Strips Here I carefully lined up the holes with the finished strips on opposite sides of the pipe above the balun. Drill holes on opposite sides of PVC pipe for brass screws to poke through from the inside.

9 Step 5: Insert the copper buss bars inside the PVC Pipe With the screws soldered to this single strip, it was easy to get the screws lined up with the holes if they were carefully spaced the same distance (5.5 inches) apart on each side of the pipe Not doing this would require a way to hold the screws in place from the inside.

10 Step 6: Bolts on outside of Copper Strips All screws get capped with Wing nut or other type of nut as long as it is metal to metal. On the finished project I put a nut on first, then a SS star washer, then a SS Wing Nut on every dipole connector here that is connected to the copper strip inside.

11 Step 7: Install Dipole Stress Relief Eyelets 90 degrees from each brass dipole electrical connection, install two eyelets directly opposite from each other for stress relief on the dipole. The 2 dipole ends of each band will loop around these and then become electrically connected to each brass screw

12 Step 8: Prepare Balun Coax end for Attaching to Copper buss bars This is the end going to the balun inside the PVC pipe. Here I removed 3 inches of insulation then Carefully unbraided the coax shield 2 inches back then Soldered each end

13 Step 8: Solder the Balun Coax to the Copper Buss Bars Here solder one of the ends to once buss bar going down the pipe, and the other to the other side. I did not allow the buss bars to protrude inside the balun Air coil further down the pipe. Nothing exists in that part of the pipe but Air.

14 Step 9: Insert the caps and Final Holding Loop Drill a hole in the bottom cap and put the coax coming from the bottom of the balun through it and seal. Put another eyelet or loop on top cap and seal, careful to not short out antenna wires inside pipe

15 Step 10: Prepare Dipole Wires Top wire longest Band 4% shorter than normal: (468/Frequency) x 0.96 Middle Frequency Normal (468/Frequency) Lower Band 1% longer (468/Frequency) X 1.01 I cut a lot longer just in case. But you should mark these locations with marker anyway.

16 Step 11: Attach Each Dipole leg to Antenna Lugs Each Dipole Leg goes on opposite connectors 180 degrees on pipe. I used ring connectors after looping dipole wire through stress relief several times. Longest Dipole on top Then second longest Then Shortest on bottom sets of brass lugs I used 14 gauge THNN stranded house wire

17 Step 12: Space out the Dipoles so they Fan Below Here I used two 80 inch sections of PVC pipe ($1.75 each) with holes drilled at center and both ends to attach the dipoles to. You can use halyards or any other method you can think of to keep the ends 38 inches apart to (up to 18 Mhz.)

18 Step 13: Tune it up According to the method, little if any tuning is needed. We found this to be true as I had left each side a foot longer and we ended up taking much of that off of the higher bands. The lower 80 meter band not so much, so it is preferable to mark the calculated locations, then leave some wire longer to trip back if needed.

19 Tune it up Remember to tune with the antenna up close to actual height and away from you or anyone else. You can use your radio set to 5W and read your SWR meter. If you started long, you know you only need to take off inches at a time to lower the SWR on each band. Tune from the lowest band down (Top down on antenna) We used a pulley for easy retrieval.

20 Step 14: Enjoy! This antenna proved itself on 3 bands without the need for an antenna tuner. 80 Meters: 1.4 SWR 40 Meters: 1.1 SWR 20 Meters: 1.7 SWR Contacts made on all three bands with 59 RST.

21 How Much Time and Cost? Very little.. To build Balun and Center Insulator = 3 hours and $20.50 for stuff I did not have lying around, guy rope, eyelets, etc. Just me. To Hang the Antenna, 2 well Experienced guys ~ 4 hours with a long lunch in-between rain storms last Friday. Summary: 599 REPORTS on every band without the need for a tuner!!! I will add a 10 meter to it after field day. If we can do it, so can YOU!