A HAM AND HIS ANTENNA

GAP ON A RACK

Believing that operator skill, radio equipment, and an antenna system contribute equals thirds to a successful HAM station, I spent considerable time mulling over what kind, and where to put, an effective antenna. Among the books consulted were DK Johnson's "Everything You Forgot To Ask About Mobilizing" (W6AAG, Esparto,CA), Capt. Paul H. Lee's "The Amateur Radio Vertical Antenna Handbook", (N6PL), and "ARRL's Antenna Compendium, Vol. 4". The fundamental problem is that I live in an apartment and there is in force a nothing-on-the-roof policy. This fact, plus my discretionary income limitations, led me to conclude that mid or top-loading verticals offered me the best real estate solution, lowest noise, anywhere from 3 to 4.5 db gain, and portability. The latter was attractive because I'm a camper and I envision myself in a HAM shack tent anywhere on the continent.

Two configurations were decided upon, a mobile installation suitable for freeway driving in excess of 70 mph, and a more effective portable installation that I could carry on top of my lumber-rack equipped Ranger but which could easily be erected single handed in less than 30 minutes. Don't be fooled into thinking that I thoroughly researched and planned these decisions. Not by a long shot. They were reached as a result of trial and error. I tried erecting a GAP Challenger on the flat roof over my second story bedroom but it took less than twelve hours for the landlord to inform me about their policy and I was forced to remove it the following weekend. I hung the four assembled sub-sections up on the wall in the garage where they stayed for two weeks while I figured out how to best salvage my investment. Also in the garage was Cargo Master mini-pickup lumber rack left over from my constuction business, and this rack offered a possibility to save my $250 antenna investment. After I refinished the lumber rack I removed my camper shell and in its place installed the rack, adjusting stanchion locations to accommodate a six-foot bed. Wa Lah! I now had an eye-level height steel ground-plane for any portable or mobile antenna, vertical or whatever. I tackled the mobile configuration first.

I had earlier installed on my rear bumper a Diamond Pro-Com that tuned to 80, 40, 20, 10, and 15 meters. It consists of a four foot mast, then three horizontal medial loading coils for 20, 10, and 15 meters, then either a 40 or 80 meter vertical resonator screwed on top of that so that the total vertical height was about seven or eight feet depending on the selection of the 40 or 80 meter resonator. The mast mounting base was a Hershey Kiss with an SO 239 connector on the bottom. This installation was moved to the top driver-side mid-bed location of the lumber rack where it worked much better but where wind loading from freeway driving began to permanent bend the 1/2 inch aluminum rod mast. A little tree limb in the parking lot at Home Depot finished the job by stripping the threads out of the Hershey kiss brass mounting. I concluded that this large configuration was too much of a sail and the resutant wind loading was too great for the Hershey kiss mount which had weakened to the point that a slight tap from anything would have stripped it. The Hershey Kiss would probably survive a lesser wind-loading configuration(Slower driving wasn't considered an option).

I purchased a 10 meter HAM Stick and installed it on a less robust mounting base. This antenna is a center loading vertical with a four foot steel stinger on top for a total height of seven feet above the rack. 13 feet is the legal height limit so this configuration maximizes height but minimizes wind loading. The trade off is that each bank has to be installed as needed and if I want to operate over the entire HF and VHF spectrum,then I have tocarry a selection of antennas. Since I garage my truck, take down is mandatory anyway for whatever antenna I select. The ten meter HAM Stick worked well and after a few QSO's I elected to add quick disconnects to 80, 40, 20, and 6 meter HAM Sticks. I may add 12 and 15 meters later, but in the meantime I'm waiting for Lakeview of South Carolina to send my order. The order includes two new Hershey Kiss mounts so that Lakeview's 2 meter co-linear antenna can be co-located on the rack, probably towards the driver side rear so that I don't have to run around the truck to de-mount it when I park in the garage. So far I'm committed to demounting two Kiss-mounted verticals so I may just mount them both on a rotating pipe section to reduce erection and take-down effort. The quick-disconnects, then are just for quick QSYing.

The more effective GAP antenna fully assembled is 31 feet high and resonates in the banks from 80 to 2 meters, skipping only 17 meters, and seems like an ideal match for my Icom 706. The plan that evolved was to pre-assemble the antenna into two permanent 13 foot sections, and for transport, hold them horizontally in place on top of the lumber rack with four plastic Cheesborough champs. This worked out well with the bottom section longer by about two feet to accommodate the supplied ground mount. This section is red-flagged during transport as it hangs off the rear of the rack by 18 inches or so. Final assembly and erection, it runs out, takes about 20 minutes, complete with three 26 foot counterpoise radials made up of old RG62. The complete antenna is assembled horizontally extending from the mid-rack position, forward, out over the cab.. The base is clamped to the middle rack pipe with a metal Cheesborough. The whole assembly and rack pipe is then rotated vertically and locked in place by tightening pipe mounting bolts in the rack side rails.

The manufacturer says that guying isn't necessary when ground-mounted, but that guying is recommended for roof mounts. For this installation a guying kit was installed as a safety precaution. Additional support is supplied by an erection stick made up of 15 feet of 1.5 inch PVC. This allows me to "walk" the mast into vertical position and then clamp the "T" section base of the erection stick to a rack front rail. This stick and the two guy lines should handle any normal breezes but high wind situations(80 MPH) can be accommodated by guying the mast to ground stakes located some 15 to 20 feet from the truck. You'll see this antenna during Field Days atop Torrance Memorial Hospital's parking structure and you'll have a chance to compare the FP Challenger to anything else that might be assembled there.

So far I've worked only a few QSO's as I'm still adjusting my schedule for weekend hamming. The first thing I noticed is how quiet this antenna is. Too, as a new amateur I scan the bands a lot and have found some neat nets. There's a 6 meter AM net right at 54 Mhz and, since there's not many AMers left, these guys treated me like a lost relative.

My very first QSL card arrived last Thursday from the Four-Corners are(Utah, Arizona, New Mexico, and Colorado) which was celebrating something or other special event. The Special Event station was N4C and the card is a photo of the geodetic survey marker located there.. For my own QSL card I think maybe a photo of my "GAP-on-a-rack". I;m not above wheedling and it might just yield some benefits from the GAP people. Besides, they just gotta see a picture of this.

73's. Roe, KF6PZG