Roof top Tripod for Antenna Upgrade
Springtime is antenna time.
As all hams understand… height is your friend when it comes to antennas, especially for simplex on the 2 meter band.
While I was generally happy with my current Tram 1480 dual band antenna, I wanted to improve my signal and reach our farther. My current antenna was installed on a 20 ft. pole attached to the side of my back porch deck and has performed pretty well. However, there were some more distant stations I had difficulty working and I have wanted to get it higher for quite some time.
My HF antenna, an Alpha Delta DX-CC, was also attached on that same 20ft. pole below my dual band antenna, much lower than ideal for a 10-80 meter dipole. It too needed more height to improve my signal and perhaps pull in those distant DX stations better.
It would have been great to install a tower, but because of limited real estate in my moderately sized city lot combined with interfering power lines, that was out of the question.
What I chose to do was install a roof top tripod to support a mast for both the Tram antenna and Alpha Delta. I initially bought a used 10 ft. tripod from another ham buddy, but it seemed a bit unyieldy to install without the aid of a bucket truck or something.
What I settled for was a 3 foot rooftop tripod purchased from my local Radio Shack. Into that tripod I wanted to insert two five foot lengths of 1 1/2″ diameter aluminum mast to support the 2 meter antenna and dipole.
Since I was upgrading my antenna mast system, it seemed the perfect time to also upgrade my 2 meter antenna. I chose the Tram 1481. It was a taller antenna, 15 ft. 8 in. tall compared to the shorter 8 ft. 1480 and also had more gain, 8.3 dBd gain on VHF compared to 6 dBd gain on the 1480.
To support my Alpha Delta DX-CC dipole antenna, I purchased a Proxicast X-Boom MIMO Antenna Mast Cross-Over Bracket Kit to hold a 24″ long piece of aluminum tube below the Tram antenna. I had used on my earlier installation a piece of angle iron attached to the mast with a single u-bolt, but discovered under tension it would twist on the mast.
While heavier and bit more costly, this solution was sturdier for an installation I hoped would work maintenance free for years to come.
Into each end of the horizontal tube, I attached stainless steel carabiners to support the paracord used to hoist the center conductor of the dipole. While I only needed one carabiner for the Alpha Delta, I chose to install a second one on the opposite end of the horizontal tube so I could raise another test antenna (perhaps an end fed) in the future. I considered using pulleys here, but opted for the carabiner because it would allow knots to pass through without jamming in the pulley.
I put this all together along with the guy line connectors while the tripod was still on the ground. Next, I planned to first install the tripod without mast onto the roof and then drop in the 10 ft. mast with the Tram antenna attached.
Before installing on the roof and while still on the ground with only one 5 ft. mast installed, I tested the new Tram 1481 and was amazed at how well it performed. Stations I had previously had difficulty working were now full scale and full quieting.
With the help of several ham friends, Gaylen (KEØQPG), Ron (KFØAMJ), Bill (KEØVIL), Russell (KC5UNP), and Ken (WØKRD) we got the tripod and antenna mounted to my roof and guyed at four points. Also included was the two ropes connected to the cross beam for raising and lowering wire antennas. The only problem encountered was my misjudgement of the copper ground wire that was about a foot too short of reaching my ground rod.
This now puts the base of my 2 meter antenna at about 29 feet and the top reaching about 44 feet. The center point of the inverted-V dipole is now at about 27 feet with the ends about 16 feet above the ground.
Overall, I couldn’t be happier with my results.
2 Meters @ 146.400 MHz SWR 1:1.1
My 2 meter signal improved for all stations located within my local area and everyone reported my audio had improved with less noise.
I was particularly happy that I was now able to hear a simplex station located 22 miles away that I was unable to hear before.
I couldn’t really discern an improvement in my HF signals and am still testing.
Readings from MFJ-259C Analyzer:
10 Meters @ 28.729 MHz SWR 1:1.3
12 Meters @ 24.899 MHz SWR 1:6.6
15 Meters @ 21.045 MHz SWR 1:2.6
17 Meters @ 18.130 MHz SWR 1:4.9
20 Meters @ 14.122 MHz SWR 1:1.4
40 Meters @ 7.150 MHz SWR 1:1.3
80 Meters @ 3.950 MHz SWR 1:1.3