Tower Time – Part 2 – Tower make and model

Based on confirmed research 100ft AGL would get the job done, so the hunt started. I looked at the online used tower sites and viewed a used 120ft Rohn SSV which was available in the KC area. I wanted a free-standing structure so the choices were a bit limited and I examined AN, Rohn and Universal. The distributor for AN did not return my queries and the Aluminum Universal is only rated for a 200lb climber so I passed on both. Which left me with two choices new Rohn or a used Rohn. I now have two short Rohn 25g towers at the house, both of which I have had since my teenage years and I am not concerned about their ability to age well.

Next factor to consider is wind loading, which all summed up is under 10 sqft given my current plans. The used SSV is rated at 10 sqft using the standards in effect when originally delivered, which from my research was Rev D. The same tower config SSV using the current Rev G standard is down rated even further to 6 sqft if memory serves. As by this time I was looking for other options as the SSV light duty line did not meet my expectations and the heavy duty line is crazy expensive both in structure and foundation cost.

To make this all more interesting I had begun to engage the county zoning department on antenna structures and learned that any structure would need a engineers stamp for the state of Missouri. Which I learned in practice is best gotten from the manufacturer as tower design is a specialty skill which requires special modeling tools. The problem is when dealing with a used tower, an inspection is required to ensure that the tower is in good condition prior to an engineer stamping the plans.  Which if one has gotten the tower for free it makes economic sense, and as this was not my case the cost of the tower, inspection and stamped plans was too close to a new structure to not chose new when I was considering the Rohn SSV.

I next looked to the Rohn RSL line (http://rohnnet.com/rohn-rsl-self-supporting-tower) and was impressed by the capacity to cost ratio and that bearing and rotor plates are available from the factory. It is available in several ANSI/TIA-222-G configs which is a need everywhere you need a building permit.

RSL Spec excerpt

RSL Spec excerpt

The next step is getting a building permit which requires stamped drawings so an order was placed.

Next stop the building permit process. Stay tuned…

Tower time – Part 1

When I paused 15 years or so ago I had a small tribander, a multiband vertical and a 2m vertical on two short 30 to 35ft towers in the back yard. I took it all down and stored it in the barn thinking someday I would re install it on a proper tower. When is was up, it suffered from one primary issue, lack of height as is was both below a half wave length on all but 10m and the VHF antenna was below the surrounding terrain as my property is in the bottom of a bowl.

The next step was to determine what would be an appropriate height to achieve the following outcomes.

  • Good HF performance above 40m, for 40m and 80m I will stick with a wire antenna or a ground mounted vertical.
  • Good VHF and UHF performance into the Kansas City metro repeaters.
  • Support TV receive antenna as I would like to decommission the tower in the back yard which holds nothing but the houses TV antenna.
  • Ability to access broadband from one or both of the WISP internet providers in the county, which rules out crank ups our any similar design.
  • No guy wires and nothing attached to the house.

Out of those requirements came nothing but questions.

  • How high and at what capacity?
  • How much did I want this all to cost?
  • Where to place it on the property?
  • What make and model represented the best bang for the buck?

The first priority was to determine what height would work, to begin I began to consult topo maps which I downloaded at  http://store.usgs.gov/. I also used Google earth to view the terrain profile between my location and the WISP provider towers. This just confirmed that I was in a hole and it was about 80ft deep in most directions and 100 deep in other directions. Another tool from our friends at the FCC is a height above average terrain which while intended for broadcasters over at (http://www.fcc.gov/encyclopedia/antenna-height-above-average-terrain-haat-calculator)it does a fine job of giving one a full compass view at different heights.

 

Elevation profile  to nearby WISP tower

Elevation profile to nearby WISP tower

 

None of these tools account for trees!!!

So the next step was to perform a visual survey and confirm that the paper plan and determine if a 30-50ft allowance for tree’s would be sufficient. I hired a crane service and took photos at 80ft and 100ft AGL to verify line of sight and a fairly unobstructed first order Fresnel zone view to the WISP towers in the area.

Panorama from 100ft AGL

Panorama from 100ft AGL

The conclusion, 100ft would be needed just to get a line of sight out of the valley.

On to part 2 – tower make and model.

The Baofeng BF-F8+

Part of the getting active process included a review of my current equipment situation and determining what still had useful life and what needed to be replaced. The battery pack for my handheld no longer held a charge and while looking for a replacement I was surprised to find new dual band handhelds for the price of a replacement battery. In addition to picking up a new battery from Batteries America for my old Kenwood, I also decided to take a chance and order a Baofeng handheld with accessories.

I knew that as part of rebuilding the shack I would be doing some tower work and I did not what to climb with a valuable radio so it seemed reasonable to “invest” in one of the cheap handhelds on the market. The first problem I faced was which one to choose as the model variation is a little nuts and it is a challenge to separate the wheat from the chaff. To help with that chore I found the following comparison chart over at BaoFengTech.com and with the knowledge gained I decided to go with a BF-F8+ which I ordered from Amazon along with a speaker mic and a programming cable.

A word of note on the programming cables, with cables using copied Prolific chip sets I decided to spend a few extra bucks and go with the cable using the FTDI chipset and I have had zero problems with Windows 7 recognizing the cable and loading the proper drivers.

 

CompareChart

 

Thanks to Amazon Prime in a few days the order arrived and on to the next challenge, programming. During my research I found a lot of great information at http://www.miklor.com/ and it was my first stop after the battery was charged.

The sequence to setup a new radio consisted of:

1) Download and install Chirp
2) Plug in the cable and let Windows find and install the pseudo serial drivers.
3) Connect the cable to the handheld and power on.
4) Download the current config from the radio
5) Modify as needed, save to disk as a backup, and push the config to the radio.
6) Power the radio off, disconnect cable and power back up.
7) Operate radio.

So far so good ;)

It is tiny, easily slips in a pocket and the battery life is amazing and I have gotten good signal and audio quality reports back from the local repeater crew. I did notice that if I set it on the table near my PC it is deaf as a post, not really fair to blame the radio just took a while to figure out that it was not a radio problem but and environmental issue. To be fair my other handheld exhibits the same problem when less than a foot from my PC.

The interface takes a bit getting use to and the manual is less than ideal, but so much information is available really not an issue.

The build quality is good, it is a tremendous value and well it just works.  I think I will pick up a UV-82C next.

73’s Jay

 

Getting active again

After a 15 year pause in the hobby I have pulled the gear off the of the shelves and discovered that while all of it still works, several expected items have run out of life. The first being the lithium backup batteries in my old Kenwood TH-215A handheld and of course the handheld batteries.

A quick search of EBay located vendors for the appropriate battery with the required solder tabs, and a search of the web located a source for the needed PB-2 battery packs. In a era where a complete dual band handheld can be bought for less than $40, the investment in the old Kenwood was purely sentimental.

With those items taken care of I formed a list of areas to explore and systems which I needed to re-activate or rebuild.

Inventory what I have
Operating position
Antennas and something to put them on
New handheld, mobile (maybe), HF Rig and all of the as-sundry items needed for a viable station.

Next on the list was sorting out the antenna situation as I had taken down years ago all of my external antennas. And accessing what would work best to mount all of the antennas on.

73’s Until next time