Gene, Once you go beyond 13 elements or so, a "formula" LPDA isn't too bad. But the 8-10 element versions definitely benefit from optimization to improve gain, F/B ratio and SWR in the ham bands. The
I helped a local ham build a T-8 last fall and it still has a 1.5" square aluminum tubing split boom transmission line. I've heard that some of the early Tennadynes used round tubing split booms, but
Just be fair, for the opinions of mostly-happy Tennadyne T-8 users, you might want to visit: http://groups.yahoo.com/group/TennadyneAntennas/ Their Files section has some useful info. The T-8 works -
Construction details for an 80-40m wire LPDA are in the ARRL Antenna Handbook, 20th Edition. It could easily be extended to higher bands. You need a large family to rotate it and a large field if you
Seems like a good idea, except the parasitic elements of the other antennas really mess up the pattern, etc! I took a standard LPDA and put one 10' away firing into the original and removed its sourc
There are two reasons to stack yagis or LPDA's: 1. To increase gain by using a phased array. Maintaining a specific wavelength spacing is important. 2. Taking advantage of the different take off angl
Jim, The concept of sloping the booms of two vertically stacked LPDA's is to maintain proper phasing between the wave fronts from the two antennas as the frequency changes and the active region moves
Maybe it's an X510MA? It is now called the X510HDM. They added the HD a while ago for "Heavy Duty" -- not to be confused with X500HD repeater antenna. http://www.rfparts.com/diamond/x510series.html S
The two common solutions to grounding the Tennadyne LPDA elements and boom is to: 1. Use a shorting stub at the rear of the boom, which helps tune out some anomalies also. 2. Use a Collins choke (coi
If you have a portable AM radio, use it as a sniffer to locate the source of the noise. The ferrite rod antennas are fairly directional. It's not uncommon to have other areas of the house tapped into
If you are active in local ARES/RACES groups, generally the county emergency management staff has access to government surplus lists and can get anything that isn't classified (it wouldn't be on the
Wiring the J-bolts and rebar is generally not considered adequate for lightning protection! Welding or exothermic bonding is used for the commercial towers I've seen. http://www.polyphaser.com/techdo
Contact US Tower's customer service and tell them you need the Installation and Maintenance Instructions and also the Formal Stress Analysis Document for the MA-40/MARB to complete a building permit
Kevin, The three crank-up towers I've seen a stress analysis for (MA-550, MA770 & TX-455) all have the greatest F.S. ( 0.48 - 0.56) for the top section and the least margin (FS= 0.90-0.93) in the nex
I'll just respond to the pipe grade portion for now: ASTM A53 Type E Grade B may have a TENSILE strength of 50-60k, but not a YIELD strength -- that would be 35K typically. Big difference. The issue
If all you want to do is determine deflection under a static load, yep, that's all you need to do -- hang a weight on it. But that is the least of the issues. What is the composition of the steel? Ho
Kevin, Based upon your assumptions and rough estimates, you are correct that the top section in your example would be operating near its max stress limit with the rated load at the top of the tower a
Kevin, Without seeing the full report, I can't answer your specific issues, but I would accept the analysis as valid for the standards used at the time. It appears that the tower's wind load is limit
Kevin, Based upon the info you supplied previously, any length of mast you add, while staying within the allowable base moment loading, will not exceed the top section's max of 7638 ft-lbs. Rather th