You are right Mike! Welding tower sections together (known as Cadwelding as well) on vertical towers (radiators) is done 100% of the time for AM broadcast station antennas (I was chief engineer of an AM & FM local commercial broadcast station - started when I was 15 years old) - I was taught an early age/high school (by Carl Smith Engineers, Cleveland, Ohio). https://en.wikipedia.org/wiki/Cleveland_Institute_of_Electronics The K3LR vertical elements for 80 meters here (8 of them) and on 160 meters PiRod), are all welded together. Even the new K3LR 20 meter tower installed in 2018 (230 feet tall) is entirely Cadwelded together (all PiRod Tower). PiRod towers are topend durable communication structures known for their solid steel rod construction, custom engineering, and used in broadcast and wireless networks . They are now produced under the Valmont Telecom<https://www.valmonttelecom.com/> infrastructure portfolio. Design and Features
* Solid Steel Rods: Built using solid steel instead of hollow tubing, preventing internal corrosion and offering high strength. * Hot-Dip Galvanizing: Coated to ASTM 123 specifications after fabrication to resist outdoor weather elements. * Custom Configurations: Engineered individually for specific antenna loads, site requirements, and local soil conditions. Info on the entire layout is here: https://www.k3lr.com/Hardware/ Passive intermodulation distortion (PIM) is a "real thing" - in major ham radio Multi Multi operations, it is a significant problem (issue). Same for HamSCI - nightly results of 24 hour unique WSPR reports are shown here: https://wspr.rocks/topspotters/ look for K3LR Some of my ham radio story (audio) is here: https://www.k3lr.com/K3LRsuperstation.m4a 73 Tim K3LR ________________________________ From: Topband <[email protected]> on behalf of Michael Tope <[email protected]> Sent: Wednesday, July 29, 2026 7:27 PM To: [email protected] <[email protected]> Subject: Re: Topband: The Big Guys I've heard from a friend who is big into repeater building that they swear off using LMR-400 at repeater sites because of the passive IMD. I guess the shield sitting on top of the bonded foil can cause very low-level intermodulation that can raise the noise floor of a repeater's receiver when in the presence of strong signals from multiple simultaneous transmitters (imagine the RF environment on some of these RF jungle mountaintops like Mt. Wilson overlooking Los Angeles). I don't know if it requires water ingress, or whether it will do this when pristine. I have a suspicion that is what Tim is trying to prevent by CAD welding sections together. I would imagine that K3LR is a pretty hostile RF environment when six 1500 watt transmitters are on the air simultaneously. 73, Mike W4EF...................... On 7/29/2026 5:45 PM, Jon Zaimes, AA1K via Topband wrote: > > > Hmmm....never thought about cad welding the sections together! > My version uses 119' of Rohn 25, with a 6m yagi for top loading. It's > electrically a bit longer than 1/4 wave. Sits on some big power company > ceramic insulators I scrounged from a local salvage yard just before erecting > in 1998. Initially this tower was 100' but I wasn't happy with the > performance with the shortened parasitics. Later increased height. And added > 2nd director toward Europe (adds 0.9 db gain). > After 28 years the open-air relays at the base of each parasitic are due for > an overhaul. It's "on the list." > Too late to weld the sections together. But perhaps paralleling the tower > with copper wires could help. > I did use Noalox on all the joints when constructing. > A photo of the base on my website. > 73/Jon > > Jon P. Zaimes, AA1K > Tower climber for hire > Felton, Delaware > http://www.aa1k.us/ > Cell: 302-632-2353 > > Reviews of AA1K tower work on eham website: > http://www.eham.net/reviews/detail/12922 > > Hug your favorite tower every day, and always stay connected to it. > > On Monday, July 20, 2026 at 02:35:57 AM EDT, Tim Duffy <[email protected]> > wrote: > > Speaking of base fed insulated towers on 160... that happen to be 90 degrees > high (about 120 feet) - by design... I have had this for over 30 years - it > is what I think is the best vertical antenna array for 160 that I have > found. Bandwidth performance is narrow - but it tunes up easy and it really > works. AA1K, VE3EJ, K9CT, W5ZN and NR5M and others all use the K3LR Yagi > vertical design. WA3FET and K3LC worked with me on the early designs. > > This is a very effective gain antenna (almost 6 dB) with good front to back > ratio (30 dB and can be used on RX with attn.) is described in editions 3,4 > and 5 of the ON4UN Low Band DXing book by ARRL. Only takes a single 120 foot > tower (all tower sections must be Cad welded together). It is a Three > element vertical parasitic beam (shoots in four directions). BUT needs FIVE > radial systems of 1/4 wavelength radials... I use 120 radials per element - > one quarter wavelength long - 130 feet. > > The most recent version of this antenna has been updated by work (28 pages) > from Greg, W8WWV here: > https://www.k3lr.com/engineering/160m/K3LR160m2024Revisit.pdf > > This is currently what is in use at K3LR. Twice this array/station at K3LR > worked more than one hundred countries in a single CQWW CW weekend on 160 > (48 hour contest). > We have just installed a brand new broadcast style radial system (all silver > soldered) for all five vertical elements - this summer of 2026 (old one was > 35 years old). Thanks W3YQ for engineering the installed solution. > > The performance is spectacular. > > 73 > Tim K3LR _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
