WB4IUY's Random Blog

I've been in Amateur Radio since 1974, and still find new and interesting things to do. I like to build, restore, and operate on the air. This is a blog of various info about my Ham Radio operations and activities, projects, and opinions. Visit www.WB4IUY.net for the lowdown at WB4IUY.

Sunday, November 26, 2017

Antenna work - 11/26/17

Finally had a little time to get back on my tower and get more antennas pulled up. I broke my Force-12 6 element HF yagi into 3 sections, pulled it up the tower, and reassembled it from up top. The assembly went well and it was an easy one-man job. Once in place, I got the feed line and rotator cable pulled up and connected. Here's a few pics from the work...

 A shot down the tower as I pulled up part of the yagi...


 Looking south at the reflectors...


 Looking north at the driven elements...


 Looking at the horizon to the west from about 105' up...


 A pic from the front yard, the yagi sits at about 105' up now...


 Looking north, over the boom, cam at about 107'...


 Looking down the tower, my feet are perched on the rotator plate...



 The view to the west is awesome from this height...


 Looking up from my driveway, things are beginning to come back together, finally.


 Looking up from the northern part of my front yard...



Time to build the next antenna for the stack and get it in position #2!


Dave WB4IUY
http://www.WB4IUY.net












Sunday, November 12, 2017

Antenna work - 11/12/17

I completed my HF yagi today, for installation on the rebuilt tower. For those who don't know, my tower of 23 years was torn down in a storm in April 2016, destroying all of the 17 antennas that had served me well for all those years. Everything from the vertical that had it's tip at 138' up, right on down to the lowest antennas that were only 30' up. In addition to storm damage to the house and workshop, the tower and antennas system created such a mess that I had to rent a crane / man lift to get it all down from the surrounding trees and untangle / remove the mess of tower that loomed over our home. You can see the system as it was before the storm on my website at www.wb4iuy.net , mouse over the [WB4IUY] in the toolbar at the top, and click on [Antennas] in the dropdown that appears. 

Today I completed the feed harness for the driven elements, built and installed a new RF current choke on the boom, and tuned this 6 element Force-12 HF yagi. I got this antenna used for a great price...it's a $1200+ antenna that I otherwise would have never bought, it just needed a little TLC to bring it back to life. It is a trapless design, perfect for operating with high power. 

If all holds well, it'll be going up on the tower next weekend, and I'll start the rebuild of the next antenna for installation. I can't wait to get this baby in operation!

 RF Choke wound from RG-214 and attached to the boom.


 Bottom view, coax attached and jumpers installed between driven elements...


 Side view, feedline attached and jumpers in place between driven elements...


 Shack side of RF choke feed strapped to the boom...





 Antenna tuned on 10m, had to shorten the elements, drill, and re-rivet to set length...


  Antenna tuned on 20m, lengthened the linear loads a little to move the sweet spot down the band a little...


  Antenna tuned on 15m, had to lengthen the elements, drill, and re-rivet to set length...


 Antenna analyzer connected for testing...


 15m elements lengthened a little...


 10m elements shortened a little to move the sweet spot up the band a bit...

Dave WB4IUY
http://www.WB4IUY.net









MFJ-259 Antenna Analyzer Repairs...

I pulled out my MFJ-259 antenna analyzer to start tuning my Force-12 antenna, and discovered that it had a problem... It would not operate on the last 2 bands (lowest frequency ranges). Upon inspection of the internals, I discovered a battery had leaked acid on the main PCB and caused some damage. I washed the board with electronics cleaner and windex to remove oils from the cleaner, scrubbed it with a brass brush, and blew out the excess liquid with canned dry air. Acid had leached into the L2 (a 7.8uH inductor) and damaged it, it was electrically open. I poked around in my bins and found an inductor that was close in value, and installed it on the trace side of the board. This brought the lower bands back to life and restored the operation of the antenna analyzer.

The little hole in the PCB in the middle of that exposed copper area (seen in the photo), leads directly into the adjustable 7.8uH coil. I was able to get close in value with a fixed value coil, and the oscillator covers about the same range it did before the damage. At first I feared that the band switch was contaminated, but it was fine. The frequency range is controlled by a string of adjustable coils, all in series. The band switch shunts around them, so for lower frequencies, more coils are in the path and increases the inductance of the string. That one coil was open, so it wouldn't oscillate in the two bands controlled by it and the next series coil to the right. I was lucky that was all the issue was.


The schematic seen in the following pictures is also on my website at http://www.WB4IUY.net , mouse over [WORKSHOP] in the menu at the top of the page, then click on [SCHEMATICS MANUALs] in the drop down that appears. 

The analyzer was dead on the 2 lowest frequency ranges...


The PCB, after cleaning and scrubbing with a brass brush...


The fixed value coil I installed on the back side of the PCB. I slipped a piece of cardboard between the coil and the PCB to prevent possible contact between the coil and PCB traces / solder joints.


Yipee!!! Back up and running...


I connected the output to the bench counter, just to verify the VFO. 


 This schematic is also on my website at http://www.WB4IUY.net , mouse over [WORKSHOP] in the menu at the top of the page, then click on [SCHEMATICS MANUALs] in the drop down that appears. 


Dave WB4IUY
http://www.WB4IUY.net






 

Antenna work - 11/11/17

I picked up this Force-12 6 element HF yagi right after my tower came down in the storm of April 2016. Being a used antenna, there were a few things I needed to do before installation. After sorting through things, I decided to modify the boom mount to best suit my installation, and split the boom into 3 pieces to allow for re-assembly from the top of the tower, as opposed to hauling the entire fully assembled antenna to the top. All bits are now assembled and installed on a temporary tower section, and ready for tuning.

Some of the parts laid out, prior to assembly...


Boom mounting plate on my old manual mill, about to be modified for best installation on my mast...


Awaiting surgery...


Drilled, milled, and ready to go...


Mocked up with some new hardware...


Modified mounting plate attached to the boom plate, ready for installation...



Mid-section of the boom bolted to a temporary tower section I stood up in the back yard for assembly of the antenna and testing, prior to being hauled up the big tower.


A shot down the boom after fitting all boom parts together...


Another look at the boom, assembled, from an angle...


20m Reflector installed...


20m driven element now installed...


All elements installed, and ready for the feed harness...

Dave WB4IUY