Since the Eastern States Exposition (AKA “The BigE”) which is New England’s largest fair located right near my QTH is at peak attendance, traffic is everywhere and makes leaving my house difficult.
Since I’m not really going anywhere, it’s time to work on some smaller projects at my QTH. Since there wasn’t a single functional HF antenna. It’s time to get at least one of them back on the air.
Attention focused on the Butternut HF9V vertical since it’s the easier of the two to repair. This antenna was purchased used and installed 9 years ago. Nothing has been done to it since. It’s no longer resonate on any of the bands and the tuner can’t “match” anything as the SWR was always changing.
Investigating what’s wrong
The antenna has seen better days. Lots of overgrowth to the point where the radial plate at the base is barely visible. The antenna is fed by a 130ft run of LMR-400 buried underground with 30 radials of various lengths.
There is a remote relay system in between because there are two additional antennas in the area but have been since removed because the trees used for support have been removed earlier in the year.
I’ve decided to bypass the relay system for now and tested the LMR run from the house. Placed a 50ohm dummy load at the far end and used the NanoVNA on the other. Thankfully all is well
Next was inspecting where the 75ohm patch cable connects to the antenna. The original Butternut antennas had the end of the patch cable stripped with terminal rings covered by shrink wrap. It was corroded and breaking apart.
The antenna was removed from the ground and noticed that the 28″ section of aluminum tubing broke. This was most likely caused because a steel pipe that was used as a sleeve. Due to the high water table in the area and using dissimilar metals, corrosion happened just below ground level.
Tubing Repair
It was decided to start with the most obvious. First would be to repair the broken section of aluminum and 2nd would be to rebuilt the 75ohm patch able and connection to the antenna itself.
Any ham that’s been involved in HF for awhile will eventually have a supply of random tubing. I was hoping there was an exact match in diameter but couldn’t find any. However, there was some tubing that was slightly larger and allowed the corroded pieced to fit snugly within. Ended up trimming off the bad stuff and riveted it the larger diameter tubing.
Patch Cable Repair
Earlier in the week I attempted to repair the 75ohm section by trimming the coax and replicated exactly the same setup. It might have been fine but the antenna was still not working.
When referencing the new manual, it appears they’ve changed how the patch cable is connected to the antenna. The 75ohm section now has two PL-259 connectors on each end and there is a SO-239 to two wire adapter hooked up to the antenna. I wanted to replicate the new system.
Modified the patch cable so it now has two PL-259 connectors and created an adapter using a thick walled pill bottle, SO-239 chassis mount connector, 2 12ga wires with ring terminals crimped and partially soldered. Passed the continuity tests, filled the void with 2 part epoxy and covered with splicing tape.
Also decided to wrap the 75ohm section around a 4″ PVC Pipe. There is no particular reason why it was done other than keeping things neat. Much better than it coiled up wrapped with electrical tape.
Still Not Working
With the tube repaired and the 75ohm patch cable better than ever, I was hoping the antenna would be operational again. Nope! The antenna wasn’t even close to being resonate in any band. The NanoVNA was showing dips but nowhere close to in-band.
Started looking for cracked/broken insulators and any damage or corrosion to the coils and their mounting points. Couldn’t find anything wrong.
Only thing left are the capacitors. The HF9V uses three door knob capacitors. These are high voltage capacitors that allow for higher power to be used. Uses two 67pf and one 200pf caps. They have threads on each side of the cap for mounting.
Soon as I attempted to remove the upper most cap, it easily broke apart without any effort. I was actually excited hoping that this was causing all the issues.
Thankfully someone gave me spare parts that included two brand new capacitors. I swapped them out and re-tested the antenna
Back In Business… Sort Of
The NanoVNA SWR plots are showing DEEP dips close to band frequencies which made me very happy. However, the upper frequencies in the 10, 15 and even 20m weren’t looking so good.
I’ve removed the antenna and attempted adjust the overall length of the antenna but couldn’t see any noticeable changes. The lowest SWR was just outside of the band.
The day was coming to an end and decided to call it quits. However, I did tune 40m which was excellent (SWR Wise) and tuned 80 to the FT8 frequencies since it has a narrow bandwidth. At least I’ll have something to use.
Getting Back On The Air
If I really cared about contesting, I would have done this repair the week before because the CQWW RTTY contesting was going on and the bands were packed with signals. Could have spent time getting the rest of my station ready as I don’t have the proper software installed due to a full format.
In between other projects throughout the rest of the weekend, I hopped on the air and mostly did FT8 contacts. I was having fun. Managed to make about 100 or so contacts. Lots of DX and possibly some new band contacts.
What’s Next?
The vertical still needs work. Need to clean around the area and prevent future vegetation infestation. Also going to replace the 200pf cap and tune the rest of the antenna. Finally add more radials cut for various bands/lengths
Then focus will be towards the beam. I’m being hopeful it’s just something wrong with the pigtail section. Since I don’t like climbing my roof I might have to solicit the help of local hams.
If there is something wrong after the repair, I have a 2nd CL-33 that I’ll rebuild/repair and just swap it out entirely. If I can’t get that to work then I’ll save up for a new beam.
Thanks for reading! 73
Jeff (NT1K)