Repair – NT1K – Welcome

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.

Worst traffic to the BigE I’ve ever seen in my 15 years living here

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.

Repaired tune (right side) using larger tube

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.

In one of the newer manuals, it’s shows coax adapter (R1)

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.

Broken 67pf Doorknob Capacitor – Missing/Broken Thread

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.

80M Plot Off The NanoVNA – 1.08:1 SWR @ 3.568Mhz

40M Plot Off The NanoVNA – 1.23:1 SWR @ 7.12Mhz – Covers The Entire Band

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.

Looking at all the RTTY signals on 20m using the HF9V

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.

Just some of the QSOs I’ve made (taken from my LoTW logs)

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)

After the K3, I had no real intentions of obtaining another HF rig. But when a deal comes by, I couldn’t resist jumping on it. There was an SK estate sale that I found out through another ham. However the estate was not located near by so everything had to be shipped. Among the items, the Yaesu FT-840 stuck out at me as the perfect HF for someone who is getting involved in the hobby. The guy was asking for reasonable offers. I didn’t want some commercial seller to swipe it. Since I had no need for the radio, I put in a low bid and sure enough it was accepted.

The horrors of buying before trying

Since the price was so tempting, I made a foolish mistake of buying the radio without seeing a picture of the radio, without asking questions and placing my trust in people I don’t know. I’ve done this a couple times in the past and thankfully I never had a problem. This time wasn’t the case.

When I received the radio, it didn’t look good. Knobs were bent and there was a giant dent in the corner. The dented corner had some very shiny metal expose with no rust/oxidation. However the box it was shipped in was in excellent condition. It led me to believe that the radio was dropped just prior to shipment. There was also a missing part. I’ve contacted the middle man explaining what happened and that’s when I’ve learned that other shipments from the estate were just as bad, if not worse than my radio. According to the middle man, the handler of the estate didn’t seem to care and that I would have to take it up with the shipper’s insurance company. I wasn’t even close to being happy with the situation.

Mic Gain / PWR adjustment pots after some attempt at strightening. Still rubbed and was bent so I had to strip it to the chassis

I’ve learned from this though. I will never jump on anything until I am certain that I am getting what exactly I want. Even if the deal seems too good to be true, It’s better to pass up the unknown rather than getting stuck with an expensive brick. I guess I am keeping the radio

Fixing the unknown

Soon as I started tearing into the FT-840, It started to look promising. The front panel chassis was bent and thought I can strip it down and straighten everything out. I was able to do just that. While I was in there, I cleaned everything I could and replaced the internal battery. When I thought I was finished, everything went back together nicely and now all the knobs move smoothly. the VFO wasn’t sticking and it looked much better than when it came in. I thought I was done. But once again, I was wrong.

Who needs ALC?

While checking power output, I found that when I went the SSB modes, the ALC meter was showing either almost nothing or full scale with only a minor adjustment to the pot. I thought something was wrong with the mic at first but it turned out to be okay. Once again I contacted the middle man and was informed that the seller was aware of the issue but didn’t think anything of it. So now on SSB, I will either be barely heard or my signal will be overdriven. It made me more angry knowing that seller was aware.

I ended up tracing it to the pot that controlled the mic gain being faulty. It was also the same pot / knob that was damaged during shipping. With a DMM I checked the resistance while adjusting the pot. There wasn’t a consistent change throughout the adjustment. The service manuals were online and I was able to find the part numbers of the pot

The hunt for the dual pot

Pulling the number from the pot itself found many hits online. However the part sources didn’t have any in stock and were not planning to put them in stock unless there was a 10,000pc minimum order. I thought I was out of luck and called Yaesu USA in California and contacted their parts dept as a last resort. Sure enough they had them in stock. They had the pots and they had the sub assembly. I must say that it was wonderful dealing with Yaesu. The parts were here in just a couple days.

It’s FIXED!!! YESSSS! Or so I thought.

The pot was easy to replace and I thought the radio was finally fixed. I turned on the radio and I am now able to adjust the mic gain to where I am no longer over driving the ALC while outputting the proper wattage. I was happy! Until I heard it.

What’s going on now?

While playing around with the radio I noticed something weird. I would tune into a conversation and while I was listening, I would notice the conversation start to move around and sound off frequency. OH WHAT NOW!!! Now I am back to being angry. Thinking something was up with the oscillator, I left the radio on and took a walk with the family. Upon return I notice the drifting was no longer happening, That led me to believe that the changes in temperature both in the air and in the case caused the drifting to happen. It would drift up to 400hz. The new operator in me never had a radio without some kind of controlled LO so I never had to deal with drift.

Put a jacket on that LO!

Why should I care about a slight drift? Well if you are into digital modes. If you are into low noise modes like JT65 and WSPR, having a stable LO would be beneficial. There is an TCXO or Temperature controlled oscillator that would help keep drift at bay but it’s not easy to get due to the age of the radio. There are not many 10.48576Mhz TCXOs out there either. So the next best thing is to insulate the LO to keep it from changing temperature drastically. I’ve do stuff similar to icom rigs using cotton balls. It appears FT-840 owners used styrofoam. I guess I will follow suite and make a nice little foam block to protect the sensitive LO.

I took a nice little block of foam, placed it on top of the reference LO and press down a little bit. I would remove the box and hollow out the impression. I kept doing that until the block sat flushed with the PC board. The crystal and trimmer is now shielded from quick changes in temperature. I’ve also adjusted the reference trimmer using WWV to make sure it was close to being on frequency as possible.

Much improvement

The LO insulator is doing it’s job quite well. The radio doesn’t noticeably drift around anymore. Been able to make many contacts with it. Too bad I didn’t have a soundcard interface because I would like to try out WSPR to see what I was getting back from those who could hear.

I think it’s safe to say that the FT-840 is now back in working order. However I may not hang on to it long enough to enjoy it. But I sort of grown attached to it now.

Thanks for reading,
Jeff (NT1K)

Tag: Repair

Back On The Air… Sort of (HF9V Rebuild)