Re-tuning 12-year old coax stub filters


Of late, I’d noticed that the SWR on the 10 and 15 meter stacks on tower 1 seemed to be getting higher and higher. Sometimes our first reaction is to head up the tower to the antenna to find out what is the trouble. This time, however, I didn’t go with that first gut reaction.

Rather, I began with a very methodical testing routine, with my AA-55 ZOOM connected to the coax in place of the transmitter at position A. I then inserted a precision dummy load at the next coax junction. Next, using the AA-55 I swept the coax on all 6 ham contest bands. I followed this pattern until I found SWR readings higher than 1.2:1.

The first thing I found was my ICE 419B bandpass filter. Even in bypass mode, it drove the SWR higher than 1.2:1. I inserted a brand new barrel connector in its place, and continued my testing.

The next problem found was on the output side of my 10-m coax filter stubs. I replace the stub assembly with another barrel connector, and continued the testing. Likewise, I found the 15-m coax filter stub assembly and the 40-m assembly to be causing SWR problems. More barrel connectors and the testing continued until I reached the distal ends of the six runs of hardline at the inputs of the various Stack Matches at the base of the tower.

The first step at remediation and repair was to test each individual coax stub in the 10, 15 and 40 meter assemblies. I found all of them to be considerable low in frequency relative to what I desired them to do. So, I retrimmed each of them to return them to the proper frequency. Then I reassembled everything, and retested. SWR was flat all the way to the base of the tower.

The second step was to replace the position A ICE 419B with a Dunestar Model 600. Following that, I again retested all the way to the tower. SWR was flat!

Things that make you go “Hmmmm”. My stubs reside in a shed, out of the sunlight and out of liquid rain. What caused them to drift over time and appear too long electrically?

Springtime + Aluminum (12-m OWA construction)

3/27/2022 – With a box of shiny tubing from DXE, and an OWA design from my friend, I tackled an antenna construction project today.

Shiny tubing for tower bling!

Since selling my Lightning Bolt 2-element 5-band cubical quad a few years ago, I have not had an antenna for 12 meters. My DXCC count is low on that band, so I figured that with the uptick in propagation, now is as good a time as any to tackle this project.

Some time ago I asked around for an OWA design to use a 24-foot boom (salvaged from an old TH6?). Once I had the design in hand, I plugged it into EZNEC 6.0, and agreed with the designer’s conclusions. Download my EZNEC file for this antenna. I made a parts list and placed an order from DXE for the tubing (surely there are others suppliers around, but I can’t find them using Google search) and another from McMaster-Carr for the hardware needed.

With some aluminum flat bar cut to length, a drill press made quick work punching holes in the boom-to-element plates (I used a DXE model as a template).

A pile of shavings!
Stack of six boom-to-element plates

The Sawzall was employed to cut the tubing to the needed lengths, followed by a thorough deburring of all tubing ends. Measured and marked the “exposed” lengths of tubing, inserted to the marks, and drilled three 1/8″ holes for pop rivets. Pulled the tubing out, deburred the drilled holes, then coated the insertable tip with a copper-impregnated anti-seize compound. Aligned the holes and riveted the tubing together. The halves of the driven element are separated by 2-inches, supported by a 0.75″ fiberglass rod inserted into both halves.

With the elements assembled, I moved outdoors to assemble the boom and install the boom-to-element plates. After that, installing the elements was a piece of cake.

This perspective doesn’t present the antenna well

Still sitting on sawhorses, the initial SWR and R,X sweeps are nearly identical to the EZNEC model.

Initial sweep still sitting on sawhorses
EZNEC 6.0 model’s SWR curve

I’ll update this post when the antenna is in service. I think it is going to be a flamethrower!

EZNEC 6.0 modeled pattern

4/15/2022 – Good Friday, and good Friday! I was off work. Woke up at 0400 and was wide-awake. Decided today was a good day to install the antenna. So, working alone with tractor and pallet forks, along with an 8-foot ladder, I was able to remove the KT-34 and install the 12-meter yagi. Initial tests are promising – worked YV4 and VP2V right away, 100 watts CW.

4/15/22 – 12-meter yagi now flying at 50 feet


This past weekend (Thursday, March 3 to Monday, March 7) was a road trip of 2,200 miles. I drove up to K8AZ for my 9th time as a guest operator for a major DX SSB contest.

As always, I thoroughly enjoy being with Tom and the ‘AZ Crew. Tom has built a fantastic station, and every time I go, there has been an improvement since my previous visit.

During the drive home, I was reflecting on these trips to K8AZ and how many other hams I’ve enjoyed the camaraderie with while there. I’ve shared shack time with 21 hams at the ‘AZ station: AA8OY K3LA K3LEA K8AAV K8AZ K8BL K8MR K8NZ K8RR KE3X N5OT N8AA N8TR ND8L W3YQ W5WZ W8CAR W8WTS W8WWV WB8K WT8C. Lots of fun and memories!

All of the scores are posted on, just use the search in the top right of the 3830 page.

W5WZ and N5OT at K8AZ

2022-Feb NAQP RTTY

2/27/2022 @W5WZ – M/2, ops W5WZ, WM5H, KD5YS

We played well together and in the contest, with an apparrent 4th place finish.

During NAQP RTTY, SWR and RF PWR bargraph seemed weird. High SWR, low RF output. RF power set to 100 watts. Outboard LP-100A power meter showing SWR in normal range and power in normal range. As contest progressed, we noticed zero bars on SWR meter, and a single bar on RF meter. LP-100A was showing 100-126 watts, with normal SWR. After contest, connected a dummy load to the K3 Ant2 (easiest to do; normal antenna connected to Ant1) and the meter behaved the same. It was midnight, so didn’t do any other troubleshooting.

Within a day or two, got a support ticket open with Elecraft.

Maintainence – KT34M2

12/18/2021 — Checking out the KT34M2 in preparation of the NAQP series in January and February has revealed issues on all three bands.

Some queries to TowerTalk and the responses all pointed toward bad coax/water in coax, or loose connections between balun and front driven element and/or rear-driven element. On 1/13/22, we tested the coax and even swapped with another run. Same symptoms. A call to M2 support; they suggested perhaps water in one or more of the capacitors. We tilted the tower over to access the capacitors. Removed all 16 end caps, finding no water. We did, however, find much insect debris and dirt dauber nests. Cleaned all that out with compressed air and a long rod to push through the 3/8″ inner tube. We also verified all the mechanical connections on the driven elements and confirmed good continuity with an ohmmeter. The SWR curves are improved, but still too low.

Eyeball QSO with K7BFI

Back in January 2018, I met George K7BFI on the air one evening. Turns out we had a few things in common. So while on vacation, I took the opportunity to stop in and meet him at his home in Utah face-to-face. Thanks George and XYL Karen for a wonderful breakfast, and even better conversation!

Casual photo of Scott and George with his tower in the background

BIC – An important part of contesting

Keeping your butt in the chair is an important part of contesting. Sometimes the chair is the source of discomfort that leads to diminished BIC time. The chairs in my shack were a mixture of cheap and hand-me-down office task chairs that were not very comfortable.

Mixture of chairs – 3 very cheap task chairs and one moderate quality chair that I selfishly always use.

Yesterday my wife KW5MOM and I were shopping for a new bed for the guest bedroom. I saw some used chairs in the corner and asked about them. The proprietor told me they were $50 each. So I made a deal for five of the Herman Miller chairs.

A pair of the five “new-to-me” Herman Miller chairs, which are highly adjustable.

I hope my shack guests will find them more comfortable. At the very least, all the chairs are the same now.

If you have thoughts or experiences regarding chairs for the contest station, please comment below!

Tower Guy Tension – You do check it regularly?

All tower owners should regularly inspect their complete tower system – guys, guy anchors, guy wires, tower base, section bolts, turnbuckles, etc – the complete tower system. Before I climb, I visually check all I can see. When I climb, I check section bolts. And about once a year, I check guy tension and adjust as needed.

10 Feb 2021NW GuyNE GuyS Guy
Top 1/4″292928
Mid 3/16″191818
Bottom 3/16″202019
Using Loos Model PT-2, I adjusted my guys to these tensions

This process led to me emailing Tim W3YQ to ask his thoughts. Here is the reply:

Well, here’s my thoughts.  Plumb is much more important than guy wire
tension – within reason.  To have a tower in plumb, the whole
structure is in compression.  It won’t fail.  Just like a pencil – you
can’t smash it with a downward force, but you can snap it by bending
it in the middle.

I know of only two ways to plumb a tower.  The first, best, and
easiest is to set up two transits; 90 degrees apart.  Sight both
transits to the bottom of the tower then move up to the first guy
level.  Get the tower straight up to that point.  I usually use the
width of a Rohn tower leg as my “good enough” standard.  If the
tower’s way out of plumb, you might have to mess with the other two
sets of guy wires simultaneously.  Sometimes it’s really hard to pull
that first guy wire set in when the rest of the tower is fighting you.
 Once the lowest set of guys is done, move up to the next set.

The tension of the three guy wires of any level will (almost) never be
equal.  The only time that would occur is if you were on a perfectly
flat plane and your guy anchor points are exactly on the money.
Theoretical but not practical.  Someone who adjusts all three guy
wires to equal tension almost certainly have a crocked tower.  Don’t
worry about guy tension.  Go for plumb.  Use the tension gauge to help
you get things set “close” to the suggested tensions.  Err on the side
of loose instead of tight.  That 10% rule is a guideline and it’s
purpose is to prevent the guy wires from galloping.  They’ll do that
in the wind if they’re much too loose.  Loose guy wires, again within
reason, exert less force on the structure.  Yes, when you climb, there
will be a little more movement with loose guy wires, but the tower is
not going to fall over.  Too tight, on the other hand, is exerting an
extreme downward force on the tower.  True that if you’re perfectly in
plumb it won’t collapse, but why go there.  So just use your Loos
gauge as a guide.  Never go above the 10% value on any guy wire, but
try to get close to that value on the one that needs the most tension.
 Then adjust the other two guy wires for plumb and not tension. I
usually check the tension of all three and I generally find that
they’re way off from each other.  That’s OK.

The second method:  It IS possible to plumb by attaching a small rope
at each guy level, one at a time.  Center it in tower, hang it down
through the middle of the tower, and attach a weight at the bottom.
Then stick a bucket of water for the weight to rest in.  I guess you
call that a plumb bob.  The water keeps the weighted rope from
swinging.  It’s kind of a PITA, but it works. 

So, this led to me purchasing a transit and acquiring another to be able to properly do “Method One” above. Once all the components arrive, I’ll post an update on the project.

CST Berger model 136