Tag Archives: Doublet

A day with a doublet

I have some vacation days this week coinciding with the Thanksgiving holiday so today was largely new doublet day. I spent a fair amount of the morning testing with my AA-55Zoom and then sorting out tuner settings on my Dentron Super Tuner Plus.

Unorthodox antenna chart

As illustrated by my somewhat unorthodox antenna chart, looking straight into the antenna through the Balun Designs 4115 balun, the SWR ranges from 1.37 to 7.5 from 10m through 80m and then jumps to 13-15 across 160m. All of the bands are well within reach of my Dentron Super Tuner Plus. With extremely few exceptions, the tuner brings the SWR down to less than 2:1 and in most cases down to 1.1-1.2 or less. On the 20m band I don’t even need to use a tuner and many of the bands are within reach of the tuner in my TS-590SG.

The first contact with the new antenna was Jeff, W9GY on 40m. I was able to do some A\B testing with my 4BTV and the new doublet. In this case the signal from the doublet was stronger. More contacts through the afternoon on 20m and 40m with some additional A\B testing further illustrates the fact that it’s nice to have options. I was able to make some of the first contacts I’ve had in quite sometime on 160m tonight with good signal reports even with 100W including  a nice QSO with Loren, W5HIO. In many instances the doublet was quieter than the vertical.

Thus far I am well pleased with this new antenna. As I said before, Brian, WB2JIX was very helpful and he builds a quality product. I’m glad that I was able to add this antenna to my station and I believe that it will serve me very well.


True Ladder 240 foot doublet install complete

With some help from my friend and fellow operator Josh, KD9DZP and no help from the weather I was able to complete the installation of my new True Ladder Line 240 foot doublet. It was 28 degrees F and windy. In other words great antenna weather. Thankfully there wasn’t a lot of outside work to complete. We largely had to mount the balun and then run the ladder line over to it.

I’m using a Balun Designs 4115. While the Balun Designs package is very hardy and should be fine in a Wisconsin winter, I placed it in a utility entry box that Josh had in his junk box. It might be belt and suspenders but it will be bearing the direct brunt of winter so it seemed like an easy bit of added insurance.

Feedline and balun

All buttoned up for winter

Once everything outside was closed up the last bit of work was to route the coax into the workshop for the run to the shack.

With the coax work complete I made a quick scan with my AA-55 Zoom:

Initial scan

This is the 240 foot antenna with approximately 50 feet of feedline.

I’ll have some time this week to do make some additional measurements and do some tuning. For now it’s time to continue thawing, have a bowl of chili, connect this thing to my Dentron Super Tuner Plus. and operate on 80m and 160m tonight.


Antenna season is upon us

With a shiny new BITX40 sitting in its box waiting to be assembled and a True Ladder Line open wire fed doublet sitting in its box waiting to be deployed I took one look at the weather and decided to head outside.

Antenna weather

The warmth of a soldering iron was indeed preferable but given that winter is closing in fast combined with rolling back to standard time from daylight savings time having pushed outside work in the daylight to the weekends, I’m probably not getting too many more “nice” weekend days.

My main wire antenna has been a Cobra UltraLite Senior. I put it up just over ten years ago and it has served me well. The Cobra antennas always need a tuner. Initially I used it on 10-160m with an LDG AT-100Pro and my IC-718 and later with a Kenwood AT-230 and my TS-830S. These tuners always found a match. With the addition of the 4-BTV I’ve primarily used it on 80m and 160m with a Dentron Super Tuner Plus and my TS-590SG. As expected, the Dentron always finds a match. (In some cases the internal tuner of the 590SG would find a match but most times I just used the Dentron.)

Over the years I’ve had a growing interest in operation on 160m and while the Cobra version that I have will work there it’s not terribly efficient. With the addition of an SB-200 to my station I was interested in improved efficiency on 40m and 80m at power levels around 500W and even though I’ll still only have 100W on 160m an improvement in efficiency would be welcome there as well. As always a wire antenna is nice to have in addition to a vertical and finally, a longer wire antenna will get me closer to what I’ll need when I’m ready to operate on the new 630m band.

My initial thoughts for replacement of the Cobra was to build an Off-Center Fed Dipole (OCFD) however after a lot of research and exchanging some emails with Brian, WB2JIX I elected to purchase one of his 240 foot open wire fed doublets. Brian was very responsive and informative in our exchanges. The information that he provided in our email exchanges and on his site, coupled with some additional reading tipped the balance.

The new antenna and feedline arrived within a week of placing the order.

New antenna

Packed in the box is 240 feet of antenna and 100 feet of open wire ladder line.

Antenna and ladder line

The antenna is well made out of good quality materials. One of the appealing things is that each leg of the antenna is a continuous wire from the tuner to the end of the antenna. I did the build or buy analysis and figured that by the time I purchased the wire, purchased material for the spreaders, fabricated a bunch of spreaders, and assembled the thing it would be next spring and what’s the fun of putting up an antenna when it’s sunny and warm?

In addition to replacing the antenna it was time to replace some of the rigging that supports it in the trees. While the end supports had been replaced over the years the center support was the original lines and pulley.

10 years of service

After a quick consultation with my friend Bob, The Boat Doctor, I purchased some nice new Harken 340 blocks (and I had one used 348.) Harken blocks are made here in Wisconsin, about 25 miles southwest of my QTH, in Pewaukee.

Harken Blocks

These new blocks are much lighter (at least 3 times lighter) and spin much more freely than the hardware store versions I’ve used previously. Due to their construction they will last much much longer than my prior hardware. I also laid in a supply of nice new black Dacron line.

Given that this new antenna is 100 feet longer (240 feet vs 140 feet) I had done some initial rough measurements and it appeared that I could accommodate an additional 100 feet without moving the end supports. I replaced the original halyard and center support line, and added a second center support halyard and support line so that the antenna would be pulled into the clear away from its supporting trees. Once this work was complete I laid out the antenna and feedline on the ground.

Ladder on the ground

The center support lines were fed through the center support tube:

Center support

Upon beginning the operation of raising the antenna (with the assistance of my two sons) it quickly became apparent that I had done my trigonometry or analytic geometry or some kind of math wrong. Or maybe I should have used a tape measure instead of just pacing it off. The north end of the antenna was hoisted as far and high as it would go, the center was where it needed to be for feedline position, but the south leg was sagging to about 15 feet off the ground. Oops. I hauled the south end down and after re-positioning the support line farther south and a bit higher all was well.

Antenna in place

Thus far it is sitting much nicer than the Cobra ever did. The antenna wire itself is arguably lighter even though it’s 100 feet longer, as the Cobra was actually three parallel conductors (thus the Cobra.) Hopefully it will be less of a wind and snow load as well. The Cobra wire would always load up with snow and sag. Additionally, the open wire feedline is laying nicely and may arguably be less wind and snow load as well. Supposedly open wire feedlne is less susceptible to rain and snow build up. The 450 ohm window line of the Cobra was always effected by rain and snow. The SWR would always move around when it was wet.

By the time I had the initial placement complete it had started to drizzle and the sun was well on its way down. I called it a day, cleaned up, and went inside to thaw. I need to do a bit more work on the center and end points including the addition of tension relief with some additional blocks and weights. I also need to make some initial measurements and work on getting the feedline positioned. Unfortunately I’m not able to run the feedline all the way into my shack. It will terminate outside at a Balun Designs 4115 balun with the run to the shack in coax. This will need to wait until next weekend and the following week with some vacation days for the Thanksgiving holiday. I’m really looking forward to getting this thing on the air.