Review: MFJ-1906HD telescoping mast

Ordered an MFJ-1906 fiberglass mast from DX Engineering over the weekend and it arrived at the house yesterday.

I ordered the 33′ hose clamp version of the mast, but what ended up at the house was the 38′ quick clamp version (MFJ-1906HD). Even the label on box said it was the hose clamp version. Factory labeling error I guess. Can’t really fault DX Engineering for sending the wrong item.

MFJ-1906 box label
MFJ-1906 box label

Instead of the expected six 6′ sections of fiberglass tubing inside the box, there were seven 6′ fiberglass tubes along with 6 quick clamps. It’s a pretty compact package. One 6′ x 2.5″ OD tube with all the others nested inside.

The quick clamps need to be glued to each mast segment so that they don’t come off while you’re extending each segment. The only suitable glue I had was epoxy, so I just used that.

Final assembly is just a matter of adjusting the quick clamps so that the tubes slide into each other and holds securely when the clamp lever is in the down position. I marked the bottom end of each tube at 12 cm (the instructions suggest marking them at 1 ft (~30 cm) as an indicator to stop pulling each tube out.

Final length is just over 2.1 m (7′) and fully extended (leaving about 12 cm nested inside the previous segment) the mast is about 12.2 m (40′) long. Leaving about 30 cm nested in each segment would bring the total length down to just over 11 m (37′), which is still plenty long enough for my purposes. Probably a good idea to leave the thinnest tube nested a little further inside for extra strength, especially on a breezy day.

The mast seems pretty sturdy, although I can tell that getting it up is going to be at least a two person job. At somewhere around 10 kg (~20ish lbs), the mast doesn’t weight a whole lot, but the length can make it bulky and unwieldy. The quick clamps should easily hold each segment well enough for the mast to support a wire or other light weight antenna.

The quick clamps seem like they’ll need readjusting, especially if they’re being locked/unlocked frequently. Don’t drag it on the ground while you’re carrying it around, especially on hard surfaces or you’ll end up grinding away the mast.

Now to figure out how to secure the dipole to the top of the mast.

8/10 stars. (10/10 for value in my case).

Shack is QRT

The shack is QRT.

With the move coming up at the end of December, the next few weeks are pretty busy and there probably isn’t going to be much time for any significant radio for a while.

Brought the antenna down this afternoon. After being in the trees for almost three years, it still looks in pretty good condition.

ZS6BKW antenna ready for packing
ZS6BKW antenna ready for packing

Didn’t see any significant wearing on the wire insulation anywhere. A good spraying off and it would probably look just like new aside from the label on the center insulator fading a bit.

ZS6BKW antenna center
ZS6BKW antenna center

It’s not likely I’ll be able to set up an antenna or shack while we’re in the apartment, so playing serious radio will have to wait until we get things set up again at the new house. Might put the radio in the car and try to do some mobile work, or find a nice tree to throw some wire into and play radio out in the field between now and then.

SWR check

With the radio all set up now in the new shack and connected to the antenna with a slightly shorter length of coax than before, and after being up in the air for two years now, I figured it was a good time to check the SWR performance across the bands to see how/if it changed.

SWR measurements across the bands
SWR measurements across the bands

Compared with two years ago, there haven’t been too many changes. SWR has gone up a little bit in general for all the bands, but not a whole lot. The biggest change seems to have happened on 80m, with the SWR around 3.8 MHz dipping down to a range that I think the radio’s tuner might be able to handle. The SWR on 15m has also gone above the range the radio’s tuner will handle, so that’s one band I seem to have lost.

Things still seem to be looking pretty good for the antenna so far. Hopefully I’ll be able to get a few more up this year.

6m dipole testing

Tested out the 6m dipole with a nice QSO with W4QYV (who happened to be pretty close by) up at 52.525 MHz (FM) and it worked out pretty well except for towards the end when I mysteriously stopped receiving/transmitting anything. The noise was still there, but apparently W4QYV wasn’t hearing me. Very weird.

I was also checking out the JT-65 activity at 50.276 and noticed that the signals there look a lot stronger with the ZS6BKW antenna than they do with the 6m dipole. The ZS6BKW is a good deal higher though and doesn’t have a bunch of houses in the way.

At any rate, I know that it can reach out at least a mile from the house. I was getting a bit concerned after tuning around the band and hearing nothing but noise. Now to decide if I want to leave it up at the house permanently or keep it handy to go portable with. Then again, I have enough wire around, so I could always make another one.

 

A 6m dipole

Built myself a 6m dipole using a dipole center and some of the hamfest wire I picked up back in February. As it’s also Towel Day, I had mine handy just in case.

Makings of a 6m antenna
Makings of a 6m antenna

I wanted my antenna to be resonant at 51 MHz. Using l = 149.35/f 1 gave me a length of 2.96m, so I cut a 3m length of wire and then cut that in half. I soldered some stranded wire to one end of each wire to connect to the dipole center and attached a couple of ceramic insulators to the end. One end got tied off against the house and the other end to my PVC mast propped up against a ladder.

6m dipole in the air
6m dipole in the air
6m dipole up in the air
6m dipole up in the air

The first look with my antenna analyzer showed the antenna resonating around 49.3 MHz with an SWR of 1.0 (wires a bit on the long side). A bit of math (49.3MHz/51MHz = 0.97) told me the antenna needed to be 2.9m long (3.0 * 0.97) so I trimmed 5 cm off each end and got 1.0 SWR right at 51 MHz.

SWR=1.0 at 51MHz
SWR=1.0 at 51MHz

With the dipole connected to the radio, the receive is definitely louder than the ZS6BKW on 6m. I wasn’t able to pick up any other stations, but there was a lot of electronic noise. In the fldigi waterfall, there were lots of periodically spaced vertical lines all across the band. I’ll have to give a listen later when it cools down a bit and people turn off their AC units. Maybe it’ll get better then.

At 2.9m long, it’s small enough to be very easily portable. I’ll need to get a much shorter length of coax to use with it to minimize losses (it’s connected to the radio using about 23m of coax) and something to hold it up in the air. Could be neat to carry this around and break it out when a 6m opening pops up.

1. Take l = 490/f, which gives you the length in feet when f is in MHz, and multiply by 0.3048 to convert to meters. Metric is how I roll.