Antenna – Page 2 – AB4UG Radioblog

Antenna works!

The antenna works. There wasn’t a whole lot to hear on the bands, so I’m not sure if the antenna’s performance is crap in its current configuration, or if it’s just the bands are crap today. I’ll spend some more time on the antenna and playing on the radio tomorrow.

The radio’s internal tuner will match the antenna from 20 m up to 6 m, but not on any of the bands below that. Better than I expected, although not having 40 m is a bit of a downer. The noise level on all the bands below 20 m was pretty high too (S7-9).

Now the dilemma is what to do with the antenna when the radio isn’t being used. The antenna and mast are pretty conspicuous when deployed, and we would no doubt get some naughtygrams from the HOA police.

With the mast down, there’s not much to see from the road or even the side of the house.

The antenna becomes pretty messy though and obviously makes mowing more difficult if I just leave it lying on the ground. The antenna would also exposed to full sun, which would probably shorten its life.

I think what will most likely end up happening is that the antenna will come off the mast and get coiled back up when it’s not being used. I can use an S hook to attach the antenna center to the top of the mast which will make for one less rope to deal with.

That means playing radio will end up being a little bit more work and a more planned activity. Won’t have to worry about the inevitability of the antenna or coax getting chewed up by the lawn mower though.

Finally an antenna in the air

The fiberglass mast is attached to the fence, and the antenna is finally up in the air!

After pondering a few options for the mast, I decided to prop it up against one of the 4×4 fence posts and secure it in place using some hanger strap material.

By standing on a ladder so that I can reach the clamps, raising each of the mast sections is fairly easy. The hard part is not getting tangled up in the antenna wires and feed line while raising each section.

The antenna is a little more conspicuous than it was at the old house. With all but one of the mast sections extended, the center of the antenna is somewhere between 25-30 feet up in the air I think.

Lowering the antenna can be done by either lowering it from the rope (like a flag) or lowering the mast sections. With the mast sections all the way down, only a couple of feet or so of mast are left sticking up above the fence.

A quick look at SWR with my antenna analyzer suggests the arrangement isn’t optimal. The proximity of things like the house, fence and mast might be interfering with the window line segment of the antenna. Getting high SWR readings on 40 m, and 20 m looks marginal. 6 m and 10 m look ok, and parts of 80 m and 160 m might be doable (although the low-ish SWRs there might just be because of coax loss).

I haven’t connected the radio yet, so I don’t know how much noise there is yet. One of the antenna legs comes pretty close to the AC condenser outside, so there could be a fair bit of noise when the AC kicks in. With one quarter of the antenna more or less sandwiched between two houses, there’s no telling what the radiation pattern will look like.

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.

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.

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.

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.

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.