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.

Mast secured to the fence
Mast secured to the fence

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.

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).

Power supply: Updated schematic

I’ve updated the schematic for the power supply. Made a few corrections and rearranged a few things.

Still haven’t figured out why the outputs are behaving like they’re shorted out. Putting a my DMM across the output terminals gives me about 148Ω, which seemed on the low side to me.

Power supply schematic 20170716
Power supply schematic 20170716

A quick check of the SCR shows that it seems to be ok. I think I’ll check the pass transistors next. Looks like they should be easy enough to remove for a quick test. I should probably check the big filter caps too, although I wouldn’t expect those to be bad.

In the process of troubleshooting, I’ve removed the 6 pin connector and large capacitor (1.4 mF) associated with it. I’m planning on replacing them with Powerpole connectors. Three of them will fit nicely in the space occupied by the 6 pin connector. Just need to figure out how to secure them in place.

CARS President-elect

So I’m now the President-elect of the Charleston Amateur Radio Society.

The nominating committee put forth their selections for the club officers at the June meeting, and at the last meeting this past Monday, people at the meeting voted for them. Since nobody else stepped forward to throw their hat into the ring, the officers selected by the nominating committee were all elected by acclamation. Of the officer positions, the only new person was the President (me).

I’ll start my new job with the August meeting. It’s a bit of a higher profile position than I’m used to taking, but I’m looking forward to serving the club as President as the club heads towards its 50th anniversary in a few years.


Power supply: It lives!

The power supply lives!

On my initial inspection of the power supply, the only obvious thing wrong that I had found was a blown fuse. After replacing the power cord, I noticed the power on lamp had burned out too.

Off I went to the last remaining Radio Shack in my area (a franchise store, also known as Hurricane Electronics) to see if I could find some fuses and a replacement lamp. Found some replacement fuses easily enough (35V, 20A), and much to my surprise, replacement bulbs that were the exact same style as what was already on the power supply.

Replacing the light was easy enough, but took a bit longer than expected. The original pair of wires for the light kept breaking when I tried to put the light back into place, so I ended up just replacing the two wires with some 18 gauge stranded wire I had. Once the light was back in place, I plugged the power supply in and on came the light. Yay!

Power supply light
Power supply light

Then I replaced the fuse, turned it back on and was greeted with the meter telling me there was 13ish volts. With my DMM, I read 13.3 V DC at the meter.

13.4V DC output
13.4V DC output

I tweaked the pot at the control board to bring it up to 13.7 V DC.

Tweaked up to 13.7V DC output
Tweaked up to 13.7V DC output

So it looks like the only problem with the power supply was the blown fuse. Now to see how it works with a load applied.

Power supply schematic 20170708
Power supply schematic 20170708