Antenna Projects

2e0svt

My Antenna switches project

The antenna Switch before I looked inside

The wiring did not impress me

My attempt at an improvement

It didn’t improve thing much. I believe because being a common earth the earth element is active oin both antennas regardless of what antenna is selected. Only way I think it can wotrk is to be in a plastic box and use dpdt switches.

This antenna switch was seriously lossy and a peek inside didn’t inspire confidence. so I tried re-routing the wiring which helped, but not by much. Of course anything placed in the antenna line is going to create a loss, but this was to much to live with. Moral don’t buy cheap antenna switches, I think the rocker switch was the main culprit myself though. Rotary switches seem better.

Above the original wiring on this 2 way antenna switch Bellow the rewired version. It made a little difference though.

I have just put a SWR meter in line with the radio’s and did a comparison check.

With a radio plugged directly into the so239 socket at the back of the radio and with a SWR meter wired in series, running 5W out of the radio. The meter showed just a shade under 5W and I am assuming the drop was because of the break in the antenna line for the SWR Meter which is pretty acceptable as I use 5W most of the time.

However with the rotary antenna switch in line as well my power reduced to 4W which is quite a drop, but this is what I have in effect been running when the radio was set to 5W and I rarely need to increase the power from this.

With one of the 2 way switches above replacing the rotary antenna switch the power dropped to 3W. A massive 2W drop.

So I have now decided that I am going to cannibalize the above switches for the SO239 and the rocker switches, a 2W loss is unacceptable.

Brings it home when you have something to compare power ratings to.

Portable 2m dipole

DSCF0042My homwbrew 2m dipole all folded up for transportation

 

My latest project is this dipole. I have not though used a separate balun, or ladder line, as I have neither of these items handy.

Fired it up and managed to get the SWR to 2 all the way across the 2m band, but it was only just above my head and it was pulling in signals to the same level as the collinear on the roof, so seems promising for when it is in free air.

The idea is to use it as a portable set up. The wire is in the plastic tubes and the PL259’s that it is connected to are glued in using hot melt glue. The other open end of the tube has had the tubes for vitamin tablets or denture cleaners also hot melt glued in to keep it waterproof

The box is a plastic project box I already had with the SO239 sockets cannibalized from the the antenna switch used for the connections.

Test 7th June 2013

When the ugly balun was built into the antenna I plugged it into the baofeng hand held set on 4W and via a pigtail SMA to SO239 adapter connected the radio to a SWR meter and the new antenna.

I made no attempt to gain any height and merely rested one element on the floor and held the top element in place
with the door handle in vertical plane.

SWR was less than 1.5 and I conducted a QSO on the local repeater and the person I spoke to was used to my original
signals and reported I was doing fine on the input, bearing in mind I usually run 4W ERP.

This antenna looks like it will be great for what it was intended, Portable work.

I am generally happy with it.

I did another test with some rg58 coax connected to a small length of mini 8 to connect the antenna out into the garden. It wasn’t that high and there were some obstructions and nearby metalwork, but around 144.000 the SWR was at 1.5 around 146.000 it went up to 1.8 But this I think will improve with more height and less obstructions. plus a single length of coax as well. Even so I am quite pleased with that sort of performance, from a simple home brew lash up.

However I had built an ugly balun inside the centre box, but I found the box was getting hot. So I have now wired in a separate ugly Balun.

We used it for real over the weekend we activated at the Miniature railway and it performed very well indeed. We just hung it from a tree and were using it to send and receive SSTV pictures via the Leicester Radio Societies SSTV repeater running just 5w. It worked very well indeed. One plastic tube came adrift on the day, but it still worked OK. As we now know it is a working so well I am now finalising the project and it has become part of our portable kit.


The beat goes on

Tape measure yagi beam times 3

When the weather gets a bit warmer a few friends and myself and perhaps Julia will be doing some fox-hunting.Kelvin has already made his DF beam but I found I had pretty much enough parts to make 3 of these tape measure yagis and that is exactly what I did

This site was the basis for the plans

But I did change round some of it. The handles are my invention as are the radio mounts. The mark one needs a few modification and that is the one shown in the pictures. But they are all basically the same.

Cost well main expense was the tape measure at around £4 for all 3 antennas. The saddles I had to buy which work out at around £2 per antenna. The pipe Velcro, coax and pl259’s I already had, but I did need adaptor for the radio and 3 of these were needed at around £3.50 each and was the most costly item really. If you had to buy it all I guess you are looking at £10-15  each as it was they cost me around £6 and a long afternoon of construction.

DSCF0038

Prepping the tape measure yagi prototype for testing

DSCF0035

Quite comfortable to use though vertical polorisation is a little more awkward then expoected.

Shown above  is the mark III antenna. This evolved from the previous 2 antennas, but they all work very well indeed

DSCF0029

Finished Yagi with radio attached and the compass. Compas was attached via velcro, but it proved unreliable so it was finally glued directly onto the beam.

Here is the last antenna I made in its completed form. including Radio, mic and compass.

Ladder Line antenna’s

I recently bought 10m of ladder line and have been making Slim Jim’s and J pole antennas from this material.

I had some very good results, but my conclusions are that the Slim Jim antenna is much better and more efficient than j pole antennas. But this is just my personal feeling having compared both types of antenna in a similar package. Bit of a fiddle tuning them especially without an Analyser but managed to get all the experiments so far below 1.5:1 across the whole of the band. I suspect had I more time and the inclination I could get them lower. But other than a mention in dispatches I see little point in struggling to get the SWR lower when 1.5:1 is a perfectly acceptable reading.

Why did I make them? Well for one reason they are roll up and pick up when finished with them and with the yaesu FT 817 in a small bag along with the wonder wands it is in effect a full QRP station in a bag.

A friend and I have plans to try out qrp from a couple of local hill tops on using the bikes., in my case this will probably be the last season I will be using my motorcycles, for reasons I wont go into here.

Another is an alternate home antenna is always a good idea and for this the experimentation continues. Next experiment is to drop a slim Jim and a Jpole  into a drainpipe and compare the reading of them  naked and covered. Watch this space to see the results I achieve.

SOTA BEAMS SB270

Just bought a BS270 which is a 2m and 70cm beam

Sotabeam SB270 beam antenna. Can work for 2m or 70cm in either Horizontal or vertical axis

This is the complete system shown here including the mast and the guying kit I could add a second feeder (one is supplied) which would allow both 2m and 70cm to be used without changing feeders at the antenna However the feeders would either have to go into  duplexer or they have to be swapped at the radio end as well.

I envisage it will be used mainly for 2m SSB

Not tried it in anger yet. I have put the analyser on the antenna just in the house and it was showing less than 1,5:1

The antenna mounts at about 4m off the ground. and the mast is 7m long. I could remove the unwanted sections. But I have plans for the top part of the mast. Even if only for our flag. Though at that length we could probably have a full wave 6m vertical as well.

My model is the old model. There is a new model released which is a 2m beam or 6m beam, But I shall not be upgrading to these antenna/s