PA1JIM » Antenna’s

Neighborhood noise

PA1JIM — Fri, 30 Apr 2010 07:59:48 +0000

The other day when I was testing my brand new Cobwebb antenna I noticed something weird. I worked a few stations (EA7IQQ, RV3DMX and RV9LM) and I was pretty happy with the results so far. So I went on the roof to do some finishing touch on the Cobwebb. A little tape here and there to make it a little more waterproof.
When I came back down and listen again, the noise level increased from S1-2 to S8-9! At first I was thinking: maybe the band just closed when I was on the roof. Still it’s a weird thing for the noise level to come up.

But then again I remembered changing something else: I rotate the Cobwebb to be able to reach the elements. So it was in a different position now. Not that that should matter, the Cobwebb is multi directional. Time for a new experiment: the XYL behind the s-meter and me on the roof turning the Cobwebb around. Results? When I turned the front side of the Cobwebb (where the element ends are bound together) to the east, noise level drops to S1-2. When I turned the front in any other direction, noise level increases from S5 till S9! If you take a look at the construction of the Cobwebb, you notice there is less length of element in the front side. Maybe the Cobwebb is multidirectional from a bigger distance, but maybe when a signal (interference) is nearby, the Cobwebb behaves a little directional. It seams like there is a big interference east from my house. When I look at the other side of the street, there is a big old peoples home there. Maybe the source of interference is located there. Time to find out more about this. Although not sure how to begin… Any tips?

First impression Cobwebb 0.2

PA1JIM — Thu, 29 Apr 2010 07:35:39 +0000

A while ago I did a first try to build a Cobwebb antenna. I noticed that even on a very low operating height (about 2 meters above the ground) the Cobwebb received very well. Last weekend I did my second attempt to build a Cobwebb antenna for 10, 12, 15, 17 and 20 meter. Gave the construction a little more thought and this time I tuned the wires individually before putting the Cobwebb on the roof. I’ve made sure every element was resonant within the amateur band. No problems. When I put the Cobwebb on my dormer, this thing works like a charm!

On the receiving part I notice very strong signals. The signal strength seems the same as on the 3 elements beam over at the club. Weird thing though is sometimes at 20m suddenly there is an enormous noise level. Up to S8! But a little later the noise level drops to S1 or 2 and I hear a great deal of signals from all over the world. Can it be the opening and closing of the band?

Cobwebb version 0.1

PA1JIM — Sun, 28 Feb 2010 14:01:15 +0000

After studying several articles on the webs I tried to figure out a concept construction for my first Cobwebb antenna. An awful lot of tie wraps, a few fishing rods and a almost 50 meters of electrical wire. A few hours DIY in the rain and you see the result beneath. First test results: even at only 2,5 meter height very nice reception! In comparison to my end fed wire it’s a lot less noisy and picks up even very weak signals. Last night I was even listening to local QSO’s of amateurs in North America on 20m! Transmitting is another story on this height of course. No one heard me since, but almost all dipoles are resonant in the band and SWR is good. I think it will be even better when it’s on good operating height of 10 meters. I’m planning to put it on a pole on the roof, then it will be 14 meters high and more ore less 360 degrees free around.
The construction is of course just for testing purposes only. I need to construct another feed point which is waterproof. I’m not satisfied with the tie wrap solution to attach the wires to the spreaders. I think it’s not UV-proof too. I’m thinking about drilling little holes in the spreader to put little screws in them. And the end of the dipole wires I want some elastic pieces in. Then the wires will be tight all the time. Just haven’t figure out what to use for the elastic material yet.
And the baseplate needs some adjustment too, no possibility to attach a vertical pole in it now and the spreaders are not properly aligned. So need to do some rework… Then again, it’s only version 0.1!

Back in town

PA1JIM — Wed, 14 Oct 2009 07:34:28 +0000

Hi all! We’re back in town from two weeks of holiday! It was very nice. We did a lot of hiking, site seeing, enjoying meals etc. Unfortunately I wasn’t able to set up my portable radio kit in Italy at all. The chalets where so tight packet together, it was impossible to throw a wire over something. And if I was able to do that, I would have interfered with at least 10 satellite receivers. So I kept the goodies in the trunk for the first week of the holiday.
In France of course I had more possibilities to setup a nice configuration. I did bring a 1:6 balun with me to experiment with. Two wires of 13,8m and 27,7m where attached to it and hung up between two tree’s. It worked kind of nice but of course only on the lower bands (40 and 80). And there was not much of interesting activity on those bands that week. Then I’ve tried to work my open dipole for 20m and my long wire (16m) that are already installed at the house. But not much luck either. Lots of static (at least I think, or even there are appearing noise generators) and very little signals. All in all I’ve made 4 QSO’s. Not enough to even bring the stuff with me. I consider to buy a dedicated (old) radio for that location to leave. Then I don’t have to bring the heavy stuff with me all the time and I’m able to use a good radio with all filters and stuff even on holidays.

So when someone has good suggestions for a good (second hand) transceiver with (kind of) modern filter methods but isn’t too expensive (I’ll only use it for maybe one week a year), leave me a comment or a message!

Cable thrue the roof

PA1JIM — Fri, 28 Aug 2009 07:58:44 +0000

Since I placed my antennas last year, I just put the coax cables thrue the roofwindow. A pretty fast solution but far from ideal, especially in wintertime since I can’t really close one window. Some time ago I bought an rooftile of lead. I think it is originally destined for some kind of mast. But if you mount it up-side-down it could be a great way to put coax cables thrue inside.
So I removed one rooftile and gently drilled a hole in it. Mounted the lead on top of it and put the tile on the roof again. Putted the cables thrue and sailed the whole thing with vulcanization tape. It looks pretty solid, let’s hope that is survives the winter!

First 10 meter contact!

PA1JIM — Wed, 13 May 2009 08:42:48 +0000

This week I visiting my parents in Hautes Alpes, France (JN24XM) again. Last sunday evening we arrived and the next morning I did check the wire antenna’s on the roof. They were all broken due to heavy snow slidings.
After fixing the open dipole for 20 and the long wire for the other bands on the roof, I put up my famous full wave 40 meter horizontal loop behind the house.
All antenna’s are up and running again and work great.

This morning I did see some 10 meter spots on the cluster so I tuned 10 meter on my long wire. After listening for a few minutes there was a great clear and crisp signal from Henk, PA0RKS. He was CQing. I gave him a call back and as a total surprise Henk did hear me! My first QSO on the 10 meter band had happened! It must have been some sporadic E-reflection. Thanks Henk!

Cat moustache antenna

PA1JIM — Sat, 25 Apr 2009 10:52:47 +0000

Okay, so I got it finally up and running, my cat moustache antenna! First I build a decent 1:1 balun with an 4C65 core. I did want to attach more then one set of wires on a single feeding point. I did it with a piece of drainage pipe and some nuts and bolts. Insert the balun from under and ready! The wires where the right length in the first run. Only the 40m wires I had to shorten a little.

40m, 20m and 10m wires a nice harmonic within the middle of each band, swr is okay even without tuner. I’m a happy camper!

1:1 Balun

PA1JIM — Wed, 18 Mar 2009 13:53:27 +0000

Last night my good friend Fred, PA3YH was visiting me. We’ve made a 1:1 balun for my new multiband dipole. I did think Fred has a funny name for such a antenna: cat-mustache-antenna.
The design of the antenna is still in my head mainly. But soon I will make a drawing of it and I’ll build the thing. The balun I needed anyway, so that has been made!

Antenna problems

PA1JIM — Mon, 02 Mar 2009 10:01:34 +0000

Last weekend I’ve done some work on my multi band open dipole. Seems that the wires for 40m, 20m and 10m where all too long. That way the antenna was not resonant inside those bands but lower.
So last weekend I went on the roof with a cutting tool. After a few hours tweaking the results where promising. 40 and 10 where resonant inside the band! Made a nice QSO with Rick, G8KSM on 40m. Beautiful signal and Rick told me mine was too. But 20m still wasn’t resonant inside the band. So I went up again.
Then for the third time, the wire for 40m broke. Grrrmbl! Replaced the wire, but then the whole thing went fubar. Nothing was resonant anywhere…
A little frustrated I ripped everything off the roof and placed my good old single open dipole for 20m up. First I gotta figure out a good firm construction for this mulit band dipole. I’ve got some ideas already. Will post an update on this issue soon!

Skywire loop antenna

PA1JIM — Thu, 01 Jan 2009 15:41:40 +0000

Some time ago I was reading about an full wave loop antenna. I was interested in this antenna right away. Since the preparation for the full radio exam I was told that full size antenna’s always outperform half wave or quarter wave antenna’s. The only problem is the space you need to make such an antenna operational.

Well, over here in the Hautes Alpes there is space enough! So I already bought some fishing rods earlier. A few days back I assembled the fullwave loop antenna for 40 meters. I placed the rods in a square with 10 meters between each rod. Put a wire in between and hooked it up to my TS-50. Immediately I noticed the difference between an open dipole (as setup in earlier article) and this skywire loop. It is much, much more quit on all bands, therefore I can pickup so many more signals. Almost every signal is stronger on the loop then the dipole. Only a few signals are stronger on the dipole. So as I already suspected from all the reading I did on fullwave loops: they perform very well! I will think about a more permanent setup of a skywire loop over here in de Hautes Alpes.