16 December 2016

My best Travel-Loop crafted by John PD7MAA

In former times I had severe antenna restrictions so I bought a heavy Loop and it worked. But when I managed to put some wires in the garden and the signals were about 1-3 S-units above, I switched. Beside that I was enjoyed by constantly re-tuning the antenna.

But times have changed and my experience and expectations grew. I have an EndFed hanging only 6 m above the ground between two houses ... and I wanted more. Of course there are a lot of tips and tricks in the internet how to build a magnetic loop. But I wanted to have something electrically perfect and the construction should be sturdy.

With permission of  J. Scheepers
John Scheppers was experimenting for a long time with theses kind of antennas and he reported very good results. So I kindly asked him, if he was willing to build one for me.

And when she came every thing was as he promised and what I expected.

The main loop consists of a 50 ohm RG-cabel. The construction is perfectly sitting on a plastic tuning box. The strutting from model making is solid and the connectors for the stiffeners are sitting perfectly. All in all the workmanship is up to a professional product.

The antenna arrived in a small plastic back and weighted nearly nothing.

All parts of the Travel-Loop c J. Scheepers

So no RTFM was necessary. I just had to put things together and there were no ways to make mistakes. It stands on the table and is nearly unbreakable. Of course I tore on the cable and the antenna went down to the floor. But seconds later it was on its dedicated position without any damage. There is nearly nothing which could be damaged and if you are able to repair it by yourself.

The promised frequency coverage was between 6,5 – 31 MHz, but I could only test it between 40m and 10m.  When put together the loop has a diameter of about 80 cm and the maximal ouput should not exceed 20 w. As always I have not tried that QRO-power for my max. power is only 5 watt. And that's enough.

Of course I connected the Travel-Loop with my TRX.

Tuning is easy:

1. Start the RX on the desired band
2. Turn the dial until the background noise reaches the loudest level
3. (Switch the ATU off)
4. Give some CW dots and look for the min. SWR and max. output
5. (Switch the ATU on)

And you are done. When you have some experience you know where the 40 m and 20m band is on the dial and you can preposition it. No need to search and the tuning process is very fast.

The bandwidth you can use without retuning is very small on the 40m band (few KHz). On my favorite band 20 m I can at least tune within 30 or more kHz without re-tuning the loop. So with the help of the SWR and some dots in CW tuning is done in a few seconds or as fast as a slow auto tuner ;-)

J. Scheepers

J. Scheepers

The handling, as told before, is easier than with other antennas when you operate outdoor.  If you want to use a wire antenna you have to look out for a tree and have to get the wire up about 5-10 meter or you use a GFK-mast which wants to be attached somewhere. The you have to lay out the radials and the dog will be happy to stumble over them tearing down the whole construction. In the last years I used mainly a MP1 which is easy to tune but is sensitive to your body or any other object.

But most of the time the weather is bad so I use the Travel-Loop indoors for I have no balcony.

And the performance is astonishing:
The EndFed is optimized for 10m, 20m and 40m. On all other bands I can listen but when transmitting you can just forget it. So after a year of experiments here is my setup:

The EndFed antenna (North/South directions) on 10m, 20m and 40m meters is compared to the Loop in my room with the same directions most of the time between 2-3 S-units stronger.
On all other bands the loops is about 2-3 S-units better. But I changed the settings: I positioned the 90 degrees (west/est) and things changed due to the circular polarization of the HF. Now sometimes the signals also on 10,20 and 40m ist much more stronger compared to the EndFed. The antenna is sitting just a meter from my TRX so I could turn the loop and optimize.

Example 5 Watts
Loop 20m ES5PC, 30m ON5KG GW8IZR
Loop and EndFed 40m no results
Endfed GW8IZ 30m ES5PC 20m
So again I changed again my configuration and am making kind of diversity RX. The EndFed is connected to the Kx3 which controls via a Null-Modem cable the Kx2. The Kx2 is connected to the Travel-Loop and I instantly see which antenna works for the receiving station best. I could not believe how often the loop produced better results and I was happily DX-ing with my 5 watt into the magnetic loop. Using this setup I would not generally say that my bad hanging EndFed is better than the loop: Two different antennas two different results and it works great and if you want to check the output just use RBN and you will see that the ionosphere does strange things also with signals coming out of my room.

So if someone wants to have a solidly build magnetic loop for indoor or outdoor use for a decent price just ask John PD7MAA. Further information can be found on his homepage. (and of course don't forget to look at his other projects, they are fascinating.

All in all: Very Well Done! and of course I am not affiliated with John.

Stay Tuned!