Indoor Antennas

by Dave G0HVN

I have spent many years enjoying amateur radio from locations that allowed me to put up full size HF dipoles and verticals. I have worked people in many parts of the world on Phone, CW and Data modes. But if you find you are living somewhere with restrictions by or lack of space then do not despair, there is light at the end of the tunnel.

I now live in an area that does not allow the erection of antennas of any sort. While Satellite and TV aerials are tolerated they need to invisible from any of the estate roads. So moving here I found I had to make a choice; either give up the hobby (no chance), or see if I could utilize the loft space.

As my interest are more on the HF bands this proved to be quite a challenge. I tried many types of antennas. A loop antenna round the perimeter of the loft but this did not perform as well as I thought it should. Then experimenting with a none resent multi band dipole did not perform that well. Finally I tried a resonant 40 meter dipole. This worked very well. I soon discovered I was having regular good contacts across the UK and well into Europe.

In order to remote match this dipole, I installed an automatic antenna turner in the loft space, about 30 feet of coaxial cable from the Radio to the tuner and about 10 feet of coax from the tuner to the Antenna feed point in the apex of the roof. My loft is more or less 30FT square so I managed to fit the dipole in by bending it, following the roof line and along the ridge and down along the eves. Ugly Balun was deployed with approx. 20 meters of RG58 Coax onto a 2.5 inch former (It was all I had at the time) and gave me a good balanced match.

As the dipole is resonant on 40M, the tuner allowed me to match for other bands. I soon moved on from this adding from the same feed point a 80M dipole, further adding a 20M. Recently adding a dipole. All cut resonant and all from the same feed point to reduce the risk of interaction. Some people refer to this configuration as a fan dipole, however mine is not fan shaped but parallel wires separated by plastic clips at about 3 inches in length. Because my antennas are in the loft I do not have to worry too much about physical strength as they are shielded from the elements that break externally mounted antennas.

One of the things to consider is if your licence restrictions limit the amount of power, then you need to make the most of that power by having the most efficient antenna you can fit into the space available. While there is nothing wrong with a multi band antenna strung high between supports, they work very well, however when you start squeezing or bending antennas to fit into a smaller plot they become less efficient. Therefore in my opinion and at my location resonant antennas work far better than multi-band antennas. They say you get out what you put into a ‘resonant’ antenna.

The loft also contains a number of vertical antennas which include a motorised HF vertical ground plane for 20M through to 6M, a dual-band 2m and 70CM vertical, a 6M,4M,2M,70CM vertical and finally (not in the pictures) another 6M,2M and CM vertical. I also have a 6M horizontal Dipole installed as well.

 2015-06-13 12.31.40 2015-06-13 12.29.37   2015-06-13 12.35.42

The pictures above show the vertical antennas The closest one being the HF motorised vertical, then the 6M horizontal dipole then to the dual-band verticals at the far end. The photograph in the centre shows the coaxial balun and the feed point of the dipoles. The photograph on the right shows how the wires are separated with plastic clips. This antenna has since been removed but it illustrates how the dipoles have been separated.

As far as VHF and UHF are concerned, I can work a reasonable distance and have enjoyed many contacts. I recently had one well into Europe on 6M band SSB with the dipole antenna. Also perhaps helps being 650 feet above sea level.

 

Dave G0HVN