160 m EH antenna

 

     Now I complete my new experiment with EH antennas : I built and tested an EH antenna for 160m band. As a material for it were… two home tanks for a hot washing of the bed-clothes ( see Photo 1 ). They made of a  thin steel, zinc covered sheets and have the following dimensions : bottom diameter 324mm, upper diameter 384mm, height 380 mm. Yes, of course, the copper or aluminium are preferable, but for a 160m band zinc has not the bad parameters. Antenna made as a short, slightly conic “dipole”. Pole elements connected by the three wood, wax covered stems ( see Photo 2 ).A polyethylene pipe 50mm diameter, where mounted an isolation coil, having 10 turns, between the centers of bottoms mounted additionally. Unfortunately, this construction not allows to get the all features of EH antenna, because the E-field lines, replaced between the bottoms, don’t create a radiation. On the other hand, it allows to increase a capacity between the elements of antenna. A distance between the elements is equal to a bottom diameter – 320mm. It may be and less, but, as I understand, this choice allows slightly decrease a curvature of the E-field lines. A curvature of the E-field lines decrease, because the elements of antenna are slightly conic, also.

     On the inner side of the lower element bottom the polypropylene pipe 1 meter length, 50mm diameter mounted. I tried to mount on it a main coil, but for a coil, having so high inductance, the length to diameter ratio has been founded as critical. Then I put on it a new plastic framework 100mm diameter. In this construction I prefer the following configuration : resonance coil – feeding coax – L-T network near the transceiver. Why? Because I plan to convert it into a double band antenna : 160 and 80m. I think, it easy to do : to short by the relay some turns of the main coil, beginning from the inner conductor of the coax, to get a resonance on a 80m band. And there is a problem to switch two separate L-T networks under the very high RF voltage.

     In my case the capacitance between two elements of antenna equal to 30 Pf.. I’m very grateful to W5QJR and W0KPH for the L-T network design programs. There were no problems to tune the antenna to the desired frequency – 1830 kHz. The frequencies, where VSWR = 2, were 1815 and 1845 kHz. So, the antenna has a good features in a band of 30 kHz.

     I tested my antenna on the alternative QTH : 16 storeys building. The base dimensions of it – 16 x 28 meters. There is a building for a technical communications on the roof also. It has the following dimensions : 8 x 6 meters base, 4 meters height. 4 meters up over the roof of the technical communications building my EH antenna for a 160m band was mounted ( see Photo 3 ). Why I did it? I plan to check a version, that so high building may be as a “thick tower” for a 160m band.

     I know, that the elements I use for my EH antenna are MINIMUM MINIMORUM (lat.) for a 160m band. But I have been inspired, that W0KPH tested an EH antenna, having a diameter to length ratio equal to 0.86. Moreover, the slightly conic elements…

     I tested my antenna in CQ WW 160M CW contest. Sorry, I had a free time for an one night only : from 21:30UT in Saturday,25, to 03:30UT on Sunday, 26 January 2003. But for this short time I got the answers for many questions. For my 6 hours in the contest I made 150 QSO, worked 33 countries. I worked mainly in a Search&Pounce mode. About 20 QSO were made on CQ only. Not too bad, as for the first time, but…

1.All worked countries replaced in a sector, limited by PA, ON, 4X, 9K, EY, UA9. Distance no more, than 3000 km. From an American continent I heard VE1ZZ only, but he worked at a S&P mode at the time.

2.At my primary QSOs I asked my real RST. My reports, received from UA6LV and UA9AT were 579. It is too bad as for the amplifier, having Ua = 1200V, Ia = 0.5A and antenna, mounted on the roof of the 16 storeys building, that replaced on a height. I remind, that my QTH, and 16 storeys building also, replaced in the QTH-locator KN67rw.

3. There were the strange moments during the contest. For example, stations of PA, 9K I worked with no problem. But some stations of 9A, YU, OK, replaced nearer, sometime ignored my calling ( not heard me, I believe ). Some stations asked my callsign for several times.

4. I tried to work on the frequencies up of 1845 kHz ( VSVR = 2 ). I made QSOs, But after several callings. Especially I “like” my attempts to make QSO with G6PZ, called CQ at 1869 kHz. For about 10 attempts I have no QSO with him.

5. But there is one positive moment. As my QTH, as 16 storeys building replaced near the power lines 150Kv, 63Kv and 38Kv AC. When a dump weather, they make a very strong noise, to S9 on 160m, when I use an Inverted Vee antenna. During the contest I had a noise less, than S5.

     What I can to say about? It is clear, that the 16 storeys building seems not as a “thick tower”, but as a “thin ground”. The reinforced concrete roof does it’s job. And the height minimum 20 meters over the roof is needed.

    Now I ask myself, where is better expenses to efficiency ratio : 20 meter vertical with four radials or EH antenna 20m up over the same roof?  Now I can’t to reply, because not built and not compared. It may be a good solution for the Hams, living on the few acres. For example, in ex-USSR private houses in the cities replaced on 1.5 – 2.5 acres.

 

    UT4EK, Alex.