An experiment with an EH Antenna for 27 MHz Packet Radio.
The first test results.
 
PACKET RADIO TEST

FIRST CONTACTS
ROOF TERRACE
1 M POLE MOUNT


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An EH Antenna for 27 MHz Packet Radio

  The First Packet Experience...

The late afternoon was perfect for staying inside improving the EH Antenna. Wind and rain outside. The balcony mount came in handy. The first prototype got one more turn on the upper coil and was adjusted in the shack with a multiple of a half wavelength of RG-58/U. Fine tuning of the capacitors resulted in even better SWR in the shack, and after having mounted in the pet bottles the result looked like this:

 
CHANNEL110203040
SWR 1:1,91,821,651,501,47
TNC2 I hooked up a TNC2 Packet Modem to the Zodiac transceiver and connected to my PC.
HEN210, channel 23 on Homberg confirmed my call immediately. First try OK. The distance to Homberg from Biberstein is about 17 km.

A second try to HEM255, channel 22 on Rigi in central Switzerland connected up without problems. The distance to Rigi from Biberstein is about 50 km. Of course these are nodes located on mountain peaks, but there is no direct line of sight from my QTH to Rigi anyway. I was merely interested in the distance my EH Antenna could cover. Even so, the transmitter's output is reduced to 2,2 Watts at the EH Antenna connection point due to cable losses. The next step will be to change the cable to RG-213/U.


The First Contacts On The Air...
Sunday thru Tuesday, 10th thru 12th Nov. 2002

Would you believe it? A wideband CB antenna only 23 cm long?

My PET antenna

In the garden

Sunday evening. I'm still using the first prototype in the same location as for the Packet Radio test. The CB band was quiet. It was raining. I received a very strong signal on CH27 and tried a break. The QTH was Berikon, about 560 m. above sea level and 23 km to the East-South-East from Biberstein. One hill, about 540 m. high was in between our QTHs. I got a fairly good report, and the only comment on my RF signal was that it had a fairly rapid fading, which I cannot explain. Was it because of the rain? Or airplanes? There is always an average of three to five aircraft passing overhead at high altitude in the evenings.

A second try Monday evening, which was also a quiet evening without QRM. This time the weather was quite clear. I caught a station 34 km away, roughly East of Biberstein. His location was Uitikon Waldegg, about 600 m. above sea level compared with my 420 meters. In between there were hills reaching 520 m and 600 m respectively. The readability was still very good.

Tuesday 12th November: Mounted the EH Antenna on 3 meter Plica Tube in the garden. The SWR changed compared with the balcony mount, perhaps while the coaxial cable now was on the ground in the grass. After slight re-tuning, the values were fine.
Connected to a Packet Node on Honegg. Distance is about 50 km. This is the record so far! The node sits on Honegg which is in Central Switzerland to the South-South-East from my QTH.
So for you people who dismiss the EH Antenna as "an April fool and a dummy load", remember, in my case the coaxial cable runs from the shack, is connected to a very good ground (cold water pipe and the earth of the house ligthing system), then through a duct UNDER my house and then the coaxial cable runs on the wet grass in the garden until it is finally fed vertically through the 3 meter PLICA PVC support pipe to the EH Antenna.

The EH-Antenna is very quiet, there is practically no static noise. It is indeed an interesting antenna concept. The next step will be to change the coaxial cable to RG8 to minimise the cable losses and to place the antenna in the garden, so that it can "breathe". I cannot imagine that the balcony mount is the ideal position. But so far, the two 10 cm high cylinders, all together 23,2 cm in total prove to radiate.

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Now it is placed on the Roof Terrace...

Sunday 17th Nov. 2002

Roof Terrace mount

The only sunny day in November!

Latest location - the Roof Terrace. The camera is looking almost exactly to the East through the gap between the two trees. At least the EH Antenna is now at least high above ground. Here it is depicted on its 1,6 meter long PVC tube. But we'll see - so far the 3 meter PVC pole in the garden was the most efficient location!
If the reception turns out good this evening in this position, the next step will be to try it out in the same place on the 3 meter PVC pole.

Just a short notice on comparing the roof terrace mount and the 3 meter PVC pole in the garden: There is no difference! The two locations compared show the same coverage. Tests have been made with the 1st prototype on the roof terrace and the 2nd in the garden.

Soon the work will start on the third EH Antenna prototype.

 

Without PET bottles

12th January 2003

VSWR re-measured on 12th Jan. 2003:

CHANNEL12040
VSWR: 1:1,5 1:1,22 1:1,36

The EH antenna is stable. It has been mounted on the roof terrace since 17th november and the VSWR has not changed at all since then. The picture at left was taken without the pet bottle covers. I have noticed slight changes in the VSWR when the antenna was cold at -10 degrees C and the pet bottle was covered with ice crystals. Recently, the EH antenna was covered by a hat of snow, and that could be seen on the SWR meter as well.

Close-up of the EH-Antenna

Close-up

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Collection of contact data...
Nov. 2002 - March 2003

EH with the coax down thru the drain pipe

30th March 2003

STATIONDATEDISTANCE (km)MODE
BerikonNov. 200222FM Voice
ThalwilNov. 200250FM Voice
UitikonNov. 200235FM Voice
RigiNov. 200250Packet
RotenfluhNov. 200275Packet
ZugerbergMar. 200355FM Voice
BodenbergMar. 200330Packet
HittnauApr. 200372FM Voice
SchindelleggiApr. 200354FM Voice


LEFT
I changed the coaxial cable (March 2003) to a good quality RG-213/U coaxial cable. The decreased cable loss improved the overall performance. The RG-213/U runs through the copper rain drainpipe from the terrace down into the ground, then 3.7 meters on the ground along the house wall, into the ground once more and through the ventilation duct into the heating room of my house to the transceiver. The coax is connected to earth at the main cold water pipe at a half cable wavelength from the transceiver.


RIGHT
Today, just for fun, I placed the EH on 1 meter "mast" on the grass, about 2,5 meters from the house wall. The coax was put on the grass. The grass was wet. I checked against a packet radio node 50 km away. The received signals on the S-meter were recorded. I then fed a signal from my signal generator and noted the levels. The generator level for 1 meter pole was 23,0 dBuV and the roof terrace reading was 25,6 dBuV. The difference was 2,6 dB between the two locations. Then add 0,3 dB cable loss. The terrace was 2,9 dB better. Shows that the EH can be placed almost anywhere!
 
1 meter mast in the garden

April 2003
On 1 m pole on the grass in the garden

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