Performance of the ROOMCAP Antenna:

There are many antenna books where you find:
You need "much wire in the air" in order to obtain an efficient antenna.
Short antennas have an efficiency of 1 to 5 percent ...
Now the time has come to revise these statements!

The radiator length was 3m and the antenna height was 1.5m above ground,
mounted on the car, with 60 W PEP on 160m:

Date: Thu, 31 Aug 2006 22:57:42 +0200
From: Heino Held
To: hb9abx (at) tiscali.ch
Subject: Mobilantenne oder Festantenne

Hallo Felix,
nach unserem tollen QSO auf 160m waren Peter (DL1BLD) und ich (Heino, DJ5ER)
total erstaunt mit welch einer tollen Feldstaerke Du in Bremen angekommen bist.
Wie man eine solche Antenne bauen kann moechten wir gerne wissen (auch fuer die
anderen KW-Baender).

73 aus Bremen von Peter (DL1BLD) und Heino - DJ5ER

Translation:

Hello Felix,
after our fantastic QSO on 160m we (Peter,DL1BLD)
and I (Heino, DJ5ER) we were completely surprised
with what a strong field strength you arrived in Bremen.
We would like to know how such an antenna can
be built (also for the other HF bands).

73 from Bremen .... (QRB = 600 Km)
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5th September 2006:
Now I have reduced the length of the radiator to 2m = 1.25% of the wavelength,
and I still get the same good reports, as can be seen on the email I received after a few
fine contacts last night. Still with 60W PEP, at the border of the city, antenna mounted on the car:

Hello Felix.
Congratulations for your antenna work.
You are the first mobile station on 160 meters for me.
Even you are stronger as the Germans on 160 meters.
I give you on 1.862 Mhz S 9+15 db in the peak!!
The background noise level was S 8 during our QSO

Hope to meet you agn for next report and test.

Piet Schipper / PA0QRS (near Rotterdam)

Schipper mobiele Telecom
2931 LH Krimpen a/d Lek

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Such experiences show, that you can transmit with this small antenna
as effective, as with a 60m long wire, up in the air.

This is possible with:
- Radiating planes and not wires
- Differential feeding system
- Elaborated grounding system to minimise ground loss
- Perfect, low loss matching of antenna radiation resistance

With best 73s

Felix HB9ABX