HV7CX  MOBILE WHIP QRV on 9 BANDS

Modification of HV7CX for 40,20,15,11,10,6,4,2m and 70cm

my goal for this work:

  Small and limited space in the city needs some good ideas
to be qrv on hamradio. So it is interesting to see what can be
done with small antennas. I tested the Diamond HV7CX and want
to see what is possible with this small antenna mounted on the balcony.
In original version the antenna works on 40m,15m,10m,6m,2m and on 70cm.
For 30m and 20m there is an additonal KIT needed and the upper coil
and the correction elements have to be replaced. 
But I want to use the antenna on 40,20,15 and 10m without
changing the mechanical parts...!

So I "played" a bit ... and got some more!

The mounting conditions.
HV7CX_MOUNTING

THE MODIFIED HV7CX
HV7CX_MOD_DG0OPK 

ANTENNA TUNING:
At first tune the antenna for 6m by cutting the tuning element lenght (c).
After this cut length (d) for 10(11m). In my case it was not possible to get
resonance over 28MHz so I tried to get a peak between 10 and 11m Band.
Then tune length (b) and lenght (a) to the best compromise for 40,20 and 15m.
This is very difficult because there is a big influence between the tuning
elements (a) and (b).
You  also have to change the space range between (a) and (b) for
best tuning  but the results looks not bad.

After some "hard work" I got the following results.

The measurements were done on the antenna connector
in my shack  after about 7m RG58 cable .

40m BAND:
hv7cx 40m
The antenna bandwidth is very small, only some kHz because of the
big loading coil for 40m and the small size of antenna.
For better operation an antenna tuner is needed.

20m BAND:
hv7cx 20m
The SWR 1:2 bandwith is about 200KHz.
15m BAND:
hv7cx 15m
The bandwidth is also very small on 15m, but it works.
For better operation an antenna tuner is needed.

10 (11)m BAND:
hv7cx 10_11m
Bigger bandwidth can be seen. I tuned to 27.6MHz and it was  possible
to  get low SWR on 10 and 11m with an antenna tuner.

6m BAND:
hv7cx 6m
Very good bandwidth and SWR on 6m.
4m BAND:
  hv7cx_4m
Surprise: Also useable on 4m with good SWR and bandwidth.
2m BAND:
hv7cx_2m
SWR around 1:1.6 not very good,but good and useable for all band.
and finally

70cm BAND
  hv7cx_70cm
Good  SWR on the whole band,very nice.
Thats all...but this is
NO WONDER ANTENNA !
Think on the small size and be happy if it works !


 IMPORTANT NOTE :
THE PERFORMANCE STRONGLY DEPENDS ON THE LOCAL
MOUNTING CONDITIONS. I CAN NOT GIVE ANY
GUARANTEE THAT IT WORKS IN YOUR LOCAL CONDITIONS.

If you need more information please write an email

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last change: 20.nov 2013 (DG0OPK)