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Vertical UN7CI for 7, 14 and 21- MHz

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ANTENTOP- 01- 2008, # 010

Vertical UN7CI for 7, 14 and 21- MHz



Figure 2 Design of the Vertical


Omega matching network is tuned to the resonance with help of C1 and C2. At power up to 100-Wtts capacitors C1 and C2 may be used ceramic ones. For high power (more the 100-Wtts) it should be used high quality capacitors. There are: air variable capacitors with gap more the 1-mm, lengths of a coaxial cable having the needed capacity or just fixed high voltage capacitors having high reactive power.


Parts of the matching networks (L and C) were placed inside a plastic box. Radials are placed above the heat insulation of the roof. Radials should have a plastic insulation (with good insulation of the ends) if these ones would be contacted with stuff of the roof. Figure 2 shows the design of the antenna.


My vertical was fixed to the roof beams. No

guys were used for the fixing of the vertical.

Hole through the roof (where the vertical is

going on) was water proofed. However,

conditions for the installation of the vertical at

another roof may differ from mine. So, guys

for the fixing of the vertical and hard

waterproofing of the hole may be needed.



Tuning of the antenna made to minimum SWR at the center of the working band. At the 14-MHz the tuning is made by C1-C2. At the 21-MHz the tuning is made by the lengthen inductor. It needs to choose numbers of coils or by changing of the physical dimension of the inductor. Since the antenna is tuned to 21-MHz no additional tuning needed at 7-MHz.


The antenna was compared with I.V. No difference at local (up to 2000-kms) contact. The vertical beat an I.V. at DX- at distance more the 5000-kms. At the distance the vertical gave 1-1.5- points at S-Scale at reception and 1.5- 2 points at scale S at transmitting.


73! de UN7CI


Page 36


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August 2, 2016 23:12

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