The unipole must be tapped at some point to get a proper match. You really
need to look at the as X and J, not resonance. You can tap for a high
impedance and zero reactance on for 50 ohms and reactance. In either case
some kind of matching will be required. I would go for the high impedance
option and then just use a transformer to get back to 50 ohms. You get
better bandwidth that way and some claim a higher efficiency due to lower IR
On 9/15/09 11:42 AM, "Glen" <email@example.com> wrote:
> I would like to speak with anyone running a unipole on 160M.
> I have constructed the basic antenna on a 120' Rohn 25 tower. 3 wires
> dropped off the top of
> the tower, 30" away, to a hoop 3' off the ground. Of course, all the guy
> wires are insulated
> and broken up according to the antenna handbook.
> At first, it seemed resonant on 4.03Mhz and 7.3Mhz. It was an outstanding
> receive antenna for 40M, equaling
> my 1650' Sky Loop, and very QUIET when compared to the InvL.
> It also seems to receive well at 80M. 160M is a mystery right now...added
> about 25 feet to
> each wire run on a piece of PVC drain tile up at 70' point. Seems to find
> resonance now about
> 3.65Mhz and 6.6Mhz. Very complex impedance from what I can tell right now.
> No resonance that I can
> find on 160M.
> Entire ground system not in yet, but did roll out 8 radials for some initial
> I suspect that my tower feed lines may be a source of trouble. I have all
> the 7/8" hardline
> and rotor cable coming off at the 40' point and traveling down a guy wire
> towards the shack.
> Need advice on this. It has been suggested to me that I must run the
> hardline straight down
> the tower and bond them all to the ground system.
> What do you guys think???
> Glen K4KV
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