[TowerTalk] More Radials = Higher SWR???

[Michael Tope]

Dennis,

Once you figure out what your impedance converges to as you add more 
radials, you might be able to bring the VSWR back down to something more 
acceptable with an Unun transformer. I have a 55ft top-loaded vertical 
for 160 meters. The feedpoint impedance with a dense radial field is 
about 12 ohms (VSWR > 4:1).  With a 4:1 Unun transformer, the VSWR 
improves to 1.1:1 at around 1830 KHz. The 2:1 VSWR bandwidth is about 
~50 KHz. I got the unit I have from Balun Designs.

73, Mike W4EF...............


On 2/5/2023 3:34 PM, Test wrote:
> I recently erected  my first Vertical (Hy-Gain AV-18HT) antenna and the more
> I try improving it, the more confused I become.
> I added the Hy-Gain MK-160A kit that converts the Vertical to an "L" antenna
> on 160M. For the first time in 50 years of Ham Radio, I was able to work EU
> stations on 160M. WOW!!!!
> I decided to start "Improving" and added my first 4 radials. There's a
> rumor: "You gain and extra 6db of signal if you install antennas in the
> middle of winter in a blizzard." NOT TRUE!!!! The SWR went up a little
> higher, but still workable so I added 4 more.  Now the SWR is over 2:1 on
> all of 160M and is not usable for transmitting.  I disconnected the last 4
> radials from the ground plate but left them in place and now the SWR is back
> to 1.6.
> Grounding Issues? Maybe?
> The ground here is very poor with MANY rocks and solid basalt 18 inch down.
> 8ft ground rods are not practical.  Instead I have installed three 20ft
> galvanized 1 1/2 inch pipe buried as deep as possible in 3 directions from
> the base of the Vertical.  Also I have 500 ft #2 solid tinned ground wire
> bonding all antennas, towers, Vertical, Power entrance point and all devices
> in shack.  I'm located on an 800 ft cliff above Lake Coeur d' Alene in North
> Idaho and we get lots of lightning strikes but that's another story...
> All radials are evenly spaced and 65ft long.
> I'm not sure if I can included attachments of the comparison SWR Graphs so
> I'll also describe the comparisons:
> The colors refer to the attachment if present. The shift in resonates is
> explainable: The antenna wire was slightly lengthened.
> Below are the minimum SWR on 160M taken at the base of the Vertical..  All
> other bands were just slightly affected .
> No Radials= 1.2 SWR (Fuchsia)
> 4 Radials = 1.6 SWR (Red)
> 8 radials =  2.2 SWR Green)
> Any comments would be greatly appreciated!
> 73 es gud DX
> Dennis - K7OGW
>
>