Did one of my last 2015 Antenna projects last week building a 20 meter quarter wave ground mounted vertical. Based on what I learned recently I added all 8 radial before I tuned the antenna.
Started with the vertical wire 18' long and the 8 radials are 17'6".
VSWR results .....
Didnt need to cut the vertical element which was quite a surprise, It seems to be optimum around 14.2 MHz. I may try 6" on the vert el before the tuning is completed.
Freq Initial ( 4 radials ) Initial ( 8 radials ) - 6" Radials - 6" Radials - 6" Radials
13.8 MHz 2.1 2.45 2.1 2.1 2.4
13.9 MHz 1.9 2.1 2.0 2.0 2.1
14.0 MHz 1.8 2.0 1.9 1.9 1.9
14.1 MHz 1.7 1.8 1.7 1.7 1.7
14.2 MHz 1.6 1.7 1.6 1.6 1.6
14.3 MHz 1.8 1.7 1.6 1.6 1.6
14.4 MHz na 1.8 1.7 1.7 1.7
14.5 MHz na 1.9 1.9 1.9 1.9
So it sure doesn't look like tuning the radials had much of an affect. The VSWR is OK where it is now however the experience I had with the 4 other verticals I recently built was very much different then this one. This antenna is connected to the MFJ switcher that also has the 20m 5/8 Vert so I am goign to be able to do some A/B testing which was one of the reasons why I purchased the switch. On receive it doesnt seem to make much of a difference , 5/8 or 1/4 but the shorter one seems to ever so slightly edge out the 5/8 in receive performance.
The 5/8 an the radios antenna tuner didn't seem to get along. Under 50 watts output power is solid and the VSWR constant but when I crank it up to 100 watts using the built in tuner it starts clawing back TX P top 70-90 watts and the VSWR climbs. I thought it was a function of the antenna but the new 1/4 antenna exhibited the same sorts of characteristic. When I bypass the tuner the phenomena goes away.
May or may not tinker with this antenna further. The night that I tuned it was wet and wet seems to change the characteristics of these antennas ... a little bit anyhow!
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