[Antennas] tuning my 4-BTV
Dick KF4NS
kf4nsradio at verizon.net
Mon Apr 9 18:24:42 EDT 2012
I need some advice on tuning my 25 year old Hustler 4-BTV (never used). It is mounted centered on my
house roof over shingles and the house has aluminum gutters. I installed it on a 5ft metal tripod with
14ga metal pipe covered with PVC pipe.
The radials are 2 ea. band 14ga poly insulated stranded wire. Each was cut to spec in original Hustler
manual and DX engineering specs excluding fold-back of about 1ft at end of the 8 radials. Each is
terminated with a ceramic insulator then tied down to screw eyes with RADIO WORKS kevlar+dacron .075 in.
dia. rope and tensioned with adjustable line tensioners. (same was done for guy lines attached just above
the spider hub (no insulator).
Radials do not come closer than 6 ft. to the gutters (40M closest) and are sloped as instructed and
spaced at 45deg. angles from antenna base. Hope I did not leave anything out. Oh, yea, the house roof is
70ft long rectangle with 40M and 20M run to the farthest corners in an 'X' configuration, the others
spaced evenly along the longest sides of the rectangle.
Here are the MFJ-259 test readings (did not include X) all taken at shack end of RG-8X feedline, readings
were close to these at antenna base before connecting feedline but were swinging too much to be useful.
B/W shown < 2:1 SWR:
10M = min. SWR freq 28250 khz 1.2:1 SWR 42ohms, B/W 28.0-29.0 khz 40-98 ohms Z
15M = min SWR freq 20942 khz 1.1:1 SWR 57ohms, B/W 21.0-21.2 khz 65-76 ohms Z
20M = min SWR freq 14000 khz 1.2:1 SWR 62ohms, B/W 14.0-14.21 khz 63-33 ohms Z
40M = min SWR freq 7182 khz 1.4:1 SWR 45ohms, B/W 7.0-7.3 khz 95-27 ohms Z
First thing I will try is adjust the length of radials. Of concern is the wide spread of the Z under 2:1
SWR.
Any ideas will be greatly appreciated. THANKS
73, Dick KF4NS
St Petersburg, FL 33714 USA
Keep The Glow!
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