[Antennas] tuning my 4-BTV

[Terry Conboy]

If this were my antenna, I'd say it was ready to put on the air.  I'd be 
surprised if you could make any adjustments that would noticeably 
improve its on-the-air performance.  Trap antennas always involve many 
compromises, compounded by variation in feedpoint Z depending on the 
height (in wavelengths) above ground or other conconductors (e.g. 
gutters, house wiring, plumbing, etc.).  Most guys would be delighted 
that it works this well!

73, Terry N6RY

On 2012-04-09 3:24 PM, Dick KF4NS wrote:
> 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!
>
> _