I have been playing with 75/80 meter 4 sq. since I acquired a Colatcho ( SP)
unit back in the late 80's ... First were wire 14 ga suspended from trees.
This was on sloping ground and the radial were 1/4 wave laying on the ground 8
per antenna . I choked the feed line at the antennas bases with slide over 43
mix, 8 pieces per feed line. The performance was questionable IMO because of
the 18 ft. difference in antenna orientation NE/SE .
I moved to my now QTH in 99 and erected a 4 sq. out of modified Hi Gain high
towers. I first used elevated radials 4 per base tuned and at first 1 ft off
the ground . talk about erratic performance from a RAIN to DRY day .. RAIN =
GOOD Dry =POORboth in FB and forward gain ... I then did the gull wing @
antenna base and 6 ft height. the dump power bandwidth narrowedand the pattern
was not effected AS much from dry to wet
I then bit the bulled and striped the area installed 14 ground rods , a X
grid of 8 ga copper wire and 106 1/4 wave radials 20 ga insulated silver
soldered at the intersecting 8 ga X grid .
WOW Stability was achieved . The feed lines at first were NOT choked off at
the base of the verticals I then installed new feedline in the PVC emt and
choked off the base with 8 43 mix beads .. the dump power lowered and the
bandwidth tightened up . with most DX reports = antenna #1 (NE) being the
only one detectable
???? No NEC, just real world performance evaluation . Could the choke
keep re reradiated RF out of the Comtec BOX ???But there was a noticeable
difference with and with out the Beads.
Wayne W3EA
> From: k1ttt@arrl.net
> To: towertalk@contesting.com
> Date: Sat, 24 Sep 2016 17:07:17 +0000
> Subject: Re: [TowerTalk] 4 square for 80
>
> Personally I have never choked the 4 feedlines to the verticals. I fail to
> see why the shield of the feedlines is different from the radials it is
> connect to at the base of the vertical. On my raised 80m 4-square I have 7
> radials from each base, starting with the one going to the adjacent vertical
> they go outwards every 45 degrees using heavy aluminum wire, then the 8th
> one to complete the pattern is the shield of the coax going to the comtek
> box.
>
> David Robbins K1TTT
> e-mail: mailto:k1ttt@arrl.net
> web: http://wiki.k1ttt.net
> AR-Cluster node: 145.69MHz or telnet://k1ttt.net:7373
>
>
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim
> Brown
> Sent: Saturday, September 24, 2016 16:30
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] 4 square for 80
>
> On Sat,9/24/2016 7:15 AM, Steve London wrote:
> > How much better would the performance be with a multiturn choke ? Over
> > real ground, in the presence of real, possibly interacting structures
> > within N wavelengths, isn't there a finite limit to the performance,
> > regardless of your choice of "excellent" vs. "superb" common-mode
> > chokes ?
>
> Hi Steve,
>
> The primary reason for using common mode chokes in our antenna systems is to
> reduce RX noise. A string of beads choke is NOT a good choke at HF for the
> reason cited -- it's effectiveness is strongly dependent on the electrical
> length of the feedline considering it as an antenna (that is, considering it
> as a wire, not a transmission line). This is not a matter of "excellent" vs
> "superb," it is whether it is effective at suppressing RX noise, and whether
> signal pickup on the coax fills in the nulls a bit.
>
> 73, Jim K9YC
>
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