Assuming the twin-lead feeds are coax at the bulkhead and convert closer
to the antenna I would start with a high value choke set (per Jims
guide) at _BOTH_ ends of the antenna coax.
In the tranceiver -> antenna direction, one right after the bulkhead and
one right before the antenna or BALUN.
The feedline can feed RF shack to antenna and antenna to shack
The feedline can act as an antenna feeding noise into the antenna
The feedline can act as an antenna feeding RF to the shack.
Both choke sets help isolate antenna from shack, one helps isolate shack
from feedline the other antenna from feedline.
On 2/26/15 14:46, Wm.Glenn Pearson wrote:
>
>
> Where does one need to place chokes with multiple RF handling boxes in the
> chain? My layout is”
>
>
>
> 160 M Twin Lead (300 ohm ladder line) and 80 M Twin Lead (etc.).
>
> 40 M – 12 M 43 ft Vertical
>
> 20 – 10 M tribander.
>
> (Total of 4 antennas)
>
>
>
> Each antenna connects to a ¼ inch thick copper bulk head plate outside the
> window of my shack. The bulk head is bonded to my house ground (and
> utilities). My system ground inside is bonded to the above mentioned
> bulkhead.
>
>
>
> Each antenna feeds a multiple position Alpha Delta Switch. Then the chain
> flows as: antenna selected > auto tuner > low pass filter > transceiver. The
> cables between the bulk head and the switch are approximately 10 feet in
> length. Inter connecting cables between the switch, tuner, amp and low pass
> filter are no more than 3 feet long (if that much). The cable between the
> transceiver and the amp is RG-214 and about 12 feet long. I am not able to
> get the transceiver any closer to the other equipment due to the physical
> layout of the room and my operating desk.
>
>
>
> Currently I have each jumper between boxes broken with inline RF chokes. I
> now realize they are the wrong material and not sufficient for suppression.
> I am having significant interference on 10 M. The same is present on 15 and
> 20 M to a much lesser extent. The same interference is not present (the best
> I can tell) on 160 and 80 M (Twin Lead Marconi’s) although there are other
> noises sources who origins have not been determined as yet.
>
>
>
> Initially I was going to construct two of Jim’s chokes (type 31 Fair-rite
> toroids) and place them (in series) at the transceiver. The second choke
> will have fewer turns of RG-213 to get the 10 M coverage I need. Where else
> do I need to place a choke (s). I am trying to put together an order for
> Fair-rite suppression materials, toroids, clamp-ons, and etc. I have a very
> good idea of what I need to suppress noise relating to the interconnects
> between computers, monitors, cable modem, router, network switch and etc.
>
>
>
> The source(s) of the interference is another topic in itself but I am on top
> of that.
>
>
>
> Thanks
>
>
>
> Glenn Pearson, WU2G
>
>
>
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>
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