[600MRG] Super Chocker

[Carl]

Hi David

Palomar is likely the most expensive souurce for those ferrites and either 
Mouser or Digi Key the better choice.

The Fair-Rite part is 2643803802 but is far from ideal at 600M; it isnt even 
great on 160.

The 31 mix is the "in thing" these days on 80M and lower and its part is 
2631803802.

I suggest reading  the links below on how to address common mode.

http://audiosystemsgroup.com/RFI-Ham.pdf

and

http://audiosystemsgroup.com/NCDXACoaxChokesPPT.pdf

I havent found any common mode problem that couldnt be solved by no more 
than 2 of those cores and enough turns depending upon frequency. Adding 
another choke several feet away is more effective than stacking 5-7 and 
using an intermediate ground rod or three at intervals is often very 
effective. See ON4UN's Low Frequency DXing 5th edition for indepth 
discussion..

At 600M power levels RG-58, 8X, 42 and 400 should take care of everything 
and get lots of turns.

I use 31 mix to 20M and 43 from there to 2M at 1200-1500W and all over the 
house for noisemakers.

Carl
KM1H

----- Original Message ----- 
From: "D.J.J. Ring, Jr." <n1ea at arrl.net>
To: "600 meter group" <600mrg at w7ekb.com>
Sent: Friday, February 21, 2014 6:45 PM
Subject: [600MRG] Super Chocker


> Michael Laronda, WA1OMI used a highly effective torroid from Fair-Rite who
> manufactures them.  I remember the Mix 43 part, but not the rest of the
> designator, but some snooping around on eBay I found what Palomar 
> Engineers
> is using in their Super Choker™
>
> ♥♥♥♥♥♥♥♥♥♥♥♥♥♥
>
> The Super Choker™ uses eight FT-240 Mix 43 ferrite toroids and a five foot
> RG-8 coaxial cable preassembled with nylon ties. There are 4 turns of 
> cable
> through the ferrite cores which is the maximum turns for cable with
> connectors as supplied. All you need to add are two coaxial barrel
> connectors to connect to your existing cable. We have measured impedances
> of 2-3K between 1 and 10 Mhz with our AIM 4170 and it really works well in
> reducing common mode current in our 1.5KW station (see case history 
> below).
>
> If you want to use your own coax you can get up to 7 turns of cable thru
> the center of the toroids increasing the choking impedance even more (up 
> to
> 10K).
>
> Case History:
>
> I run an 80 meter loop antenna about 30 feet in height and have previously
> been using a coaxial balun common mode choke of 25 turns of RG-213 on a 6
> inch form attached about 6 feet under the corner feed point of the loop
> (configured in a triangle). Using a Dentron 3000 antenna tuner I was able
> to tune all the ham bands and the lowest SWR was about 1.4 on most bands.
> The antenna feed line was led away from the corner of the loop and was not
> under the loop. Feed line length was about 105 feet as measured on the Aim
> 470-TDR.
>
> I first placed a Super Choker™ at the antenna tuner leaving the coaxial
> balun in place. As I retuned the antenna tuner, the first thing I noticed
> was that I could now tune down to 1.1:1 on 80, 40 and 20 meters and I 
> could
> not do that before. The noise level which had been running about S7 on 40
> meters during the day had dropped to about S6 on my TS-870 receiver. I was
> pleased that the reflected power was now almost nil and the noise level 
> was
> lower.
>
> I then took the next step and replaced the coaxial balun with another 
> Super
> Choker™. The antenna tuning was about the same but now the SWR was 1.0:1 
> on
> 160-10 meters and the noise level on 40 was down to S5. I tuned up on 20,
> 15 and 10 meters and worked a couple of JA’s and noticed that the noise
> level on 10 and 15 was not even S1 – something I had not experienced 
> before
> on the 5 acre plot of land we call home.
>
> What a welcome relief to find such a simple solution to RF feedback I had
> experienced and I got a lower noise level to boot!
>
> These kits are all NEW production kits under the new management of Palomar
> Engineers.
>
> 73
>
> David
> N1EA
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>
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