[600MRG] Super Chocker

Fri Feb 21 21:22:28 CST 2014

----- Original Message ----- 
From: D.J.J. Ring, Jr.
To: Carl
Cc: 600 meter group
Sent: Friday, February 21, 2014 10:08 PM
Subject: Re: [600MRG] Super Chocker

Wonderful Carl.

I had forgotten the type and Mike - you met him and discussed his antenna at 
NearFest in NH several years ago before he passed on - had  gone through the 
list.

Which is the material that will produce the most inductance, handle the most 
power safely at 400 to 500 kc/s?

Is it the 31 mix you mentioned?

** "The 31 mix is the "in thing" these days on 80M and lower and its part is 
2631803802".
One core will handle 1500W, additional ones are to increasce choking 
reactance; 5000 Ohms is a good target to shoot for but less is fine if it 
does the job.

You mention RG-58, 8X, 42 and 400, are they all cables?

The 400 must be LMR-400 but what is the 42 cable you mention?

** They are all standard RG cables, 42B and 400 are Teflon which often shows 
up cheap as cell phone and other surplus. The coax specs charts will  tell 
you power and voltages but the Teflon will handle several KW.

Carl
KM1H

Thanks for sending the info.

DR

On Fri, Feb 21, 2014 at 7:53 PM, Carl <km1h at jeremy.mv.com> wrote:

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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