[600MRG] Super Chocker

[D.J.J. Ring, Jr.]

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