I recently did some work on chokes for 6M and posted the result to an
email reflector devoted to grid chasers for that band. Two turns of
RG8-size coax through a 1-in id. #31 clamp-on is optimum for 6M, and
yields about 1K ohms resistive choking Z. I recommend at least two such
chokes in series at the feedpoint. For RG8X or RG400, two turns through
TWO 3/4-in i.d. cores is optimum for 6M, and yields about 1.2K choking
Z. Again, use at least two such chokes in series.
For 2M, use multiple #31 clamp-ons, sized to fit the coax. Use the link
below to select the size that fits your coax. Each will provide about
250 ohms choking Z on 2M. Do not wind turns, just clamp them onto the
coax. I would use at least five, and ten is better. :) Arrow is a good
vendor for parts they have in stock.
https://www.fair-rite.com/product-category/suppression-components/round-cable-snap-its/lower-broadband-frequencies-1-300-mhz-31-material-round-cable-snap-its/
73, Jim K9YC
On 6/28/2019 11:50 AM, David Gilbert wrote:
I've never been much interested in VHF/UHF, but with the current level
of solar flux and the summer static I'm thinking of giving it a try
using homebrew antennas based upon DK7ZB designs. For 6m I'll
probably use a coaxial sleeve as a common mode choke (unless somebody
can suggest something better/simpler), but for 2m/70cm I'm planning to
build a dual band yagi with a common feedline and I'm not sure a
sleeve would work.
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|