Common mode choke for ocf

Homebrew equipment discussion, show off your projects.
User avatar
M0VMT
Posts: 1005
Joined: Thu Sep 27, 2018 10:23 pm
Location: Doncaster

Common mode choke for ocf

Unread post by M0VMT »

After doing a little research to make a common mode choke I'm going for a t240 type 31 and RG 142 to handle the power, have you seen the price of the toroids and some rg142 :o
Theirs one on the net for £40 built but wound on 1 toroid, now by the time I've got 2 toroids a length of rg142 a ip project box and two so239 sockets I'm about at £40.
I wanted 2 toroids to up the saturation factor, it's for a ocf fed with twin line which acts like a widom and yes before you say just feed at the center with a 4-1 and coax no I was experimenting and I've got a nice performing ocf dipole fed with ladder line and it's one of the best wire antennas I've made and to say it was just a bit of a laugh to feed with twin and get the analyser on and when I did I was shocked to see the results.
I use a 4-1 at the bottom of the home made ladder line and so I guess the ladder is radiating hence wanting to choke it although I've not experienced any RF back in the shack I'd like to be sure if anything is floating around it gets nipped at the feed end.
It covers 80 through to 10 and it's loaded for 80 which was another experiment and it makes it a tad narrow but still at around 80 ft with the coils and using the ladder It doesn't do too bad on 80 metres.
When the weather picks up I shall take pics and measurements.
So I will have to sort a choke either way, I wanted another 100ft doublet but their just isn't the room here to get one in unless it's a crammed in.
M0VMT Mark
Doncaster
RSARS
Happy to be here :D
VK5TM
Posts: 242
Joined: Sun Oct 28, 2018 11:40 pm
Location: South Australia
Contact:

Re: Common mode choke for ocf

Unread post by VK5TM »

M0VMT wrote: Wed Mar 13, 2019 8:33 am ....have you seen the price of the toroids and some rg142 :o
Yep, that's why I buy them out of the States from Diz ( https://www.kitsandparts.com/).

Even with shipping, they turn out to be about 25% of the price of buying locally (unless your only buying 1 or 2 that is, I normally buy 100 at a time).

You need to join the GQRP club, good shop for members and good prices.
User avatar
M0VMT
Posts: 1005
Joined: Thu Sep 27, 2018 10:23 pm
Location: Doncaster

Re: Common mode choke for ocf

Unread post by M0VMT »

Thanks for the link and advice Terry I shall take a look, you could have some fun with 100 toroids :lol:
M0VMT Mark
Doncaster
RSARS
Happy to be here :D
VK5TM
Posts: 242
Joined: Sun Oct 28, 2018 11:40 pm
Location: South Australia
Contact:

Re: Common mode choke for ocf

Unread post by VK5TM »

Winding the wire on them isn't fun though :roll:
Yeah I will let the wife do it when she's on a nagging spree, here love follow those instructions :D
Post Reply