VHF coax chokes using RG59 or RG11

[mr_fx]

I am building a set of stacked halos (2/twin/pair) use use from 144.00 Mhz - 144.275 Mhz for CW and SSB. Anyways I have been sick the last few days, vomiting and recovering from last weeks back surgery and thinking about redoing the entire setup

Right now I am running RG59 on the phasing harness and RG58 on the chokes, the biggest issue I see here is that there is a lot of loss and 7 connections, consisting of 13 connectors counting the 'TEE'... I could lower that to about 5 connection points and 5 connectors counting the 'TEE' I would also only be using RG59 (JSC 3210), or RG11 (3640)

The chokes I am using right now are these Winding a RF Choke - YouTube

So if I am using RG59 (JSC 3210) or RG11 (JSC 3640) then how many turns should I make and what size form should I use

 

[RADIOOMAN]

You could dispense with the rg58 and make the phasing harness longer and incorporate the chokes into the extra length of the phasing harness.
This would eliminate some of the 'connectors.'
I am assuming that the phasing harness is 1/4 wl (velocity factor corrected length) and if that length is not enough to span the distance and leave enough for the choke then you could make the phasing harness 3/4 wl (v.f.c.l.) and that would leave plenty to wind the choke.

Additionally: I think the choke in the video would perform better if it was made with fewer turns but larger diameter dimension.
If the diameter is made larger you need fewer turns to achieve the same value inducatance and this might also reduce capacitive coupling between the turns.
Making the turns in larger diameter would be more compliant with the manufacturers recommended minimum bend radius figure, also.

 

[W5LZ]

I won't get into the phasing harness thingy, that just depends on the input impedance of the antennas being 'phased'.
I can say that multiple chokes aren't needed, one should do fine for the whole array. Placing it at the point where the feed line attaches to the phasing harness is also the most common way of doing it. A coaxial choke at VHF isn't very 'big' at all, maybe a couple of loops of the feed line. The choke shown would probably do well at HF but is a lot of 'over-kill' at VHF. What size coils? Sorry, no idea. I've seen graphs of coil sizes for HF but not for VHF/UHF. Since they are frequency 'sensitive', the chokes at VHF/UHF are correspondingly 'smaller'.
Have fun.
- 'Doc

 

[hookedon6]

...I can say that multiple chokes aren't needed, one should do fine for the whole array....
Have fun.
- 'Doc

I wonder WHY an RF choke is needed at all.
if it was a J-POLE antenna, I can understand them being used.

I would just use a TEE and 2 1/4wl (or mult odd wl) Q sections.


if it ain't broke, don't fix it**Jump_im**

 

[Captain Kilowatt]

I agree with Doc. Those chokes are FAR to big for 2m. Speaking of that, I have never heard of using a coaxial choke on VHF. Far easier, neater, and effective to just slip a ferrite core or two over the coax cable if you feel you really need one in the first place.

 

[mr_fx]

I get that is would be easier to do slip over ferrites, but I didn't ask that, I don't have easy access to #43 mix cores, I do however have easy access to coax...

 

[Captain Kilowatt]

I get that is would be easier to do slip over ferrites, but I didn't ask that, I don't have easy access to #43 mix cores, I do however have easy access to coax...

God forbid anyone should suggest an easier way to do something in an effort to help someone out. :glare:

 

[mr_fx]

God forbid anyone should suggest an easier way to do something in an effort to help someone out. :glare:

It's not that, I already am aware of the slip-on/snap on ferrites, but there are other issues that come along with this, like the need for a new harness as the harness needs to be 1/4 wave multiples and the ferrites would throw that off, I guess it could be done with a jumper, but the point here is that I really don't have access to the correct snap on ferrites, and had already looked into that

 

[Captain Kilowatt]

Why would snap-on ferrites throw of the length of the phasing harness? The length is determined by the frequency of operation and velocity factor of the coax. The ferrites on the outside of the cable have no effect on the overall electrical length of the cable being used.

If you are really set on using a coaxial choke then start with three or four turns about an inch and a half inside diameter. Anything larger like 6 or 8 inches in diameter will tend to radiate more in an axial mode I would think. think helix antenna. Any more turns and you are lowering the series resonant freq. waaaay below the 2m band as will too many loops much larger in diameter. The choke has to be effective in the 2m band and using turns/diameters similar to that used on 11m just is not going to work.

 

[mr_fx]

If you are really set on using a coaxial choke then start with three or four turns about an inch and a half inside diameter. Anything larger like 6 or 8 inches in diameter will tend to radiate more in an axial mode I would think. think helix antenna. Any more turns and you are lowering the series resonant freq. waaaay below the 2m band as will too many loops much larger in diameter. The choke has to be effective in the 2m band and using turns/diameters similar to that used on 11m just is not going to work.

thank you.

 

[Captain Kilowatt]

You are welcome but what's so funny?

 

[mr_fx]

You are welcome but what's so funny?

Just how hard it can be to get a straight answer sometimes.

 

[Captain Kilowatt]

Next time I won't bother at all. I Googled that info. You could have done the same in far less time than it took to ask and wait for all the wrong answers first.