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Random Wire and MFJ-941e Question

CB590

CB590

W9WDX Member
Jun 29, 2016
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Trenton Nj
www.590dx.com
I have some well insulated satellite TV coax and have been looking at charts for random wire lengths.. I also have 12AWG stranded as well.

Seems like 59' is the amount I need to get 80,40,20,10 (this is also the longest I can run here down the side of my mobile home and up into a tree at the other end to maintain stealth). I do plan on grounding the tuner to a rod as well.. I can't do a dipole here, I only have 1 tree and HOA don't allow antennas.. I can do a sloper type of setup as noted above from wooden deck to my only tree.

Someone said shielded is better to cut the RF bleed into the shack.

I do have 1 vertical antenna but that is a 5' Firestik II going vertical and again that is semi hidden by the tree on a 10' section of 'top rail post' just on my deck.. I don't think anyone on here would approve on modding that with a 1/4-20 screw for a tip running to a 'random wire'..

Anyone else try this length on here.. Again I'm a newbie..
 
Last edited:

K3ACZ said:
Seems like 59' is the amount I need to get 80,40,20,10 (this is also the longest I can run here down the side of my mobile home and up into a tree at the other end to maintain stealth)
Click to expand...
Make it as long as you can, remember it does not need to be straight, if you need to bend it do so. If you can try for 66' but again 59' is better than nothing.
 
K3ACZ said:
.... I don't think anyone on here would approve on modding that with a 1/4-20 screw for a tip running to a 'random wire'..

Anyone else try this length on here.. Again I'm a newbie..
Click to expand...

i have a 6BTV antenna, at the feedpoint screw connection, I just added 44 feet of wire and tossed it over a tree limb to add 60 meters......... works fine
 
vkrules said:
And your going to need a good ground system and balun or choke to try and keep the RF out of the shack.
Click to expand...

The MFJ-941e tuner has a built-in 4:1 balun.. Not sure if that is for balanced line and random wire tuning or just balanced line only.. My first tuner..

Planning on using 12AWG THHN for ground wire to ground rod for grounding tuner..
 
Last edited:
The mfj balun is for balanced to unbalanced with a 4 to 1 impedance transformation..
Sorry got distracted with work !
This suits a balanced feed line, but the problem is it should be outside the shack with a clear run to the ant,( it's hard to run balanced line through windows or walls ,you have to keep it away from metal) or directly feeding the ant. Not next to the rig inside the shack.
If you want to feed with coax ,you want a 1 to 1 balanced to unbalanced balun ( or a good choke )fitted in the feed line to keep the coax from radiating. And believe me you can get some serious cmc with this type of antenna if you are not careful .
Yes it will get you on air but to get the best out of it requires more work.

And ground loss can be horrific without a good ground .

If using a end fed, I like to run it horizontal with the feed point mounted as high as I can get to reduce ground loss. then I fit a choke down the feed about 10 or 20 ft.

I also have an extensive ground network using 1/2 inch copper pipe as the ground strap IE 3x5ft ground rods bound to the tower legs 3x 20 ft 1/2 inch copper radials buried just under the ground all tied to the station main ground with more 1/2 inch copper pipe and another 5 ft rod ground rod.Then fed to the radio with 1/2 copper pipe. That keeps the earth points all at the same potential and avoids ground loops.
And I still consider this as just adequate. If I had the room I would run 360 1/4 wave radials just under the turf.
12 # wire and a 2ft ground rod just doesn't do the job.But it is better than nothing.
Of course if you are lucky to have good soil continuity you can get by with less.
 
Last edited:
vkrules said:
The mfj balun is for balanced to unbalanced with a 4 to 1 impedance transformation..
Sorry got distracted with work !
This suits a balanced feed line, but the problem is it should be outside the shack with a clear run to the ant,( it's hard to run balanced line through windows or walls ,you have to keep it away from metal) or directly feeding the ant. Not next to the rig inside the shack.
If you want to feed with coax ,you want a 1 to 1 balanced to unbalanced balun ( or a good choke )fitted in the feed line to keep the coax from radiating. And believe me you can get some serious cmc with this type of antenna if you are not careful .
Yes it will get you on air but to get the best out of it requires more work.

And ground loss can be horrific without a good ground .

If using a end fed, I like to run it horizontal with the feed point mounted as high as I can get to reduce ground loss. then I fit a choke down the feed about 10 or 20 ft.

I also have an extensive ground network using 1/2 inch copper pipe as the ground strap IE 3x5ft ground rods bound to the tower legs 3x 20 ft 1/2 inch copper radials buried just under the ground all tied to the station main ground with more 1/2 inch copper pipe and another 5 ft rod ground rod.Then fed to the radio with 1/2 copper pipe. That keeps the earth points all at the same potential and avoids ground loops.
And I still consider this as just adequate. If I had the room I would run 360 1/4 wave radials just under the turf.
12 # wire and a 2ft ground rod just doesn't do the job.But it is better than nothing.
Of course if you are lucky to have good soil continuity you can get by with less.
Click to expand...

So if I did want to run a single random wire off the tuner I definitely need to use some type of shielded wire and not just normal 12 THHN. Since the tuner uses 4:1 balun would you say 75 ohm or 50 ohm coax would be better?

I can't do dipoles,ladder wire, or tall verticals here (hoa/mobile park crap)..

I have 1 tree near shack (aka bedroom) and that's it..

My current antenna coax (12' of LMR-240) goes thru wall and up the 10' metal post to a 5' CB Firestik II antenna with three 9' 12AWG radials on downward angle to wood fence rail tops.. I get 1.2-1.4 SWR.

My plan was semi-sloper reverse L.. Go toward 10' pole (which I acquired a wood post to lash to that for this project to act as insulator), go to top of wood pole and reverse back (to the left) toward and up the tree..

Note that the current CB antenna and mount would be removed all together.
 
Last edited:
K3ACZ said:
So if I did want to run a single random wire off the tuner I definitely need to use some type of shielded wire and not just normal 12 THHN....
Click to expand...

Am I reading this correctly?

Do you want to put your radiator inside a shield (which is probably grounded)?
 
K3ACZ said:
So if I did want to run a single random wire off the tuner I definitely need to use some type of shielded wire and not just normal 12 THHN
Click to expand...
I use standard 14g stranded wire which has a plastic coating on it. Nothing more nor nothing less needed. That is feeding into a 1:1 current Balun. This is a fan dipole not an end feed but the parts are the same.
 
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w9cll said:
I use standard 14g stranded wire which has a plastic coating on it. Nothing more nor nothing less needed. That is feeding into a 1:1 current Balun. This is a fan dipole not an end feed but the parts are the same.
Click to expand...

That's what I've seen done online basic THHN wire antenna. Then some other guy showed using coax and trimming back shielding on 1 end and using center conducter only.

I'm guessing the 4:1 balun inside tuner helps balance things a bit in conjunction with the variable capacitors.

I do plan on grounding tuner as best I can with what I got available..

Again.. All new to me..

Further comments and suggestions welcome.
 
sp5it said:
I see that you stubbornly going to waste as much power as you can instead of radiating that. Pity.
Mike
Click to expand...

I'm entertaining ideas. Feel free to offer up..

I listed what I have.

10/50/100w 160-10 radio
MFJ-941e tuner with 4:1 balun option built in
12AWG THHN wire spool
RG-6/U 75 ohm Coax also..

So what would you build??

Restricted HOA and 1 tree.. No antennas allowed.
 

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