EFHW mobile deployment

[Northcutt114]

I've watched about eleventy billion videos and read just as many articles, but I wanted to ask here, where I know there is a good knowledge base and where I also know that I can get feedback.

I broke down and bought a 49:1 balun and added roughly 70' of silicone tinned copper wire to it. I know it should be shorter, I'll trim it and tune it when I get out there. I keep hearing about "slopers." So here's how I am thinking of running it, tell me your thoughts?

I have a piece of PVC that fits over a spike, roughly 3' off the ground with a hole drilled through it. Paracord through the hole into the balun. From there, at an angle of roughly 45 degrees, I plan to attach the end of the antenna to the top of a 33' carbon fiber mast that I will either lean into a tree or zip tie to a park bench leg or fence or something. 15' run of RG142 from the balun to the radio which, as I understand it, should function as counterpoise.

How'd I do?

 

[WRYZ926]

Yes that will work. You will definitely need some type of CMC - common mode choke if using the coax as the counterpoise. The best place is to put the CMC is 5% of a wave length from the unun. With 70 feet. I am guessing that you are making a 40m EFHW, if that is the case, put the CMC on the coax 2 meters/6.5 feet from the unun. Otherwise put the CMC at the radio end of the coax cable.

Another option is to use a separate counterpoise wire. Again the counterpoise length for a 40m EFHW will be 2 meters/6.5 feet. If you use a sprat counterpoise then place the CMC at the unun feed point.

I have found that putting a CMC on my coax where it connects to the unun and using a sprat counterpoise wire works better for me. You can make a CMC by installing 5-7 clamp on ferrite beads on the coax or by wrapping the coax through a toroid, you want 7-12 loops of coax through the toroid.

Five clamp on ferrite beads works well for the higher HF bands while 7 ferrite beads works better for the lower HF bands. 

You will definitely want a CMC on the coax to keep RF out of your radio.

[Northcutt114]

37 minutes ago, WRYZ926 said:

Yes that will work. You will definitely need some type of CMC - common mode choke if using the coax as the counterpoise. The best place is to put the CMC is 5% of a wave length from the unun. With 70 feet. I am guessing that you are making a 40m EFHW, if that is the case, put the CMC on the coax 2 meters/6.5 feet from the unun. Otherwise put the CMC at the radio end of the coax cable.

Another option is to use a separate counterpoise wire. Again the counterpoise length for a 40m EFHW will be 2 meters/6.5 feet. If you use a sprat counterpoise then place the CMC at the unun feed point.

I have found that putting a CMC on my coax where it connects to the unun and using a sprat counterpoise wire works better for me. You can make a CMC by installing 5-7 clamp on ferrite beads on the coax or by wrapping the coax through a toroid, you want 7-12 loops of coax through the toroid.

Five clamp on ferrite beads works well for the higher HF bands while 7 ferrite beads works better for the lower HF bands. 

You will definitely want a CMC on the coax to keep RF out of your radio.

Lots to respond to:

Yes, a 40m half wave. As I understand it, an antenna cut to that length will also work on 20m, 15m, and 10m because of the resonant harmonics. I'm trying to get an all-in-one wire antenna for POTA.

Common mode choke...interesting. The balun (or is it unun?) I bought does not have a terminal for counterpoise so I had planned to use the coax, as I read that was possible. But I now see what you mean about needing to keep RF out of the radio. If the coax is the counterpoise, it will be carrying RF into the radio. Duh.

I googled it and couldn't come up with an answer, so I'll ask. What do you mean when you say "sprat counterpoise?" I understand the "counterpoise" part of it, but what's "sprat?"

 

[WRYZ926]

46 minutes ago, Northcutt114 said:

I googled it and couldn't come up with an answer, so I'll ask. What do you mean when you say "sprat counterpoise?" I understand the "counterpoise" part of it, but what's "sprat?"

 

That is my fat fingers making typos and the dang stupid auto correct. That should have been separate. 

Since the unun does not have a place for a separate counterpoise wire, get some clamps ferrite beads and place them on the coax 2 meters/6.5 feet from the unun.

Yes using the coax as the counterpoise works but you will need a CMC to keep RF out of your radio. And the preferred length of a counterpoise for an EFHW is 5% of a full wave length. 

You are smart to go ahead and make a 40m EFHW. Yes it should work on 40m, 20m, 15m and 10m. And if you use it with your G90 then it will definitely tune for 17m and 12m.

[TNFrank]

These come in handy for securing masts and other things where you need to tighten things down.

https://www.amazon.com/s?k=nite+ize&rh=n%3A3395071

[Northcutt114]

54 minutes ago, WRYZ926 said:

Since the unun does not have a place for a separate counterpoise wire, get some clamps ferrite beads and place them on the coax 2 meters/6.5 feet from the unun.

Thanks, again. Another question. I understand why the CMC is needed when running the EFHW and using the coax as counterpoise. Will it hurt or otherwise interfere to leave the beads on the coax if I'm running the 1/4 wave vertical?

 

[Northcutt114]

31 minutes ago, TNFrank said:

These come in handy for securing masts and other things where you need to tighten things down.

https://www.amazon.com/s?k=nite+ize&rh=n%3A3395071

I use these.

[TNFrank]

The nice thing about the ratchet deals is that I can clip one end to a tent stake and the other to whatever and ratchet it tight.

I used a couple today to stabilize my tripod when I put my inverted V antenna up. I ordered 2 more 4 packs today because they come in so handy. 

Also, it looks like the link didn't go to where I wanted it to. I'll post a screenshot.

[WRYZ926]

58 minutes ago, Northcutt114 said:

Thanks, again. Another question. I understand why the CMC is needed when running the EFHW and using the coax as counterpoise. Will it hurt or otherwise interfere to leave the beads on the coax if I'm running the 1/4 wave vertical?

It won't hurt one bit.

All of my coax cables I use for POTA and at home have some form of CMC in place. On my POTA cables, they all have clamp on ferrite beads that are covered with heat shrink. And I use them with every type of antenna I have. 

I even have common mode chokes on my VHF/UFH and GMRS antennas to help keep stray RF from the coax. The coax from those antennas and my HF antennas all run close together along the house and into the shack.

I will spend a little more for quality coax and usually get my POTA coax cables from ABR Industries. I always order them with 5 ferrite beads installed on one end.

You will want to invest in different sizes of clamp on ferrite beads for all of your radio and computer cables once you start using the 40m and 80m bands. They will introduce all kinds of RF into the shack if you don't use common mode chokes on the coax and ferrite beads on all cable in the shack.

[Northcutt114]

16 minutes ago, WRYZ926 said:

It won't hurt one bit.

All of my coax cables I use for POTA and at home have some form of CMC in place. On my POTA cables, they all have clamp on ferrite beads that are covered with heat shrink. And I use them with every type of antenna I have. 

I even have common mode chokes on my VHF/UFH and GMRS antennas to help keep stray RF from the coax. The coax from those antennas and my HF antennas all run close together along the house and into the shack.

I will spend a little more for quality coax and usually get my POTA coax cables from ABR Industries. I always order then with 5 ferrite beads installed on one end.

You will want to invest in different sizes of clamp on ferrite beads for all of your radio and computer cables once you start using the 40m and 80m bands. They will introduce all kinds of RF into the shack if you don't use common mode chokes on the coax and ferrite beads on all cable in the shack.

That's a good tip on the heat shrink. 

I'm having some RF interference on my GMRS base station that I think I've narrowed down to the street lights near my house. Maybe some ferrite beads on that coax would help too. More to look into!

And as for me ever having a shack, alas, it isn't in the cards. The plan is to become an RV nomad once the kids leave the house. I'll be portable and mobile for my Ham journey.

Again, I'm grateful for your help. God bless the Midwest!

 

[WRYZ926]

Common mode chokes will help no matter what your setup is. The Smoking Ape has several videos on why you should use common mode chokes. His videos are worth watching.

And using clamp on ferrite beads on the radio power leads helps keep electrical noise out of the radio, especially in mobile installs.

The heat shrink does two things. It helps keep the ferrite beads in place and it protects them from UV light.

I'm glad to help others. HF can be frustrating and rewarding at the same time. RFI and EMI becomes more of an issue with HF, especially the lower HF bands.

[tweiss3]

This is my setup. Transformer is in the box, wire end goes in the master link, and eyelet goes on the stud with the wing nut. The wire is wound up in the chalk reel, attached to 40' of paracord. I just pull it all out, then toss the chalk reel over a branch and pull. The other side is just paracord, So I could get the other end up too, between two trees. Attach coax to the PL on the box and hook up the radio. It's been very effective in my testing, and worked better than the expensive Budipole.

[TNFrank]

I picked up a couple of these on sale. One is set up with 14 gauge wire for 10M and it seems to work pretty well.

[WRYZ926]

@TNFrank Hopefully you are using some type of common mode choke with your setup. You really need to use one with an EFHW antenna.

[TNFrank]

1 hour ago, WRYZ926 said:

@TNFrank Hopefully you are using some type of common mode choke with your setup. You really need to use one with an EFHW antenna.

Doesn't the Balun have a choke built into it? 

[WRYZ926]

6 minutes ago, TNFrank said:

Doesn't the Balun have a choke built into it? 

Some do but some do not. Most 49:1 ununs do not have a built in common mode choke.

[hxpx]

19 hours ago, WRYZ926 said:

I have found that putting a CMC on my coax where it connects to the unun and using a sprat counterpoise wire works better for me. You can make a CMC by installing 5-7 clamp on ferrite beads on the coax or by wrapping the coax through a toroid, you want 7-12 loops of coax through the toroid.

I DIY'd a choke with 3' of SO239/PL259 RG58, an FT-240-31, and a couple of zip ties. Was shooting for 12 turns but only got 11, which seems to still work okay for 20/40m. Should've bought longer coax.

@Northcutt114 Check out https://www.karinya.net/g3txq/chokes/ for more info on building your own common mode choke. It's easy and only like $20-30 for the toroid and coax off amazon.

@TNFrank I think that's the same 49:1 64:1 I use. I put the choke right at the unun.

[TNFrank]

This is a 64:1. 

[WRYZ926]

Just now, hxpx said:

I think that's the same 49:1 I use. I put the choke right at the unun.

Are you using a separate counterpoise wire? 

IF you are using the coax as the counterpoise then you want to move the CMC a few feet away from the unun. The standard is 5% of a full wave length on the lowest band.

[WRYZ926]

1 minute ago, TNFrank said:

This is a 64:1. 

It doesn't matter if it's a 49:1, 56:1 or 64:1 unun. Most do not include a common mode choke.

[hxpx]

1 minute ago, TNFrank said:

This is a 64:1. 

Yes, that's what I said, 64:1.  (Fixed my post.)

[hxpx]

16 minutes ago, WRYZ926 said:

Are you using a separate counterpoise wire? 

IF you are using the coax as the counterpoise then you want to move the CMC a few feet away from the unun. The standard is 5% of a full wave length on the lowest band.

I do on the 9:1, but I didn't have a way to attach one to the 64:1 (I think the random screw hole is for a counterpoise) nor did I have a coax jumper to put in between at the time. I do now - I'll have to try it.

Also, @TNFrank I was wrong. Very similar, but mine has a random screw hole near the top.

Update: No continuity between the connector threads and the random screw.

[TNFrank]

No Counter Poise, just a 16'or so 14 gauge wire on a 15' tripod with the balum on the porch overhang at about 8'. It seemed to work well, I was getting some decent signal reports. There was a noise floor of about S3 and I get the same with my inverted V antenna too. It's just all the stuff in the neighborhood. I'm sure that's what's being picked up. 

[WRYZ926]

You can reduce some of that noise along with keeping RF out of your radio with a common mode choke, You can put the choke at 5% of a wave length from the unun or at the radio. Either way you do want to keep the RF out of the radio.

Counterpoise lengths needed:

10m - 0.5 m/1.5 ft

20m - 1 m/3.3 ft

40m -  2 m/6.5 ft

You have two options. Place a common mode choke the required distance from the unun onto the coax or use a separate counterpoise. If using a separate counterpoise wire, then place the CMC at the unun.

Trust me, you will see an overall improvement by using a CMC with an EFHW antenna.

[TNFrank]

Here's a pic of the inside of the balun I got from Amazon. Doesn't this choke do anything?