Antenna tuners

[acyddrop]

Hi all,

Quick question about antenna tuners. A friend of mine is putting up a ZeroFive 10-40M vertical antenna (small plot of land, it's a very good choice I think). From all I've read and seen so far it's a solid antenna with pretty decent performance and best of all excellent customer service. Anyway, I digress... Since I'm still new to Ham generally and more specifically antenna tuners I thought I'd ask those smarter and more knowledgable than myself about them.

What if any are the difference between a "rolling inductor antenna tuner" and one that isn't? Obviously there is some sort of rotation system in the roller version that allows you to increase inductance. But they look confusing and unwieldy. So is there any reason to favor one over a more "standard" or perhaps I should say "more simple" tuner? Specifically I'm looking at these MFJ products (if it helps to make an informed reply)

MFJ Enterprises Inc. (what I call more standard)
MFJ Enterprises Inc. (roller)

These question are in relation to this antenna:
10-40 METER MULTIBAND GROUNDPLANE FREESTANDING VERTICAL ANTENNA | ZEROFIVE-ANTENNAS

I've looked at a lot of antennas this weekend trying to help my friend out and this one looks like it's right up there and suits the space limitations very well. Other antennas I looked at were the Gap Titan DX but it looks like a nightmare to assemble (and eham reports confirm that it is), I looked at the Cushcraft R8 and wasn't impressed either. Lastly I loved the cost of the Hustler 6-BTV sadly it's a trap antenna and tuning that to work well is hellish, not to mention the bandwidth is very narrow on all the bands it covers. The ZeroFive is a bit on the more pricey side but has full bandwidth on all the bands it covers (40, 30, 20, 17, 15, 12 and 10). Of course it requires an antenna tuner, which is why I'm asking about them.

Thanks in advance for your guidance.

 

[potbellyperch]

Hello there
by all means have him get an ant...... tuner
it makes your S.W.R. &tricks your ant.. thinking you got a good match
so you can get out there <your.Signal> with out damageing your finels
witch is very expencive

hoped I helped you out

 

[K9WG]

Get the rolling inductor. Simply, a non-rolling uses a switch to choose the inductive value so you are fixed as to the value if inductance. a rolling inductor can be tuned for any inductance within the limits of the inductor. Much easier to tune an antenna that way.

 

[zz0468]

What if any are the difference between a &quot;rolling inductor antenna tuner&quot; and one that isn't? Obviously there is some sort of rotation system in the roller version that allows you to increase inductance. But they look confusing and unwieldy.

The difference is that a rolling inductor allows continuous variation of values to be selected, where the other type taps the coils and gives you a limited selection. The end result is the tapped coil type is not always capable of providing the optimum match. They usually can come pretty close, though. Neither is really more difficult to operate over the other.

So is there any reason to favor one over a more &quot;standard&quot; or perhaps I should say &quot;more simple&quot; tuner?

You pay more for a more capable tuner, that being the roller inductor type. It becomes a question of cost vs benefit. If you're running high power, a better match might be more important.

These question are in relation to this antenna:
10-40 METER MULTIBAND GROUNDPLANE FREESTANDING VERTICAL ANTENNA | ZEROFIVE-ANTENNAS

Just off the top of my head, and after a quick look, I see a few things that would definately turn me off to that antenna. First, the radials are only 100" long. That's entirely too short for any sort of efficient operation at 40 or 20 meters. The other thing that really makes me wonder is the minimum coax length is 100'. This tells me that the antenna probably runs with a high VSWR on the cable, and relies on either the radio's internal tuner, or an external tuner to provide a match to the transmitter. Coax loss under high VSWR conditions is a hole lot more than under matched conditions, and an antenna designed to operate this way seems like a poor way of doing things, in my opinion. Some of those other antennas require either a good ground system (as in a whole lot more than just a ground rod), or radials installed above ground. Trap verticals can work pretty good, but like you pointed out, tuning can be a nightmare. For the ultimate in simplicity, use a dipole fed with open wire line to a tuner. Open wire line can tolerate high VSWR, and the tuner allows multiband operation. The dipole can be cut to fit whatever space is available although the shorter it is, the less efficient it will be.

 

[acyddrop]

The difference is that a rolling inductor allows continuous variation of values to be selected, where the other type taps the coils and gives you a limited selection. The end result is the tapped coil type is not always capable of providing the optimum match. They usually can come pretty close, though.

Sadly in this case it's going to come down to what he can afford, as always it comes down to compromise I guess. Seems a lot of ham radio works that way, LOL.

Just off the top of my head, and after a quick look, I see a few things that would definately turn me off to that antenna. First, the radials are only 100" long. That's entirely too short for any sort of efficient operation at 40 or 20 meters. The other thing that really makes me wonder is the minimum coax length is 100'. This tells me that the antenna probably runs with a high VSWR on the cable, and relies on either the radio's internal tuner, or an external tuner to provide a match to the transmitter. Coax loss under high VSWR conditions is a hole lot more than under matched conditions, and an antenna designed to operate this way seems like a poor way of doing things, in my opinion. Some of those other antennas require either a good ground system (as in a whole lot more than just a ground rod), or radials installed above ground. Trap verticals can work pretty good, but like you pointed out, tuning can be a nightmare. For the ultimate in simplicity, use a dipole fed with open wire line to a tuner. Open wire line can tolerate high VSWR, and the tuner allows multiband operation. The dipole can be cut to fit whatever space is available although the shorter it is, the less efficient it will be.

I was using Coax Calculator to look at what the coax loss would be with LMR-400 (which is what will be used). Mind you he's pushing a mere 100 watts, which is the maximum output of his rig. I looked at the various feedline losses:

The following table is assuming a 4:1 ratio of SWR (which is bad) in 50 feet of coax (the tech said 50 feet with this antenna is fine). The numbers are also for "center" of each ham band from 160-10 (even though this is 40-10). The coax used is LMR-400 and base xmit is 100 watts in.

1.9MHz = 0.174db loss (96.076watts out)
3.6MHz = 0.238db loss (94.662watts out)
7.1MHz = 0.332db loss (92.631watts out)
10.135MHz = 0.396db loss (91.295watts out)
14.1MHz = 0.464db loss (89.859watts out)
18.1MHz = 0.524db loss (88.633watts out)
21.2MHz = 0.566db loss (87.789watts out)
27.8MHz = 0.644db loss (86.211watts out)

What's angry making about that chart is he'll primarily be operating in 40 (which is fair as far as losses go) but it gets progressively worse as you go up in frequency due to the nature of reactance I guess. Still, a maximum theoretical loss of 14 watts isn't the end of the world I guess, again it's all about compromise. On the other hand, I would love to get a dipole in there, I don't think it'd be possible to run two (ie: EAST/WEST and SOUTH/NORTH) so it'd most likely go slightly north axis of EAST/WEST which might be tricky on this piece of property. Also the entire plot of land we've got to work with there is probably 100ft by 100ft give or take 10-15ft, such is the way of most city plots. I was looking at a G5RV dipoles I just couldn't find consistent total length and length per side. The thing can go up 30 feet in the are which helps with the plot of the land I guess, but going east west or slightly north tilted of east west would result in the thing going over the roof line and a section of that is a metal sun awning. Ugh, makes me glad I have a large plot for my antennas. Any thoughts or dipole suggestions?

 

[prcguy]

Here is my 2c on some of the things discussed so far.
A good roller inductor tuner is nice and will give a bit more precise tuning out of the ham bands but I have many tapped coil tuners and have never been in a situation where they would not tune. Roller inductor types are also a bit more time consuming to get tuned initially but if you record the settings for future use it speeds things up. I also have a Collins 180L tuner with roller inductor and at times have spent over 30min trying to find a match due to all the inductor and configuration possibilities.

When I mentioned a "good" roller inductor tuner I did not include anything made by MFJ in that statement. Most MFJ products I have owned live up to the "Mighty Fine Junk" name they so deserve. Also look at the tiny little roller inductor they use compared to some of the other brands rated at the same power.

Awhile back I shopped and compared vertical antennas for a remote controlled HF station and settled on a 43ft vertical from DX Engineering because of the good mechanical construction and the fact people were buying DX Engineering baluns to replace the stock units supplied by Zero Five and others and getting increased performance.

On my 43ft vertical installation there is 125ft of LMR400 to the rig and I have about 30 radials 30ft long each and for DX on several bands like 60m, 40m and 20m it noticeably outperforms a ZS6BKW 94ft dipole at 30ft height on the same property. It also receives things on 160m with good signal levels that the dipole cannot even hear.

On more close in contacts like 500mi or less the 94ft dipole takes over and is much better but that is expected due to the NVIS nature of these signals. The dipole also works better on 80m for local and DX.

These new breed of vertical antennas are a compromise using a 4:1 balun at the feedpoint and relying on some coax loss to help match the antenna. The coax loss chart posted above is more for matched conditions and when operating into a severe mismatch the coax losses can go through the roof. With that said in some antenna shootouts its been reported the 43ft verticals are outperforming just about all the common trap type verticals on the market. This includes the Cushcraft R7 types, GAP Titan (big dummy load), Hustlers, Benchers and many others mainly because these are much shorter (20 to 26ft) and the 43ft radiator is much more efficient on the lower freqs even though its not really resonant anywhere.

I've used a many of the common verticals sold today and have been disgusted with all of them except for one install using a Bencher HF6V but it was mounted on a 100ft X 100ft solid copper sheet metal roof as the ground plane and it really worked well. The poor performance of all the antennas mentioned is what started me looking at the 43ft verticals.

The best thing you could do for 43ft vertical is place an antenna tuner right at the feedpoint and you will really make an improvement on bands like 80 and 160m where the antenna is lower impedance than 50ohms and the 4:1 balun is really inappropriate. I would have done that but its a remote station 3000mi from my home and hard to remote control the tuner or make changes and repairs.

Another thing is they need a lot of ground radials to work well. When I was installing radials I laid down four then checked tuning and performance, then did the same at 8, 12, 16 20, etc. There is a big difference going from none to four and four to eight then it starts diminishing somewhat from there. The tuning was also interesting where the radios internal tuner worked fine on 160m with none to about 8 radials then would refuse to tune after that. This is mainly because of ground losses bringing the normally very low impedance of the antenna on 160 up to something higher that was easier to tune but it was pure loss at that point. Later addition of some lightning arrestors and jumper cables changed things just enough to allow the radios internal tuner to work on 160m again.
prcguy

 

[acyddrop]

The DX Engineering MBVE-1 looks like a decent solution. I have a question about ground radials however, this is a subject I'm very sketchy on. Well actually I have four questions...

Radials
In the location this antenna would be put it's only possible to run any ground radials in 3 directions, which as I understand is OK.. As the principal is generally "3 directions is better than none". However, I'm pretty sure that in 2 of the directions the best length of ground radial one would get is around 20 feet and at best 25 feet, in the east/west direction. Now they could be bent in the L shape with some difficulty, and manage 25-30 feet at most. This is a SMALL plot of land like I've said. In the south direction, radials of about 35-45 feet can be used and again if they are bent in an L shape they could go 55 or 65 feet. I would rather avoid the bending as much as possible. So my questions is this...

If there are 5-6, 20 foot long radials on a side (ie: 10-12 total radials) for the east/west, and, 5-8 30-35 foot radials run south of the antenna.. Is that enough ground radial support for this antenna to work effectively? At the maximum that would be 20 radials albeit shorter than 65' long in the ground.

Coax
Is it OK to feed this DX Engineering antenna with 50 feet (or less) of LMR-400? If it needs to be fed with 100' or more this might be a no go unless the coax can be curled up or something and stuff away somewhere.

Current Choke
Is a current choke on your coax a good idea with vertical fed antennas? Since it might help with a less than ideal RF ground system. I was looking at the http://www.dxengineering.com/parts/dxe-fcc050-h05-a choke.

Antenna tuner
Does one NEED to use a remote tuner with these antennas or will one up by the radio work nearly as well? As I understand it, a remote tuner will give a bit more power into the antenna, but that may NOT be possible this go around as money is tight on this build.

 

[prcguy]

Read this on ground radials vs ground resistance, etc: http://www.sherweng.com/documents/GroundScreen-sm.pdf A run of chicken wire or hardware cloth for the ground may be a better solution for your location.

All of the 43ft verticals need a tuner and with 50ft of LMR400 you will probably be out of range for most radios with a built in tuner. The coax losses will be less and if you have a good wide range tuner you will be slightly better off with the shorter coax run. If your stuck with a radios internal tuner you can cheat and use smaller coax like RG8X or RG58 and 50ft of that would probably simulate the loss of the recommended 100ft of RG213.

The DX Engineering balun supplied with the 43ft vertical is somewhat of a current choke but another choke near the radio is not a bad idea since the coax is one of the radials and I did this for my DX Eng vertical.

A remote tuner at the base of the antenna will give you the best performance and would be most noticeable on 80 and 160m.

You should also consider a horizontal wire antenna to compliment the vertical since each has its own strong points. If you talk to people within a few hundred miles the vertical may be disappointing due to ground wave diminishing after about 75mi where a horizontal dipole will fill in the 0 to several hundred mile range nicely. My new favorite multiband dipole is the ZS6BKW which you can make yourself and it provides a good match on 40-6m and also works great on 80m with a tuner.
prcguy

The DX Engineering MBVE-1 looks like a decent solution. I have a question about ground radials however, this is a subject I'm very sketchy on. Well actually I have four questions...

Radials
In the location this antenna would be put it's only possible to run any ground radials in 3 directions, which as I understand is OK.. As the principal is generally "3 directions is better than none". However, I'm pretty sure that in 2 of the directions the best length of ground radial one would get is around 20 feet and at best 25 feet, in the east/west direction. Now they could be bent in the L shape with some difficulty, and manage 25-30 feet at most. This is a SMALL plot of land like I've said. In the south direction, radials of about 35-45 feet can be used and again if they are bent in an L shape they could go 55 or 65 feet. I would rather avoid the bending as much as possible. So my questions is this...

If there are 5-6, 20 foot long radials on a side (ie: 10-12 total radials) for the east/west, and, 5-8 30-35 foot radials run south of the antenna.. Is that enough ground radial support for this antenna to work effectively? At the maximum that would be 20 radials albeit shorter than 65' long in the ground.

Coax
Is it OK to feed this DX Engineering antenna with 50 feet (or less) of LMR-400? If it needs to be fed with 100' or more this might be a no go unless the coax can be curled up or something and stuff away somewhere.

Current Choke
Is a current choke on your coax a good idea with vertical fed antennas? Since it might help with a less than ideal RF ground system. I was looking at the http://www.dxengineering.com/parts/dxe-fcc050-h05-a choke.

Antenna tuner
Does one NEED to use a remote tuner with these antennas or will one up by the radio work nearly as well? As I understand it, a remote tuner will give a bit more power into the antenna, but that may NOT be possible this go around as money is tight on this build.

 

[acyddrop]

That was an interesting read, thank you for that! So I can achieve a reasonable system with 2 or 3 25 foot runs of 48" wide mesh it seems. Rolling it up to mow the grass would be a synch too. Maybe a combination of the radial system and some mesh might be the way to go. The article seemed to indicate that it was a good adjunct to an existing radial system. Since he's purchasing the kit with a radial plate and 500ft of 12ga copper jacketed wire we can run the less than "perfect" radial system out and attach two 25' sheets of mesh East and West of the antenna to beef up the radial system and that could be attached to the radial plate easily enough I would imagine.

At this point he'll be using an external wide range MFJ antenna tuner he has already, but it's up by the HF rig and not a remote version. The current choke looks like a pretty reasonable idea all things considered and it should also help a bit with the RF grounding overall too.

Thanks for all your help, it's truly appreciated.

Read this on ground radials vs ground resistance, etc: http://www.sherweng.com/documents/GroundScreen-sm.pdf A run of chicken wire or hardware cloth for the ground may be a better solution for your location.

All of the 43ft verticals need a tuner and with 50ft of LMR400 you will probably be out of range for most radios with a built in tuner. The coax losses will be less and if you have a good wide range tuner you will be slightly better off with the shorter coax run. If your stuck with a radios internal tuner you can cheat and use smaller coax like RG8X or RG58 and 50ft of that would probably simulate the loss of the recommended 100ft of RG213.

The DX Engineering balun supplied with the 43ft vertical is somewhat of a current choke but another choke near the radio is not a bad idea since the coax is one of the radials and I did this for my DX Eng vertical.

A remote tuner at the base of the antenna will give you the best performance and would be most noticeable on 80 and 160m.

You should also consider a horizontal wire antenna to compliment the vertical since each has its own strong points. If you talk to people within a few hundred miles the vertical may be disappointing due to ground wave diminishing after about 75mi where a horizontal dipole will fill in the 0 to several hundred mile range nicely. My new favorite multiband dipole is the ZS6BKW which you can make yourself and it provides a good match on 40-6m and also works great on 80m with a tuner.
prcguy

 

[LtDoc]

A tuner only changes the system's input impedance to something the transmitter will 'like'. It does nothing else, doesn't change anything -after- the tuner. If the antenna and feed line isn't what it should be, it will still be whatever it was but the tuner makes it 'better looking' to the transmitter.
'Roller inductor' tuners can make things easier to tune in some instances, but are also problems sources because of how they work. 'Tapped' inductor tuners tend to be a little more inconvenient because you have to make/change those taps manually. Other than that, there's no real difference between them, either type can certainly work just dandy.
Remote tuners, located at the input to an antenna, eliminate the feed line as part of what they are 'tuning', and that's good, one less variable the tuner has to contend with. Are they worth having? If I didn't have to pay for the things I'd say YES! If I have to empty my pocket to have one, I think I could put up with some inconvenience/less efficiency, you know?
ALL of these simple, non-resonant length, multiband antennas are compromises. They are never very efficient on more than one band or two. But, if they are the best compromise that 'fits' the situation, go for it.
As for radials, any antenna will benefit from having them, the more the merrier until it get's totally ridiculous. Metal platting the ground within a 1/4 mile of an antenna would be very nice! I don't think I'll hold my breath for that though (take pictures please??).
Good luck.
- 'Doc

 

[prcguy]

You don't need large wire for the radials since the current on any individual wire is very small and I bought 1000ft of 16ga solid copper wire from DX Engineering for my radial system.
prcguy

That was an interesting read, thank you for that! So I can achieve a reasonable system with 2 or 3 25 foot runs of 48" wide mesh it seems. Rolling it up to mow the grass would be a synch too. Maybe a combination of the radial system and some mesh might be the way to go. The article seemed to indicate that it was a good adjunct to an existing radial system. Since he's purchasing the kit with a radial plate and 500ft of 12ga copper jacketed wire we can run the less than "perfect" radial system out and attach two 25' sheets of mesh East and West of the antenna to beef up the radial system and that could be attached to the radial plate easily enough I would imagine.

At this point he'll be using an external wide range MFJ antenna tuner he has already, but it's up by the HF rig and not a remote version. The current choke looks like a pretty reasonable idea all things considered and it should also help a bit with the RF grounding overall too.

Thanks for all your help, it's truly appreciated.

 

[acyddrop]

How about 18ga? Seem we have 500 feet of that already.

You don't need large wire for the radials since the current on any individual wire is very small and I bought 1000ft of 16ga solid copper wire from DX Engineering for my radial system.
prcguy

 

[acyddrop]

Good to know about the antenna tuners, I had never personally seen a roller inductor tuner before this whole thing so I've certainly learned a lot on a wide array of subjects. Yeah I understand how the tuner works with respect to, well.. Essentially "faking" a good match to the transmitter, would that be a correct way to express it? I'm also glad to know that one can get away with a tuner up near the transmitter and do OK with it as opposed to having to go with a remote tuner nearer to the antenna load. That's something I was pretty unclear on prior to all this too. I can certainly see an advantage of a remote tuner now though where-as before it was all a very gray area to me. Thanks for your help!

A tuner only changes the system's input impedance to something the transmitter will 'like'. It does nothing else, doesn't change anything -after- the tuner. If the antenna and feed line isn't what it should be, it will still be whatever it was but the tuner makes it 'better looking' to the transmitter.
'Roller inductor' tuners can make things easier to tune in some instances, but are also problems sources because of how they work. 'Tapped' inductor tuners tend to be a little more inconvenient because you have to make/change those taps manually. Other than that, there's no real difference between them, either type can certainly work just dandy.
Remote tuners, located at the input to an antenna, eliminate the feed line as part of what they are 'tuning', and that's good, one less variable the tuner has to contend with. Are they worth having? If I didn't have to pay for the things I'd say YES! If I have to empty my pocket to have one, I think I could put up with some inconvenience/less efficiency, you know?
ALL of these simple, non-resonant length, multiband antennas are compromises. They are never very efficient on more than one band or two. But, if they are the best compromise that 'fits' the situation, go for it.
As for radials, any antenna will benefit from having them, the more the merrier until it get's totally ridiculous. Metal platting the ground within a 1/4 mile of an antenna would be very nice! I don't think I'll hold my breath for that though (take pictures please??).
Good luck.
- 'Doc

 

[prcguy]

Should be fine unless your only using one radial elevated at 1500w and there are many other reasons not to do that.
prcguy

How about 18ga? Seem we have 500 feet of that already.

 

[AK9R]

The best thing you could do for 43ft vertical is place an antenna tuner right at the feedpoint...

I've been doing a lot of reading lately about non-resonant vertical antennas and everything seems to point towards using a remote antenna matching device (aka, tuner) mounted at the base of the antenna. Theoretically, this should reduce or eliminate SWR-induced losses in the coax between the radio and the tuner because the tuner will make the radio see a 50-ohm load.

An automatic, remote-mount tuner would seem to be a good choice for this application.

 

[prcguy]

Yes it would but even with the stock 4:1 balun the 43ft verticals work much better than their trap or other loaded counterparts on 40 through about 15m and are probably better on 80m even with the high VSWR.
prcguy

I've been doing a lot of reading lately about non-resonant vertical antennas and everything seems to point towards using a remote antenna matching device (aka, tuner) mounted at the base of the antenna. Theoretically, this should reduce or eliminate SWR-induced losses in the coax between the radio and the tuner because the tuner will make the radio see a 50-ohm load.

An automatic, remote-mount tuner would seem to be a good choice for this application.

 

[acyddrop]

After all the back and forth about vertical antennas, he bought an OCF Windom (which is an OCF Dipole, I know I know) for 6-80M. I believe the long side is 88ft and the short is 44ft. The good news with this setup will be it'll be about 50 feet up and a slight inverted V setup. It'll be going over the top of his house (clearing it by about 15-20ft) and tied off to a tree in the front of his property and another in the back. The plan is to put this up, wait for hurricane season to end then put up a vertical which I think is a mighty fine idea.

I do have just ONE more question... Since we're both in Florida what is an ideal direction for the Windom to ensure contacts in the US and give a good chance for DX in Europe/elsewhere. Thanks guys.

 

[w2xq]

what is an ideal direction for the Windom to ensure contacts in the US and give a good chance for DX in Europe/elsewhere.

There is no short or simple answer to the question. Factors include the operating frequency (wavelength), wavelength height of the antenna above ground, adjacent structures et al. In free space, as the frequency increases the antenna lobes change from a right angle to the wire plain to lobes off the ends of the wire.

That said, I opted to mount open-feedline-fed 80 and 20 meter dipoles running N-S to take advantage of the changing lobes on higher bands and minimize reception of signals from a southerly direction.

Wire antenna theory hasn't changed over the years. Look up some of the early bibliography in a library rather than just depend upon the 'net. Perhaps a radio club member has a vintage 1950's or 1960's ARRL Antenna Handbook. You might be lucky to find a collection of vintage Jim Fisk's 'ham radio' magazines; the annual 'antenna' issues were fascinating reads.

Your mileage may vary. Experiment. HTH a bit.