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Author Topic: Maxx-com tuner revisited  (Read 4005 times)
WA4HND
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Posts: 42




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« on: February 03, 2004, 04:59:06 AM »

To anyone that is interested.

I just picked up a maxx-com this week ( my curiosity got the best of me and I figured if it didn't work, I'd get my monies worth out of the bad press I would send Maxx-com's way.

If anyone is interested in what I found, let me know and I'll post the details here.

One clue ... after my first day of doing some tests ( on and off the air )... there is no doubt in my mind that the unit is NOT going to be sent back for a refund.
Al
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K0BG
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« Reply #1 on: February 03, 2004, 10:26:10 AM »

You sound like you work for them. Do you?

Alan, KØBG
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WA4HND
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Posts: 42




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« Reply #2 on: February 03, 2004, 01:44:30 PM »

Nope, own my own software company here in Colorado, but I'm an EE and have been working with communications gear most of my life.

This is a copy of a post I sent someone over in Tower Talk.... he thought I was a succer for buying it ( a reasonable idea really <G> ).. but not after yesterday....

>> There's one born....

Not sure if I'm one of those... but this "one" had a nice qso with JI1 land as their first contact with a new antenna system.  ( while driving down I70
in Western Colorado. )

I've got lots of toys to compare this tuner to, DU antennas, SGC's, Hamsticks.... etc.  If you're interested in what I found out, let me know.
If not, I'll go back to the rest of my emails.

I understand where you are at.... I fully intended to get the unit in, test it out, find out the performance ( or lack there of <g> ) and send it back.  It just didn't turn out that way.

73,
  Al
Al Acker ( wa4hnd )
Colorado State / Mesa County RACES officer
Dist 3 ARES asst. EC
http://www.ColoradoRACES.net
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K5LXP
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« Reply #3 on: February 03, 2004, 03:54:27 PM »

Of course they work.  So do light bulbs, window frames, bedsprings, or even a column of saltwater in a pipe.  *Match* is one thing, *efficiency* is another.  If all you care about is *match*, you've got it made.  Sometimes that may actually be desirable and the resultant (in)efficiency acceptable.  Thing is, if you're running a compact HF antenna, you're already in the hole efficiency-wise and using a resistive match will only dig you deeper.  If your antenna is big enough to have decent efficiency, then you've got the room to make one of the correct proportions to match efficiently without a resistive match.  You may think it's working great because you can hear/work stuff with it.  But you wouldn't think it was so great once you find out what you're *not* hearing.  The ARRL did a product review of these things and it was a joke- looks like they threw spare parts in the box before they potted it just so you'd see something in an X-ray besides the load resistors.  

http://www.arrl.org/members-only/prodrev/pdf/pr8411.pdf

Mark K5LXP
Albuquerque, NM
k5lxp@arrl.net
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WA4HND
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« Reply #4 on: February 03, 2004, 06:39:02 PM »

Mark,

I think you're missing the point.... the advantages of this tuner ( at least to me ) is that I can band hop and not worry about the delay in tuning ( or having a problem if the tuner decides not to work. )... I'll gladly give up a db or two to make that happen.   Read my reply in tower talk to get where I'm coming from here.

No, getting a "match" is not what I care about.... I care about communications... IE making a contact, getting a message from point A to point B etc etc.... so far, the worst report I've received with this tuner
is a 5-8 and that was from my mobile here in Colorado to a JI1...    Sure it could have been 5-9 with a tuned ant.... but so what.  I made the contact cause I had just changed bands and heard his call.... all I had to do was hit the vox and I was calling him.   After using this tuner and seeing what it can do, my respect for the ARRL just went down a few notches, they obviously missed the point.    It's also hard to respect people that degrade things without ever using them.

I admit, in my mind, I was going to try the thing out for a few days and then send it back...  I had a preconceived notion ( after reading all the messages here ) that it would present a great load, but not get out...well I was wrong, and because of that, I thought I'd come up here and talk about what I found.

I do a lot of contest work and know the advantage of lots of metal, high up and exactly tuned for the right band width.  If I want to get "big signal" reports, I know how to do it...  but I use my mobile for a lot of emergency work where you're changing freqs a lot and it's important to be able to transmit without delay where ever you need to do it.

In these instances, you don't have time to change coils, move screwdrivers, or dink with an SGC that just decides because there's some snow on it, that it's not going to tune this particular freq today.   One of our local hams designs mobile antennas.... they work great , I carry one in the jeep all the time... and if I want to blow out a big signal, it goes on the roof in
under 5 minutes.   But for general use, band scanning, and fail-safe transmit under all conditions.... I haven't found a better "communications" tuner than the maxx-com.


Al
Al Acker ( wa4hnd )
Colorado State / Mesa County RACES officer
Dist 3 ARES asst. EC
http://www.ColoradoRACES.net
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AA4PB
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« Reply #5 on: February 03, 2004, 10:17:37 PM »

You can't compare an antenna by stating that you worked some DX station or even that your worst signal report was 5-9. I don't care how good an antenna is you can certainly find stations that will give you far less than a 5-9 (unless you have a very poor receiver). As an EE you should know that.

What you need is a side by side comparison (an A/B test). Take the Maxxcom to the next 75M mobile shoot out and report back to us how it compared to the other antennas. I think you'll find that its a lot more than a dB or two down from a bug catcher or screwdriver. If a well run shootout qualifies it as only 2dB down from a bugcatcher I will order one immediatly.

One of Maxxcom's problems is that they apparantly try to hide what it is by a bunch of advertising "gobbily gook" about tuning in so many microseconds, etc when in fact it doesn't "tune" anything at all. At least the one evaluated by QST was nothing more than a resistor. If Maxcomm has discovered some new "magic" system to tune an antenna then they should explain to us how it works and provide some realistic modeling data to prove it. They could probably sell a lot of them and go down in the history books as well. My guess is that they will never do that because it is hard to get people to pay around $200 for a resistor in a box.
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KC2MMI
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« Reply #6 on: February 04, 2004, 12:29:26 AM »

Al, since I'm looking to buy a first set of gear I've seen the maxx-com. And being one of those guys who likes to understand the WHY of things, I emailed them.

<*Match* is one thing, *efficiency* is another>
 Sonny Irons is still running it but when I asked him about details he said "Please don’t over-think the tuner. " rather than explaining anything about how it worked. And that it has about a 20% or 1dB loss, which isn't bad for a solid state no-fuss box.

All I could get out of him was "Maxx-Com’s unique tuning circuits do not resonate your radiator(s). Rather, in the manner of a traveling-wave system, it uses an expanding/collapsing field mechanism to apply RF to the radiator. "

 Now, maybe I'm just undereducated, but I'd swear that what he said about using a field mechanism to apply RF to the radiator means there's a transformer inside. Or, some of those fancy plasma regurgitrons that power UFO's.<G>

 Numbers convince me, vague talk about the aether didn't make a sale. I guess I'll have to join ARRL sooner than I planned if I want to read their article and see what they found in the box.<G>

Jared
KC2MMi / WCO3103
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WA4HND
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Posts: 42




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« Reply #7 on: February 04, 2004, 02:16:33 AM »

AA4PB... et all,

You guys have not been listening to my posts.  I __have__ an SGC QMS system with a SGC 230 tuner ( I have two of them in fact ).

I __have__ hamsticks... I __have__ a home made antenna that is better than both.  I __have__ done side by side comparisons with  those systems and screwdrivers ( name your brand <g> )  and I check into a 75 meter net ( Columbine ) and 40 meter net ( high noon net ) every day.  I also check into the Maritime net on 14.3 almost every day.    I also run our state RACES net on 75 once a week.

 I __can__ attest to the 1 to 2 s-unit difference and that's all.  I __can__ hear the same weak stations on the net that are still weak with my other antennas.  

In fact what I did to test the maxx-com is slide out my sgc tuner out of it's QMS system case, and mount the maxx-com inside... that way I was using exactly the same whip, ground and placement on the jeep.

One thing I will agree with you all on is that Maxx-com PR sucks.  Who ever they got to write up that crap should be shot.  If they would market to hams the real truth they'd be a bunch better off.  The instructions that come with the unit are much better than the PR they put out.  It's very clear that who ever has been doing that doesn't know beans about RF ( or common sense <g> ).

Yea, it "tunes" in what ever they said.... 1/1200 of a second or something.... if you calc it out, it most likely is the time it takes a wave to travel the length and back a few thousand times and register something on an swr bridge <g>.   "Solid state" is another POS PR ploy.... the thing has some kind of transformer in it ( .2 ohms from so-239 center to ground ) and what ever doesn't load into the inductive match, gets tossed to a resistive load.  It doesn't take much of an EE to figure that out.... I did that in the first 15 seconds after I opened the box.

BUT.... like I said, aside from the poor marking moves.... the thing DOES work as advertised and has a place in any emergency vehicle and ( take away kit ) at least.  In every em unit I outfit, there will be one of these guys and a whip ant on it... ( most likely an sgc-303 until we find or build something better. ).  It may not be the prime ant...but it __will__ be there.

I think in the wake of 911, if the ARRL did another review of the unit ( and looked at it like I did ) the results would be much different.

In my opinion, if your life doesn't depend on communications and you just want to talk DX when conditions are perfect.... this is not the unit for you...  But if you want to make sure you can use your rig under any conditions, on any freq and are willing to give up a s unit or so for the sake of safety.... this guy does do the job.  

If you guys want to( once the weather warms up some and it stops snowing), I'll be happy to do some on the air tests with you as time permits ).

Like I said before, it takes me under 5 mins to change coils and get a DU antenna on the roof with a mag mount....  I'll put that antenna up against ANYTHING out there,  but if moving down the road I need to changes freqs __fast__ ,  the maxx-com of course is instant.  

Depending on the band change, it may take a screwdriver 60 seconds to get there... you may end up on a freq or have something else cause an SGC to NOT tune at all. )

You never know when 60 seconds may be too long.. to move a screwdirver.... or the drive freezes up, or an sgc quits... and your rig won't even transmit at all into the mismatch.

All I'm telling you guys is what I found.... I'm not a part of the company and have nothing to gain or loose here.... If I told you I wanted a passive system with no moving parts that could get me on any freq __instantly__ 1.6 to UHF ( they don't advertize it but I've tested it on UHF )... you would come up with exactly the same design... or close to it.

Al

Al Acker ( wa4hnd )
Colorado State / Mesa County RACES officer
Dist 3 ARES asst. EC
http://www.ColoradoRACES.net
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AA4PB
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« Reply #8 on: February 04, 2004, 11:06:23 AM »

Al, apparently they've changed the design since the evaluation unit they sent to ARRL. As I recall it measured around 50 ohms DC resistance and didn't have any transformers in it. At that time Maxxcom was rather unethical in their dealings with ARRL by hiding disconnected junk in the device that would show up on xray examination. They really made themselves look bad.

In an earlier post you said the unit was 2dB down from your other antennas. This last time you said you measured 2 S-units. 2 S-units is 12dB down which is a lot more like it. And remember, a Hamstick is already a number of dB down from several other mobile antenna designs on the lower bands.

Using a resistive load to smooth out the SWR change is nothing new or magic. Other antennas like several of the B&W models and now the Ten-Tec antenna uses this technique in one manner or another. What you are trading is efficiency for broad band - which may be a good trade off to make in some cases. I'm sure the actual efficiency is very much dependent on how long the antenna is in terms of a wavelength. The longer the antenna, the better the efficiency. These are the types of things Maxxcom should be telling their users.

Again, my problem with Maxxcom is their refusal to give anyone a straight answer. Even when you (a customer) asked questions all you got was a bunch of "garbage" and you were left to guess at what they might have meant by that. Their advertising and even their direct response to you was clearly designed (in my opinion) to hide the truth and to give the impression that thay had some new, high-tech, solid-state antenna tuner in the box. When you purchase an SGC tuner, for example, you get schematics and a technical write up that explains how it works. You know what to expect when you purchase one.

If the Maxxcom works for you and meets your needs than that's great. There is nothing wrong with that. People need to be aware of the trade offs they are making however.
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WA4HND
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« Reply #9 on: February 04, 2004, 02:41:29 PM »

>>
 Al, apparently they've changed the design since the evaluation unit they sent to ARRL. As I recall it measured around 50 ohms DC resistance and didn't have any transformers in it.
>>

Yes, that's the very first thing I did when I opened the box.... if I would have seen 50 ohms DC, the unit would have been taped back up on the spot. <g>.   On the other hand, I'm not above thinking the ARRL had some kind of axe to grind here.... not sure, but nothing would surprise me.  In the software industry, I've seen bad reviews for products that just happened to NOT advertise in the publication doing the review <g>.  I'd hate to think the ARRL played those games...but nothing would surprise me here.

>>
At that time Maxxcom was rather unethical in their dealings with ARRL by hiding disconnected junk in the device that would show up on xray examination. They really made themselves look bad.
>>

I don't recall the ARRL review....but back in the early 80's I was still a Tech and wasn't concerned with HF ( other than fixing my dads gear when something went wrong with his station <g> ).   I do recall back then the  "friction" between the ARRL and Wayne Green and company.... maybe these guys were somehow trying to make the ARRL look bad.... I don't know.

>>
 In an earlier post you said the unit was 2dB down from your other antennas. This last time you said you measured 2 S-units. 2 S-units is 12dB down which is a lot more like it. And remember, a Hamstick is already a number of dB down from several other mobile antenna designs on the lower bands.
>>

I looked over my notes again and what I saw vs the SGC was 1 s-unit down from the SGC on 20 and up and 2 s-units down on 40 and 75.  ( That makes sense since my whip really needs to be longer for those bands. )  Even the SGC sometimes has trouble with those bands when the jeep is wet ( which it has been for a long time.... we're getting more snow here than I've seen in 10 or so years ).
 
>>
 Using a resistive load to smooth out the SWR change is nothing new or magic. Other antennas like several of the B&W models and now the Ten-Tec antenna uses this technique in one manner or another. What you are trading is efficiency for broad band - which may be a good trade off to make in some cases. I'm sure the actual efficiency is very much dependent on how long the antenna is in terms of a wavelength. The longer the antenna, the better the efficiency. These are the types of things Maxxcom should be telling their users.
>>

I totally agree with you.   It's a pity when you think about it.... The facts are that I've found that the unit really does what they say and if you know what you're doing, I'm sure you can get very close to what an SGC can do.  When you think about it, that's very cool considering it's a passive device with no moving parts and you don't need to transmit to "tune".   But they are definitely not doing themselves any favors with their advertising concepts.   Maybe they guess there are more suckers in the ham community, than people who will understand the trade offs and take advantage of them.... I don't know the answer here.


> >
 Again, my problem with Maxxcom is their refusal to give anyone a straight answer.
>>

Agree.

>>
Even when you (a customer) asked questions all you got was a bunch of "garbage" and you were left to guess at what they might have meant by that. Their advertising and even their direct response to you was clearly designed (in my opinion) to hide the truth and to give the impression that they had some new, high-tech, solid-state antenna tuner in the box.
>>

Well that's not what I got on the phone.... but it is what I've seen on their website...  I already had a decent idea of what  "could be in there", and that's why I spent the $$$.  I figured either it was a resister ( and I would have sent it back ).... or it was in fact an inductive device with resistive overload protection.... in which case I felt I could make it work and accept the trade offs.  ( which in fact I'm doing )  But you're dead on with your assessment of their advertising.  You know with 911 and "emergency service" being in vogue right now... I think they could sell a ton of these things if they were honest and gave out the tech specs.... Maybe they're afraid of being copied and I can see that being the case.... but at least they should tone down their PR about 1/1200 of a second to "tune".... and the "solid state" stuff <G>.  Maybe that's technically correct...but it seems to me to be aimed at the less than technically inclined in our community <g>.

>>
 If the Maxxcom works for you and meets your needs than that's great. There is nothing wrong with that. People need to be aware of the trade offs they are making however.
>>

Totally agree.

Al
Al Acker ( wa4hnd )
Colorado State / Mesa County RACES officer
Dist 3 ARES asst. EC
http://www.ColoradoRACES.net
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AA4PB
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« Reply #10 on: February 04, 2004, 03:13:35 PM »

Al, their first unit really was a 50-ohm resistor across the coax with one leg of a dipole attached to each side of the resistor - at least that's what the measurements and x-rays at the ARRL lab indicated. My guess would be that they now have a broad band toroidal transformer to raise the 50 ohms up to some higher impedance and then place the resistor and antenna across the secondary making it have less loss than the original unit.
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AA4PB
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« Reply #11 on: February 04, 2004, 03:42:51 PM »

Here's a cut from their web page:

"A resonant tuner when properly tuned causes the radiators to vibrate from side to side like a string in a piano or guitar, thus creating the R. F. field."

They really do need to find a new "technical" writer :-)
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WA4HND
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« Reply #12 on: February 04, 2004, 05:08:46 PM »

Not exactly I think....

I measured the output and it seems to be another winding... something like .6 ohms.  Once it warms up some and I get my test equipment on it,  I can come up with some answers.  

But I'm not really that interested in that part... as long as the unit does what it's supposed to do and it does... I'm happy.  In fact if I figured it out exactly, I don't think I would post the info here.... if maxx-com doesn't want to "expose" what they're doing... I'll respect that.  But I do wish they'd change their sales pitch a little. <g>.


Al
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WA4HND
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« Reply #13 on: February 04, 2004, 05:11:56 PM »

>>
They really do need to find a new "technical" writer :-)
>>

I think even a bad technical writer may be better than they have now! <G>.  

At least the unit works <G>.

Al
 
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N3ZKP
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Posts: 2008




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« Reply #14 on: February 04, 2004, 07:47:16 PM »

<< At least the unit works >>

You sound just like the "engineer" from New Zealand on the previous thread on this bit of snake oil.

And I repeat ...

There's one born every minute.

Lon
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