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Author Topic: Maxx-com tuner revisited  (Read 4338 times)
AD5X
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Posts: 1430




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« Reply #45 on: February 08, 2004, 04:59:34 PM »

Al - A 1-foot (or less) alligator-clip to PL-259 shouldn't introduce much of a discontinuity at HF.  So a power meter at the output of the Maxx-com connected to a 50 ohm load should look very close to a Maxx-com mounted right at the feed point of a resonant (50 ohm) antenna, and the power meter should give a pretty good idea of what the power transfer is.

Again, how do you reconcile the Maxx-com "80% efficiency" to your measured "1-2 S-unit" differences?

Phil - AD5X
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WA4HND
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Posts: 42




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« Reply #46 on: February 08, 2004, 07:34:51 PM »

Phil,

I'm thinking I'm trying to tell you guys things about 10 times before you understand what I'm saying.

>>
 Al - A 1-foot (or less) alligator-clip to PL-259 shouldn't introduce much of a discontinuity at HF.
>>

The output is NOT a so 239... the output is two connections for hot wire and ground ( or both sides of a dipole. )  

You also say "shouldn't" but you don't know.... , I don't know... I would figure any impeadance bump will cause a difference.  I want to test the unit as it's used.... So the only pure way to test this thing is with a FS tests on a test range.  Because it's not the power transfer to the wire that counts, it's the rf into the air that counts.  If I put a 50 ohm resister on the output and measure 95 percent transfer.... what would that prove?  It's how the thing works with a real ant that counts.

>>
So a power meter at the output of the Maxx-com connected to a 50 ohm load
>>

I doubt the ideal wire would present a 50 ohm load... but that's my theory.  I'll test all this in warm weather.

>>
Again, how do you reconcile the Maxx-com "80% efficiency" to your measured "1-2 S-unit" differences?
>>

That's easy, they tested with 100 ft dipole... I used a 9ft whip < GGG >.  I'm sure with some playing around with coiled whips, or base coils etc, you can get the efficiency up.   You see that's why you guys are not understanding.... the ant you attach to the thing makes a difference.. ( which of course dispoves your dummy load theory ).

The bottom line.... even with a 9 ft whip, it's working well enougth for me right now ( I'm sure none of you understand that <g> ).

In any case, this conversation isn't going any place... right now the unit works for me as well as I need it to... I can talk local on 40 and 75 and have worked some great dx on 20.  Everytime I check into nets I get good reports.... so until the wx warms some, I'll leave it alone.

I'll report back when I do some better testing after the snow melts.

Al
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AD5X
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Posts: 1430




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« Reply #47 on: February 09, 2004, 10:21:09 AM »

Al - I meant an alligator clip-to-PL259 to go from the Maxx-com to the power meter/50 ohm load.  The only impedance bump would be the very short transition from coax to alligator clips (this could be inches).  Since the Maxx-com can match to everything, it should be interesting to see the loss into the matched "antenna" (i.e. the 50 ohm load).  I'm not saying it doesn't work - obviously it does.  I'm just trying to get a feel for the loss if you had an antenna that was resonant on one of the frequencies.

On the Maxx-com specs, they say efficiency is 80% or greater.  They don't say that it has to be connected to any specific antenna length in order to achieve this.  Or to any specific impedance.

Phil - AD5X
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WA4HND
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Posts: 42




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« Reply #48 on: February 09, 2004, 12:29:47 PM »

>>
Al - I meant an alligator clip-to-PL259 to go from the Maxx-com to the power meter/50 ohm load. The only impedance bump would be the very short transition from coax to alligator clips (this could be inches). Since the Maxx-com can match to everything, it should be interesting to see the loss into the matched "antenna" (i.e. the 50 ohm load).
>>

Ok, I think ( or maybe I'm mixing up the ad pr with the info that comes with the unit )... but they say that the unit works better into a non-resonant load... IE in a perfect world the load should be resonant on a freq that is lower than the lowest freq you intend to use with the unit.   That             info  may not be  in the sales info but in the info that comes with the unit...but in any case, I'm not sure that's going to prove anything.  Right now I have the unit mounted inside my qvs case so it can use the exact same setup as my sgc tuner... so it's a little bit of a pain to dismount the thing and put a clip lead on it.... but once warm weather hits, I'll be happy to do that for you.... one test I do want  to do is play with ant lengths and see how it effects the fs  readings... so when we get into that kind of testing, I'll have the unit out and won't have any problem trying your test for you.  I do have a few 100 watt and 1 or two kw loads here so that won't be a problem.

Al
                                       
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WA4HND
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Posts: 42




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« Reply #49 on: February 19, 2004, 07:56:01 PM »

fyi for everyone.... it hit 50 here yesterday and the snow is melting !!!! ( but more snow is on the way tonight ).... but I think as March gets here, I'll be able to do some of those tests that people have asked about.

In the meantime, look for me on 14.300 for the next few days, I'll be in travel mode.   I'll also work some on  17 since that band seems to be doing good lately.
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ZMA3607
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Posts: 1




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« Reply #50 on: February 27, 2004, 08:30:09 AM »

Well, I have a Maxx-com unit. I picked it up for $20 at a junk sale. I expected it to be of litle use.I should say I'm a marine radio operator, just sat my amateur exam.

What I've found is this: I can throw a 15 meter wire over a tree, connect the Maxx-com, ground it through a house earthing wire!! throw 150 watts into it from an Icom 700Pro and happily talk on the marine bands (mainly 4417 and 6224) to boats all over the Pacific,up to more than 2000 miles away, with signal reports much the same as the coast station running much more power into a bunch of dedicated antennae.

Who cares what's in it,who cares what the efficiency is,who cares what I could do with a lightbulb on top of a telephone pole or a resistor loading a whip??? The point is this thing actually does whats required,it enables me to very simply set up a test antenna system that works,is incredibly robust, and on my next boat will be my ATU. I'd much sooner use this than an ATU that might break, might get full of seawater, costs me a lot more and may be the one thing that stops me transmiting in an emergency.

All the tecdhnical discussion of lack of efficiency etc are largely irrelevant, everyone seems to be missing the point that the purpose of radio is to communicate, and this allows communication, simply,robustly and on any band.

I suspect they're hugely overpriced at retail,and the Maxx-com site is full of BS, but they do do a job well enough, and are potentially so much more reliable than conventional ATU's that I can't figure out why so many people waste their time calling them rubbish! Hey guys, they work!!! If everyone knows so much about them, then why don't some of you build the same thing and bring it to market at a fraction of Maxx-com's price?? I'll find lots of buyers for you.

One last puzzling thought,Icom sells a MN-100L "magnetic balun" for matching longwires on HF that sounds very similar in concept to a Maxx-com, if it's snake oil, how come it's as expensive as their autotuners, which contain a mass more electronics?HuhHuh I don't think Icom are in the snake oil business...or are they??
 
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WA4HND
Member

Posts: 42




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« Reply #51 on: February 27, 2004, 03:40:45 PM »

>>
everyone seems to be missing the point that the purpose of radio is to communicate, and this allows communication, simply,robustly and on any band.
>>

EXACTLY what I've been saying... but as you'll soon find out, lot's of "hams" seem to have nothing better to do than to argue.  Sometimes that's healthy if the debate is kept to a high standard.  But all too often it ends up with one person or the other telling the other that he/she doesn't know what he/she is talking about  < g >.

I've been playing with a maxx-com for over a month now and so far have been impressed with it.  I have found that it sometimes takes some effort to make it work on every band.... the unit wants a decent load ( ie wire /whip length ) or it won't get out well.  ( ie if it were nothing more than a dummy load it wouldn't make any diff )  Don't try to work 160 on a maxx-com connected to a 8ft whip ant and expect to get the same reports you would with a maxx-com connected to a hundred feet of wire.  BUT the neat thing is it does work and presents your rig with a decent load.  The bottom line with this tuner is the same as with other tuners, if you want to get the RF into the air... you need a decent ant.  Using a manual tuner to load a bedspring won't get you the same reports as connecting the tuner to a 100 ft dipole.  Same thing goes for the maxx-com.

The neat thing about the maxx-com is I can move ANY PLACE on ANY BAND ( up through 440 or so ) and do nothing but key the mike.... no manual tune, no waiting for an auto tuner to click me into a decent match... it's instant and sometimes instant is what's needed.

I agree with the PR... it needs some cleanup and a better presentation on the advantages of the unit.  

As for the price, I think they sell a lot to the government and marine types.  In those cases, failsafe operation is more important than price.  I guess if I were out in the midst of major water and my only contact with help was the radio... I doubt I'd complain much about the price < G >.  

Al
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KC8AON
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« Reply #52 on: October 20, 2009, 03:24:18 PM »

I agree with you Phil - into a 50 ohm load the Maxx-com is going to show a lot of loss.  But just for the heck of it, connect the Maxx-com to your analyzer with no antenna or wires connected to the Maxx-com and see what happens.  The swr will be very very low - just as if you have the analyzer connected to a dummy load !

Rick
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