Reading the postings here about the Maxx-com tuner it seems that everyone has an opinion about it but no one has actually bought one to find out what it does, i did! Let me explain, i live in Europe (Netherlands) so excuse me for any weird language and misspelled words. I restored a 40yr old army radio truck (Mercedes-Unimog S404) that i use purely for my hobby. Among others there is a GRC-106 transceiver aboard (400W PEP) that i use for RTTY. I started out with putting up dipole antenna's in the field on three 11mtr high masts but i soon found out it just was to much work, if the field trip was just one day i would not get to my radio's at all! Just setting up and breaking down antenna's. In my shack i had a SG230 autotuner that worked very well in the radio-truck also. I just had to erect 1 mast (instead of 3) and run a 100ft single wire from the vehicle to the mast. If i needed to be really quick i could use one of the 3 whips that are always in place on the shelter. The only problem with the SG230 is that it is only 80 Watts on RTTY (200PEP) and the GRC106 will easily put out 200W. So i went looking for another solution. It had to be an autotuner, lots of other stuff to do in the shelter and i need both hands to tune the amplifier of the GRC106. I looked at the bigger SG autotuners but i found them a bit pricy... Also looked at surplus tuners like the Harris RF-601A but they are hard to find and sometimes very expensive. Then i stumbled on the Maxx-com tuner, at first it looked to good to be true (and then ususally it is), but if it worked it would be the perfect solution. The Maxx-com is obviously not a "tuner" in the normal sense. It needs the radiators to be non-resonant so it is most likely an impedance transformer plus a means to flatten the SWR at the transceiver side. A Coupler would be a better description. Clearly this setup can work, ICOM sells one too and i am sure if you look hard you will find more examples, so there is no need to discuss the principle, it will work, also there is no physical law that claims radiators have to be resonant to be an efficient radiator (look at this excellent piece:
http://www.vk1od.net/iobr/)
What i liked about the Maxx-com is that somehow they found a way to let it handle 1Kw PEP wich is a lot more than the ICOM model. I decided to order one and see for myself. Maxx-com claims the tuner to be 80% efficient, i figured that if it can do that, it would be OK by me, 100% power in, 80% radiated power out and no tuning hussle: GREAT!
At my QTH i have a 200ft dipole with a Diamond BU-50 balun and 100ft of Aircell-7 cable to a manual tuner. This is a common setup for hams like me that have trouble routing a balanced feedline into the shack. Before installing the Maxx-com i took FS measurements at carefully defined places (FS can vary hugely in the antenna's near-field at different places) and at several frequencies including the F.res of the dipole. After hoisting the Maxx-com up into the middle mast i retook the measurements at the exact same frequency and places. The results were stunning: at the F.res + 250kHz (Maxx-com instructions ask you to avoid resonance so i added 250kHz) the FS was just a tiny bit lower, my best estimation would be between 5 and 10% down on the old situation. On all other frequencies however the FS with the Maxx-com in place was way up! This can easily be explained, with the tuner at the transceiver i had a widely varying SWR on the feedline that causes great losses in the feedline. The Maxx-com is always under 1:1,5 so feedline losses are down to a minium. After that came the real test, i started working stations in CW in the middle of the day on 40m and got fine results from Poland, Italy, France etc. In the evening i reduced power to 20W and had no trouble working the other stations in the Dutch Amuture net on 80m.
Some time ago i also aquired a new surplus transmitter, a Telefunken S2525/3 (weight: 260kg!) with an output of 1KW. Way more than my tuner could handle so i ordered the new MFJ998 autotuner that will be available to Europe somewhere in the end of 2007. But, after only one week working with the Maxx-com i totally dreaded the idea of going back to the tuner hussle, The MFJ, beeing an "autotuner" will still need a few watts to tune wich means that i must reduce power at the Telefunken, tune, switch to high power, etc. Noting wrong with that and i am sure the MFJ is a fine tuner but by that time i was already used to working with the MAxx-com: just dial a frequency and hit the key! End of story: I cancelled the order and got myself a second Maxx-com for the shack.
Now there will always be postings of people that have never even seen a Maxx-com for real calling it a "resistor in a box", i cannot help that, but saying the Maxx-com is a dummy is like calling me a dummy, you wouldn't want that would you!
Regards,
Willem PA1WAN
