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IMAX 2000/40 METERS

Discussion in 'Amateur Radio Antennas' started by doctor, Apr 19, 2015.

  1. doctor

    doctor
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    Anyone ever use one of these on 40, I just happened to listen on 40 and had the IMAX on the tuner, and gave him a call, came right back 5/7 to NORTHERN OHIO.
    I run the antenna straight thru on the tuner.
    Just curious if anyone else ever did this..I forget swr...1.6, power50 watts.
    DOCTOR/795


     

  2. The DB

    The DB
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    40 meters is pushing it. I've heard of using antenna tuners adjusting the antenna as far 20 meters successfully, but I haven't heard anything that was successful beyond that until now.

    Does it surprise me that you made a DX contact on 40 meters with that antenna? No not really. I've made DX contacts with less.

    Do I think other antennas that wouldn't cost much to make would work better in the place of your Imax for 40 meters DX? Yes, definitely, no question about it.


    The DB
     
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  3. fourstringburn

    fourstringburn
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    W9WDX Amateur Radio Club Member K5KNM

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    Ever hear the expression " I can tune a rain gutter".

    There is a lot of truth to that but you have to consider ERP (effective radiating power).

    Your tuner may show an Ideal SWR and your watt meter may show 50 watts, but your actual radiated transmitted power from the antenna is probably less than 10 watts if that. This is due mainly to the losses from using an antenna that's too short and far beyond it's designed range. So your contact was theoretically QRP.

    I deal with using less than ideal antennas with my mobile HF screwdriver antenna. Even though I can compensate for the missing antenna length with the screwdriver antennas loading coil adjustments and a cap hat, I still lose a lot of transmitted power efficiency especially on the lower bands.

    Even the best mobile antenna on 80 meters by a field study I read measured less than 3 watts ERP from a 100 watt radio. Even though I run a 400 watt amplifier, at best I might have 12 watts ERP on 80 meters.
    However I can and have made many good DX contacts from my mobile. but I can never gain ERP unless I lengthen the antenna which I can with a 17 ft. telescoping whip and it takes 80 meter mobile antennas to a whole new level.

    The DB who posted above has working knowledge of field strength meters and can probably give you more insights on antennas and ERP.
     
  4. 918Oklahoma

    918Oklahoma
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    A contact is a contact at the end of the day. Doesnt matter if you are doing it on a imax pushing the brink of your antenna tuner, or on a 40m resonant beam 100ft in the air. Great job on the 40m contact using an Imax.
    I know my sirio 2016 5/8 wave vertical has amazing ears on 40m, can't wait to try it with a tuner. I can routinely hear short signals 100+ miles on 40, and you know what they say, gotta hear them to work them.
     
  5. DainBramage

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    ... and that is a two way street,.. just because you can hear my QRO signal, doesn't mean I can hear you.

    there is also another phrase,..... "go buy a signal":D
     
  6. Captain Kilowatt

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    Anyone that thinks their Imax2000 or any other CB antenna has really good ears on 40m has never tried a REAL 40m antenna. Even a simple 40m dipole will blow an Imax2000 away on 40m.
     
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  7. 918Oklahoma

    918Oklahoma
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    Well i have both, so it will be interesting to compare them soon once i upgrade license classes To general. Maybe i'll resurrect this thread and post the results.
    i know with my 10m antenna when i tune to 40m, its always full of activity and i can hear a lot of good signals.
     
  8. Captain Kilowatt

    Captain Kilowatt
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    I could hear a lot on 80m with my 80m mobile antenna too but it was nothing compared to either my 80m dipole or even my random wire antenna. It's all relative. Most newcomers think a G5RV is a great all band antenna and brag about their contacts with it. When they eventually get even a lowly simple three element tribander they realize the pitfalls of the G5RV. The truth is that the G5RV was designed as a 20m antenna, and it works quite well there. It just happens to have a half decent SWR on other bands as well. Single band dipoles will outperform it on the other bands. A truly great all band antenna is a doublet about 102 to 115 feet long or so and fed with ladder line. Loses are low even with extreme SWR and gain increases as the frequency increases. You do need a tuner with a balanced output or an unbalanced output feeding a good 1:1 current balun connected to the ladder line.
     
  9. ghutch

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    DX contacts sometimes have no bearing on efficient antennas.....it's conditions and luck of having your radio tuned to a particular spot on the band....the luck of the Irish, right time at the right place.
    I operate mobile and portable almost 100% and only wish I had a way to get more metal in the air. ERP makes a high power station a QRP operation with an antenna not resonant at freqency. I worked the CQ Phone contest the last couple years with a 10 meter ground plane at 10 ft over saltwater. The saltwater had a much larger effect on my results than the antenna even on 10-12 meters, it the best ground plane we have. I did however make many dx contacts....needed and few more multiplier so I tried to work a few guys on 40 and got a few. Tried 80 mtrs. and the tuner covered the mis match?? Somehow??, I could hear many guys calling,wanting to make contacts with anyone! I was not able to make a single 80 mtr contact. I could also hear some contesters on 160 calling.....tried but zero! This was under contest conditions where they want to dig out a weak station for the points....they want any contact.
    My ground plane at 80 meters is about like a rubber ducky antenna on a handheld walkie talkie versus a real two meter antenna.....the rubber duck hears but can they hear you? In many cases they cannot. Dx contacts is my thing but it is not a good indicator of antenna efficiency or ERP.
    A single band dipole even at a low height would have made contacts on both 80-160. Good luck 73 , KF5VDX
     
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  10. KD2GOE

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    I have made contacts on 20 meters with a Wilson 5k ;)

    I have a 40 meter horizontal and an i max 2000.... the i max is deff on 40 it is 0 to 9 s-units is most cases
    the i max in on a 25' steel tower with 100' of davis bury flex < "on the FLEX part that stuff is harder then me on my prom night.. had to say that :D..."
    the 40 meter horizontal is ran with Belden RG8u through a switch box.
    quick test i did

    "ant1" I-max2000.. "ant2 40m dipole"

     
    #10 KD2GOE, Apr 26, 2015
    Last edited: Apr 27, 2015
  11. Captain Kilowatt

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    Something to consider too is that while YOU may be in a low noise environment where your noise floor is typically S-0 to S-1 and you can hear someone with a really crappy antenna the opposite may not be true and usually is not. Most urban operators have a lot of noise and a noise floor of S-5 or higher is not uncommon. That crappy antenna just will not be heard by those operators. I have heard some operators claim their noise floor is S-8 or higher in some cases and they will not hear anybody other than the strongest signals on the bands.
     
  12. ghutch

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    I agree the noise floor can keep you from hearing most signals at times. I at one time had an S6-7 noise level in my tacoma. All I heard was the guys with big signals that could bust thru the automobile generated noise. After using the bonding techniques from K0BG.com website I've been able to get to S0-1 running and S0 or atmospheric levels while parked.
    What is down in the noise are all the stations with less than the noise level signal levels. After getting all the noise reduced, I began to hear and work many stations I could never hear
     
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  13. TonyV225

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    I tell people all the time that if you think your super scannet or other cb antenna hears good on 40 and 80 meter if you hook up a wire flat or dipole your going to get 3 times the signal and probably fallover!! My Antron will tune 20 meters but my multiband vertical and my inverted Vee antennas show what an actual antenna for the band will do. dont get me wrong Im amazed the Antron 99 will tune these bands as mine will tune 6 - 20 meters but again as Ive said in simalar threads its not going to be efficiant but Ill admit its still fun to make contacts there with a 10 - 11 meter antenna ;)
     
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  14. Justme

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    My experience is that the Imax 2000 even with added 17 feet radials works good on 10/11 and 12 and 15.
    17 already is down on my OCF antenna or my 25 foot vertical situated behind the house at ground level with 1:4 unun and 100 feet of RG 58........
    20 and lower it is a leaky dummy load, in which most powr will be dissipated in the network at the bottom of the antenna and coaxial cable.

    The 25 foot vertical behind the house with good radials and FT 240 - 43 1:4 unun ( homebrew) works from 40 - 10.
    Even with the lossy coax on it it outperforms the Imax at 17 20/30 and 40 meter while the Imax is on the roof at 40 feet high.
    Even the European equivalent of LMR400 is on the Imax at 60 foot length has lots less loss as the vertical that is behind the house...

    The Imax is good for 10/11/12/15, decent on 15 and crap at all other lower frequencies.
     

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