Super Antenna MP-1 issues

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W5SUM, Apr 1, 2020.

ad: L-HROutlet
ad: l-rl
ad: Subscribe
ad: L-MFJ
ad: Left-2
ad: FBNews-1
ad: Left-3
  1. W5SUM

    W5SUM Premium Subscriber QRZ Page

    my late wife bought this for me for Christmas 3 years ago and I have yet to use it. I set it up on the TM-1 Tripod mount today. I have the whip fully extended, the coil set to 40M using their cardboard chart. I have the fan radials spread out and laying on the ground.
    I am using a MFJ259B antenna analyzer trying to set this thing and NO WHERE on ANY BAND will it show less than a 5:1 SWR. What the heck am I doing wrong with this thing?
    I read on another forum to put a longer radial set on it so I added a couple of 80M radials on it and it made absolutely NO difference.
    I checked to be sure the 3/8-24 antenna rod mount was still insulated from ground and it is.

    Idea's?

    Thanks W5SUM Ronnie
    Shreveport, La
     
  2. AF9US

    AF9US Premium Subscriber QRZ Page

    Ronnie:

    Test the feed line - presumably, it is coaxial cable. With an DVM (or an analog Ohm meter) measure the continuity of the center conductor - end-to-end, and the same for the shield. Center conductor: end-to-end should be 0 ohms, or very close to 0. Likewise for the shield: end-to-end it should measure 0 ohms or very close to zero. Measure center conductor to shield, there should be no conductance, or infinite ohms.

    If the coax does not measure-up, replace it with a known-good section of coaxial cable between the transceiver and the MP-1 antenna.

    If the coax does measure-up, inspect the MP-1 connector. Make sure the connection to the whip from the center conductor is continuous, and the connection from the shield to the radials is continuous.

    Lastly, remove the MFJ-259B Antenna Analyzer from the coaxial cable and antenna path. Reconnect the coaxial cable to the MP-1 antenna. At the transmitter, see if the antenna loads-up; either by measuring the SWR with meter in the radio, or, watching the power meter to see if the antenna system accepts power from the transmitter. If the antenna seems to work without the MFJ-259B Antenna Analyzer in-line, then the problem appears to be in the antenna analyzer.

    Good luck,
    Bernie, AF9US
     
    KC8QVO likes this.
  3. K6CLS

    K6CLS Ham Member QRZ Page

    you are likely turning the 259 frequency knob too fast and spinning through the "notch" of lowest SWR on 40m. MP-1 is very narrow bandwidth on lower bands.

    The printed guide is just a guide. The coil will tune differently in each different situation: by the ocean, top of mountain, etc. But don't try it indoors.

    I never got much improvement from longer radials. And, resonant radials are exactly what you don't want, voltage nodes at the ends.

    I've had some improvement with raised radials. Also try raising the entire antenna assembly up, perhaps 6, or 10 feet.

    Does your rig have a tuner? Grt the MP-1 to 3:1 or better, use the tuner, and go for it; good enough.
     
    AJ5J likes this.
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I've found the only thing Super about the Super Antenna is the amount of frustration it causes when trying to use one.:)

    I agree as stated above, the resonance on a band like 40m is very, very narrow. Once you have the antenna "dialed in," the 2:1 VSWR bandwidth might only be 10-20 kHz and departing from that frequency it can climb to nearly infinity very quickly.
     
  5. K7JOE

    K7JOE Ham Member QRZ Page

    One must understand the characteristics of a high Q coil/antenna configuration to understand how to tune and then how to use the Super Antenna on lower frequency bands.

    Use of the MP-1 coil setup is no different than any mobile "screw-driver" (when fixed) or classic "bug catcher" or variant (eg. Wolf River) antenna- the bandwidth at 7 mhz is very narrow. Typically a 20-30Khz bandwidth is all you can expect without re-tapping the coil or adjusting the whip length.

    One well documented solution is to use a capacity hat, which will lower the Q and widen the bandwidth.

    There are some upsides to high Q antennas too, but bandwidth is not one of them !
     
  6. N4AFK

    N4AFK Platinum Subscriber Platinum Subscriber QRZ Page

    I had similar frustration with my MP-1, until I replaced the stock whip with a Buddipole long whip. Now, I don't need to tap the coil as far and I get 2:1 SWR or less almost across the entire 40 meter band.
     
  7. KM6PRA

    KM6PRA Ham Member QRZ Page

    I have a superantenna and never had any problems. I have it on an eight ft. Tripod. With three set of conterpois. I can get 1.7 or less across 20 & 40. It does take some fiddling to get it right.
     
  8. KC8QVO

    KC8QVO Ham Member QRZ Page

    I second Bernie @AF9US 's post.

    About 10 years ago I had a friend's Buddipole to work on. He had to use a tuner with it. The tuning of the antenna never made any sense - it should have been a lot easier to tune.

    Long story short, the generation of coils that they used at the time (not sure on the exact date range - I graduated college in 2009 and it was somewhere around there, seems to me after college some time) used a machine screw/bolt that bridged the electrical connection between the 3/8"x24 sockets on each end of the coil and the wire on the outside that made up the physical coil. There was no continuity across the coil - the machine screws/bolts were not touching the 3/8"x24 sockets well enough to make the electrical connection.

    Once that was resolved the antenna worked 100% like it should have.

    So the likely issue is continuity, or lack there of. Start there. Check the components individually first (coax and antenna). Then put them together.

    If you still have problems track someone down that has an instrument that will do TDR measurement. You can also do the same thing with an Oscilloscope for the level of seeing whats going on you would need. See the video here for how to do it - you need an extremely fast rise time of a signal pulse to do it.



    Good luck with it and post back how you get along with it.
     
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    That happens with any length radials. Highest voltage is always at the ends.
     
  10. KC8QVO

    KC8QVO Ham Member QRZ Page

    On second thought...

    The coax IS 50 ohm coax, isn't it??

    I visited a repeater once where a lot of "swap-nostics" had been performed over time trying to surpass some issues in performance without proper equipment and knowing what was up. The receiver seemed like it wasn't hearing. I checked over the duplexer and fine-tuned it as best as I possibly could. I also checked the loss in all the interconnect cables. There were two pieces of coax going from the duplexer to the receiver port on the repeater. One had an N connector and BNC connector on it. The other one had a PL-259 on one end and an N connector. The PL-259 is what was on the duplexer and the BNC was what was on the repeater receiver. It was easy to see why they hooked it up that way - the two cables were already there with connectors that fit.

    Come to find out - the BNC to N cable was NOT 50 ohms. I want to say it was something like 63 or 72 ohms. The swept insertion loss was horrendous. I can't recall what the exact loss was on the frequency the repeater operated (VHF) but I do recall it was sky high. And one of the concerns was a "deaf receiver". Gee, I wonder why...

    The type of coax will point to the impedance. If it doesn't have a legible label on it you can use the TDR method with an oscilloscope shown in the video in my previous post to figure out what the impedance is. If you are not sure if it is 50 ohm coax you can put a 50 ohm resistor across the far end of the cable and do the test. The ping reflection on the 'scope should be at the same level. If the resistance is different at the end of the cable than the nominal impedance of the cable you will see a step in the ping's reflection. The other way to go about it is to use a low resistance potentiometer (maybe a couple hundred ohms to 500 ohms, if you can find one, otherwise a 1k might work) and sweep the pot's range until the step on the ping's reflection flattens out. Then take it off the coax and measure the resistance across the pot with an ohm meter. That will be about what your nominal impedance is of the coax.

    The main idea here - ensure your coax IS 50 ohms... Not surplus TV or some kind of networking coax etc.
     

Share This Page