Is this the worst antenna for portable use? - Comet HFJ-350M Toy Box

Discussion in 'Amateur Radio News' started by KM9G, Sep 1, 2021.

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  1. M1WML

    M1WML Ham Member QRZ Page

    :D:D
     
  2. NL7QY

    NL7QY Ham Member QRZ Page

    I have one of these antennas for about a year and found it a good match for my G90 and go box set up. I use it with a magnetic mount when stationary for the car and a picnic table mount that I made. With the magnetic mount it will tune 1:1 but I can tell that the radiation is limited because of its size. It is very easy to set up and only takes a couple of minutes. This antenna allows me to fit everything in a small plastic box that I carry in the car and it allows me to check in to nets when I'm away from the house. I am very satisfied with the antenna and I'm glad I bought it.
     
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  3. W4FJT

    W4FJT XML Subscriber QRZ Page

    There is a lower cost version without the 160 add-on coil and that's a better deal. Use it on 20, 15 & 10 with a counterpoise wire and you can probably get it resonant. I've used the similar MFJ single band 20 meter version with some success. The purpose of these is to provide an easily deployed antenna in conjunction with the IC-705 and LC Backpack. At least that's how you see most of them used on the Tube. The popularity of these small QRP rigs accounts for the popularity of this device. I use BuddiStick parts on a tripod combined with a Wolf River Coil and a single elevated radial and its a cinch to tune that with an analyzer. Right now I'm using an IC-705 without a tuner.
     
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  4. W9HJ

    W9HJ QRZ Lifetime Member #294 Platinum Subscriber Life Member QRZ Page

    I have one, and it works, but it's very compromised. I mainly got it so I could use it attached to the iCOM LC-192 backpack and walk and transmit, while I was dragging a counterpoise behind me. Kinda silly I know, but hey, I'm a ham and I've done even crazier things ... don't follow too close to when I am wearing a backpack on my motorcycle. :D
     
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  5. WD4IGX

    WD4IGX Premium Subscriber QRZ Page

    BUWAHAHAHA!!!!

    I rate this "biggest nonsense statement I've ever read on the Zed - EVER."

    I haven't had a resonate antenna since I discovered balanced feed line in the mid 90s. Granted coax has its place. But there is absolutely NOTHING magical, or even inherently better, about resonance. NOTHING.

    A non-resonant antenna will radiate just as well as a resonate one, provided you can couple the power into it efficiently. Resonance makes that easier, but it's far from impossible without it. That's ALL it does. A tuner also makes it easier for the transmitter, yes, but that's just part of the equation. Use that with a lossy feedline and an inherently high SWR system and you'll get such feedline loses that you'll believe this old nonsense.

    Put up a 100' doublet (that's "dipole" really but people confuse "dipole" with the special case of "half wave dipole") and feed it with low loss open wire feeders and use it anywhere from 80 up where your tuner can match it. It CAN be longer, but it's not ideal to have it resonant at its lowest frequency, in this case 80 meters. If you cut it resonant on 80 it will work fine there, but present very high impedance and thus SWR at even harmonics and bands close to that. This will be harder for a tuner to match and also make things like arcing more likely. It will also increase that loss slightly but with good open wire, or even the better quality of window line, not enough to likely matter. But cut a little off resonance, which is why I like 100' for 80 and up (long enough, much shorter gets too short, longer is too close to resonance unless you go longer than resonance which is fine it you want to also run 160 but otherwise not needed) it will present a middlin' impedance on most all ham bands, will match easily with most tuners, and will work at least as well as any resonant half wave dipole cut for each of those bands installed at the same location and height. It IS true that such antennas develop some rather odd directional lobes and increasing numbers of them but given HF propagation and the narrowness of the nulls I just find this doesn't matter much in practice.
     
    Last edited: Sep 10, 2021
    W9HJ, PA0MHS, M1WML and 2 others like this.
  6. WD4IGX

    WD4IGX Premium Subscriber QRZ Page

    Nope. This lie has been repeated for decades, but it has never been true and it still isn't.
     
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  7. G0OIL

    G0OIL Ham Member QRZ Page

    I'd never seen one of these devices before, but just looking at the design of it, well it's going to be incredibly inefficient especially on the low bands. You've got a massive base loading coil (the least efficient possible) and a teeny weeny little whip that actually puts RF out. Remember that it's the RF current carrying bit of the antenna that does the radiating, hence base loading being so inefficient. Add to that the fact that it's a telescopic whip with possibly poor RF connections between the sections and made out of material that's a poor RF conductor then yes, it's probably going to be lousy and less than 1% efficient ..... but it's marginally better than nothing. Having said that, I've worked a lot of DX stations from my car /M with G-Whip antennas. They're also base loaded with a stainless whip like a CB antenna.

    The Comet antenna folds up very small and if you use a decent set of radials (on the beach, for instance) it might just work, but my experience is that a simple dipole strung up in a tree works far, far better .... if you have a tree.
     
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  8. G0OIL

    G0OIL Ham Member QRZ Page

    I've never tried wet string but I did work VK0IR on 30m CW using a Kirby vacuum cleaner matched with a tuner. Probably one of my most memorable QSOs. I probably worked every television in the village too.....
     
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  9. M1WML

    M1WML Ham Member QRZ Page

    Never had and never will have a tuner in the shack.. why warm a tuner total waste of rf power in my opinion.. and im sticking to it..
    :p:p
     
  10. W2NC

    W2NC Ham Member QRZ Page

    True but ladder line has negligible losses at high SWR so you’re still delivering all your power to the radiator.
     
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