| KB0SFP |
Rating:  |
2023-06-15 | |
| Comet Antenna HFJ-350M Dont Buy! |
Time Owned: more than 12 months. |
Unlimited distribution of the below material is authorized, and encouraged.
My interest in the HFJ-350M was spawned by my use of the similar MFJ-1899T, and the hopes that the limitations of the 1899 might be resolved. I was disappointed! It was a good idea, very poorly implemented.
Let me begin with the MFJ-1899T. This antenna utilizes a band tapped coil(5 tap points) combined with a detachable 50 inch telescopic whip(62" assembled length). Marketed for use on the FT-817, it has a BNC connection base, and an advertised frequency range of 80-6 meters. Does it work? Well yes, after a fashion.
If your radio has a built in tuner, the 1899 can be effective. If it does not, band adjustments can be tedious and difficult to repeat. The band taps are resonant high, or just above each band. This works well when used with an auto-tuner, but is a pain for manual adjustment. Some bands are doubled up on a single tap making for a very short whip when finally adjusted.
The BNC antenna base on the 1899 is extremely fragile. It was never intended for use as an antenna base, and if you'll notice, not even VHF/UHF hand-helds use it any more, Commercial radios abandoned it's use in the 60-70's, and the BNC began to disappear from Ham HT's in the 90's. So if a BNC is ill suited for a 6" long rubber antenna, how would it fair on a 62" long ridged one? Badly! Mine broke off and has been replaced with a PL-259.
Lastly, the 1899 has a rather unduly high profile because of it's 80 meter coverage which would very seldom be used(if ever).
I should note that a very similar antenna is marketed by Moonraker. It is nearly identical except it offers the advantage of multiple bases including BNC and PL-259. It's more common in Europe than here in the US so I've never been able to compare it to the MFJ..
Enter the Comet BNC-750. I first saw this antenna at the Comet booth in Dayton 2010. This antenna covered 40-6 meters but those in attendance at the booth could tell me nothing about it. I inquired with Comet over the following year. Their responses ranged from, they had no idea what I was talking about, to yes and order had been placed. Well, it never materialized, in the US anyway.
Finally, the HFJ-350M. I came across this antenna on Gigaparts web site. It appeared to fix all the failings of the 1899, and at $110 it was cheaper than the MFJ. I ordered two of them.
The 350M dispensed with the fragile BNC connection in favor of the far more durable PL-259. The advertised frequency range was again, 80-6 meters with an overall assembled length of 65 inches. It's design included a separate 80 meter add-on load coil which allowed not only a much lower profile when used on 40 meters and up, but a much shorter disassembled package for transport & storage. It also improved on the 1899 in that it had 5 band taps rather than 4.
The bad. In nut nutshell, none of the band taps are anywhere near resonant on any ham band. Comet, in SOME advertising professed that the antenna was designed for use with an antenna tuner. For this to work, the resonant frequency of the antenna should be higher than the operating frequency. This would have been acceptable, but all the band taps were well below their respective bands. On BOTH antennas tested! It was found that when the telescopic whip was reduced to 1/2 it's length you could get it in the ball park on some bands.
The following is the resonant frequency of each band tap as measured with a MFJ-259 and counterpoise attached. 3.2mhz(80meters), 6.3mhz(40meters), 9.3mhz(30meters), 11.7mhz(20 meters), 16.1mhz(17/15 meters), 25.9mhz(10meters).
I returned both the antennas and Gigaparts gave me a full refund. I'm sure they put them right back in inventory.
To close, I received a third 350M as part of a package deal. I keep it in the 50cal ammo can that houses my Xiegu G90. The only reason I keep it is because it's collapsed size allows it to be stored with the radio, and the G90 has a very good auto-tuner.
Dennis Starks
Military-Radio-Guy
KBØSFP |
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| K1RCT |
Rating: |
2022-03-20 | |
| Performs like it should |
Time Owned: 3 to 6 months. |
Instructions specify how initial setup is made. After that one must make a counterpoise. Mine is 50 feet long. I extend it fully and keep it off the ground. I use the full counterpoise from 80M to 6M.
6M (50.175): Full CP, no 3.5 section, #5 tap, 9 sections extended. 1.4:1 SWR
10M (28.375): Full CP, no 3.5 section, #4 tap, 5 sections extended. 1.7:1 SWR
15M (21.130): Full CP, no 3.5 section, #3 tap, 6 sections extended. 1.3:1 SWR
18M had a hard time getting below 5:1 SWR so I won't include that data here (I didn't record it).
20M: (14.090): Full CP, no 3.5 section, #2 tap, 5 sections extended. 1;5:1 SWR
20M: (14.290): Full CP, no 3.5 section, #2 tap, 4 sections extended + 4" of the fifth section. 1.6:1 SWR
30M: (10.300): Full CP, #1 tap, no 3.5 section, 7 sections extended. 1.2:1 SWR
40M (7.150): Full CP, no tap, no 3.5 section, 6 sections extended +2.5", 2.1:1 SWR
40M (7.300): Full CP, no tap, no 3.5 section, 6 sections extended. 1.8:1 SWR
75M (3.800): Full CP, no tap, +3.5 section, 6 sections +3" of the seventh section. 1.9:1 SWR
Nomenclature: I use a Manfrotto 290 camera tripod with three axis head movement, a custom aluminum bar (1/4" x 3" x 12") with threaded holes (1/4"-20) and thumbwheel knobs to attach the counterpoise. A quick connect camera adapter is fitted to the bottom of the custom bar which snaps to the tripod head. I drilled a hole which is fitted with a double female SO-239 about 2" long to adapt the antenna to custom bar to feedline.
Loading coil of the antenna is about 65" off the ground, the maximum extension I can get from the Manfrotto.
Counterpoise is 50' of 16AWG insulated MTW.
When compared to my OCF Dipole at home, this rig had about 3db more noise than the dipole but as a vertical, I expect that. A/B antenna switching proved the antenna 'hears' almost as good as my OCF which is up about 40' as a sloper.
POTA season is upon us just now. After a season of activations, I will review this again.
YMMV! |
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| W4AMP |
Rating: |
2021-09-27 | |
| Works fine. Use ground and patience. |
Time Owned: 6 to 12 months. |
| Antenna comes with a ground lug on base. Attach a wire to it and use it. Tuning will be much easier. |
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| VE7HJ |
Rating: |
2021-09-26 | |
| Tuning Trick |
Time Owned: 0 to 3 months. |
I purchased this antenna understanding that its compromised and not going to work like a larger vertical.
When trying to follow the instructions on the telescopic whip I like many others got frustrated. I also own a Alpha Mag Loop which took me some time to understand how to tune. So I decided to start tuning the Comet by selecting the band with the jumper and then adjusting the whip for the strongest signal just like the mag loop. I then check the SWR and notice its close. I use either my AH-705 or Electraft T1 tuner to do the rest. Perrin VK3PT told me he uses a shorter counterpoise of 7 meters (21 Feet) on 40. This seems to work quite well. I like that the antenna is compact and fits in my LC-192 Backpack and on the Windcamp bracket on the Icom 705. I live in an apartment with very limited space so the HFJ-350 is my go to antenna on the deck. |
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| W8IJN |
Rating: |
2021-07-17 | |
| There are way better portable antenna options |
Time Owned: 3 to 6 months. |
I do a fair bit of beach radio, portable stuff, Parks on the Air & such. So I saw the HFJ-350M as one of the more viable alternatives for those rare moments when I drag the FT-891 out of the shack. The antenna was rated on the packaging as 100W. Recent exploration of other websites says it's good for 75W.
. . . My other option was the GRA-1899t (an eBay Chinese clone of the MFJ-1899t), which I also have for the X5105. Rated at 25W it's just a little too on the edge for use with the G90's 20W. My previous experience running POTA activations on the GRA-1899t proved that antenna format to be moderately successful at 5W. Thus I got a HFJ-350M in hopes of running the G90 as a POTA radio at 20W. Once I had a mounting system, took it out for tests.
Right up front, I got the impression that something was wrong with this antenna. It tuned up nicely on 40m, although I had to use a NanoVNA to find the lowest SWR. On 30m it was even more dodgy and 20m was totally impossible just using the SWR scan on the X5105. The NanoVNA made the adjustments even more troubling.
. . . I figured something was loose and decided to see if I could figure out what was wrong.
. . . I ended up stripping off the heat shrink around the tapped coil and found some questionable solder joints. But even more interesting was the pin -- yeah, a brass pin -- that went into the base of the coil and which was supposed to make contact with the center pin of the PL259 style mounting connector. Measuring that point showed a resistance that varied from about .1 Ohm up to infinity, depending on the pressure I put on the pin in measuring it. I pulled that pin out, put in a sliver of solder & flux, pushed the pin back into place with pliers and reheated the pin & the wire of the coil that was fastened to it.
. . . That made all the difference.
. . . I stuck the NanoVNA back on the antenna via a 25 ft piece of coax and ran some tests. Finally I could get decent dips and tune ups on all bands between 40m and 10m. The tap settings, however, did not jibe with the manufacturer's instructions on 17m, 15m, 12m and 10m. Making up my own picks for tap points I managed to get the antenna to tune. At which point I hooked it up to the X5105 and gave a few calls on all the bands between 40m and 10m. Of course I got no responses.
. . . Checking the Reverse Beacon Network online showed no hits for my CQs. Not that I was expecting any.
My gut feeling is that this is, as one might expect, not that great a compromise antenna. A few extra Watts, as it is supposedly designed for, might help but in the end, I get better results (and RBN hits) with the GRA-1899t. I get better results with a long wire hanging from the trees in the yard, sans insulations even. Rather disappointing, to say the least.
In all, I was not impressed with the HFJ-350M. |
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| VE7IVN |
Rating: |
2021-05-15 | |
| Jury is still out. |
Time Owned: 0 to 3 months. |
| I just got this yesterday and immediately took it out into the field to play with. I was using a 1/2' copper pipe driven into the ground instead of a counterpoise which perhaps isn't good enough. I was able to get a good match (1.5:1 or better) on the bands I tried. It seems to receive well but I was not able to make any contacts on any band. I'll do some more trials, this time using counterpoise wires cut to length before I pass final judgement on the antenna. To be fair, skip seemed to be very long...I was hearing plenty of stations in EU but practically nothing from North America on 20 meters. I'll update this review once I've had a chance to play with the antenna some more. Observations so far: it receives well and I am able to get an acceptable match on the bands I tried. My general impression is that a random wire thrown over a tree branch fed through a small transmatch would outperform it, though. |
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| N4ZDX |
Rating: |
2021-01-20 | |
| Compromise Yes, but impressive. |
Time Owned: 0 to 3 months. |
| This antenna came in today. I set it up on the Ziegu G90 with 20 watts on the kitchen table. I used a 15 ft wire as a counterpoise laid across the floor. First station I heard I called and he came back first time. I'm in Tn. and he was in Vt. on 20m. Then I tried 40m and made contacts in NC and Va. This antenna appears to be working better than I expected. It is a major compromise antenna but then again, anything this size is. 40m and 20m are the only bands I've tried but so far I am impressed. |
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| KQ4KK |
Rating: |
2020-11-03 | |
| Compromise is the best you can say |
Time Owned: 0 to 3 months. |
When I bought this, I knew it was not a beam, full size dipole, nor a short screwdriver.
I made up a couple of radials and tried to tune it on 20m or 40m. Spent about 3 hours of my life trying to get a reasonable SWR. Got it down to 2.3 on 20m, once with my new ICOM 705. Could not repeat it. I gave it 1 star because you can hear stations with it. Would look for other portable antennas. I have 20m and 40m dipoles and a 10m pushup pole that I have been using portable. |
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| KB1HXO |
Rating: |
2020-10-16 | |
| Portable HF antenna for outdoor use |
Time Owned: 0 to 3 months. |
| Let me start by saying this is a compromised antenna. If you think that’s it’s going to work like a full length dipole think again. Will it get you on the air yes it will. I cut to 20 foot pieces of wire and was able to get it to tuneup on 6 m through 20 m with one wire added the second wire and was able to get 40 m. Now granted I was using an Icom 703 with only 10 Watts. To sum it all up it does what it’s advertised to do it will get you on the air. How efficiently that’s up to you to decide. |
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