Cushcraft A270-10S Dual Band VHF/UHF Beam antenna

Discussion in 'Amateur Radio Equipment Reviews' started by N8FVJ, Apr 27, 2019.

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  1. N8FVJ

    N8FVJ Ham Member QRZ Page

    Dual band VHF/UHF beam antennas are kind of rare. The Cushcraft A270-10S uses 5 elements on each band for an advertised gain of 10dB on each band. Boom length is slightly over 6 feet and has a wind load of slightly under .75 square feet. Antenna weighs 1.8 lbs. Power is limited to 350 watts. My 4CX250B 2 meter amp works well with this antenna without issues. The higher power 350 watt solid-state 'brick' amps would be excellent with this antenna.

    I set up the antenna and got a flat SWR on 2 meters and 1.3 to 1 SWR on 432 mHz. 2 to 1 SWR bandwidth is advertised as 4 MHz on VHF and 15 MHz on UHF.

    10dB gain is enough for long haul earth bound SSB use and the 60 degree beamwidth at -3dB is not too narrow allowing monitoring for signals without constantly changing the antenna direction.

    Most newer multiband radios have a single coax input for VHF & UHF making a splitter unnecessary with the A270-10S antenna single coax feed. It is a good value for $170.
     
  2. N8FVJ

    N8FVJ Ham Member QRZ Page

    Note- the antenna is supplied with RG-8/U coax splitter cable and poor connectors that can have a grounding issue. Replace this factory supplied splitter cable with RG-8/U (mini X) and the better connectors with the associated reducer. Now, I believe this antenna would have no issues with 1KW or higher due to the spacing and insulators on the gamma matches. But, for high power replace the RG-8 splitter coax with LMR-400 coax for high power.
     
  3. K2FOX

    K2FOX Ham Member QRZ Page

    Instead of the splitter, could two feed lines be used instead?
     
  4. WQ6N

    WQ6N Ham Member QRZ Page

    I just purchased one of these to reduce the numbers of antenna and get a little gain with the 4 elements. So far, I am not having much luck getting the SWR down below 2.51 on 2m. 70cm SWR looks ok at 1.6 (Measurements taken with the 2m element up. It got worse when I flipped the 2m element down as in the drawings). Then again, I am only inches above a 6ft chain link fence with 3 rows of barbwire on top. Guessing the boom is at 10ft.

    The antenna is on a mini 8ft rooftop tower that is on the ground with a rotor and thrust bearing. I may also look into purchasing a 10ft of EMT to raise it a up little. I am trying to keep a low possible profile as possible (good neighbor).

    I am not to happy with the T-splitter and phasing harness. I have purchased a duplexer (MFJ-916B) in hopes of getting a better SWR and performance.

    I have a R8 and a dual band 2m/7cm vertical that are in the antenna's near field and I am pretty sure there is coupling even though they are behind the reflector element.

    Currently my mobile JetStream JTBM270 is out performing the A270-10S. The JetStream dual band is not made to stay up for long periods and needs constant maintenance due to corrosion of the cheap materials.

    Reading eHam, appears others had phasing harness and T-splitter issues. I am determined to get this investment working and am open to discussion from others who have already gone down this road.

    Best 73, JohnF
     
  5. WQ6N

    WQ6N Ham Member QRZ Page

    Sharing the journey...
    I could not get the SWR down. Ordered the diplexer and will have to do some kind of weather wrap since they are for indoor use.
    I measured the RG-58 feedline harness cables length at 32in each. These RG-58 are crimp connections and look pretty weak. RG-8(U) would be a better cable for sure. Might even use some of that RF coax that came with the ICOM AH-4 solid center conductor.
    The JetStream has very good SWR 1.16 on 2m and 1.18 on 70cm. This confirms the LDF2-50 hardline is spot on.
     
  6. WQ6N

    WQ6N Ham Member QRZ Page

    Well I believe I found the root of the problem. One of the two 32-1/2 harness center conductor was shorted to the shield.
    This begs the question regarding MFJ and Quality control. I did a MFJ contact email with the request for replacement and we shall see how long they take to respond.
    This problem was also noted in one of the eHam reviews. My luck of the draw....
     
  7. WQ6N

    WQ6N Ham Member QRZ Page

    I took the shorted cable length back to the store and demonstrated with a megger. They replaced the cable with a new segment. Put it all together and replaced the T with a MFJ-916B duplexer. The tests were awesome. 1.16 on 2m and a flat 1.0 on 70cm. Remounted on the rotor system and all is well. Journey complete.
     
  8. KC7JNJ

    KC7JNJ Ham Member QRZ Page

    I have one I gave up on a long time ago. SWR always sucked on 440. I might have another look. I just popped up a Ed Fong duel band in its place.
     

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