1.25 Meter Amps

Discussion in 'Amateur Radio Amplifiers' started by K7JCN, Jul 12, 2014.

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  1. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I can build a 250W output amp using a 4X150A for 222 MHz for about $600 or so. So can you, actually!

    It's not difficult with basic tooling and soldering skills.

    Using transistors might be slightly more expensive since it would involve a more complex power supply to convert 120VAC to lower voltage regulated DC.

    My dual 4X150A amp started out life as an FAA transmitter, I just converted it to 222 MHz and added a homebrew power supply since the original one weighed about 200 lbs and that was silly. I published some construction articles in 73 magazine on this stuff in the early 90's, it's all on line at archives.org

    However, that doesn't answer the "mobile amp" question at all. For a mobile amp, Mirage may be just about the only thing on the U.S. market right now.

    222 MHz is only an amateur band here in the Americas, so the market is very limited. I'm impressed the Japanese/Chinese even make anything for this band, as their "local" market is nonexistent.
     
  2. K7JCN

    K7JCN Ham Member QRZ Page

    One day when I have the time I'll try to build one. In the meantime, gotta buy what I need. I enjoy putting together antennas, a bit nervous building stuff that could possibly go boom!
     
  3. W0AAT

    W0AAT XML Subscriber QRZ Page

    55 watts to 100 watts is not worth the trouble really... a better antenna can get you that same gain. What are you planning on using it for? What Antenna?
     
  4. K7JCN

    K7JCN Ham Member QRZ Page

    I have a Comet Super22. Seems like it does fine. 25 feet at the base of the antenna is as high as I can get it safely right now. Overall 33' height. If I can push out 150 watts I'd be ok with that too. There's a spot in town where 50 watts won't cut through the interference especially on 2 meters. When I got my 2 meter amplifier for my base Echolink node it gets through just fine. Medium power on the TYT is 25 watts so if the amp I get is 150 out with 25 in I'd be quite happy with that. I may switch and put my Echolink onto 1.25m instead of 2m.
     
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Hmmm. I have a solution that I know for certain is the one I'd use if looking for greater range on 222 MHz from the home station; and it costs less than a good amplifier.

    Swap out the Comet for a Hustler G7-222. Right there, you'll improve your coverage by about 3 dB or so (both TX and RX) and that might be enough. However I'm quite sure I'd also get that antenna higher above ground -- safely! 25 feet is really low in a residential neighborhood that has houses and trees and utility lines and stuff. Going to 40 feet or so (safely) is nearly always possible for minimal or very reasonable cost and can easily add 10-15 miles to your "full quieting" range on 135cm. Thanks to geometry, that's an enormous improvement.

    If you have 25 miles range now (radius), that's a coverage area of 6168 square miles. Add 15 miles to thar range (radius) and it would be a coverage area of 15791 square miles -- almost triple the area. And this is just about guaranteed to happen if you can raise the antenna fifteen feet higher.

    The G7-222 is a better antenna than the Comet, and just changing it without doing anything else might yield enough improvement to be satisfactory.
     
  6. K7JCN

    K7JCN Ham Member QRZ Page

    I thought about the Hustler but I've had good luck with Comets and not so great luck with Hustlers. I wanted to stay with a familiar product. Yes, I'd love to get that thing up higher and if I ever inherit a free tower from an unknown Sk that says "I want K7JCN to have my tower..."I'll definitely do that. I actually live more in the country, sandwiched between several small towns, 7 miles to the north and south and about 10 miles west. Farther north there is higher elevation and even with my 2 meter I can't do better than 15-20 miles with the amp. Although in spots I can hit my node but it's spotty for sure. East basically the elevation starts to triple as I'm right along the Cascade range. Lots of hills that I'm not getting around, so my best bet is my immediate north, south and west. As much as my base set up, my mobile is probably where my issues lie. I could hear my xyl from home clear as a bell but she lost me in several spots only 5 miles away...with my Hustler mobile...LOL. So I thought maybe the amp and as you say elevation might help the receive on the base from my mobile.
     
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The Hustler G7 series are the best affordable VHF omnidirectionals on the market. It's very rugged (stronger than the Comet) and has wider operating bandwidth due to thicker radiating sections and a very efficient phase shift system that places the elements in phase without adding loss.

    The Comet internal radiator (as you likely know, if you put it together) is really equivalent to a piece of wire and the phase shift network is lump components made of the same small conductors. Its relatively low power rating reflects this, as the components have loss. Hustler rates the G7-222 at 600W FM power, but I've put a kilowatt into them several times with no issues.

    When I was "VHF" column writer for CQ magazine back in the 1980s a friend (KT2B) and I set up a real working antenna range to actually measure gain of VHF and UHF antennas. That was not easy and involved taking a lot of lab instrumentation out into the field, and figuring out how to power it all! But after doing so, we compared the Comet with the Hustler, directly, using the same apparatus, cables, height above ground, location and everything else and the Hustler won by a good 3 dB. That's 3 dB on TX and on RX, so for a "path," it's actually a 6 dB station performance improvement.

    However, the Hustler's angle of radiation is extremely low -- lower than the Comet's (which is how it gets its extra gain), so the higher above ground it is, the better it will work. If it's too low, it'll be squirting its signal into whatever is at the same elevation above ground, which could be trees and stuff, depending what's around you.

    Nothing works better on VHF than raising the antennas higher.:eek:

    I have a 2m omni on my extendable tower, so I can adjust its height above ground from about 35' (fully retracted) to about 65' (fully extended). In a neighborhood of single-story homes without too many tall trees, and no trees that are higher than the tower when extended, the "difference" in 2m FM simplex coverage is too amazing to be believable. The XE2 beacon about 160 miles to the southeast of me is "rock solid" with the tower cranked up, and "in the noise" with the tower cranked down, and I can make that change in sixty seconds. This isn't a few dB -- it's "S units." Just one example.
     
  8. K7JCN

    K7JCN Ham Member QRZ Page

    Definitely, if my Comet fails I'll get a Hustler and try it out. My Echolink has a Comet GP 3 antenna at 55 feet and 100 watts with the amp and it does well with the obvious degradation of signal in lower lying places like the town south of me until I get out of town but it does ok. This is on top of my shop across the property. My 222 is on an "extended" TV mast attached to the house, as is my Comet GP15 tribander for my 2m/6m/440 use on my ts 2000. If I ever come across a way to get them up higher I'll do it. I have no restrictions except what the xyl wants to look at!
     
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The Hustler is longer and heavier than the Comet and might require a stronger support.

    I don't do "TV masts.":eek: But I do roof towers with proper antenna masting (the Hustler will accommodate a 2" mast, but then I think the Comet probably will also), and it's easy to get an antenna 20' above a roof peak with very little work.

    I tell my XYL "don't look up" and she never sees any antennas.:p
     
  10. KM1H

    KM1H Ham Member QRZ Page

    The FAA AM-6154 amp works almost as is on 222-225 and will run 200-250W on FM with 5W drive. There are a ton of those amps still in use on 144 and 222 plus the AM-6155 on 432-450.

    About $150-200 should get you one ready to go as many are replacing them with SS or find no activity on 225.

    Ive been using an old Mirage, long before MFJ, 211 amp at 2W in for 110W out for all modes after I modified the bias circuit for clean SSB. It drives a homebrew 8877 to 1500W with 65W.

    Carl
     
    Last edited: Jul 13, 2014
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