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Thread: Homemade quarter-wave ground plane base antenna

  1. #71
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    Awesome. Thanks!!!


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  2. #72
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    They actually make kits specifically for that JAF0. Depending on coax size they have a copper piece that gets attached to the coax at the either the entry point and/or base of the tower as well as inside shelter or radio room onto ground buss bar. Andrew, Commscope, makes the kits, as well as I am sure other companies do as well. Not sure about a small coax like RG8X. But LMR400 and such and I believe they even make a kit for LMR240. Yes it is just slightly larger than most RG8X. Just slightly!! They may have kits for RG8X, I just don't use that particular coax so I don't truly know. Anyhow, all very good tips!! Have a good one.

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    mattsowders1989 (10-19-2016)

  4. #73
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    Well I went out on a limb and installed a swing kit in the radio. After lots of testing, I've found that my dead key at 3/4 watt works best on my amp. At 3/4 watt, I modulate to 5 watts barefoot. I get a real nice swing with the amp, and not backwards! Haha


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    222DBFL (10-19-2016)

  6. #74
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    Good deal! Did you happen to use a 50 ohm dummy load when you tuned your dead key and not your radio connected to the antenna but rather the dummy load? Obviously a watt meter was used, but was a 50 ohm dummy load used as this is the proper way to tune a radio as the dummy load will remain a constant VSWR and also impedance and reactance. With your antenna you might see 3/4 watt on channel 1 and 2 watts on channel 40 or vice versa. Just some food for thought. Having a 100 watt 50 ohm dummy load that is of a good make is a great tool to keep on hand when you start messing about with radios as you can check output of other radios and not worry about VSWR issues. Even the paint can dummy loads work well. They are filled with mineral oil I believe. But at any rate, glad to hear you got things working and more of an understanding to what you're accomplishing! Good deal man! Have a good day and be safe!!

  7. #75
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    I used the antenna. Not a dummy load. I just found out that the lower I put my dead key, the bigger a squeal is transmitted, so much it almost takes my audio. Now I'm back to square one. I have my dead key at 3.5 watts and am back to getting a backswing on power meter. The reason I haven't paid someone to do what I want the radio to do is because I don't have any extra money to spend. Plus I want to know how to do whatever I want to do to my radio. I followed a guide on cbtricks specifically for the cobra 29 line of radios with the final that my radio has in it. (2SC2078). I'm confused as to why is seems like the lower wattage I go, the more over driven my audio sounds. I tried bumping my modulation down a bit and it seemed to help a little but not much at all. I've also tried multiple mics. I have also hooked it up in my car witch has a Wilson 500 on top of it. As it sets right now with the amp on, it sounds ok but it still has a big backswing. I have a second transistor amp at the same wattage (150) that I have switched out with as well. The guide to the swing kit I used entails these parts:
    Tip120
    100 ohm resistor
    100uf 16 to 25v capacitor
    1k or 5k ohm pot

    I did read somewhere about using a 220uf cap I read of the 100uf but I really don't see that fixing my problem. I know I'm a hassle and I apologize in advance.


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  8. #76
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    Also before I say anything about needing things, how many amp power supply do you have? And is this same power supply running your radio and amp. The radio won't draw much at all I know that, but your amp may draw up to 20-25 amps and maybe a little more on some voice peaks and depending on mode of operation. If your PS is only rated at 20 amps then it's going to be hard pressed to get all the power that amp might and I say might need at times. Best to have head room when messing with power supplies. For a 2 pill amp like yours it shouldn't draw more than 15-20 amps max. It may just be your PS is not up to the task. Most PS amperage ratings aren't the most accurate!! Something like a 30 amp power supply is what I would use, or more amperage. Between radio and amp and anything else you have on that circuit that that PS is plugged into, you may not be getting enough power to the entire system under a load. I don't know what you are using for a power supply so it's hard for me to know. I use one of the MegaWatt power supplies, the S400-12, I have it set at 14.0vdc and it operates at 33A at 100% duty cycle and up to 40 amps I think for short periods of time. It's a small switching power supply but they are clean and don't produce any hash!! Anyways, I have run a 2 transistor amp on it and that amp has toshiba 2879's in it. I only used my uniden 980 to drive the amp, but was able to get 200 watts on SSB just fine with about 10 watts of pep input. Dead key on that radio into the amp was set at 2 watts dead key and 8 watts of pep swing on AM, and 10 watts of pep power on SSB. I don't have a true peak reading meter but if you take your time you get decent at just performing little things. I don't make the radio perform at more than a 1:4 power ratio or a little under it. This is done by setting the carrier to 2 watts and then tuning modulation up slowly while keying radio until it reaches about 8 watts on the meter. I use a 1khz tone from an app off my phone which is something you will want to do as well. I am no radio tech and really a radio should have this work done by a tech or someone with the proper equipment. I have some of it, but there are many important things that I don't have LOL!!

    You truly need a 50 ohm dummy load, an App that can make a 1khz sound and then you can inject that into the mic instead of your voice, a watt meter that can also check modulation percentage preferably, if you can adjust for a 1:4 power ratio without one or near that, you are getting 100% modulation or more which can be bad. 90-95% is plenty. Do this by again slowly adjusting AMC. Set dead key to 2 watts and see what amp does. Or 1.5 watts. And make sure all your coax jumpers are good! This is one area that when you add power things can get funny. You will know straight away if you have installed connectors properly or not. A sliver of shield wire might pass with only 4 watts, but add the amps power and things go to shit. Also having an antenna analyzer like this helps tremendously.
    Let me ask this. Is your antenna mast grounded to a ground rod. Have you also grounded all your radio equipment to a ground rod. Like JAF0 stated earlier you can cut into the sheathing of your coax and use some 1/2" flat braid or even some flat braid from a piece of coax if it's good shielding and take it to a ground rod. Also make sure all your grounding rods are tied together. Look into how commercial towers or radio towers are grounded and how they go about doing it. This may help with your squeal issue. And you truly need the right equipment to properly tune a radio. A meter that can read power correctly, which you really want a true reading PEP meter, and a good dummy load of 50 ohms. Make sure that your power supply is up to the up to the task like I mentioned above and hope some of this helps. Like I said and will say again, I am not an amp tech and best thing that I know to do is send both radio and amp if possible to a good tech and he can match the radio to the amp and align radio and such. I know it's not what you want to hear, but it's the best way if you don't have some decent money to spend. You just need certain things to tune and align radios the correct way and that is the truth man. Like I said I don't have most of the things to do a proper tune and such! That is why I stay very simple and most of my radios have variable RF power or were bought setup. The only radio I've really messed with a lot is my 980 and a cobra 25. But I did learn how to at least set my dead key and modulation!! That is all I need. Would like to have a full alignment done and a proper tune but I have HF radios as well and use them now mostly!! An Icom 746 and a kenwood ts140s. And like I said, i don't need to get inside them or need an amp! Good antenna setup and 100 watts on SSB is plenty for me! Heck I get on AM every so often when the conditions are good here. I started out as an AM guy. Anyhow, just my own experience and how some things should be done.
    Again I know most of it is stuff you don't want to hear LOL, but I promise you need some gear to accomplish things the correct way. Tuning the radio with your antenna may be the issue. Things change as you move up/down in frequency on an antenna due to reactance and resistance. Just because your VSWR is flat from channel 1 to channel 40, other variables change. And when you are tuning a radio you need set things and no reactance which a dummy load provides across that large frequency span like 0-3GHZ or more on some dummy loads. Your VSWR, impedance, and reactance pretty stay the same across that entire frequency span. Your antenna can't do that. Anyways. Keep researching about properly tuning and alighting radios and see what equipment they recommend at the very least. And make sure all your equipment is grounded. Look into grounding a radio base station. It's an important thing to do as well. Again, just want to help man. May seem harsh but I am not trying to be that way I promise man!! Just want you to know what is right/wrong and is needed as well. Have a good one and hope you get it all resolved!! Be safe as well!!

  9. #77
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    I'm sorry 222, I thought I had posted a response to your last post. Yes, I got it all worked out. All is good with the antenna. I have a Hy-Gain Super Penetrator 500 coming in the mail in the next few days. That'll be fun. Thanks for all of the help and taking YOUR time to help me. Skip seems to be picking back up here in Kentucky. I hope we can make contact some time in the future. Thanks again for everything you have helped me with and shared. 677 is getting on down and back quiet.


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    222DBFL (10-29-2016)

  11. #78
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    No worries man. Others helped as well. But I am glad to see you have gotten everything working well and now have a better antenna coming. Take your time putting it together and follow the directions to a T!! You'll be happy with that antenna. I am in the process of placing up a dipole facing your way at about 50ft give or take. That should get me to you no problem if the conditions are there! I will also be placing my vertical antenna back up as well here soon. Think I am just going to re mount it where it was before and use the existing 2 2" pipes as braces for the 3rd pipe. Going to go a little higher this time, getting above 30ft to the base. At any rate, if conditions per
    It I will catch you on the air 677! Be safe putting up the new antenna and have fun man!!

  12. #79
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    Sounds good buddy. I've been thinking about setting up a dipole to just play around with. Anywho....... I'll be out there when the conditions come about. I'll be looking for you. Honestly, it'll be an exciting day for me. I'm all about that DX! I have my local buddies. But I love skip.


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    222DBFL (10-30-2016)

  14. #80
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    I used to have 2 dipoles up at about 35ft up gone or take. One headed N/S and the other E/W. They were far enough away from my vertical antenna as to not cause any issues. I also used a Low Pass Filter with them and a Diawa switch box. At any rate they worked very well! If I had a rough time hearing someone I would flip over to one of the dipoles and it would kill a lot of unwanted noise from places I wasn't trying to talk to!! I took them down as the DX starting dying off as my Sirio vector 4000 did a well enough job. Not to say I don't like the dipoles as at least one is going back up real soon. Then I need to get my vertical back up. But with the dipole up at least I can talk locally to about 4-5 miles and DX is not an issue as long as the way I am facing has the conditions!! They are easy to put up if you have a couple large trees in your yard not too far apart. Or do like some and use only 1 branch and make an Inverted V. I like being horizontal as I have the trees to do it and it cuts down on the noise a lot! And they are truly easy to make or buy one. Just make sure if you buy a pre made one that it has a 1:1 current/matching balun. This will help with CMC issues and also match your unbalanced 50ohm coax to make it balanced to 50ohms going to your radio. There are many different names used for them so just be aware what to look for.
    Dr. Dipole makes a pretty good one. But you can find others that are just as well made. This seller that I posted photos of seems to make a good one.

    If you build one you can use the proper mix of ferrite chokes and they make a kit that goes around most coax sizes and come with heat shrink. These work too but I don't think as well as the 1:1 balun.

    If you do decide to make one you can use some RG6 or Cable TV coax. It's 75ohm coax. You can make a matching stub with a piece of it and get your impedance down to 50 ohms. It is just about cutting the antenna to be resonate on one frequency. The one I posted pics of is precut to 27.200MHz. That is pretty much Center of the CB band and you should have a good bandwidth to cover both above and below the regular 40 channels or freqs for CB. Just some babbling LOL. Seriously. After I built my first one and hung it no more than about 10-12ft off the ground and having nothing more then a radio shack VSWR/Power meter to use for tuning, I managed my first time contact to Australia on a uniden PC122XL. That is from the east coast of FL!! Granted conditions had a lot and I mean a lot to do with it. But it goes to show you can make contacts worldwide on a homebrew 1/2 wave dipole!
    Have fun putting that penetrator 500 together! Take your time and make sure you follow the instructions to a T and if you feel uncomfortable about what the actual length of things are supposed to be, come here and ask. A few guys use or have used that antenna and say it's a bit hard to tune, but if you tune them right they work very well!!! Be safe as always and make sure to use some corrosion aid on all your screws and bolts and such. Self amalgamating tape is really good stuff to use on the joints as it keeps water out! You can get the stuff on Amazon or even at Home Depot. 3m makes it as well as a bunch of other companies. Also goes by self fusing tape.
    Anyways. Hope all goes well and will hopefully catch you on the air man. Be safe and take your time!!

    73 and God Bless.
    222 Daytona Beach, FL.

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