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HomerBBOffline
Post subject: HomeBrew Mobile Antenna Comparisons  PostPosted: Dec 22, 2010 - 04:00 AM
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For background on the thread it may be necessary for some to go to the Knockarounds thread at this location: http://www.dxradioworld.com/index.php?name=PNphpBB2&file=viewtopic&p=6131#6131. This is a breakaway from that thread so the comparisons can stand on their own merits.

I've begun the process of making comparisons between the several models of the antennas I built to each other, a K40, and an straight 1/4 wave whip.
First of all I had to put a reliable means of mounting the antennas on the roof of the SUV with quick change capabilities. Where this antenna is attached to the mount on these two photos I put a 3" piece of PVC into which I dropped each antenna shaft with a set screw through the PVC wall into the bottom of the antenna shafts. To this set screw I attached the coax center conductor. Here is the mount:


Next I mounted the antennas one after the other on the roof and reset the SWR across the band capabilities of the SuperStar 3900 in the mobile. I was dead keying 3/4 watt, swinging around 12 watts PEP; no kicker online. I was talking with a base station 10 miles from me, I will do a 15 or 20 mile base station later when I can get them to cooperate for a little while. The antenna on the base is a vertical groundplane with the coax connector at 70' above ground. He was talking to me with 2 watt dead key. I do not know what his PEP is at this time.

The antennas are a K40:


a whip:


By order of build -
#1 homebrew:


#3 homebrew (#2 was rewound into this one):


#4 homebrew:


#5 homebrew:


Here are the results so far:


What I will have to do, perhaps tomorrow, is add the overall dimensions of the various antennas in an additional post. It got dark on me today..

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Post subject:   PostPosted: Dec 22, 2010 - 07:06 PM
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New info regarding antenna dimensions:


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Post subject:   PostPosted: Dec 22, 2010 - 11:36 PM
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Side-by-side of the antennas:

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WR954Offline
Post subject:   PostPosted: Dec 25, 2010 - 03:29 AM
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Ok, I missed the roof rack mount somehow. Out of curiosity, take antenna #1 and take it up to 28.500 and see how the SWR is, I am still impressed with the bandwidth. The RX on it is great due to it's length and by doing a coil and a larger diameter base section, that allowed you to greatly increase the bandwidth yet very little sacrifice on the gain. I still like #1 the best so far.
 
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Post subject:   PostPosted: Dec 25, 2010 - 04:12 AM
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I'll have to take the 88 out to the mobile to do it. The SS 3900 is unable to go there: 88 eight bands, 3900 six bands.
I am curious, too, so I'll try to check it out soon.

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Post subject:   PostPosted: Jan 29, 2011 - 07:20 PM
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Another attempt and on the mobile:


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Post subject:   PostPosted: Jan 29, 2011 - 10:48 PM
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Homer it look like you just found the perfect antenna for 10/11/12 meters in Whip #1. When will we see them on the market? And if it will handle at least 500 watts it could be the best antenna ever made for the everyday radio operator. Look out world here comes the HBB-1.

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Post subject:   PostPosted: Jan 29, 2011 - 10:53 PM
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I don't plan to market these things. I'm just having fun. But I'll measure everything on it so you can build one if you wish.

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Post subject:   PostPosted: Jan 31, 2011 - 03:55 PM
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I threw this together yesterday. No testing other than to temporarily mount it on the SUV and check SWR on CB band. More finessing it to be done, but it works.


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Post subject:   PostPosted: Jan 31, 2011 - 08:08 PM
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One step closer to that assembly line for production Laughing Seriously though, looking great. Glad you are getting some joy and fun out of experimenting there. That is a thing that is dying out in the hobby.
 
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Post subject:   PostPosted: Jan 31, 2011 - 10:24 PM
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I will have to slow down, someday. For now I just plug along playing.


SWR:
28.305 ----------- 1.8:1
27.855 ----------- 1.4:1
27.555 ---------- <1.2:1
27.405 ----------- 1.1:1
27.205 ----------- 1.1:1
26.965 ----------- 1.1:1

26.515 ----------- 1.3:1
26.065 ----------- 1.7:1
25.615 ----------- 2.2:1

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Post subject:   PostPosted: Feb 01, 2011 - 06:02 PM
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With that range on the SWR's, any freebander would love that! I wonder what the power capability would be?
 
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Post subject:   PostPosted: Feb 01, 2011 - 08:29 PM
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This one it 1/2" copper from end to end, except for that 1/4" chromed steel stinger in the top. I wanted the stinger on it for adjustability and looks. Knowing it would be in a permanent install I could have made it all copper.

It should do pretty good. I just wonder what kind of heat is generated by high wattage. No more than I ever run mobile, there's no heat at all - 100 watts. Maybe the soldered joints would liquify?

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Post subject:   PostPosted: Feb 03, 2011 - 09:45 PM
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HomerBB wrote:
This one it 1/2" copper from end to end, except for that 1/4" chromed steel stinger in the top. I wanted the stinger on it for adjustability and looks. Knowing it would be in a permanent install I could have made it all copper.

It should do pretty good. I just wonder what kind of heat is generated by high wattage. No more than I ever run mobile, there's no heat at all - 100 watts. Maybe the soldered joints would liquify?


Use Silver solder. It's SUPER STRONG and won't melt with power applied.

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Post subject:   PostPosted: Feb 03, 2011 - 10:09 PM
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I will. Thanks.

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