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High swr monkey made

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Free2fly
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High swr monkey made

Post by Free2fly » Tuesday, 28 December 2010, 22:26 PM

I have a monkey made 5, with mini 8 diesel coax, and general lee. Mounted on a 08 f250 diesel. The mount is home made galvanized L Bracket screwed upside down with self tapping screws over the middle stake hole; to allow coax to run under bed and into cab through rear drain hole. Swr's run 3.5:1 to 4:1. Top of coil is level with cab. Continuty is .1 on outer shield of coax to bed and .1 with center pin to stinger. Mag mount on roof; swr is 2.5-2.9.
Will cutting stinger actuall drop swr's down to 1.5 or lower or do I have another problem.
Thanks for all your help and experience. Loving my new frustrating hobby lol.


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Re: High swr monkey made

Post by North Texas Mudduck » Tuesday, 28 December 2010, 22:31 PM

can you take a picture of this setup
sure will give everyone a better idea whats going on
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Re: High swr monkey made

Post by 'Doc » Wednesday, 29 December 2010, 1:53 AM

One simple way of finding out if cutting that whip will do any good is to take SWR readings on channels 1, 19, and 40. If it's higher on channel 1 than on 19 or 40, then the whip is too short, don't cut it! If the SWR is lower on 1 than on 19 or 40 then that whip is a bit too long. Cut it very carefully, as in small 'bites'. That's a very common way of checking and tuning an antenna.
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Re: High swr monkey made

Post by HomerBB » Wednesday, 29 December 2010, 6:44 AM

Easier, yet, is to use a piece of wire, such as a straightened our wire clothes hanger to substitute for the stinger. Do your cutting on it until you find the proper length for your stinger. If the stinger is already too short it will be apparent when you use the throw away tuning wire. Try to use a piece of wire longer than your stinger to start out with.
I use this method every time I adjust for SWR. It is frustrating to cut your permanent stinger too short. This method prevents that occurrence every time.
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Re: High swr monkey made

Post by Free2fly » Wednesday, 29 December 2010, 9:51 AM

Image

Image
Hope I uploaded pics correctly. I want to first say thanks for the replies.
The mag mount was what I was using and a K-40 with a 6" tunable tip. I had 1.4:1 when tuned. I swapped out antennas and the monkey had 2.5+ up to 3, same mount.
I'm going to use secondary stinger like suggested and see if this will work on getting swr down.
Second radio, and mount has been changed out. Didnt help. As soon as can get another coax I'll try that too.
Read on another, or maybe this one, forum about checking ohms of antenna. Said should get 8-10 ohms when touching probes to tip and bottoms center? Im getting a reading of .0.
Once again thanks for all your help and replies.


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Re: High swr monkey made

Post by 'Doc » Wednesday, 29 December 2010, 17:00 PM

That checking the antenna with an ohm meter is not the smartest thing you can do. If you're checking resistance between the center conductor of the feed line and the tip of the antenna you shouldn't see much resistance at all, it's a 'short'. If you are checking between the braid and the tip of the antenna it can be either an open circuit, very high resistance, or it can be a short too, depends on the antenna. There's no reliable way of using that resistance as a sign of how good/bad an antenna is. Just on the face of it, it sounds like someone is handing you a 'line' for some reason.
Try tuning that antenna.
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Re: High swr monkey made

Post by jessejamesdallas » Wednesday, 29 December 2010, 17:57 PM

More than likely your problem is that antenna..."TOO SHORT!" The coiled section of the antenna needs to be higher up. meaning you need a longer lower shaft. (shaft under the coil) The coil needs to be "above" the roof line of the Cab, or you'll never get the thing to tune.

Another thing...where you have your mount it looks like you have the L bracket in the center of the stake hole and the lug mount for the antenna, mounted to it...But where ever your screws are that holds the L bracket down, if you didn't scrape the paint off the Bed (or finder), your probably not getting a good ground... If you haven't already done so, I would suggest running a ground strap off the L Bracket, to the frame of the truck...Same go's for the Bed itself...Run ground straps off each end of the Bed, to the Frame and be sure to scrape off any rust, dirt, or paint off where the ground straps are attached.

You could still use the antenna you have, and get it to tune better than your last antenna by adding a riser...(something that would get the antenna higher) A Riser is just something to mount the antenna higher so the coil is above the roof...

Example:
Image
Image
Image
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Re: High swr monkey made

Post by Free2fly » Monday, 03 January 2011, 18:35 PM

Ok, update. I used the mag mount and tried to tune the mm5 and only had to cut 1/4 in off the whip to get same swr reading on ch 1 and ch 40. Problem is it's 2.7:1. I've ran a 6" ground stap to top tail light on cab (before cutting whip). So it's well grounded and on the roof, so the coils should b high enough. Could there b something wrong with antenna? And how could I test to see?
Can the antenna b a different ohm or for a different band? I would really like to solve this. With mm5 on; it's ears are very noticeable. I'm worried about swr's harming my new General Lee.
Nice setup Jesse. If I can solve these issues I'd like to try something very similar.
So far I've swapped radio, coax, and mounts. And 2 different 4' fiberglass k-40's will install on post hole mount with 1.2:1. These k-40's will tune to 1.4:1 on the mag mount on the roof.
Thanx for all the help and please keep them coming.

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Re: High swr monkey made

Post by Free2fly » Tuesday, 04 January 2011, 10:08 AM

Just to let everyone know. I bought General Lee w/top gun mods (mods where suppose to be installed and must be retuned and align afterwards and wasn't installed at all) a tram tri-mag mount, and a monkey made 5 antenna from Sparky's Cb Shack. Total $376.51 with shipping. He refunded the mods $36 total but says I'm having a ground plane issue with mm5 and has no solution and won't refund or trade-in for equal, lesser or greater value antenna with less ground plane dependencies. As asked if this means I'm stuck with $80 antenna that won't work and they replied "afraid so". Glad I didn't also order a new setup for my peterbilt.
Does anyone have any advice or knowledge on helping out with this ground plane problem or can it be something else. I know there are very knowledgeable people here. Thanks once again for all you folks helping me so far. Hope to learn and help others someday.

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Re: High swr monkey made

Post by AR 228 » Tuesday, 04 January 2011, 19:13 PM

that is what i was going to say need to get that coil above the roof of your truck. then go from there.
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Re: High swr monkey made

Post by genesbro » Monday, 10 January 2011, 20:01 PM

Just to update on this I gave him a hand and we got the swr down where they should be with it mounted right where he wanted it. Used a stainless steel k40 whip to test it and see what we needed to do and after some careful tuning it is working great and it also lowered his receiver noise so now he can now pickup weaker stations.
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Re: High swr monkey made

Post by Nagant » Tuesday, 11 January 2011, 5:46 AM

Glad to hear it's fixed and that a fellow memeber helped do it.
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