I have a 102" whip mounted on my trunk I am getting an swr reading of 1.3-1.4 my trunk is not grounded other than the mounts that hold it normally to my vehicle. Is there any chance adding straps would help take the swr down to a better state if they were added. I am using a beehive mount also. It is very tight and before tightening it down all the paint was grinded off and then sanded by hand. So I think all that could have been done in that department is ok. Perhaps a strap directly from the ground point of the mount to the frame of my vehicle would be beneficial ? Not to sure. Used magnet mounts back in the 90's finally got a sedan I felt comfortable drilling into the trunk of and it seems to talk ok so far. Just don't want to run serious power through it until the swr is 100% as good as it can be. Thanks.
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102" whip swr issue
- Thread starter Roddrick333
- Start date
You can run ground strap to the trunk lid, might help, might not. Lots of trunks don't have a great ground.
In my old car I ran big battery cable from trunk to frame under spare tire. Brought my swr from a 1.4 to a 1.2, Not huge difference but helped a bit.
Only way to find out is to try. Prob want to try to run right from mount area down to frame. Also keep in mind many 102" whip require extra spring to make longer to get SWR down. On my truck I had to run extra spacer to get 102" to flat.
In my old car I ran big battery cable from trunk to frame under spare tire. Brought my swr from a 1.4 to a 1.2, Not huge difference but helped a bit.
Only way to find out is to try. Prob want to try to run right from mount area down to frame. Also keep in mind many 102" whip require extra spring to make longer to get SWR down. On my truck I had to run extra spacer to get 102" to flat.
You should bypass the hinges, or at least one of them, with ground braid. Use as short a piece as possible while still allowing the trunk lid to open fully. Hinges = sliding contact. Sliding contact = no contact (worst case basis).
And while you're bypassing hinges, do the doors and hood hinges. Get all the metallic sections bonded together to form one continuous ground plane for RF.
And while you're bypassing hinges, do the doors and hood hinges. Get all the metallic sections bonded together to form one continuous ground plane for RF.
A 102 whip is not exactly a 1/4 wave antenna at 27 MHz in the CB band nor is it 50 ohms. Lengthening the antenna with a spring may give you the proper electrical length but it doesn't change the feed point impedance so you still have a current loss at the antenna feed point. A perfect match for this antenna is when you can get the antenna feed point impedance the same as the feed line itself, in this case 50 ohms since you should be using 50 ohm coax. When you get this antenna's feed point at 50 ohms, you should have a low SWR if not near perfect.
You can relatively easily remedy it to get a flatter match if it is worth the trouble to you. However, there won't be one bit of difference to the station on the other end so an SWR under 1.8 is still good except for people hung up on SWR readings and dirty amplifier manufactures claims.
As is, this antenna should work well for you if you have it mounted to a solid base mount on your mobile setup. Ground straps shouldn't be needed for your antenna if your antenna mount is D.C grounded by being attached to a solid metal surface. If ground straps are to be used, keep them as short as possible.
All I use on a HF mobile antenna is a single 30 in. X 1 in. wide strap as shown in the pic below.
You can relatively easily remedy it to get a flatter match if it is worth the trouble to you. However, there won't be one bit of difference to the station on the other end so an SWR under 1.8 is still good except for people hung up on SWR readings and dirty amplifier manufactures claims.
As is, this antenna should work well for you if you have it mounted to a solid base mount on your mobile setup. Ground straps shouldn't be needed for your antenna if your antenna mount is D.C grounded by being attached to a solid metal surface. If ground straps are to be used, keep them as short as possible.
All I use on a HF mobile antenna is a single 30 in. X 1 in. wide strap as shown in the pic below.
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Definitely going to try some ground strap to see if it helps why the heck not. I have some big battery cable laying around and can put a rub from each side of the trunk to each frame rail directly and can get my torch out and solder a lug to the ground washer on my my and go directly to the frame as well. I'm off work today so I'll let you know how it works out. Thanks guys
NOOOOO. If you've got some RG213 lying around, flattened braid taken from that is far better. The battery cable isn't very flexible.
All you need to do is this from the trunk to the main body:
You can also buy short flat braided ground straps with ring terminals already at most auto parts stores for around $5.00 like these below. I bought mine from O'Reilly's auto parts. These are good for bonding your trunk and doors where you need smaller flexible ground straps as shown on M0GVZ's pic above. The larger 1 inch wide straps I get at Napa auto.
Ok ill see about getting some. Also just put a little deposit on an 8 pill so my gumdrop mount has to go my buddy said. He advised to me get an older RadioShack ball mount. Also went to west marine and found out I can get a 400$ 8D battery for 165$ brand new going to need it atleast with the stock alternator. It's 130 amp so hopefully it will hold up
A couple suggestions.. look into either a riser or spring to get your whip to around 108 in (for cb use). Or just get a 108 in whip. Also check out breedlove. Well made stuff. https://breedlovemounts.com/#2828
1.3-1.4 SWR with a 102" whip...Think I would leave things as-is and call it a day.
Forget them, hardly anyone makes decent ball mounts any more, they're all basically white metal. The exception to that is Breedlove Antenna Mounts who make an excellent range of them for amateur screwdriver antennas, CB antennas and quick disconnect built in as well.
I was looking at xforce's website and they sell a 12 inch 102" whip adjuster you cut the 3/8 24 off the bottom of your whip and slide it in and have 12 inches of room to make your adjustments to tune it to whatever works best for 34.95 if you guys think it will help I'm gonna give it a try. Just paid car insurance so next week I'll get the fatboy competition style puck mount with the lug connection and they sell a six foot run of 213 with the eyelets soldered on already and the connector on the other end. So with that said. UNTIL NEXT PAYCHECK!!!