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Tuning 102" Whip?
- Thread starter buickid
- Start date
Redbeard - CB handle in the Great state of South Carolina
I have been using a 102" whip on my cars & trucks for 50 years. From imports to pickups I always had 1.1 SWR . I never used spring, I had buddy in machine shop make me Spacers 6.25" long to replace spring. out of Stainless steel and still using original on my Truck now. I use 18ft coax, tried 12 ft and SWR jumped up to around 1.3 using CB with 3-4 watts output. I have talked from South Carolina to OK state using skip no problem. can talk local for around 25miles barefoot ,haven't tried long distant using my 100 watt booster ,I also use a 2 tube Elkin linier dead keys 35Watts mod's to around 100watts, it's 50 years old also. I also have in shop a Gold Eagle 3 SSB receiver with Am transmitter. Browning only made 6 & I have one of them. You can't beat a 102" whip it works when the others don't. I'm planning on using one for a base antenna also soon. By the way I've checked SWR in my driveway and other places ,it never changes, Front yard or back yard
Robert, welcome to the forum. Your comments sound a lot like me talking back in the days when CB was a big deal.
Here is what I call my Marconi 7x, where the hub is made with a mobile L bracket, a hub from an A99 GPK, and a short mast pipe for mounting. This setup provided vertical and slanted down radials, but just using 3 slanted down radials did the best job for me.
Here it is in the air. Some times I used a 3" - 4" riser, but most of the time I just used the 102" whips. In the picture below the radials are 102" whips and in this case the 6 radials were set to both horizontal and the slanted down positions with the A99 hub I modified.
IMO, the extra radials made little difference as I recall...and I don't think it was necessary. I could get this antenna up to 50' feet, and it worked great. With the whips the Marconi 4x did not need radial supports, which often fail due to the constant wind and weather. The match was always rock hard and steady...just like your described above.
Here is what I call my Marconi 7x, where the hub is made with a mobile L bracket, a hub from an A99 GPK, and a short mast pipe for mounting. This setup provided vertical and slanted down radials, but just using 3 slanted down radials did the best job for me.
Here it is in the air. Some times I used a 3" - 4" riser, but most of the time I just used the 102" whips. In the picture below the radials are 102" whips and in this case the 6 radials were set to both horizontal and the slanted down positions with the A99 hub I modified.
IMO, the extra radials made little difference as I recall...and I don't think it was necessary. I could get this antenna up to 50' feet, and it worked great. With the whips the Marconi 4x did not need radial supports, which often fail due to the constant wind and weather. The match was always rock hard and steady...just like your described above.
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If you think the antenna is too short, stick on a 10 inch shaft at the bottom of the spring
https://www.wearecb.com/procomm-10-stainless-steel-shaft.html
and then if it is overall too long, cut the crimp-on ferrule off the bottom of the whip and shorten the whip a bit at a time from the bottom, using a replacement 0.200 whip ferrule with set screws to re-mount the whip in the top of the spring.
https://mfjenterprises.com/products/mfj-7715?_pos=2&_sid=1edc0370d&_ss=r
To cut the whip at the bottom with a metal file, score/file about 1/3 to 1/2 of the way through the diameter of the whip, then use pliers to snap off the rest.
If the 10 inch is way too long, stick on a 5 inch shaft
https://www.walcottradio.com/wilson...-p-339.html?osCsid=rjuek1ufcn6ekglp8ac7ddqub1
with some shaft nuts
https://www.walcottradio.com/wilson-shaft-nut-for-2000-and-5000-antennas-880900908-p-2597.html
If 10 inches is still too short, try a 12 inch shaft extension
https://www.wearecb.com/ss34hs12-procomm-whip-shaft.html
[Edit: Egads, I just noticed this thread is 6 months old. No doubt the OP has long ago solved his 102 inch whip SWR issues.]
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Turns out, I'm still around after all these years. I ended up running the spacer and spring as shown in the first pic. The SWRs seemed acceptable to me and I ran a 979 with a DX500 for a year or so before selling my equipment and moving onto other pursuits. Now I'm back with a different mobile, a different 979, and a different DX500. 102" and spring didn't look real good right off the bat, so I slapped on a 10K I got from a SK friend of mine for now. There's something to be said about being able to tune it with a set screw. I'll revisit the 102" when I have more free time. I still have to make time to run some wire for the DX500...
I like many others have left the hobby before, only to return with a bigger thirst. It seems to have that affect.
As I've said before
As I've said before
Hello again Buickid,
IMO the basic issue here, when installing a 102" SS Whip, like both you and 505 are describing, is the lack of an adequate ground plane mix of horizontal surfaces and vertical surfaces...that are nearby the feed point, in order to effectively resonate the 102" SS whip with a good match for CB.
Your idea to lengthen the whip will work, but the 102" whip will only resonate in the CB band...if it has a suitable GP to work against. Mobile body shapes, sizes, and materials make for a lot of variables to work out when trying to match a whip at 102" inches, especially in this modern era of mobile design ideas.
This is the same issue I posted to you, regarding your buddy's Van...that had a large flat roof, and the nearest vertical elements to respond to RF were a bit to far away to make the 102" whip resonate in the CB band.
This is probably why a few operators suggested bonding. To me that would be "iffy" at best. I don't recall, but how did bonding work out with your buddy's Van project?
IMO the basic issue here, when installing a 102" SS Whip, like both you and 505 are describing, is the lack of an adequate ground plane mix of horizontal surfaces and vertical surfaces...that are nearby the feed point, in order to effectively resonate the 102" SS whip with a good match for CB.
Your idea to lengthen the whip will work, but the 102" whip will only resonate in the CB band...if it has a suitable GP to work against. Mobile body shapes, sizes, and materials make for a lot of variables to work out when trying to match a whip at 102" inches, especially in this modern era of mobile design ideas.
This is the same issue I posted to you, regarding your buddy's Van...that had a large flat roof, and the nearest vertical elements to respond to RF were a bit to far away to make the 102" whip resonate in the CB band.
This is probably why a few operators suggested bonding. To me that would be "iffy" at best. I don't recall, but how did bonding work out with your buddy's Van project?
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You should buy in bulk and sell those mounts, Eddie.
Bet you’d sell a bunch. I’d love one.
Rather than 102” whips, I’d use 4’ Firestiks for a perfect small attic antenna.
Yep Riverman, I think I got that idea after the first time reading a Homer Home Depot ad here on WWDX. 
Yep Riverman, I think I got that idea after the first time reading a Homer Home Depot ad here on WWDX.
Count me as interested!
I know this is an old thread but, my five sixteenths homemade steel mount is about 8 inches behind my pickup truck cab on the top bed rail. I drilled 2 holes in the rail and bolted it on. And a five eights hole for the breedlove mount itself. It's strong. I then ran 2 grounds 1 to the bed itself and 1 straight to the frame. I have a breedlove 2 piece mount, very strong, the bottom having a a built in SO-239 and the top threaded three eights by twenty for thread. I have a quick disconnect on my 102 SS Whip extending it about 2 inches all on top of a 53 yr old barell spring and when it is mounted on the mount I get a 1.1 SWR from channel 1 all the way through 40. I may have lucked out but, it works fantastic. (I do also realize mounting in that location makes the antenna somewhat directional).
Groundhog, just a note relayed to me by The DB, a member on this forum.
If you look between the cab and the bed of your PUTruck, you might see that there is no apparent connection between these two parts of the PU Truck cab and bed. If so, that makes a notable difference in my Eznec models for same. It shows not enough ground of the 102" ss whip.
You might see the frame rails and the exhaust, but those parts may not be making a good ground connection between these two parts.
A continuity check may be helpful here, but I never checked this out either. I don't have a truck anymore, but DB has suggested, to be sure, ground the cab and the bed well (metal to metal) together on both sides.
If you check this out, please let us know.
Marconi
If you look between the cab and the bed of your PUTruck, you might see that there is no apparent connection between these two parts of the PU Truck cab and bed. If so, that makes a notable difference in my Eznec models for same. It shows not enough ground of the 102" ss whip.
You might see the frame rails and the exhaust, but those parts may not be making a good ground connection between these two parts.
A continuity check may be helpful here, but I never checked this out either. I don't have a truck anymore, but DB has suggested, to be sure, ground the cab and the bed well (metal to metal) together on both sides.
If you check this out, please let us know.
Marconi
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I have and use that exact spring. Total length / height from hex nut to hex nut is 4.175"
I agree. Two pieces of steel, (whip and ferrel / base) connected with solder or a set-screw. What could possibly be wrong? My whip has a set-screw. I removed the screw and trimmed the bottom of the whip to obtain an acceptable SWR and reinstalled the screw.