RadioReference on Facebook   RadioReference on Twitter   RadioReference Blog
 

Go Back   The RadioReference.com Forums > Commercial, Professional Radio and Personal Radio > CB Radio Forum


CB Radio Forum - Discussions regarding Citizens Band Radio (CB)

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #21 (permalink)  
Old 12-06-2018, 1:04 PM
Member
   
Join Date: Dec 2018
Posts: 15
Default

Yeah, it got rusty Because I left the little screw they include for grounding a different type of cable installed. It rusted and then that spread.

I picked up a new mount this afternoon. Will try to install it in the next couple of days.
Quote:
Originally Posted by K5MPH View Post
Remove the ground wire and try it that way and see what happens it may be acting like a counterpoise,and also your L mount looks kind of rusty from the photo.....
Sent from my SM-G892A using Tapatalk
Reply With Quote
Sponsored links
  #22 (permalink)  
Old 12-06-2018, 1:07 PM
Member
   
Join Date: Dec 2018
Posts: 15
Default

I get that I'm losing some because of it being that low, but the loaded portion is just above roofline so it shouldn't be too bad. I don't want to put a hole in the roof, so that's not an option.
Quote:
Originally Posted by RFI-EMI-GUY View Post
That rusty old mount might have excessive resistance and not effectively grounding the RF current to the tool box or even to the fire ring connector. Also, the signal is not going to radiate well in the forward direction with it below the roof of the cab.

Sent from my SM-T350 using Tapatalk
Sent from my SM-G892A using Tapatalk

Last edited by Papageoff; 12-06-2018 at 1:12 PM..
Reply With Quote
  #23 (permalink)  
Old 12-06-2018, 3:05 PM
prcguy's Avatar
Member
   
Join Date: Jun 2006
Posts: 6,945
Default

Your antenna is not shielded very much due to the wavelength at CB and if anything your best performance will be to the front of the vehicle. If you place a VHF or UHF whip right behind the cab near a window pillar it will shield the signal and the vertical pillar can act as a reflector giving you gain to the rear.

At CB frequencies, even with a 2ft whip on your tool box that is below roof line, the wavelength is large enough where the cab is just a little speed bump. The RF wave propagating off your antenna is much bigger than the antenna.

I currently have an 8ft HF antenna mounted to the inside bed wall on the drivers side about a foot behind the cab and 2ft of the antenna is below the bed wall. My feed point and coax connector are a just few inches off the bed. My best signals on all bands including 10m (CB range) are to the front passenger side of the vehicle.

For those who put a CB whip on a trailer hitch mount at the rear of a pickup, the best signal will be to the front of the vehicle. BTW, the trailer hitch is a terrible place to mount an antenna for many reasons.

Quote:
Originally Posted by Papageoff View Post
I get that I'm losing some because of it being that low, but the loaded portion is just above roofline so it shouldn't be too bad. I don't want to put a hole in the roof, so that's not an option.

Sent from my SM-G892A using Tapatalk
Reply With Quote
  #24 (permalink)  
Old 12-06-2018, 3:13 PM
Member
   
Join Date: Dec 2018
Posts: 15
Default

Quote:
Originally Posted by prcguy View Post
Your antenna is not shielded very much due to the wavelength at CB and if anything your best performance will be to the front of the vehicle. If you place a VHF or UHF whip right behind the cab near a window pillar it will shield the signal and the vertical pillar can act as a reflector giving you gain to the rear.

At CB frequencies, even with a 2ft whip on your tool box that is below roof line, the wavelength is large enough where the cab is just a little speed bump. The RF wave propagating off your antenna is much bigger than the antenna.

I currently have an 8ft HF antenna mounted to the inside bed wall on the drivers side about a foot behind the cab and 2ft of the antenna is below the bed wall. My feed point and coax connector are a just few inches off the bed. My best signals on all bands including 10m (CB range) are to the front passenger side of the vehicle.

For those who put a CB whip on a trailer hitch mount at the rear of a pickup, the best signal will be to the front of the vehicle. BTW, the trailer hitch is a terrible place to mount an antenna for many reasons.
Neat. My intuition said that the antenna will work the best in the direction of the most metal under it. We kinda confirmed that with my buddy's tacoma. His antenna is in the back left corner of the bed and he clearly cannot reach as far off the back left as he can forward and to the right. It is why I tried to get it as close to the truck's center as possible.

Sent from my SM-G892A using Tapatalk
Reply With Quote
  #25 (permalink)  
Old 12-06-2018, 7:48 PM
Member
   
Join Date: Dec 2018
Posts: 11
Default

Quote:
Originally Posted by Papageoff View Post
Interesting. Well like I mentioned, it's not actually on top of the box. So, if we use the word under somewhat liberally, then the bed floor is "under" the antenna. I have a pic attached showing it. ...and yes I'm changing the mount to get rid of that rust.

If there is a way to get the bed of the truck to be the counterpoise then I think I'd be in high cotton. Honestly, I thought that's what I'd done by by the ground wire to the frame. I mean eventually all of the body is tied together electrically. I figured that was good enough.







Sent from my SM-G892A using Tapatalk
That spring is part of your radiating element, and being below the plane of the toolbox lid it is being partially shielded by it and also capacitively coupling to it. I would move the bracket up so the feedpoint (base of the spring) is on the same plane as the lid, or even slightly above it. If you still have problems, connect a 9 foot piece of insulated wire to the bracket. Tape up the end and put it wherever is convenient. That's better than a choke because it actually gives the RF somewhere to go instead of back down the feedline.

A Firestick works just fine as long as it's installed properly.
Reply With Quote
Sponsored links
  #26 (permalink)  
Old 12-07-2018, 9:20 PM
Member
   
Join Date: Dec 2018
Posts: 15
Default

Quote:
Originally Posted by WRCM View Post
That spring is part of your radiating element, and being below the plane of the toolbox lid it is being partially shielded by it and also capacitively coupling to it. I would move the bracket up so the feedpoint (base of the spring) is on the same plane as the lid, or even slightly above it. If you still have problems, connect a 9 foot piece of insulated wire to the bracket. Tape up the end and put it wherever is convenient. That's better than a choke because it actually gives the RF somewhere to go instead of back down the feedline.

A Firestick works just fine as long as it's installed properly.
Well, the lip of the box precludes that move. I replaced the ground wire that I had going to the frame tonight. I moved up to 10ga and this time I tied it directly from the bracket to the frame. It made no difference... But I didn't really think it would.

Have too many things going on tomorrow, but I may get to try to move it to the bed Sunday. If that doesn't work, I'll try your idea next.

Sent from my SM-G892A using Tapatalk
Reply With Quote
  #27 (permalink)  
Old 12-08-2018, 2:07 PM
Member
   
Join Date: Jan 2016
Posts: 163
Default

I plopped a Wilson 1000 magnet mount antenna on the top of my F250 and get very favorable SWR values and great communications in all directions.

Since I didn't cut a hole in the roof, I brought the coax into the cabin by first laying it backwards on the roof and dropping it between the cab and the bed, and from there pulled it beneath the truck, finding things to run it over to provide support while avoiding the muffler and any moving parts, then inserted the coax connection through a factory hole in the floor under the driver's seat. The hole was plugged from the factory with a grommet, and I cut the grommet plug about half-way through in such a way that the coax could fit in the grommet when it was placed back into the hole.

Works for me. It is easily removed if desired.

Of course, a magnet mount will not work with the late aluminum Ford bodies.
Reply With Quote
  #28 (permalink)  
Old Yesterday, 9:15 PM
Member
   
Join Date: Dec 2018
Posts: 15
Default

Got a chance to play with it a little tonight, but I fear I may have done more harm than good.

I clipped the ground wire from the frame ground and reterminiated on a bolt that mounts the bed. The ring terminal I had wasn't perfect and I think some insulation may be caught under the washer. Unfortunately, the washer appears to be perminantly affixed to the bolt, so I had to make do.

Before the change, I was getting readings like I'd noted before, CH1-1.5ish and CH40-1.4ish. After I got CH1-1.2 Ch40-1.5. Then I put the external meter in line and things started getting weird. It jumped to over 4 on both channels. I took the external meter out and tried again, and the numbers started jumping around a lot, but finally settled on similar to what they were before though much less stable. This is what made me think the insulation may be a factor making that ground inconsistent.

I'm going to see if I can find a 5/16" ring terminal for 10Ga wire in town. If I can find one, I'll take the insulation off and just use heatshrink after I crimp it. If I cannot find one, I may just run a stainless self-tapping screw and a star washer into a spot under the bed somewhere. I really don't want to do that, though.

Last edited by Papageoff; Yesterday at 9:25 PM..
Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 1:24 AM.


Powered by vBulletin® Version 3.8.2
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
All information here is Copyright 2012 by RadioReference.com LLC and Lindsay C. Blanton III.Ad Management by RedTyger
Copyright 2015 by RadioReference.com LLC Privacy Policy  |  Terms and Conditions