RF grounding, or bonding your mobile HF setup and bigfoot!

[Mudderoy]

Technically I guess bonding is good for any frequency however I notice the failure of improper bonding (or RF ground) from weird sensor and electronic responses in and from the Jeep.

I installed my HF radio (VHF/UHF) in my 1998 Jeep a few years before I lifted it. I had NO problems. Well I take that back, I did have a little problem with the radio shutting off on 20 meters. The RF was being inducted into the remote cable between the control head and the main body (radio).

Apparently the radio thought it saw the power off signal from the control head and well, shut off. At first I thought it was a poor SWR situation but then I remembered with the auto tuner there was no SWR problem.

Putting a ferrite core(?) on the line to the control head solved the problem. Of course this was a good indicator that even though this was the only issue I was getting RF into the cab of the Jeep.

It didn't seem to effect my ability to talk to people thousands miles away though. So naturally I didn't do anything about it. :D

Fast forward a few years and I install a 4.5" lift and 32" tires, this raised the bottom of the Jeep 7 inches. I found out later that your antenna doesn't use the body of the vehicle as the ground. It uses the ground as the ground.

For an antenna to be resonant it must be 1/2 wave. We can get away with a 1/4 wave because of the reflection of the antenna into the ground. This makes the antenna "electrically" a 1/2 wave. If this reflection is missing or not very good then the antenna won't work as well as it can.

I found out that what the body of your vehicle does is form a capacitive link between the vehicle and the ground, Earth! When I raised the body of the Jeep I changed the capacitive value and made the link worse.

The result was that on certain bands if I tried talking on the radio it would make the engine shudder, and miss. In some cases it would make it stop running. I finally figured out this was because the RF was being inducted into the CPS wire. It's a pretty short wire too!

So other than sitting still with the engine off I haven't been able to really talk on my HF radio.

This past weekend I installed a new factory CPS. At the same time I installed a RF core on the line, and then put black tape on it to hold it in place. I was afraid this wouldn't work because I didn't have enough cable to wrap it around the core. I just placed the core around the wire.

It worked! So far anyway. No more engine misses or dying while talking on the radio. I have not had a long conversation yet, but basic testing hasn't uncovered a problem.

Now I still have the RF ground problem but at least I can use the radio if I need to.

I'll be updating this thread on what I'm doing to improve the RF ground and therefore improve my capacitive link with the real ground, the Earth.

[Mudderoy]

I unhooked (102" whip held in place by a antenna clip on the rain gutter pass side) the antenna and started tuning around. About 2 miles down the road I heard someone "weak" calling CQ on 20 meters. I said my call and he immediately called me back. Turned out he was in Georgia(?) and he was also mobile heading home from work.

SSB on 20 meters is really just AM radio (regular AM is 2 sides) SSB (Single Side Band) is only one of those. 20 meters uses Upper Side (USB). You can legally use either, as well as AM but the gentleman's agreement is USB on 20 meters voice.

I point this out because if you've ever listened to a broadcast station during a thunderstorm you know how much static you pick up. This is partly true because of the frequency that AM broadcast uses and also because of the AM mode. There were times that I had a hard time understand "GUY" because his signal was weak, for the amount of electrical noise that was around me. Specifically at intersections. I'm assuming because of the traffic lights and switching equipment near them.

All in all I had a nice 10 to 15 minute conversation with this fellow mobile amateur radio operator several states away.

The bands were sucky yesterday. Not many people on 20 meters, and those that were weren't very strong. There was a little activity on 18 meters, and 12. I listened in on a conversation around 28.400 MHz (10 meters). Eventually I made my way to 40 meters, and found a NET. The NET is just this thing that is a meeting point for a group. Usually happens on the same day, same time, and same frequency on some cycle. Daily, weekly, etc...

I found the "Good Old Boys" NET. I tried checking in. The NET Operator was located in Conroe. He was having a hard time hearing me, but truth be told my 102" antenna for 40 meters is really really short. A quarter-wave antenna for 40 meters should be 294 inches, or 24 feet! So at only 8.5 feet long my antenna tuner is acting like a dummy load for the majority of that 24 feet!

Still he was able to hear me, and that changes as I drive down the road and change directions in the Jeep.

I tried saying a little something "WB5ZDD TESTING... HELLLOOOOO RADIOOOO" on each band. No miss from the engine.

I'll be getting on again this afternoon. There are several ways to see if the band(s) are good. Some involve the use of beacons that amateurs have put up on specific frequencies. This allows you to see if an area of the country, or world, is OPEN. Signals are making their way from the beacon to your radio's receiver. No signal, either the beacon is down or conditions are not favorable to that area for communications. This is a easy way to check by using your radio.

The really easy way is just to get on the Internet and check. I can do this before I leave work, or I can just use my smartphone. More on this later, especially since you don't even have to have a radio to use this, and some of you may find it interesting to see what areas of the world are "open" to your area, and how often. This is called prorogation.

[prerunner1982]

Now that I re-read this... I see very little mention of RF bonding as the title states.

RF Bonding can stop RFI problems (both coming into the radio and caused by the radio) as well as lower the noise level.

Bonding consists of connecting all of the isolated part of the vehicle together with braided ground strap. Hoods, fenders, doors, trunks, hatches, exhaust.... yes... exhaust. And if you have a body on frame type vehicle (CJ, YJ, TJ, JK,.. etc) then you would want to bond the body and the frame together as well.

[Mudderoy]

Now that I re-read this... I see very little mention of RF bonding as the title states.

RF Bonding can stop RFI problems (both coming into the radio and caused by the radio) as well as lower the noise level.

Bonding consists of connecting all of the isolated part of the vehicle together with braided ground strap. Hoods, fenders, doors, trunks, hatches, exhaust.... yes... exhaust. And if you have a body on frame type vehicle (CJ, YJ, TJ, JK,.. etc) then you would want to bond the body and the frame together as well.

There's no mention of bigfoot either!

[OldFaurt]

There's no mention of bigfoot either!

Last time I talked to Bigfoot, I told him to watch out for non-believers...
They could be rude and play tricks on him!

Hey Mudderoy, when are we going to have a meet & greet to compare our rigs and gibber gabber about HF seeing how I only live about 6 blocks away...?

I have been playing around on 17m - 80m on the 3 hour round trip to work and home and heard a really cool dual path greyline line. It had a cool echo effect. short path was louder then after a delay, got the long path. Never expected that mobile.

[Mudderoy]

Last time I talked to Bigfoot, I told him to watch out for non-believers...
They could be rude and play tricks on him!

Hey Mudderoy, when are we going to have a meet & greet to compare our rigs and gibber gabber about HF seeing how I only live about 6 blocks away...?

I have been playing around on 17m - 80m on the 3 hour round trip to work and home and heard a really cool dual path greyline line. It had a cool echo effect. short path was louder then after a delay, got the long path. Never expected that mobile.

Dunno. I did some work on the rig this evening. Took the new vhf/uhf nmo mount out there too, but ran out of daylight. Maybe soon. I'd still like to try to get a meet and great at the local Sonic.

[OldFaurt]

Dunno. I did some work on the rig this evening. Took the new vhf/uhf nmo mount out there too, but ran out of daylight. Maybe soon. I'd still like to try to get a meet and great at the local Sonic.

The SONIC north of you or south?
Either way sounds good.
I have been working on my mounts for the radios too!
Here is the antennas HF on the rear, VHF/UHF on Front! (Decoy for the bugs)
9105
Here is where the radios landed, I have full visibility of both from both front seats
9102
Here is the Ball mount, will be changing that soon... Want a quick disconnect for antenna!
9108
Try not to laugh at my welding... Try!
9107
Yes the door no longer drops, I could weld or I could see,
I could not get door hinges off, The TORX tool I have is too long and
I did not want to grab the Torx with vise grips...
I should pull the fender and grind it down and do it right.
But hey, the door closes real nice and I was able to weld the
door stop back together as well! I know, I'm amazing...ly red neck. (I burn easy)!

I love my jeep, Got it with way over 250,000 miles and have put about
60,000 on it since then... in about 2.5 years....:rolleye0012:



Ain't she lovely?:smiley-laughing021:

[Mudderoy]

Hey whatever works right? Do you know of any shops around Katy that can do some minor welding? I have a crack in the unibody plus I need my frame stiffeners bracket welded to the unibody and they four plug welds to tie them in properly to the XJ. I've tried Google but haven't called anyone yet to ask if they do such small jobs.

[OldFaurt]

Hey whatever works right? Do you know of any shops around Katy that can do some minor welding? I have a crack in the unibody plus I need my frame stiffeners bracket welded to the unibody and they four plug welds to tie them in properly to the XJ. I've tried Google but haven't called anyone yet to ask if they do such small jobs.

Sorry Tony Wife went into hospital today... I have not found any I could afford and bought my own flux core welder. It gets the job done pretty well, when I can get at it, Notice how funky the door hinge turned out but at least I stopped it from falling off! There was a place about a 1/2 mile this side of 4wheel drive store, but I can't find the card, will look harder!

[Mudderoy]

Sorry Tony Wife went into hospital today... I have not found any I could afford and bought my own flux core welder. It gets the job done pretty well, when I can get at it, Notice how funky the door hinge turned out but at least I stopped it from falling off! There was a place about a 1/2 mile this side of 4wheel drive store, but I can't find the card, will look harder!

Oh no! I hope it was only a brief stay, maybe she hurt her hand from slapping you back into shape, you know that sorta thing.

[OldFaurt]

Oh no! I hope it was only a brief stay, maybe she hurt her hand from slapping you back into shape, you know that sorta thing.

Oh I wish! She woke with tightness in the chest and Arm pain, her son took her down to Methodist, she came home this afternoon but needs to go back for a stress test and a nuclear imaging to see about clots (Other than me...) next week. I am so glad to have her home!

[Mudderoy]

Oh I wish! She woke with tightness in the chest and Arm pain, her son took her down to Methodist, she came home this afternoon but needs to go back for a stress test and a nuclear imaging to see about clots (Other than me...) next week. I am so glad to have her home!

Well all the best. They are doing amazing things these days, and it's only get better.

[Mudderoy]

A vehicle is not a ground plane, but rather acts like a capacitor between the antenna and the surface under the vehicle which acts as the ground plane. Since the surface in question is a poor conductor of RF, ground losses occur. If we wish to maximize the system efficiency (the mobile station as a whole), we need to maximize the RF continuity of the vehicle, hence proper bonding. Obviously, proper antenna mounting, and placement are important too. Remember, it is the metal mass directly under the antenna, not what's along side, that counts. And a ground strap is not a replacement for proper mounting!

http://www.k0bg.com/bonding.html