Amateur (Ham) Radio BS and Callsign Thread!

You measured with a DMM, right? That tells you resistance, not impedance. Having good DC conductivity does not guarantee there's no reactance and thus high impedance. It's especially true as you go up in frequency and at UHF I highly doubt such bonding is at all effective.

Anyway, never mind, the thought is going nowhere. We always tell new hams "do this" but never the why or theory. Point I was trying to get at was you can check (or infer anyway) impedance with an antenna analyzer, vector network analyzer or just an SWR meter.

 

My point was that if you didn't want to rely on the bracket nmo mount to make the bond, you can ground directly from the mount to the body if need be.


I have no antenna there. There is no coax to test the impedance. The drop of 1 s unit in noise just from bonding the hood shows a successful bond and is on par with what is to be expected for such bonding.

I could easily check the impedance by hooking a meter up to the farthest point in the strap and putting a probe to the farthest section of the hood, but why?

 

Your bed rails are grounded they are not screwed into the plastic. Drill and tap a couple of (1/4 20) holes into a piece of 1/4 aluminum that will fit inside of the rail, slide it to where you want it drill matching holes in a aluminum angle drill a 3/4" hole for an NMO, bolt it to the AL plate slide it where you want it tighten the bolts (SS prefered). Try to get over the ground plane myth it will make you lose sleep.

 

This ugly bastard is going to become my off center fed dipole. 4:1 current balun, ran it through my analyzer and got what I expected. Tomorrow I got to Home Depot to find a box. Then I'll measure up the wire. This is going to be the antenna that I bring camping with me, very excited about getting extra bands. I'm currently sitting at about $15 for the torroid, had the wire, couple of bucks for the box, and then some fasteners. Not too bad considering they go for upwards of $100 at HRO.

 

It shows you've made an effective shield, likely from engine radiated noise primarily from the ignition system. That doesn't necessarily indicate effectiveness as a conducted ground plane for an antenna, especially at VHF and higher.

 

I like this mount.

https://www.victory4x4.com/product/VT3CB-BARE.html

 

I have a set of ditch light mounts off Amazon if someone wants them. Pay shipping and they are yours. Ended up just drilling a hole in my roof instead of playing with a non-intrusive mount. Never installed.

LED Light Pod Metal Hood Mount Bracket Kit/Ditch Hood Light Brackets for 2016-2017 Toyota Tacoma - black.

$23 GREATUS LED Light Pod Metal Hood Hinge Ditch Mount Bracket Kit Hood Light Brackets Compatible with Toyota Tacoma 2016-2021 - Black

https://www.amazon.com/dp/B07PRG7MY3/ref=cm_sw_r_cp_apa_i_wodAEbDREWB0C

I'd accept a donation if you want them but not needed.

 

It's effectively the same test as running radials from your mobile to improve you stationary set up that the Arrl has published many times.

 

"A useful test of the quality of your ground is to lay out several long wires while you are stopped in your driveway. Connect them to the RF ground connection on your Smartuner. When you remove these temporary wires, reconnect your grounding system. The signal should get better. If it gets worse, your RF grounding system needs work."

 

Look, we're going in circles. Using measured resistance and radiated noise floor reduction based on a low frequency, long rise time pulse like an ignition with perhaps harmonics to maybe 1 MHz is fine as an analog for an impedance measurement at HF but isn't a complete test. If you put a VHF noise source under the hood and see a one S-unit (6 dB) reduction in radiated noise immunity to your roof antennas then I'd happily admit to being unnecessarily pedantic.

 

I agree that trusting reciprocity is fine in this case. If radials improve reception then at the same range of frequency you have improved your transmitting performance.

What I'm saying in all of this that bonding my sheet metal took a lot of effort and measurement to actually finally show any improvement on my old truck. Especially at UHF random lengths and indifferent terminations of braid doesn't work to actually create RF conductivity. That's why I didn't go to great lengths on trying to get those ditch brackets working well and just used ground plane indifferent antennas.

Bonding is important if just for local noise reduction but it's not a one size fits all solution. You might need multiple lengths of braid. A bonding jumper might work well for one range of frequencies and be completely useless at others.

 

"Pedantic" is my new favorite word. I have been using it for a few weeks (usually in reference to myself.)

 

Literally the whole point of the convo was just to say there's rf bonding between the bracket and hood because he was concerned about the bracket. Just gave reason why it was. Wasn't diving into propagation theory.

 

OK, fine.

Wave propagation in a real material is precisely what's being discussed. So sure, there's conductivity (or maybe it's absorption, which is effective at reducing EM noise in this case just changing ignition EM noise into heating the braid slightly, as well as reflection) at some unknown frequency. What's happening at the frequency of interest is being ignored, but it's critical to having an antenna mounted on a ditch bracket present a useful radiation resistance and pattern. But whatever.

 

Just use a ground independent antenna and don't worry about all this crap. There's no reason to be in the weeds about this stuff with VHF/UHF antennas. HF is a different story.....

Edit. a good ground independent antenna

https://www.diamondantenna.net/sg7900a.html

I use one on my motorcycle.

 

As someone with an antenna on a ditch light bracket this conversation makes me feel “great” lol. I’ve never felt my TX or RX was sub par, but I guess I don’t really have anything to compare to. Now I’m wondering how much better it could be if the same antenna was used elsewhere.

 

There's analytical methods that you'd do by sweeping SWR and measuring received signal or field strength while transmitting.

But mostly it's informal things like asking for reports from other hams on repeaters at various places that you've previously had trouble reaching or measuring the number of packets you get into APRS-IS. You can use beacons or common stations, like NOAA weather radio, to measure reception performance.

The easiest way I find to judge mobile antennas is rag chew every day as you commute. You'll find dead spots and places where your truck is faced the wrong way. With enough data to know your commute you can then try a different antenna or move it to see if it changes anything.

In the context of the subthread, you can compare a ditch mounted or lip mounted antenna by borrowing someone's mag mount and set it in the middle of your roof. The difference in range in town might not be immediately obvious but that you won't have as many fading or aspect issues. And drilling permanent holes will be an improvement over mag mounts in all ways.

Unless you talk on the radio you'll never really know. So key the mic and experiment.

 

Has anyone built a transformer for an efhw? On the primary winding, if the wire breaks at the point where it's doubled over, does it really matter? I feel it doesn't because it's getting soldered anyways but I figured I'd ask in case there's something I'm overlooking. Lower right side.

 

What do you mean doubled over? Where is the break? Sounds like at or near where I indicated #1. There won't be a problem for sure. If it's where I've indicated #2 or #3 it might not matter as long as you can still twist the primary and secondary together and keep them insulated. T



Took the image from a presentation by Mark Mladejovsky, WA7ARK.

http://hamfest.w7yrc.org/wp-content/uploads/2019/06/EFHWslides.pdf

 

This is my point on ground planes what a mobile system suffers from is ground loss there is a lot of energy spent heating the ground. This is also why HF installations use multiple ground radials like dozens, the ground is very lossy.