I have never seen as SWR curve anything like this...

[The DB]

We got the mount disassembled today before he had to go into work. There is residue everywhere, including on the coax. We are going to do a full replacement later this year, and by we I mean me.

I have never measured that wide. I have seen multiple peaks and dips, most well within the 2.0:1 SWR range - on my original Qv4k.

I do not know what is going on, but I think the trunk mount is a compromise location that begs for losses, but you see the graph.
My only question is more academic than diagnostic, but are you using a 1/2 wave jumper that is around 18', or is it an electrical 1/2 wve jumper cut for coax VF?

I think the coax is 18' long, however it was installed and run before I had anything to do with it so I am not 100% sure. We will be putting a new one in, and I will have control over the length, not that that matters much as this analyzer can calibrate out any length of coax and I can create a custom calibration file for his car before the coax gets permanently mounted behind that plate again.

I agree that the trunk is a compromise location, but that is where he wants it and he won't budge on that, and it is his car. I did tell him that rf bonding the trunk to the rest of the vehicle would help and rf bonding the whole vehicle would help more. He is considering it.

If a 102" whip is installed with a suitable ground plane you should easily see a 4.0> mhz bandwidth at <2.0:1 SWR at 27 mhz. So, your range setting noted above is a little shy still. I can't answer why your meter only shows up to 2.0:1 SWR out to 180 mhz, but I notice the SWR indication looks fine going below frequency.

I recall my Autek VA1 indicating an SWR of 5.0:1> before, but that would have been lower in frequency for me with my range limitations going higher.

As we go higher in frequency the losses become far more significant. My VA1 analyzer only goes up to 30 mhz, so I can't check high, but when I go low to 2.5 mhz using my Starduster, I do see an SWR of 7.9 - 8 similar to what your meter is showing.

Maybe your meter is working just fine and excessive losses are your problem going too high in frequency.

Like CB'rs like to claim, "...this is just fooling your meter."

I am in agreement with your thought on losses, and now I know the cause of them.

Unfortunately I have not had a chance to look at a VA1 directly. Looks like a descent analyzer on paper.

A few observations

I don't think I've ever seen an SWR curve like that either, that's interesting. Or so many particular aspects/characteristics/parameters displayed at the same time.
I think that by displaying all of those 'aspects' on the same graph that there are some conclusions that can be drawn. The first conclusion I would make is that this display only pertains to one particular and specific antenna set up. It means that conclusions can only be drawn about this one specific instance.
Another conclusion is that all of the 'aspects' affect each others behavior. I think that's about as 'normal' as it gets. There are a number of general conclusions that can be drawn/inferred from all of this information, it depends only on how 'well' you can integrate particular aspects of each 'piece' of information and how it relates to other 'pieces' at some particular 'time'/'place' on the graph. All of those 'inferences' are only going to be 'true' for this one set up though. So if you want to come up with a really good set of 'rules' for some particular 'aspect'/measured quantity out of this, then there are going to have to be a large number of other graphs done for other 'set ups'. 'Mix' all of those measurements, strain for particular aspects of the mix, and you have the 'dead nutz', typical way of coming to a scientific theory of operation. All things considered, that ought'a keep you busy for the next day/week/month/year/century or two, you think?
- 'Doc

ooooo, that doesn't even touch on all the incorrect conclusions you'll come to because something else wasn't considered/added to that 'mix'. Glad it's you and not me!

Actually, its not so bad. Think about when someone posts several specific frequencies and the results from an MFJ or other similar meter that actively gives you one frequency of information at a time, then put those along with all other nearby frequencies on a graph. I have used MFJ's in the past, but once you have used one of these a few times it is definitely easier to evaluate what is happening with antennas. You see patterns that you would normally miss with an MFJ one frequency at a time style meter.

I have seen a SWR curve much like that at one time, although it was nowhere that wide it covered a impossible bandwidth with peaks and dips under 3:1 and it was a I10-K base antenna, when I plotted the Curve I called Jay and asked what he thought about it, his first thought was bad Coax.
Soon after I replaced the old Coax with LRM-400 and magically the SWR plot became normal.
The thing is that the antenna worked just fine throughout the 10/11 meter band with no apparent problem.
Just my 2 cents worth.


73
Jeff

Coax is part of the problem here, as is the rest of the mount. I'm still debating if I want to clean it all up and reuse it and seal it better or if I just want to go with a new mount for him. He isn't picky but isn't exactly rich either... He just wants something that will work and not fail on him in a few years.


The DB