102" ??

[bayou1]

I am on the roof with a 102 with a 6" whip adjuster not seeing anything beter than 1.3 and r70. What's the trick to getting these things down? Anyone have a perfect match with a 102"? On a Tahoe btw

[jessejamesdallas]

1.3 I wouldn't worry about it......I would be more concerned with all the bridges and stop lights your bound to be running into...

[Deleted User 14541]

Nothing wrong with 1.3 but a shunt at the feed point can be used to get R down to 50 ohms. I'm assuming the swr on 1 & 40 is equal and dips lower as you get closer to the center of the band. It sounds like you've got it right and I really doubt any real world improvement can be made.

[bayou1]

Shunt school please

[MDYoungblood]

Shunt school please

School, lmao, here's some homework instead, http://www.k0bg.com/match.html

3's

Greg

Shunt school please

School, lmao, here's some homework instead, http://www.k0bg.com/match.html
3's
Greg

[youtube2][/youtube2]

[bayou1]

1.3 I wouldn't worry about it......I would be more concerned with all the bridges and stop lights your bound to be running into...

I want to run some power through it. Others have posted 1.1 match I don't see why I can't get to that point. Will a shunt I'm swr? Or just a impedence tweak

[Deleted User 14541]

I want to run some power through it. Others have posted 1.1 match I don't see why I can't get to that point. Will a shunt I'm swr? Or just a impedence tweak

You can run power through 1.3:1. That's actually very good. Impedance and reactance are used to calculate swr so if you change impedance your swr will change. SWR is not an indication of performance but many believe it is. A dummy load is a perfect match but doesn't make a good antenna.

[jessejamesdallas]

I want to run some power through it. Others have posted 1.1 match I don't see why I can't get to that point. Will a shunt I'm swr? Or just a impedence tweak

You can run power through 1.3:1. That's actually very good. Impedance and reactance are used to calculate swr so if you change impedance your swr will change. SWR is not an indication of performance but many believe it is. A dummy load is a perfect match but doesn't make a good antenna.

what he said...........

I am far from a perfect 1.1 match on my Base antenna...But I run a Tube Amp on it and talk all around the World!

[bayou1]

I looked into the shunt. Looks as though some of the current is diverted thru the shunt. If so is the lose worth running the whip that way? I have a coil antenna that tunes flat. I wanted to run a stick or whip for performance in street fighting. But if u loose with a shunt will the the coil outperform the whip?

[MDYoungblood]

I think we could be more help if we knew what mount you are using. I don't use a spring, risers are the way to go with a 102" whip. How are you making your adjustment? Another thing is the coax starts to radiate at the point where the center and shield separate, even inside the vehicle, so that needs to be added into the antennas calculations. Your antenna might be too long, you are using an analyzer, where is the 1:1 match (X=? R=50) showing up.

3's

Greg

[The DB]

As others have said, 1.3:1 SWR is fine even if your are running a ton of power through it. Hell 1.5:1 SWR is fine even if your running a ton of power through it. You are making a big deal out of nothing.

If your amplifier is so stringent that it can't transmit into anything other than a 1:1 match then it has problems of its own, and it would never last in a mobile environment in the first place. In a mobile environment your SWR changes constantly. Think about it, your passing by buildings, other cars, different environments, ect. I've seen a car passing over 30 feet away from an antenna I was tuning change an SWR reading on a scan with my AIM 4170c VNA by as much as .2 SWR. That was a car that was just passing by 30 feet away, what do you think the cars driving along next to you, and buildings you pass, and in some cases the differing lay of the landscaps will do to your SWR? What do you think happens to your SWR not only when you move but another car comes up and parks next to you?

A perfect SWR is never required, and doesn't actually benefit you in any way, as long as it is "close enough" (yes that is in fact a technical term) then you are fine, and yours is beyond close enough.

It is interesting, as MDYoungblood mentioned that you mention an R reading in your initial post, but not an X reading. I noticed that as well. Am I to assume that X is 0 at that point, or am I completely off track in assuming you have access to an antenna analyzer? If you do have access to an antenna analyzer the first habit you need to break yourself of is the overdependance of SWR... It only really matters to a point, and that point is is it safe to plug into your radio/amp, which you scenario it is well to the safe side of that point.

You want to know how to get your antenna to perform better using that analyzer? That is easy, you find ways to lower the R variable while keeping X at 0, which I think you want to do for other reasons anyway (I would agree that the R reading is high, but for other reasons than SWR). The first thing I would do in a mobile environment is look into RF Bonding if you haven't done that already. That will benefit you more than anything, and not because it lowers your SWR, (if that is what happens in your case), but because it tackles the real enemy to mobile performance, ground losses. In even the best case ground losses in a mobile antenna system setup will affect your performance far more than any other single component, your (or any) car simply does not make a good, ground plane...


The DB

[bayou1]

Yes 1.4 r70 x0 at that point. I am using a xforce puck. I have only about an inch from where shield stop to hot. New consideration. I open the back doors and it drop to 1.1 r52 x3. This is working me because I just can't except my coil flat and no stick or whip will tune low. Something is the culprit? I did normal bonding

-- Tuesday, 09 December 2014, 16:31 PM --

I think we could be more help if we knew what mount you are using. I don't use a spring, risers are the way to go with a 102" whip. How are you making your adjustment? Another thing is the coax starts to radiate at the point where the center and shield separate, even inside the vehicle, so that needs to be added into the antennas calculations. Your antenna might be too long, you are using an analyzer, where is the 1:1 match (X=? R=50) showing up.

3's

Greg

28.3

[MDYoungblood]

Good "X" and "R" at 28.3 means the antenna is still short, now this might not be the case but years ago Radio Shack sold 102" whips that were only 96"'s long, mislabeled, manufacturer mistake, an order to somewhere else that got mixed up, don't know, but there are still some out there being sold. The opening of the doors in the back is adding to the counterpoise/take off angle of the signal, it is curious that the vertical doors affect it that much, I'm guessing skin effect. Try adding another inch to inch and a half to the length.
Loaded antennas all act differently than a 102", adjusting them is easier (sometimes) and a good SWR can be achieved, most are designed long and can be shortened. The coil closer to the center the easier it is.

3's

Greg

[bayou1]

Ok I got a mfj 108" in today. With no avail I didn't see any better. You say that adding to counterpoise changes the angle? In what degrees? Higher or lower? Now my next move was to make the antenna see more counterpoise of possible

[Deleted User 14541]

You aren't going to get any better than you were in your first post. You might use a coil antenna or tune the 102 lower with a shunt but you will do more harm than good in the performance dept. You have been given sound advice now you have to decide what's more important. Do you want good performance or is it more important for you to see a flat swr? You were already doing very well. Good luck with it.

[bayou1]

Tks everyone for all the advice. I will let you all kniw the direction I take. Tks