Marconi demonstrates checking bandwidth.

[Marconi]

Here is a fast and dirty way Grampa checks his SWR bandwidth and I use this procedure to make my bandwidth curve graphs also, but I slow down an take 100 khz steps and record the reflection and the wattage on the chart. When I'm thru, I plot the data on the graph and connect the dots.

If you have an inline meter that is self adjusting similar to the Diawa in the video, then this works a little better. However, you can do it with a regular adjustable meter, but I find the power tends to fall off when they get out of range of the set mark, but you can at least get an idea of what the bandwidth is, and where. My regular meters tend to show less bandwidth however and a regular meter will be affected with lower watts as you go away from the frequency where you set the mark.

YouTube - Marconi Demonstrates Antenna SWR Bandwidth Curve

 

[GnG8d]

With all due respect, 29.14 - 25.42 = 3.72

 

[Marconi]

With all due respect, 29.14 - 25.42 = 3.72

You're right 359, thanks for the correction.

 

[GnG8d]

You're right 359, thanks for the correction.

LOL, the procedure is more important than the numbers

 

[C2]

you're doing it the hard way...

Did you just sweep the 10 meter band with 12W... :/

 

[mackmobile43]

Great demonstration Marconi, one question, is that the pointy stick of truth you're using and if so where can I obtain one?

 

[Kamikaze]

You might consider checking the SWR meter's calibration using a known mismatch like a 75 ohm load.

I've found a lot of SWR meters very inaccurate above 1:1.

Bird is nice because you always get the reflected power added to the forward power reading so there's a built-in check.

 

[Beetle]

Couple of quick points -

1. I'd be a bit clearer in specifying that the "SWR" reading is the point on the red scale where the two meter pointers actually cross. It sounded to me from early in the video that you were saying that the pointer that moves counterclockwise was indicating SWR, which it doesn't. It reads the amount of reflected power which is related to SWR but isn't always the same thing.

2. The frequency at which you get the lowest SWR is rarely the true resonant frequency. "Resonance" simply means that inductive reactance and capacitive reactance in the antenna system are equal and opposite, thereby cancelling each other out and leaving resistance as the only factor in the impedance equation.

One feature of the cross-needle type of meter is the ability you have to prove that SWR doesn't change with power level. The pointers will change, but the point where they cross, when read on the red scale, won't.

 

[Marconi]

Great demonstration Marconi, one question, is that the pointy stick of truth you're using and if so where can I obtain one?

Hey Mack, believe it or not that is a skewer used in cooking. The truth is the inquisitor, and sometimes that sharp point does reveal the truth.

 

[Marconi]

You might consider checking the SWR meter's calibration using a known mismatch like a 75 ohm load.

I've found a lot of SWR meters very inaccurate above 1:1.

Bird is nice because you always get the reflected power added to the forward power reading so there's a built-in check.

Good idea Kamikaze, I'll try my Bird and if it is revealing I'll also do a video and we'll see how it works.

I'm sure the SWR is not accurate in almost all cases, and that is not the purpose of the test, but it would be nice to be able to get the truth along with the bandwidth. My analyzer always tends to show a little worse SWR and more narrow bandwidth vs the inline meter, that is why I talk about using a short jumper.

This is also why I do both SWR and analyzer. For those that are curious and don't have an analyzer. Of course if you only have a CB radio with 40 channels you don't really get to see much.

 

[Marconi]

Couple of quick points -

1. I'd be a bit clearer in specifying that the "SWR" reading is the point on the red scale where the two meter pointers actually cross. It sounded to me from early in the video that you were saying that the pointer that moves counterclockwise was indicating SWR, which it doesn't. It reads the amount of reflected power which is related to SWR but isn't always the same thing.

2. The frequency at which you get the lowest SWR is rarely the true resonant frequency. "Resonance" simply means that inductive reactance and capacitive reactance in the antenna system are equal and opposite, thereby cancelling each other out and leaving resistance as the only factor in the impedance equation.

One feature of the cross-needle type of meter is the ability you have to prove that SWR doesn't change with power level. The pointers will change, but the point where they cross, when read on the red scale, won't.

You're may be right Beetle. Frankly I don't put much stock in these meters. I don't even run one on my station for general operations. I do use this Daiwa during testing an antenna for tune and bandwidth, because normally it seems to be responsive for the purpose. Sometimes I might do this same test later and get some different results, but why corn'fuse the guys with the nitty'-gritty'. BTW, I tend to use SWR and resonance in a generic sort of way. I'll try to be more specific.

I know it's hard to believe looking at my videos, that I'm not really a professional director/producer, but sometimes I do misspeak trying to keep all of my ducks in a row, commonly referred to by "democrats" as multi-tasking.

IMO, the only real way to do this would be to do it at the feed point with no feed line involved, but how practical is that. Thanks for the comments.

 

[Marconi]

you're doing it the hard way...

Did you just sweep the 10 meter band with 12W... :/

I'm open to a better way with all of my ideas. Would you share your idea.

It sounded like a question, but nope...I didn't sweep the 10 meter band.

This was a video demonstration only.

 

[C2]

I'm open to a better way with all of my ideas. Would you share your idea.

It sounded like a question, but nope...I didn't sweep the 10 meter band.

This was a video demonstration only.

You mentioned Bob's way, that's a step...But I do like the way you showed - it's simple and cheap...and I think those analog meters can be quite useful if you choose to ignore the accuracy and focus on what they can show you.

29.14 - 25.42 doesn't cover 10 meters?

 

[Marconi]

You mentioned Bob's way, that's a step...But I do like the way you showed - it's simple and cheap...and I think those analog meters can be quite useful if you choose to ignore the accuracy and focus on what they can show you.

29.14 - 25.42 doesn't cover 10 meters?

I thought the frequency police were after me. It was just a demonstration and a test. Yep Bob tells me he can do it right at the antenna with a blue tooth setup and do it is less than a second, plot everything, an see other important results and reports. Maybe we can get him to do us a video. It might even sell a few analyzer devices.

I always try to give credit where credit is due.

Thank you guys for your comments.