SWR Meter goes haywire.

Started by madball13, January 22, 2013, 03:09:44 PM

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madball13

I just picked up an 857 and a Z11Pro Tuner and i have a 1/2 wave 80M dipole with jumpers cut in for 10-20-40. I decided to do some testing with my tuner and with the dipole set at 20M i switch to 40, change the radio setting to PKT and key up. The radio flashes SWR as the tuner goes about finding a match. It eventually does but i notice my SWR meter is completely haywire, both needles pointing to the ceiling.

Anyone have an ideas?

KC9TNH

#1
Which side of the tuner is your SWR meter on?
(and what kind of meter by the way)

What freq did you cut your antenna for, and what freq were you tuning?

madball13

The meter is a MFJ and it is after the tuner, so radio-tuner-meter. The antenna is cut for 20 and I tried tuning up on 40 and 80.

KC9TNH

Quote from: madball13 on January 23, 2013, 05:41:25 AM
The meter is a MFJ and it is after the tuner, so radio-tuner-meter. The antenna is cut for 20 and I tried tuning up on 40 and 80.
OK, I don't see an actual problem; your SWR meter is showing your the 'raw' SWR for your antenna (good thing). The tuner is doing its job to alter that and present as close to a 50-ohm load to the radio as it can, also good thing. It's important to remember:

A tuner DOES NOT tune your antenna. It is (in olden days terms) a "matching device" and is used to convert a less-than-perfect load to a load good enough to present to what the radio wants to see, 50 ohms. Now, on the other hand....

What that tells you is that - AT THAT FREQUENCY - your antenna is not resonant. Where your jumpers are can matter, which is why I asked what was the SPECIFIC FREQUENCY you used to place the jumper at? The lower bands are more sensitive to freq changes because they use more wire. A slight change on a 20m frequency doesn't have the impact that a similar change would on 80. As an exercise, run the math:

using 468 / frequency, what's the distance in feet on 20m from CW to near top of voice? 14.05 vs. 14.3?
Now what's the same thing from the CW area of 80m, say 3.55 to top of the voice area, say 3.9?

See the progressive difference?  Out there at the lower bands little changes have a bigger impact.

Another exercise would be to simply tune up & down the 40m band, bottom to top in some number of steps, and watch your meter showing you the raw SWR. At some point that meter will show you where your wire is actually close to resonance.

Long way 'round the barn, but sounds like your equip in the patched order you gave is simply doing its job.

K8hid

You need radio meter tuner. That will show you what the radio is looking at. I think that line of tuners are the best value in ham radio. I have carried my Z-100 all over the world with great results.
If you have the room a full wave 80 meter loop with that tuner will let you work anthing you can hear.

KC9TNH

Quote from: K8hid on January 23, 2013, 07:49:45 AM
You need radio meter tuner. That will show you what the radio is looking at.
That's true, just depends on which end of the truth you want to examine. If the goal is to show what the tuner is doing in more detail than a tuner's blinking light that will work. I was simply addressing what madball was observing.


madball13

Thanks for the info Wes, it's pretty much what I had thought. I just need verification sometimes that I'm not crazy.

KC9TNH

Quote from: madball13 on January 23, 2013, 10:03:20 AM
Thanks for the info Wes, it's pretty much what I had thought. I just need verification sometimes that I'm not crazy.
Not a problem; I think K8HID brings up a valid point. I have an LDG tuner (and have had a couple of others) & they're great little boxes for most needs. But LEDs - even alot of them - don't often tell the whole story. So if you really want to see what the tuner has done on your radio's behalf then, yes:  radio - meter - tuner - antenna.  If the particular model of tuner has a bypass button/switch on it, you can always look "through" it and your meter will be seeing the natural SWR of the antenna.

You can always flip a couple of patches to place the meter in-line either way, and either has merit depending on the what you want to look at.  One just needs to understand what they're looking at & why.  An example on a multi-band antenna might be where you want to scroll from an area of a single band to another to see where your antenna is really in good shape.  The tuner may not feel the need to re-tune, but there might still be an important change that your meter on the antenna will tell you about, that a single green light won't.  Of course, with auto-tuners it also depends on what threshold you've set to be "acceptable" - i.e., when the tuner will quit trying to find a better match.
:)

Jim Boswell

Start with the basics. Are your coax jumpers good?
Lots of hams don't solder the shield when they assemble PL-259 connectors.
Next put a dummy load at the end of the coax opposite the radio and make sure you see a good SWR through the coax to the dummyload.
Ground? Any antenna tuner needs a good ground.
I have T/S an antenna tuner only to find the tuner good and the coax jumper the ham was trying to use was bad.
I hope this helps,

Lamewolf

Quote from: madball13 on January 22, 2013, 03:09:44 PM
I just picked up an 857 and a Z11Pro Tuner and i have a 1/2 wave 80M dipole with jumpers cut in for 10-20-40. I decided to do some testing with my tuner and with the dipole set at 20M i switch to 40, change the radio setting to PKT and key up. The radio flashes SWR as the tuner goes about finding a match. It eventually does but i notice my SWR meter is completely haywire, both needles pointing to the ceiling.

Anyone have an ideas?

I see your problem - the meter needs to go between the radio and the tuner, not after the tuner.  You want the meter to show what the tuner is doing to make sure its doing its job, so it has to go between the radio and the tuner.