Could structures and metal gutters etc in close proximity of a vertical 10 meter antenna cause some power being reflected? I noticed if I increase my power from about 4 watts to 12 my swr's increase a small amount, from 1.5 to 1.7. My antenna does have some metal gutters and roof line just under it about 2 feet away. I am thinking of adding one more 5 foot mast to get it higher, I only have it about 10 foot off ground level and the roof line and other things are just under that. It works well because I have talked all over the country with it and even to S. America with the dx being the way it is lately with just about 25 watts. I also can talk local about 20 miles or so across town. I have new rg213u and the antenna is a new ar10 ringo.
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antenna obstructions causing swr problems?
- Thread starter tvrc18
- Start date
Metal objects below the ringo should not affect it significantly.
As for SWR varying with power, there are a couple of possibilities.
You ruled one out by using rg213 (coax loss can make your SWR look better because the reflected power is attenuated).
What kind of SWR meter are you using?
Do you have a choke in your coax? (Several turns of coax to reduce radiation by the coax braid.)
I would start with a choke in the coax, say 6 or 8 turns about 10 to 12 inches in diameter.
Dave_W6DPS
As for SWR varying with power, there are a couple of possibilities.
You ruled one out by using rg213 (coax loss can make your SWR look better because the reflected power is attenuated).
What kind of SWR meter are you using?
Do you have a choke in your coax? (Several turns of coax to reduce radiation by the coax braid.)
I would start with a choke in the coax, say 6 or 8 turns about 10 to 12 inches in diameter.
Dave_W6DPS
I think my swr meter is a workman, not sure of the model but it is a mid-range to cheapo cb style. I also have a radio shack that shows about the same thing. I have a feedline current choke from dx engineering on the way to see if it helps out. It is supposed to help keep the rf in the coax and going out to the antenna. I had a Buxxcom line isolator in line but it seemed to be giving some problems so I took it out of the feedline. It did make the antenna more broad banded and lowered the swr a small amount on 10 meters. My home only has 2 prong outlets so grounding could be a problem maybe. I am using a power supply to run a mobil radio and the supply only has a 2 prong cord on it anyway. The current choke is also designed to help with less than perfect grounding conditions. I do have a ground rod at the base of the antenna and the mast is strapped to a chain link post that maybe grounded some also.
B
BOOTY MONSTER
Guest
Are you recalibrating that SWR meter after the change to higher power? And in what mode are you checking that SWR, AM, SSB, FM?
That really isn't much of an increase at all, and I doubt if those gutters, etc, are any significant problem.
- 'Doc
That really isn't much of an increase at all, and I doubt if those gutters, etc, are any significant problem.
- 'Doc
That small "increase" is insignificant. It may well be caused by the diodes in the circuit conducting a bit better with the greater voltage applied when you increase power. However, SWR itself does NOT increase with an increase in power; it's the ratio of forward power to reflected power.
And as 'Doc said, don't forget to readjust the meter every time you change power level or change frequency by more than a couple of channels.
And as 'Doc said, don't forget to readjust the meter every time you change power level or change frequency by more than a couple of channels.
Yes I recalibrate the meter before each check and I use am mode to do the test. Someone once told me to use the least amount of power to get a full scale reading for meter calibration then do your swr check. He also said trying to check swr's with an external amp turned on was no good either because the diodes in the swr meter were not rated for that kind of power no mater what type of meter it was. Most antenna analyzers like a mfj 259 use real low power in milli-watts to do the swr check and antenna test. I am not sure if he was right or not but had been into ham radios for 40 years. I fIgured a few more watts should not make a difference but it did in my case by a small amount.
Your friend was partially right, but not completely. Most SWR meters are in combination with a watt meter. If the watt meter is capable of handling the output power of an amplifier, then the SWR meter will be capable of a correct reading also. Your friend was right for as far as he went, he just didn't go far enough. Those diodes don't handle all the power through that meter's circuit, neither does the meter it's self, they both are 'shunted' to raise their power handling abilities. That's how all meters work (well, almost all of them).
I't a very good idea to use lower power to do measuring like this, it's just one way of preventing a failure because the SWR is too much to handle otherwise, something will be destroyed.
SWR is the -> ratio <- between forward and reverse power. If you increase one you increase the other, but the -> ratio <- remains the same. (Doesn't really measure power (watts), but does measure voltage, which will amount to the same thing.) So how much power is used to do that measuring doesn't matter, and the ratio between the forward and reverse voltages do NOT change with power.
If the difference in SWR readings was significant then there would be reason for concern. The difference you are seeing just isn't significant at all. Don't worry about it.
- 'Doc
I't a very good idea to use lower power to do measuring like this, it's just one way of preventing a failure because the SWR is too much to handle otherwise, something will be destroyed.
SWR is the -> ratio <- between forward and reverse power. If you increase one you increase the other, but the -> ratio <- remains the same. (Doesn't really measure power (watts), but does measure voltage, which will amount to the same thing.) So how much power is used to do that measuring doesn't matter, and the ratio between the forward and reverse voltages do NOT change with power.
If the difference in SWR readings was significant then there would be reason for concern. The difference you are seeing just isn't significant at all. Don't worry about it.
- 'Doc
Sounds to me that your antenna is on the fringes of being resonant, you may need to check the length of the vertical radiator and bring it closer to center of the frequency you're operating it at.
When you get near the antenna's bandwidth edges sharp rises in swr is common.
I got my DX Engineering feed line current choke and installed it and it made a big difference. The swr's went down a few tenths and now it does not matter what power I use it is pretty much the same 1.5 or less. The Ringo is not very broad banded and in the 11 meter band I could not get the swr's below about 2.5 but this choke has made them acceptable at least on one radio, the other still reads high in part of the band. Not sure what that is all about. I don't see how that choke can drop the swr's way away from the sweet spot of the antenna. I don't plan on using it in anything but the 10 meter band but wanted to see if it made a difference in the cb band.
Well the problem is back. I think I have rf ground issues and not sure what to try. My home has 2 prong outlets and no ground lug. I have 2 power supplies, one for the radio and 1 for a amp. The swr's seem to change daily and go higher with more power. I have the current choke that seem to fix the problem for a day or so but now have tvi and rf bites me when un screwing the coax to try different set ups. The tingle gets me after I turn off the radio and moving jumpers around to try different hook ups. I even noticed while stabbing the antenna back on the mast after a quick check a small arc from the antenna to the mast. Still was able to dx today to a few people in California and elsewhere with contesting going on this after noon. Thinking about an artificial ground but is sounds like it does not work well on verticals. Maybe a battery is the way to go.
- No one is chatting at the moment.
...runna pile-up on 6m SSB