SWR meter readings

[model 10]

The radio, an Ic 602, is putting out about 20 watts. In the SWR mode the needle reading varies. Right now it reads 10:1 in the rain. Yesterday (dry day), the needle would swing back and forth from 3:1 to 6:1 while holding down the tx button.
Here in the marina it is much worse than out in the open.
At low power (1w) the swr reading is steady at about 1.5:1

[transmitterdan]

Originally Posted by Ecos

The radio, an Ic 602, is putting out about 20 watts. In the SWR mode the needle reading varies. Right now it reads 10:1 in the rain. Yesterday (dry day), the needle would swing back and forth from 3:1 to 6:1 while holding down the tx button.

Here in the marina it is much worse than out in the open.

At low power (1w) the swr reading is steady at about 1.5:1

That would indicate that you have water getting in to the coax connection at the antenna or some other point with a splice.

Another possibility is the antenna itself is cracked and letting water get inside. But the coax connection is usually where leaks develop.

[Brian.D]

Agree with Transmitterdan. Most likely cause is a bad connector that is exposed to the elements. Whether water in the cable or corroded ground within the connector or intermittent connection with the ground within the connector.

I recommend replacing the outside connector and then sealing with self-amalgamating or vulcanizing tape.

If the antenna base is fractured or appears to have damage recommend replacing the antenna.

[continuouswave]

Originally Posted by Ecos

...an Ic 602, is putting out about 20 watts...

I think you are discussing an ICOM IC-M602 VHF Marine Band radio. Please let me know if that is correct.

Originally Posted by Ecos

In the SWR mode the needle reading varies. Right now it reads 10:1 in the rain. Yesterday (dry day), the needle would swing back and forth from 3:1 to 6:1 while holding down the tx button.
Here in the marina it is much worse than out in the open.
At low power (1w) the swr reading is steady at about 1.5:1

In order to assess the VSWR data, please inform us of:

--the length of the transmission line from the VSWR meter to the antenna;

--the type of transmission line, that is, an RG- number;

--the type of antenna and its location; and,

--the type of directional wattmeter being used to perform the VSWR measurements.

Generally at VHF when there is a long transmission line between the antenna and the directional wattmeter, any reading of VSWR of 3:1 or higher means there is nothing connected at the antenna end of the feedline or there is a serious fault in the antenna, in a connection, or in the transmission line.

That a VSWR reading varies drastically when there is precipitation is also an indication of a serious problem.

That VSWR reading vary with the power level is also an indication of a serious problem.

[model 10]

The antenna is new. The coax down the mast is newish RG 58, 45'. The other 25' to the radio is a 1975 coax with no RG number. The SWR Meter is a Workman. The jumper is 1' of RG-58 with gold connectors.
Sometimes the swr reading is all over the place. The needle swings back and forth. Sometimes it's steady. I get no watt indication at the base of the mast. The swr reading is about the same.
Out in the open we hear most boats but not all. Also the SWR readings out in the open were much better but never lower than 3:1.

[transmitterdan]

What model # Workman? Many of these are for CB radio. None of them are very accurate.

SWR should not be affected by the marina unless the antenna is less than a couple meters from a steel structure.

I don’t understand what you mean by no power at the mast.

FWIW RG-58 is a pretty terrible coax but it should not cause high VSWR. The other no-name coax or the splice between that and the RG-58 might be the culprit.

Were the connectors put in the RG-58 recently? If so, those are suspect. The 1 foot jumper could cause the power to fluctuate.

Gold connectors are not a sign of high quality. Good high quality connectors have silver plating. Gold coloring usually is put on cheap connectors to make them look expensive.

You said rain makes it worse. That’s a big red flag that the connector at the antenna is not well sealed to the weather.

VSWR of 3:1 is pretty much what you get with an open or short at the end of 50 feet of RG-58. This sounds like a bad connector to me.

[model 10]

I thought that you would see the wattage that made it from the radio to the connection at the base of the mast. I see no wattage at that connection.
The meter is a Workman model 104 and says it's for VHF.
There seems to be no new coax here so I used a piece of good RG-58 for a jumper and was lucky enough to get new connectors.
We have one of the shortest masts in the marina and we are behind a small flat island with palm trees. Out in the middle of the lake, everything was better.

[transmitterdan]

If you put the watt meter inline at the base of the mast and get nothing when transmitting then that says the cable (or connectors) from radio to mast base is bad. You don’t need the 1 foot jumper to do that test so that pretty much rules out the jumper.

The trees or hills around the boat do not affect VSWR. So I don’t think that has anything to do with it.

I would look closely at the connectors on the coax from radio to mast base. Something is probably wrong there.

[ohgary]

Originally Posted by Ecos

The radio, an Ic 602, is putting out about 20 watts. In the SWR mode the needle reading varies. Right now it reads 10:1 in the rain. Yesterday (dry day), the needle would swing back and forth from 3:1 to 6:1 while holding down the tx button.
Here in the marina it is much worse than out in the open.
At low power (1w) the swr reading is steady at about 1.5:1

I would first want to find out what kind of SWR meter your using. You need one thats good for VHF freq. a CB meter is most likley NOT going to work correctly. an SWR reading should be the same at 20watts and 1 watt. SWR is SWR, Amount of reflected power would be different but Ratio (The R in SWR) should be the same LOcation can affect SWR, but in general in a marine enviorment assuming you not next to some big freighter you SWR should be the same at the doc as at sea, If nothing it should be better at sea.
Rain should not affect the SWR much. More than likely You have water or a cut in your coax and it needs to be replaced.

[Brian.D]

Originally Posted by ohgary

I would first want to find out what kind of SWR meter your using. You need one thats good for VHF freq.

From post #7 above... "The meter is a Workman model 104 and says it's for VHF."

[continuouswave]

Based on your further information in your most recent reply, I understand more about the measurements:

--the directional wattmeter is an inexpensive consumer-grade device;

--the antenna is only described as "new", which is uninformative

--the transmission line length is at least 70-feet and consists of RG-58/U cable with some of the cable about 45-years old

--the VSWR readings vary during a very short interval of time ("while the PTT button is held")

My advice:

--discard all the transmission line
--replace with new transmission line using RG-213/U cable or possibly RG-8X or LMF-400
--obtain a better directional wattmeter whose readings will be more accurate and reliable
--re-test the antenna and transmission line with measurement of VSWR at the transmitter
--if the VSWR is higher than 1.5:1, replace the antenna

[tanglewood]

Are any of your connectors the solder-less style? Those are trash.

[Discovery 15797]

Originally Posted by tanglewood

Are any of your connectors the solder-less style? Those are trash.

Exactly...

First...before ripping out all your cables...carefully inspect each connector. (Including the connectors on the meter.)

If the connector is loose or 'spins' on the cable the connection is bad...replace it.

If it is a non-soldered PL-259 connector...it is trash...replace it.

If the dielectric (the material in the connector between the center pin and the outer case is cracked or 'burnt' looking this could be a cause of the fluctuating readings also. (This usually affects the female connectors more often.)

The wild and varied readings are likely caused by a breakdown in the dielectric between the conductor and shield either at a connector, or by water getting into the cable.

(IMHO...your Workman meter is just fine unless your job is installation of marine electronics, in which case you might consider upgrading. It may not be as accurate as more expensive meters, but for basic testing it will do.)

[continuouswave]

For some reasonably brief advice about VSWR measurement, transmission line loss effect on measurement, and coupler directivity effect on measurement, see

VSWR Measurement
VSWR Measurement - CONTINUOUSWAVE