Swr problem? 102" whip

[ogdoa]

I have my 148f hooked up to a 102" whip in my 99 explorer. With my old radio the swr was 1.2. With the new radio it is 1.7 across the band. I do not understand this. Shouldn't it be the same for both radios and trimming the antenna wont help because it is even across the band. I tried 2 different external swr meters with the same reading. I know a 1.7 is nothing to worry about but it bugs me because it should be lower. I also know that the swr likes to swing with that whip when driving down the highway.

[BruceBruce]

how is it all put together? and what is the condition of your coax connected to the radio side, if you only messed with the radio perhaps you are having some issues on that end. In my experience coax ends never last forever. Take a picture of the mount and antenna base and the coax for us if you can please.

[WK2]

You are 6" short of the 108" length needed. Either add a 6" pot belly spring or a 6" GP riser. Once added take another reading and you might see it has lowered to almost nothing.

-- Wednesday, 01 July 2015, 19:10 PM --

Just went back through the forums and noticed you are running a spring. I would also check the coax cable run. All you need is 2 small alligator clips and a piece of wire along with a digital multi-meter. Run the piece of wire between the 2 alligator clips and place one on the inner coax pin of the connector (positive) and the other to the outside of the connector (negative/shield). now go to the other end of the coax and place you positive probe on the inside connector and the negative to the outside and take a Ohm reading. If all is good you should read 50 Ohms. Also do a continuity check as well - pos-to pos (reading and beep on you meter) , neg to neg (reading and beep on you meter), pos to neg opposite ends of the coax (should not get a reading or beep). I hope that helps.

-- Wednesday, 01 July 2015, 20:22 PM --

One last thing to check in your coax run is anywhere the coax goes from the inside of the vehicle to the outside that the outside skin of the cable hasn't been rubbed through and that the shielding is now making contact with the body of the vehicle. Also check anywhere the coax might touch metal because the vibrations can also rub the skin off the coax. I have seen that happen in Military Hummers where the grommet has dry rotted and the coax started rubbing on the hole through the body.

[231]

I have my 148f hooked up to a 102" whip in my 99 explorer. With my old radio the swr was 1.2. With the new radio it is 1.7 across the band. I do not understand this. Shouldn't it be the same for both radios and trimming the antenna wont help because it is even across the band. I tried 2 different external swr meters with the same reading. I know a 1.7 is nothing to worry about but it bugs me because it should be lower. I also know that the swr likes to swing with that whip when driving down the highway.

I'm confused...are the external meters also showing 1.7:1 or is just the 148? If the radio is the only thing showing it pretty likely the meter isn't quite right. The old 148's meter was a known problem...but about the only bad thing I can say about them. That being said, if indeed it's showing 1.7:1 on the external meters then as mentioned it would be nice to know if the antenna is too long or too short. If you don't have an antenna analyzer that can usually be accomplished simply by checking the standing wave further out of band (being it's the export model) and seeing. Mounting location can play a big part as well...and if you plan on running an amp down the road you'll want it lower anyway (under 1.5:1 typically).

But you are right...1.7:1 isn't usually hard on finals. But I can't remember if that radio has built in amplifier or not? Seems to me the old 'F' was still a 4w AM / 12w SSB with more frequencies...but can't remember? If that's true they'll handle 2:1 without a problem. I'm like you though, I like having a reasonably low standing wave...mostly because of running amplifier and getting a little long winded. LOL

Let us know what you find out.

231

[ogdoa]

Ya the 1.7 is flat across the band. I'm gonna hook up the analyzer tonight and see what I get. I get a 1.7 on all the meters. external and internal. The only thing I changed is the radio. I checked the coax and it tested great. The mount is the same mount I have been using. It is one I made a couple years ago to get up over the luggage rack on the explorer. I'll post a picture later.

-- Thursday, 02 July 2015, 9:09 AM --

P7020719.JPG

That is the mount.

[WK2]

I see a rusty spring which might be the culprit. Rust = Little to No RF or bad connection. Also the wire inside the spring might be going bad as well. I would give that a try.

[MDYoungblood]

I would say lose the spring too. They themselves don't radiate, there is a braided wire inside that connects the two ends, they have a tendency to break free. Not all radios are exactly 50ohms at the antenna jack so that could be the reason for the difference in SWR with the two radios, using the antenna analyzer will give you the answer that the antenna is at resonance.

3's

Greg

[ogdoa]

I see a rusty spring which might be the culprit. Rust = Little to No RF or bad connection. Also the wire inside the spring might be going bad as well. I would give that a try.

Took the spring off and checked the connections including the wire. Everything tested out good. It doesn't look like it but that spring is less than 2 years old. I paid a small fortune for it at rat shack. I sanded all the connections and put it back on and its still at 1.7. I did all this when I put the new whip on. I will be running the analyzer this afternoon and get the results on here. I also have a brand new spring I am going to put on there and test it before and after. I'll let ya know if it changes anything. Thanks for the advice.

-- Friday, 03 July 2015, 7:26 AM --

Well I figured it out. It was the radio. I hooked up a different radio and the swr came down. Pulled the cover on the 148 and the wire going in to the coax connector came loose again. I dont know how that would affect an external swr meter but it did. Replaced the connector and soldered the heck out of it. Swr is down to 1.2. wooot.