Can we talk SWR meters for VHF?

[FIREUP]

Hey gang,
Still sort-a new to HAM stuff even though I've had my Tech ticket for over 10 years but, just haven't really dove into it. I just recently installed an older ICOM 2000 in our '15 Jeep JKUR and, I put the antenna on the back of the Jeep and ran the coax all along the floor and up the pillar at the right front and in to the radio, in front of the rear view mirror. Now, with all that being said, since the radio is strictly a VHF unit, I followed the cutting instructions for the NMO 150 CHW VHF antenna. I cut the mast to the specified height, for 146 Mhz. The boys at HRO stated that if you cut it to those specs. for 146 Mhz, it will work fine for either side, 144 or 148.

Now, this brings me to the SWR factor. I took the Jeep over to a buddies so he could hook up his SWR meter and, check my output power which, I was not sure of since there was some confusion as to whether or not my radio had/has three power levels or not. It does. Now, when he hooked up his SWR, we could not get any form of an accurate reading because he was unsure of how to adjust it.

So, with all that being said, I might be buying an SWR meter for VHF. But, may I ask, is there a reasonably priced one that is not all that difficult to use? I know with C/Bs, you hook it up and if there's a zero-ing out knob, you do that and then, key the mic on Ch 1, observe the reading and then key the mic on Ch 40 and observe the reading. But, at some point, you're trying to get the SWR to 1 to 1.5, correct? so, is it the same kind of setup and operation with a HAM? Any help here will most certainly be appreciated.
Scott

 

[mmckenna]

Yes, it's just like checking SWR on a CB radio.
Except different frequencies and more power.

You can check your SWR down near 144MHz and up near 148MHz and extrapolate if your antenna needs to be lengthened or shortened.

As for SWR meters, you do want one that specifically covers VHF, but you may want to consider one that covers the UHF band as well.

Diamond makes some decent ones. I used to have an MFJ one that was probably $30 or so back in the early 90's that worked well enough.

 

[dispatch235]

I use a cross-needle Diamond meter.. around $80, no fiddling with calibration knob and switches... just key the radio and gives you the swr and power output.

Diamond SX-20C and SX-40C SWR Power Meters

 

[spongella]

I don't have a meter, but use an MFJ-259B, a general coverage antenna analyzer from 1.8 - 170 MHz. Other models cover UHF.

There's a plethora of meters on the market these days to fit your needs and budget. In the past I've used Diamond and MFJ meters, all work nicely. You might want to check the eham.net website for user reviews of meters.

Funny that some CB radios (and some ham HF xcvrs) have built-in SWR meters but I can't think of one ham VHF/UHF radio that has/had one. Have fun on VHF/UHF.

 

[majoco]

A zero-ing out knob? Simple VSWR meter power scales are frequency dependant so the knob is used to set full scale on the power meter and then read off the SWR on the other meter. The lower the SWR is better but below 2 is good enough, the lost power is undetectable at the receiver station - the truck parked beside you will more effect! If you want to measure the actual power then you need the chart that came with the meter to set the knob to a scale, then you read off the power - the SWR reading at that time is meaningless.

 

[tdeater]

The basic SWR meters for VHF work the same as they do on CB. The simplest meters will have a set knob, you have it in the set mode, key up and adjust that knob to wherever indicated on the meter (like a spot marked set, or something like that) If it is not marked, then full scale on the SWR scale. Then you un-key, flip the switch to SWR mode then key up again. Now it will show you the SWR. If it is a better SWR on the top end of the band, your antenna is too short, if it is better on the bottom, it is too long. Beingon the ham band, make sure you ID when you are done on a frequency, and do it on low power.

the cross point SWR meters meter forward and reflected power in watts, and where the needles cross is your SWR.

 

[KE5MC]

Scott,
Good to see you getting back in...

I use one of the Diamond SX models, nice as it’s a cross needle type meter that needs no adjustment other than range select.

Friendly reminder about your ticket. They are good for 10 years and easily renewed if under the time limits.

 

[KD2FIQ]

I have the RigExpert AA-230 Zoom. It's pretty nice. Goes to 1.25 meter but not 70CM. Does all HF bands as well. Connector is N style which isn't common for me so I need to use the provided adapter to go to SO-239.

 

[W5GX]

I use the MFJ-874. Works like all the other meters, and has been good. Each model should have instructions on operation.

One note - test the SWR of your antenna "as installed", before making any cuts.

What model SWR meter is your friend using?

 

[jwt873]

I bought a Surecom SW-102 once just on an impulse.. The price was right and I wondered how good it would be. https://www.amazon.com/d/Radio-Scanners/Gam3Gear-Surecom-SW-102-Digital-125-525Mhz/B01D86IKIQ

It's actually not bad at all. The digital read out displays frequency as well as SWR and power in Watts from 125 to 525 Mhz. I've checked SWR readings on 2 meters, 220 mHz and 440 mHz. -- To see how accurate the SWR was, I compared the readings with my Rig Expert AA-600 and it's pretty well bang on.

 

[FIREUP]

Well gang,
When I purchased this set of components for setting up my antenna and cable, I was not aware of certain things. I was being guided by the HRO tech that described what I needed. So, he sent all of what he suggested. Now, the antenna is a PulseLarsen NMO 150CHW. It comes with cutting instructions for cutting to appropriate length, per given parameters for a small range of frequencies. In my case, since the radio is only a VHF unit, I was told to cut the mast for 146 mhz which, would also take care of 144 and 148. Ok, so far, so good. But, If I really wanted to tune this antenna, I'd need an SWR meter which, you boys have suggested various ones.
Well, as of this point in time, it appears, based on the cut I made, that the reading I got from a borrowed SWR meter, was 1.65 or so, to 1. I'm told that's pretty good for a starting point. But, here's the kicker. That mast, .100 in diameter, only goes into that NMO mount, just less than 1/8" below the Allen set screws that hold it in place. There is absolutely no room for any form of adjustment. If I try and raise that mast, for adjustment, it immediately rises above the level of the two Allen head set screws.
Now, in the cutting instructions, it shows that antenna, mounted to a SHOCK SPRING. The instructions also say that, "This cutting chart, only applies to NMO antennas WITH a shock spring. But, in the cutting chart, it has two columns, one with and one without the spring. Sure glad they know how to write and what applies and don't apply
Anyway, the instructions say to make sure the antenna mast is all the way down inside the spring, then make the measurement for cutting. But, the mast is assumed to be over 3/4" inside the spring. They say that, there is that much inside, just in case the antenna was cut too short. So, my question is, do I need a spring, will it allow for better adjustment and, other than going to HRO, Amazon doesn't appear to have the correct spring for this NMO PulseLarsen 150CHW antenna. Can I just check threads on both ends of a spring to see if they'll match and purchase one that will work or, do I have to get the specific one from HRO, for my antenna? I'm really only considering this because I'd like to better match the SWR, not because I actually need the spring.
Scott

 

[mmckenna]

The spring is handy if you expect to hit a lot of tree branches, parking garages, low flying aircraft, etc...

You don't need it.

It goes between the "cone" that the whip attaches to and the coil base, so it won't change how much you can move the whip up and down.

The cutting chart, as you saw, should give two lengths, one for -just- the whip and one for the spring (which works out to the same number minus the length of the spring, roughly).

You'll probably have a hard time finding a spring that fits the thread. Good idea to stick with the factory stuff. Often the springs have a piece of wire braid on the inside connecting the bottom to the top.

 

[FIREUP]

Hey Mmckenna,
As usual, very much appreciate your response here. The instructions say that the cutting measurements are based on, putting the mast, ALL the way into and bottoming out in the spring. And then it goes on to say, this will allow about 3/4" for adjustment, just in case you cut the spring short". This is all I'm concerned about. As stated, I did cut the mast, to the measurement W/O the spring, for 146. So, I'm assuming all is well, for those frequencies 144-148. Based on where the antenna is mounted and, the fact that, it's a .100 thick mast for 40", I've got plenty of flexibility for it, just in case of those low flying aircraft, teee-heeee.
Scott

 

[mmckenna]

Ah OK, misunderstood.

40 inches sounds about right.
A quarter wave 2 meter antenna will be a bit over 19 inches. A half wave (2/4th's) would be that right around what you are showing.
1/2 waves a fairly broad, and cutting for 146 would be what I'd do. It'll probably do just fine 144-148, and probably beyond.

 

[brndnstffrd]

If its just not pushing down far enough in the base, but but the base has the room for it, have you tried running a file over the cut part to remove the burr? I've seen it before where you don't think there is a burr but then you go to put the antenna in and it wont seat all the way down. Also i'm not familiar with that specific antenna but if it is one of the black antennas, it is a good idea to scratch off the coating where the antenna goes inside the base.

 

[FIREUP]

Hey guys,
Well, I know it's not a burr on the end of the antenna. I cut that antenna with a small disc on a dremel. Then, I very lightly, applied that cut tip to the fine wheel bench grinder I have. Once the rough edges are ground down, I hit it with a buffer that I use to polish stainless with. The cut edge, was a polished, squared off, perfectly smooth end when I got done with it. Nope, no burrs. And, it's not black. It's stainless.

 

[mmckenna]

You can try loosening/removing the set screws on the cone and clear out the hole with a suitably sized drill bit by hand. Just to make sure there isn't any debris inside there.