Antenna Tuning

lionseye640 · **Posted:** Wed Apr 01, 2009 9:56 pm

I've got the SWR meter, but there were no instructions for it :evil:

Question is - how does it work? How do I use it to tune the antenna?

It's the Radio Shack SWR meter, and I tried using the .pdf instructions listed on the site, but still can't get the SWR below 3. Maybe I'm using it wrong ... I dunno

Any help would be appreciated!

JeepinJarhead03 · **Posted:** Wed Apr 01, 2009 11:34 pm

ya get the 45 dollar Radio Shack SWR meter? :shock:

hehe /drool

(ignore this part below in part, i didn't catch the part where you said you couldn't get it below 3 which implies that you've got a jumper and have hooked it up already hehe sorry)

did it come with a jumper? you hook the jumper to the radio, then to the swr meter, the stud should be labled as IN or Input, or RAD, you hook the coax that goes out to the antenna to the other stud that says ANT or OUT our Output

if its the meter that I'm thinkin about you have to do this:

hook it up, turn your radio on

put the mic somewhere where it won't move around too much so that every time you check it the mic is the same distance from the radio (not 100% sure why it changes depending on mic distance but it does) i used the cup holder for mine

turn the meter to FWD or forward, hold the push to talk button on your mic and turn the meter adjustment until the needle is on CAL then switch the meter to reflected and it will show the SWR

1.0 is perfect anything under 2.0 is ok, over 2.0 needs adjustment and 3.0 is dangerous to your equiptment

try to minimize how long it takes you to do the cal and the check incase it's over 3.0 on the first shot

post back or pm or whatever if you need any further help, i just spend 2 days getting mine corrected and tuned down to as close to perfect as i could get

remember, when adjusting the antenna, to replace the weather cap every time you do an adjustment, it affects the SWR as well, use some hand soap or something to lubricate the cap so it's easier to get on and off, and if you have a space heater in your garage or one of those square room heater fans you can use that to warm the tip to make it easier for removal

JeepinJarhead03 · **Posted:** Wed Apr 01, 2009 11:42 pm

here's a few tips to help get it below 3 as quick as possible

do the tuning with the vehicle off, alternator interference can drasticly raise swr on an untuned antenna but do it with the doors and rear hatch closed as if you were driving, when I was doin mine I'd just jump in the passenger seat and close the door

you also need to be as far away from buildings and overhanging trees as possible, if you do it next to your house your SWR will be super high and as soon as you move away from the house your antenna won't be tuned anymore - parking lots or something work good , a good 20-30 feet away from obstructions is usually good enough

antenna mistakes from my own recent retardation :lol:

, the nylon washer goes between the antenna and the mount, not between the coax and the mount

if you have a multimeter you can check for continuity (connection) between outside ring of the coax and the mount , between your mount and ground (the gold colored latches on the door jambs work good enough to test grounding)

if you take the antenna off the mount, you shouldn't have continuity between the antenna stud and the mount or ground

with the antenna on you shouldnt have continuity between the metal screw part of the antenna and the ground

with the radio side of the coax off, you shouldn't have continuity between the center stud and the ground, and should have continuity between the outer ring and ground

what type antenna are you using?

if Ch1 SWR is lower than CH40 SWR your antenna is too long and the tuner screw needs to be turned down closer to the tip

if its the other way around then it's too short and needs to be screwed out

if its super high on BOTH ch1 and ch40 then you've got a bad coax or an improper mounting configuration

JeepinJarhead03 · **Posted:** Wed Apr 01, 2009 11:51 pm

this diagram helped me when I was trying to remember which pieces were supposed to have continuity

http://www.firestik.com/Meas-SWR.htm

and click Testing Continuity at the top

also, if you have a multimeter you can put it on the lowest ohm setting and test individual components for high resistance

18ft coax shouldnt have more than 50 ohms for single antennas or 75ohms for duals, mine tested out to be under 30 ohms

I've got a huge Ham antenna type WQD quick disconnect and it was under 0.4 ohms, as was the antenna coupler was at 0.3 ohms, and the stud that the coax screws to was 0.2 ohms just for reference if needed

in my experience, if your antenna has a ground strap built in, do not use it, it causes continuity between the center post of the coax and the ground since it's for use on like fiberglass boats, rv's and what not where the mount doesn't have a ground

if you're mount doesn't seem to have a good ground, depending on where your antenna is mounted at you've got several low profile options, mine is on the roof near the passenger side in the front, i grounded mine with a wire ran to the weather stripping lip that is above the passenger rear door, just pulled the weather stripping back so i could get at the screw that holds the lip, took the screw out, replaced the orig. screw with a stainless steel self tapping screw (it doesn't have to tap anything, the threads match, but it was all i had, the orig. screws don't seem to conduct ground) put the eyelet connector behind the stripping and ran the screw in and put the weather stripping back on

lionseye640 · **Posted:** Thu Apr 02, 2009 9:53 am

The antenna is a Firestik 3' Firefly. I had one before that was tuned (someone else tuned it for me). The old one broke so I bought this new one. Additionally, I have added a spring and a quick disconnect.

From the antenna downwards I've got the antenna mounted to the disconnect which is in turn attached to the spring that's attached to the mount.

I guess my problem is more about how to operate the SWR meter. I think I'm doing it right, but since there are no instructions, I'm not really sure. There is a knob and three little switches on the front of the meter. I've figured out how to connect the meter between the antenna and the radio, but after that ... not so sure I'm doing this right.

JeepinJarhead03 · **Posted:** Thu Apr 02, 2009 11:26 am

it may be helpful to take a pic of the meter and post it

it sounds like you've got a meter that you have to calibrate before taking the reading, if so it could explain your high readings

it's typically flip the switch to FWD turn cal nob till the needle is on CAL and then flip switch to reflected and it shows the reading

combo meters are a bit harder to operate, most of the radio shack meters also do watt and field measurements to thus perhaps the other 2 switch functions

whenever ya get a chance post a pic of the meter and we will get this worked out for ya!

corwyyn · **Posted:** Thu Apr 02, 2009 11:35 am

Have you tried removing the quick-disconnect and the spring? Both of those will add length to the overall antenna system and may be why you can't get it tuned. Is it this meter: CB/High-Frequency Ham Power SWR Meter?

lionseye640 · **Posted:** Thu Apr 02, 2009 11:46 am

corwyyn wrote:

Have you tried removing the quick-disconnect and the spring? Both of those will add length to the overall antenna system and may be why you can't get it tuned. Is it this meter: CB/High-Frequency Ham Power SWR Meter?

Yes, that's the meter. If I remove the quick-disconnect and the spring, then tune the antenna, will I still be tuned if I put the quick-disconnect and spring back on? Or do I have to leave those off once I tune the antenna?

JeepinJarhead03 · **Posted:** Thu Apr 02, 2009 12:20 pm

it would have to be tuned again if you reinstalled the spring and QD

Kugellager · **Posted:** Thu Apr 02, 2009 1:33 pm

You have to tune for SWR with everything in the same configuration as you plan to run it. So your cable length, any connectors, springs, etc must be the same as you intend them to be for the final installation otherwise the SWR will not be correct and your signal propagation will not be at optimum. If the SWR is really bad (pegs the meter) you can damage the radio if you transmit for too long.

John
];')

lionseye640 · **Posted:** Thu Apr 02, 2009 1:38 pm

Ok - now how do I use this particular meter? It's the one in Corwyyn's post.

JeepinJarhead03 · **Posted:** Thu Apr 02, 2009 1:43 pm

hook your jumper from the radio to the transmitter jack

antenna coax to the antenna jack

turn on your radio

set it for 20W

put the switch on CAL

hold down mic button, turn knob till needle is on CAL

release mic button, switch meter to SWR and press mic again

I think maybe you've had your meter on Power which measures the watts of power your radio outputs instead of swr? just a guess

and youll be reading your SWR from the lower smaller scale

JeepinJarhead03 · **Posted:** Thu Apr 02, 2009 1:47 pm

oh, and once you get the meter working properly, check the SWR on CH1 and then check it on CH40

Ch1 SWR > Ch40 SWR = too short antenna
Ch1 SWR < Ch40 SWR = too long antenna

corwyyn · **Posted:** Thu Apr 02, 2009 2:17 pm

Yes you would have to re-tune once you put the spring and disconnect back on. I was just thinking that they might be adding to much to the antenna to get it tuned, so if you remove them and can get it down below 2:1 SWR then you would have an idea on where your problem is (probably should have put that in my first post). You might also need to really adjust the tuning screw, say a full turn or two; how much are you turning it right now?

lionseye640 · **Posted:** Thu Apr 02, 2009 3:03 pm

Well, I got it down to "2" for ch. 19, "2.5" for ch. 1, "2.5" for ch. 40.

Is this ok, or do I need to try and get it even lower? Also, the meter has a switch marked "avg/pep". There is no middle setting for this switch. Which do I put it to? I've got the other switch "2000w/200w/20w" set to "20w".

Thanks for all your help so far!

lionseye640 · **Posted:** Thu Apr 02, 2009 3:05 pm

corwyyn wrote:

Yes you would have to re-tune once you put the spring and disconnect back on. I was just thinking that they might be adding to much to the antenna to get it tuned, so if you remove them and can get it down below 2:1 SWR then you would have an idea on where your problem is (probably should have put that in my first post). You might also need to really adjust the tuning screw, say a full turn or two; how much are you turning it right now?

It's turned out so about 6-8 threads are showing (not 100% sure, KJ is outside, PC is inside). While trying to adjust I'd go 1 turn at a time, then tried less than 1 turn at a time.

JeepinJarhead03 · **Posted:** Thu Apr 02, 2009 3:06 pm

can leave that switch on PEP, it doesn't (or shouldn't) affect SWR in any way, it's for the POWER reading functions

icky 2.5

you're not parked like infront of your garage or something are you?

and how is your antenna mount grounded (i don't remember where you mounted yours)

lionseye640 · **Posted:** Thu Apr 02, 2009 3:13 pm

JeepinJarhead03 wrote:

can leave that switch on PEP, it doesn't (or shouldn't) affect SWR in any way, it's for the POWER reading functions

icky 2.5

you're not parked like infront of your garage or something are you?

and how is your antenna mount grounded (i don't remember where you mounted yours)

It's parked in the lot at work (no tall trees/buildings within at least 15 yards).

I've got it mounted by the passenger side rear taillight (near the flipper glass). I'm not really sure how/where it's grounded - the guy who installed it for me & I aren't on speaking terms anymore. All I know is that it worked before, was tuned properly at one time, I smacked the antenna on a parking garage, replaced antenna & added spring/quick-disconnect combo, now - 2.5.

JeepinJarhead03 · **Posted:** Thu Apr 02, 2009 3:21 pm

here's what I would do, get a sharpie and mark the screw as if it was a dial so that it's easier to count rotations

I would screw it down about 6 rotations and test it again, you're basically looking for short or long symptom antenna before you can get accurate adjustments

have to do something so that it starts registering either Ch1 or Ch40 as higher or lower than the other and then you can figure out which way to go from there

it's a pain! we know!

your nylon washer is on top of the mount right? between say, the mount and the spring or QD whichever you put first

if it's not then when you key the mic, the 'juice' will feedback through the mount and ground and find its way back to the radio which will give high untuneable SWR's

it's a whiteish washer lookin doohicky

if it's mounted there he probably either ran a ground wire to a internal bolt in the tail section or it got ample ground being screwed/bolted to the body

lionseye640 · **Posted:** Thu Apr 02, 2009 4:06 pm

JeepinJarhead03 wrote:

here's what I would do, get a sharpie and mark the screw as if it was a dial so that it's easier to count rotations

I would screw it down about 6 rotations and test it again, you're basically looking for short or long symptom antenna before you can get accurate adjustments

have to do something so that it starts registering either Ch1 or Ch40 as higher or lower than the other and then you can figure out which way to go from there

it's a pain! we know!

your nylon washer is on top of the mount right? between say, the mount and the spring or QD whichever you put first

if it's not then when you key the mic, the 'juice' will feedback through the mount and ground and find its way back to the radio which will give high untuneable SWR's

it's a whiteish washer lookin doohicky

if it's mounted there he probably either ran a ground wire to a internal bolt in the tail section or it got ample ground being screwed/bolted to the body

Yeah, the washer is on top of the mount. I've got mount, white washer, metal washer, spring, quick-disconnect, antenna (in that order).

I did at one point have 1 higher (and also lower) than 40, and vice versa. Then, when 19 got down below 3, both 1 and 40 were at 2.5.

Jayme - want to help tune an antenna some time this weekend :lol:

Antenna Tuning

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