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  #1  
Old 06-01-2009, 08:01 PM
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Unhappy Need Help Setting Up Radio


First off I am new here! Glad to meet you all!

I am working very hard to get a radio installed into my vehicle and it's been a real nightmare. I want to get as much range and performance as possible using the equipment I currently have but no one ever seems to give me a strait answer on anything related to CB.

I currently own the following gear:

Radio:
Cobra 29 LTD NW

Linear:
Texas Star DX 250HDV

SWR Meter:
Dosy TR-1000

Antenna:
Cobra HG-A2000

Could someone please detail the process of getting the following hardware to play well together and generally perform the way I want it to? No one will help me install it or answer even a simple question like where do I play my SWR meter. Before or after the Linear? Also what do I do about the SWR Cal on my radio? Do they both need to be used? How do I avoid jacking my radio up while trying to figure this out?

Any help would be much appreciated!

-Neuro


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Old 06-01-2009, 08:25 PM
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First of all, I would hook up the radio and the antenna alone - w/o the linear and the SWR meter. Get the location of the radio taken care and mounted. Then put the antenna on the vehicle. The SWR meter buit into your radio might not be as good as the dedicated SWR meter you have, but it will get it close enough to know that the antenna doesn't have any issues.

Before I go any farther - do you know how to use the SWR meter that is built into the radio? If you do, you are almost done.

Check the SWR with just the radio and the antenna with the doors and trunk closed - and far enough away from any buildings or other cars that might affect the reading. Adjust/check the antenna SWR on ch 1, 20, and 40. I would try to get the SWR as low as possible on ch 20 - that is a happy medium.

If you have adjusted and rechecked the SWR on the antenna to a satisfactory 1.5 to 1 - or less - then it is time to put the linear in. A 250 watt linear is going to need some sturdy guage wire to supply the amperage in order to operate correctly. Run a 8 guage wire from the +/battery to the +/red wire on the linear. Run a -/ground 8 guage wire to the frame and from the frame to the -/black wire of the linear. Don't operate the linear unless everything has checked out OK and the engine is running. Running the linear with the engine off will drain you battery down before too long.

Use a 3 ft or 6 ft coasx cable/jumper between the linear and the radio. Re-check the SWR from the radio SWR meter. If the SWR is 1.5 to 1 or less - you are ready to go.

BTW- I am not responsible if you don't assmble and adjust everything correctly. I urge you to find some local radio operator that can make sure that the job is all done correctly. Once he has done the job right, you will have learned how it is done and what to do if something becomes a problem.
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Old 06-01-2009, 08:40 PM
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First off thank you for replying! So a stand alone SWR Meter serves no purpose? Also the local radio techs are really expensive and tend to not know what they are doing. I had one of them tell me to use an orange extension cord to wire my amp into my car....

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Old 06-01-2009, 08:48 PM
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I don't know much about the Cobra antennas. I've never owned one or used one. I'm not sure it will be satisfactory for decent receive and transmit. It may/may not be the 'weak link' in your system. Maybe someone else can chime in here and say something either way.
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Old 06-01-2009, 10:21 PM
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The stand alone SWR/power meter is a good idea for testing. The meter built into the radio is good to get you close, but they're not all that great. If you have a 3' coax jumper, you can put the external meter inline to help you adjust the antenna more precisely. This is really what you should do first, as Rob suggested. After you get the antenna adjusted the way you want, then you can take it out of line and put the amp in it's place. If you have an extra jumper, you can put the meter in after the amp to measure the output of the amp. Whether or not you leave the meter inline is a matter of space/convenience, etc. Personally, I always take it out after I have everything set up. Oh yeah make sure that Cobra antenna can handle the power output of the amp.

So to repeat: start the install with radio mounted, antenna mounted, coax run between them. Put the meter inline to adjust the antenna until the SWR is low. Don't even think about installing the amp until the antenna is good. THEN put the amp inline. Don't use extension cord wire for the amp...use about 8ga or so.

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Old 06-01-2009, 10:29 PM
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I i may repeat some things that Rob said, but this should walk you through it.

a couple of things first:

1. im assuming that your equipment all works properly.
if you bought it used, there is a chance that it does not.

2. your radio might have too high of a deadkey for your amp.
(the deadkey is the amount of power ((watts)) that your 29LTD puts out when you key the microphone but do not speak into it. a "dead" key)

if it does, then you will have to modify the radio to work with the amp.
the mod needed is called a "swing mod" and is pretty easy to do.
we will deal with how to do it in another thread.

lets get started.

mount the 29LTD where you want it, and run the positive power wire right to the positive terminal of the battery. (MAKE SURE to fuse the positive lead right at the battery to prevent fires)

find the closest spot to where your radio is mounted that is part of the chassis of the vehicle. (make sure its not just a small metal panel somewhere but actually is attached to the body and frame of the vehicle. a good determiner is if you see other things grounded to that same metal.)
attach the negative wire from the radio to this metal keeping the wire as short as possible. around a foot is great, try not to make it over 2 feet or so.

now you want to mount your antenna.
i dont know of that cobra antenna you have is a magnet mount or not, but if it is, just stick it in the center of the roof of the vehicle. if you stick it on the trunk or some other low spot, you will not get out as far and might have SWR problems.

if its not a magnet mount antenna, then hard mount it, but you might want to start another thread with all the specifics of your particular installation and get some help mounting it properly.

ok, now connect the coax from the antenna to your external SWR meter using the connector on the back that is labled ANT (ANTENNA).
you need to have a couple of coax jumpers for your install.
dont buy them at radio shack.
buy a couple on ebay that are either 3 foot or 6 foot, whatever works for your install. they should be made of RG-8x (also called RG-8 mini) coaxial cable.
make sure whoever you buy from actually solders the connectors on.

using one of your jumpers, connect one end to the SWR meter using the connector on the back that is labeled RADIO, or, INPUT, or whatever.
connect the other end of the jumper to the back of the radio.

now, turn the radio on, and set it to channel 20. make sure the CB/PA switch is in the CB position.
turn the DYNAMIKE (microphone gain) all the way down. (counterclockwise)

SWR SETTING PROCEDURE:
now set the knob on the TR-1000 meter to "SWR SET".
look at the meter on the TR-1000. you will see three different scales of measurement. the one that goes from 0 to 1000 is for measuring wattage.
the middle one is for measuring SWR (Standing Wave Ratio, which we are working with now), and the bottom one is for measuring modulation.

key the microphone and using the knob on the TR-1000 labeled "SET ADJUST" turn the knob until the needle goes all the way over to the right and aligns with the mark on the middle scale labeled "SWR SET".
unkey the mic and be sure not to bump the SET ADJUST knob during these next few steps.

turn the switch on the TR-1000 to the "SWR" position, key the mic, and make a note of the reading on the meter. (write it down!!!)
ideally, the meter would not move to the right at all, that would be a perfect 1 to 1 ratio. (almost unattainable in the real world.)
anything over 2 means you might have an antenna problem, but we'll get there later.

now, set the radio on channel 1, and go through this whole SWR SETTING procedure again.
make a note of the reading.

set the radio on channel 40 and go through the whole SWR SETTING procedure again.
make a note of the reading.

now, if your reading is higher on channel 1 then your antenna needs to be adjusted to be a bit longer.
if its higher on channel 40, the antenna needs to be a bit shorter.

adjust the antenna in 1/4" increments. you will have to re-calibrate the meter each time you make any change, whether it be changing the channel on the radio or adjusting the length of the antenna.

try to get the SWR to be about the same on both channel 1 and 40 and it should be below 1.5.
if you cant get it below this, then you either have a mounting issue or need a new antenna. ( i highly recommend the wilson 1000 or 5000)


i have to go now, but will continue with this tomorrow evening.

good luck and please post your results if you try this before i continue.


later,
LC
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Old 06-02-2009, 12:52 AM
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WOW, man yeah thanks, I am awaiting the next part of this. This is what I am looking for! Thank You

Edit: What do I do about the SWR Knob on my radio when using an external meter?

My Antenna Specs:

Cobra HG A2000 High Gear CB Antenna
Power Handling Capability: 6000 watt
Construction: 24/8 PowerCoil with 24 carat gold-plated 8-gauge copper coil
Frequency Range: 26-30 MHz
Connector: SO-239
Type: Matched braided coaxial cable
Part Number: HG A2000



Last edited by Neuro; 06-02-2009 at 12:08 PM.

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Old 06-02-2009, 04:15 PM
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the SWR CAL knob on your radio works exactly the same as the "SET ADJUST" knob on your TR-1000.
its job is to calibrate the SWR meter so that the reading will be accurate.
you ALWAYS re-calibrate an SWR meter any time you check your SWR.

your 29LTD has a built in SWR meter, and yes, we could have done the whole antenna tuning thing by connecting the antenna directly to the radio and using its SWR meter.

the reason an external meter is better is because they are more accurate, and much easier to notice small changes on.

if you want to do a quick test of the radio's built in meter, to see if it matches what the external meter is telling you, just do an SWR reading on the external meter just like i showed you in the last post.

now, without changing anything else, set the switch on the radio to CAL, key the mic, and adjust the SWR CAL knob on the radio so the needle aligns with the mark on the meter labeled CAL.

unkey the mic, switch the switch on the radio to SWR, key the mic, and compare the readings on the radios meter to the reading on the external meter.

the SWR CAL knob on the radio is only for the meter on the radio and will not do anything to the external meter.


ok, before i continue; that antenna looks to be ok for what you want to do.

ive never used one, and dont know how well they are built, but if it works the way its supposed to, it should be fine.

dont forget to give the antenna the 90mph test!
you have to find out if that magnet mount will stay on at high speeds.
you dont want it falling off and hitting another car.

also, the location you have chosen to mount your antenna will result in a radiation pattern that favors the front of the vehicle.
what i mean by that, is that you will get out further in the direction your vehicle is facing, and wont get out as well towards the back of the vehicle.

if you put the antenna in the center of the roof, you will get out well in both directions.

now to pick up where we left off:

you have just set the SWR of your antenna, and still have the meter hooked up in line between the radio and the antenna.

turn the switch on the TR-1000 to the position marked "30".
this is the 30 watt scale on the meter. if you look just under the numbers going from .3 to 1000, you will see another set of numbers going up to 30.
use this scale when reading the output of just a radio, and use the position marked "1000" when reading the output of a linear amp.

that makes sense doesnt it?

now, key the microphone and note the wattage reading.
most likely it will be somewhere around three to four watts.

turn the DYNAMIKE (mic gain) all the way up. (BTW, unless your radio has been modified, you should always leave the DYNAMIKE all the way up. it doesnt really increase your talk power, it just decreases it if you need to for some reason, like checking your SWR)
now key the mic, and, with your mouth about 1" away from the mic, say, "TEEEEEEESSSSSST" for long enough to get a reading on how far the needle on the TR-1000 swings to the right while you are speaking.
(FYI, you should always talk with your mouth about an inch away from the mic for best audio)

what you have just measured are your "deadkey" wattage, and the "swing" of the audio.
write these numbers down and tell me what they are, phrasing it this way:
"my deadkey was X watts, and the swing was XX watts."


now for the amp hookup.

there are way too many variables involved in setting up a linear amp in a car for me to go over in one thread. the amp may have a high SWR for some reason, it might mess with the vehicle's computer, etc...
RF is a finicky beast to say the least.

i will tell you how to hook it up, and if problems arise, you might have lots of reading and learning to do to get it to work right. ok?, ok.

so, first pick where you want to mount the amp.
my suggestion is to mount it within a few feet of the radio, in a place that will allow air to pass over the heatsink fins.

run the positive wire from the amp directly to the positive terminal on the battery, and be sure to adequately fuse the wire right at the battery to prevent fires.

if the wire length is 10 feet or less, you can use 8ga. wire.
if the length gets over 12 feet or so, you should step up to 4ga. wire.
car stereo places have the right stuff, and will also have the correct fuse holder.

keep the ground wire on the amp close to a foot in length, and really try not to go much over that.

you need to find a REALLY good ground to mount the ground wire to.

sometimes a seat bolt will work, but many times these bolts have glue or adhesive on them, and dont make a very good connection with the chassis of the vehicle.
you may have to drill a hole to get a good ground connection.
just be careful not to drill into your gas tank, transmission, etc... LOL

whatever location you choose, you will have to sand off some paint and make the connection all bright and shiny metal to metal.

try to find some pics on the net of how others have done theirs.

now to connect the amp inline with your radio and antenna.

disconnect all cables from the radio and the meter and start from scratch.

connect a coax jumper from the back of the radio to the connector on the TX250 linear amp that is labeled "IN" or "RADIO" or whatever.

connect a coax jumper from the TX250 connector labeled "OUT" or "ANT" or whatever, and connect the other end of this coax to the TR-1000 meter where it is labeled "IN" or "RADIO" or whatever.

now connect the coax from the antenna to the TR-1000 meter where it is labeled "OUT" or "ANT".

now we are going to check the SWR going in to the amp, and the SWR coming out of the amp, so to speak.

first, start with the radio on, and the amp OFF.
set the radio to channel 20, and turn the DYNAMIKE all the way down.

set the TR-1000 switch to "SWR SET", key the mic and calibrate the meter the same way we did before.
now switch the TR-1000 to SWR and key the mic. note the SWR reading.
it should not have changed much at all from when you checked it without the amp inline.

if it did, you have an installation issue and need to go back and re-check all your steps.

we are about to turn the amp on, but before we do, you need to understand that this amp has different power levels, and by pushing certain buttons, you will get different levels of power. find a manual online to learn about how to select the power level you want.

right now we will leave it on HIGH, which is all buttons out except the red one, which is the power switch. the white button is a receiver pre-amp and will increase the receive gain of your radio. it will not affect the power output of the radio or the amp.
i find that these pre-amps just increase the noise level and dont really use them.

so, with the amp on, re-calibrate the TR-1000 and check the SWR.
you will notice that when adjusting the needle during calibration that the needle is much more sensitive to knob movement. this happens when using more power.

the SWR with the amp on should not be over 2.
if it is, you have problems, and need to keep your mic key ups very short while trying to fix the problems.
dont try to talk using the amp until you get the SWR down below 2.

now we are going to check the SWR coming in to the amp.
with the amp inline and on, calibrate the SWR meter in the radio, and check the SWR on the radio's meter just like we did before.

this reading should also be below 2.

if both readings are below 2 then you are ready to rock!

now switch the TR-1000 to the 1000 position and check your deadkey and swing wattage with the amp on. (dont forget to turn the DYNAMIKE back up!)

make a note of all these readings and post them as you go through this procedure.

we will look at the numbers you are getting for both wattage out and SWR readings, and go from there.

make sure to actually write down all these numbers, dont just try to remember them. LOL

good luck,
LC
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