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Post by libslayer on Sept 27, 2013 11:07:38 GMT -5
About a year ago I was given a Walmart Cobra 19 , 18' of coax and a K40 fiberglass whip......I WAS HOOKED IMMEDIATELY. because of my temporary noob status this radio was the best thing since sliced bread and peanut butter. I was getting 5-6 mile range and great feedback from drivers on how the radio sounded, but alas I grew bored fairly quickly and wanted more. I did what most idiots do and went to YouTube for advice (BAD FREAKING IDEA) I started "adjusting" internal pods trying to increase modulation and I very quickly was left holding a piece of junk that sounded a lot like jabberwoky. So what did I do? Hooray I bought a 75 Watt kicker. Sounded even worse (I didn't know it wouldn't handle a DK over like 1 Watt)
Well I did a little research and found a cobra 29 lx that looked pretty good and reviews were across the board fair to excellent. So for about $110 I purchased one. The problem I'm having is the stupid SWR meter on the radio is nowhere close to the external meter I bought at radioshack and I get an antenna warning when I key up. I'm using a Wilson 1000 5/8 wave 4' tunable whip w/18' coax (90% shielded?). Any suggestions?
#DeepInTheHeartOfTexas- LibSlayer
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Sandbagger
Administrator/The Boss 
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Post by Sandbagger on Sept 27, 2013 11:19:52 GMT -5
About a year ago I was given a Walmart Cobra 19 , 18' of coax and a K40 fiberglass whip......I WAS HOOKED IMMEDIATELY. because of my temporary noob status this radio was the best thing since sliced bread and peanut butter. I was getting 5-6 mile range and great feedback from drivers on how the radio sounded, but alas I grew bored fairly quickly and wanted more. I did what most idiots do and went to YouTube for advice (BAD FREAKING IDEA) I started "adjusting" internal pods trying to increase modulation and I very quickly was left holding a piece of junk that sounded a lot like jabberwoky. So what did I do? Hooray I bought a 75 Watt kicker. Sounded even worse (I didn't know it wouldn't handle a DK over like 1 Watt) Well I did a little research and found a cobra 29 lx that looked pretty good and reviews were across the board fair to excellent. So for about $110 I purchased one. The problem I'm having is the stupid SWR meter on the radio is nowhere close to the external meter I bought at radioshack and I get an antenna warning when I key up. I'm using a Wilson 1000 5/8 wave 4' tunable whip w/18' coax (90% shielded?). Any suggestions? #DeepInTheHeartOfTexas- LibSlayer Internal SWR meters rarely track the same as external units. The reasons for this are complex, and it is even further complicated if you are using an amplifier in line with the radio. In this case, the radio's SWR meter is "seeing" the SWR of the input circuit of the amplifier, while the external meter (which is hopefully between the amp and the antenna) is looking at the antenna SWR. A good many amplifiers have poor SWR on their input. Sometimes you will get a better SWR if you run it in the low power position (if it has Hi/Lo capability), due to the resistive pad on the input. |
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Post by libslayer on Sept 27, 2013 11:27:55 GMT -5
I've actually removed the linear since starting with this new radio. I want to learn more before I start experimenting. It is barenaked so far. I'm thinking it's the antenna? This morning just fer the heck of it I put my old 1/4 wave 2' whip on and everything was great. Did a mileage check with a buddy and got to 8 miles before he lost me.
#DeepInTheHeartOfTexas- LibSlayer
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Post by BBB on Sept 28, 2013 9:32:26 GMT -5
I believe the antenna waring adjustment pot in the Cobra 29 LX's is the same as the old 29 LTD. It is VR6 right by the power jack. I had to adjust it as part of the procedure when installing an RFX75 amp on my radio.
If you know your SWR is okay when running the amp, just adjust VR6 until the warning stops and go a little past that.
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Post by libslayer on Sept 28, 2013 16:57:46 GMT -5
Cool, Thanks BBB I'll look into that.  #DeepInTheHeartOfTexas- LibSlayer |
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Post by libslayer on Sept 28, 2013 16:59:11 GMT -5
What did you set the DK at? I'm going to be adding a 300 amp Texas Star linear.
#DeepInTheHeartOfTexas- LibSlayer
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Post by BBB on Sept 29, 2013 9:37:14 GMT -5
If the amp is an HD or high drive you can be a little more flexible on what dead key to feed it with. Anywhere from 5-15 DK watts (or more) depending on the HD amp. If it's the more common standard low drive amp, usually 1.5-3 watts out from the radio should get it swinging from there.
You want to shoot for a 1 to 4 modulation ratio on AM, meaning your dead key or AM carrier, should be a quarter of the max peak swing you see on your power meter. Keeping in mind that if the amp is realistically does lets say 200 watts peak, then a 30-50 watt carrier from the amp would keep it sounding good and help the amp stay alive. I believe you would adjust L10 on the 29LX to affect the dead key on a standard 29 LTD/ LX radio. There is a section on how to adjust the transmitter in the Cobra 29 LTD factory service manual in section 4. Again, the 29LX is based on this chassis.
Since I added a RFX75 there was a resistor that I had to add to set the dead key. Funny thing though is that with the RFX75 on this radio the dead key is super sensitive to the voltage the radio is supplied. I was going to do the variable power mod to the rig, but since I use it only as a base radio at times, I just use a variable power supply to set the dead key. Not sure why this is happening but the radio sounds fine. Maybe something about "Volting" the final that's done in the conversion that bypasses the voltage regulator; dunno.
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Post by libslayer on Sept 29, 2013 16:18:45 GMT -5
Great information, thank you so much. Do you have any experience with the Texas Star brand?
#DeepInTheHeartOfTexas- LibSlayer
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Post by spitfire441 on Sept 29, 2013 16:48:41 GMT -5
One of the better CB amps available.
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Post by libslayer on Sept 29, 2013 19:50:53 GMT -5
That is indeed very encouraging to hear. Thank you.
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