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Sitm
Member
Username: Sitm
Post Number: 89
Registered: 1-2004
| | Posted on Wednesday, April 07, 2004 - 10:49 am: | 
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I purchased this amp accouple months ago after reading some post on it. I took my radio in and had the suggested modifications done by a tech, not a hack. But someone that does this for a living from a radio shop. The radio produces 2.09 watts on dead key. The amp produces 22 watts at times then 18 watts at others. The amp started buzzing and keeps the mic radio keyed after releasing the key. Shows 6 watts to 8 watts. It buzzes and I push the button. Sometimes when I push it right back on it still locks up. I called copper and talked to a tech. Told him the set up that I had and he suggested putting a nine foot jumper from the radio to the amp. I did and the problem persist. Did I get a lemon or am I having some other problem. Let me tell you my set up.
I have a cobra 138 xlr with a nine foom jumper going to the KL 40. Then there is a six foot jumper going to a E01-01008 EURO AS-100 ANTENNA SPLITTER. From there it goes to the digital meter with a six foot jumper. Then to 100 ft of coax to Imax 2000. The other radio that goes to the E01-01008 EURO AS-100 ANTENNA SPLITTER produces 10 watts dead key, as to why I by passed the amp with this radio. The standing wave is 1.09 on the meter with the amp on. with the other radio the standing wave is 1.06. All coax with the exception of the 100 ft of heavy coax to antenna is from coppers. It is the flexable medium coax. I would like to use this amp or another when talking past 50 miles. I generally don't use it at all, maybe 1 hour at most per week. I wanted to use it on my base to see if it is something that I might want in my two trucks and maybe my wife's Bronco. But this is the reason that I purchased one for the base unit first. I put the mobile in the house with the wattage recommended to see what the performance would be. I am running the amp off of a 14 amp regulated power supply along with the radio. I would like to get this problem solved so that I can use the amps in my mobile units. Please advise. I have also purchased 100 ft of the best coax that copper offered and it has arrived. The tower is 60 ft with ten ft of heavy antenna pole then the Imax 2000. Thought about dropping the coax and checking the wattage output at the antenna connection. Anyhow, what do I do. I would like to order more amps, but not if this is going to be a problem with all of the KL40 amps. |
Ca346
Advanced Member
Username: Ca346
Post Number: 687
Registered: 8-2003
| | Posted on Wednesday, April 07, 2004 - 5:08 pm: |
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I had the same problem with a different amp (Galaxy350) when I used an ICOM706 turned down to 2,3 or 4 Watts AM. It was driving me crazy. Moved it to an HR2510 (Lincoln) in the garage which puts out 4 Watts AM and it works fine. Now I use a KL-500 with the ICOM and it works fine. Made no other changes.
The tech will have something.  |
Kc0gxz
Advanced Member
Username: Kc0gxz
Post Number: 712
Registered: 3-2003
| | Posted on Thursday, April 08, 2004 - 2:50 am: |
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Sitm
If set up correctly, your old 138-XLR will do an easy 22 or more watts on SSB. Single sideband far out-performs A/M. But you never did say what mode you are using. Man how I love those old 138 and 139-XLRs. Even by todays standards, they have more capabilities than any of the SSB Cobras built today.
As far as your little KL-40 goes, or for that matter even the KL-60, they are both 40 watt apmpifiers. DO NOT EXPECT MIRACLES WITH THEM. These are extremely low-drive amps and have proved to be a disappointment to many people. The reason being is that most dual final radios will out-perform them or at least do just as well as a KL-40-60. But as far as your radio goes, we are talking about a single final radio.
Since RF output power has to be a little more than doubled just to see a 1/2 S-unit increase at the receiving end, a KL-40 or 60 just doesn't have what it takes to do this. You might sound a little louder out there but that's about it. What you did here was detune a good working radio just so you could run a tiny underpowered amplifier that doesn't do much better than your radio itself.
For just a few bucks more, (and I do mean a few) what would really compliment your XLR would be a little KL-200 or 300. These amplifiers do not draw much more than about 12 amps. Check the prices out. Copper sells these cheaper than anyone else that I'm aware of.
One more thing. I am not trying to ridicule you with my post. In my opinion, you own one of the best 40 channel SSB radios ever designed. Running it into 2 or 300 watts will add some real bite to its bark. If that old XLR were mine, that's exactly what I'd be doing.
Jeff, kc0gxz. |
Sitm
Member
Username: Sitm
Post Number: 90
Registered: 1-2004
| | Posted on Thursday, April 08, 2004 - 9:27 am: |
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Jeff,
Thank you for your post and reply. That makes alot of sense. The 138 xlr is a mobile with sideband. It seems to perform well in both modes. I also have an old Cobra 132 xlr mobile SSB. I think that I am going to take both radios back into the shop, (which is a ridiculous two hour drive) and have them peaked and tuned. What kind of output do you think that these radios will have once tuned and peaked responsibly? I have a TRC 485 that was tuned and peaked. It dead keys 10 on am and nearly 22 on ssb. I have had this tuned now for about eitght years and it seems to perform great. I would imagine that I will eventually buy a two final radio and call it a day. Or pick up a larger amp. I would prefer a tube type as I have read that they are better at TVI interference. But thank you for your post it was very informative. |
Kc0gxz
Advanced Member
Username: Kc0gxz
Post Number: 722
Registered: 3-2003
| | Posted on Saturday, April 10, 2004 - 2:16 am: |
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Sitm
In reguards to you TRC-485, here's a little trick you can do "IF" you have a Peak Reading Meter.
First of all, I would NEVER peak a single final radio to 10 watts. You are almost always guarenteed downwards modulation, aka, backwards swing. On a Peak Reading Meter (PRM) you will never see this backwards swing when looking at the wattage scale.
If you own a PRM, try this little trick. With your radio set on A/M, go to either the Modulation or SWR mode on your test meter. Key the radio and dial the meter-needle up to half or near full scale and then LEAVE THE KNOBS RIGHT THERE. Now say a long auuuuuuuw into the mic. If you see the meters' needle go backwards, you indeed have "downwards" modulation even though your wattage reading may be swinging upwards.
If this is the case, one of two things is very wrong here. Either the RF power stage is out of tune or the RF output-power setting itself is set way too high. Heck, 10 watts is the "VERY MAXIMUM" I will ever set dual-final radio to.
If you are getting a "backwards or downwards" swing, just open the speaker side of the radio and turn down VR-16 to around 6 watts, or just keep backing the power down until you see the needle start to swing upwards.
A single RF final just doesn't have enough room in it for both high-output power and massive audio at the same time. The higher the power is set, the less modulation you will have. The lower you set the power, the more modulation you will have.
Before "maxing out" a radio, I always asked my customers this question---Would you rather be "seen" on the air or would you rather be "heard" on the air?
LOL. If this "backwards-swing test" on your radio turns out to be an actual "forward-swing", then disreguard this whole post.
PS: I'm not real positive if the power setting in the TRS-485 is indeed VR-16. I could be wrong about that--which of late wouldn't surprise me one little bit.
Jeff, kc0gxz. |
Sitm
Member
Username: Sitm
Post Number: 94
Registered: 1-2004
| | Posted on Monday, April 12, 2004 - 11:34 am: |
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Jeff,
I have a digital meter on the TRC 485. The radio was set by a licensed technician. He asked me the same thing you just did. "What do you want from this radio?" I told him that I wanted good clean radio sound. Not booming, "hey you are loud." I have always gotten good reports on this radio. Generally its "well your not LOUD, but man you are crystal clear. More like ham than cb." Generally they tell me I need a different mic, or to turn this up or turn that up. I simply tell them that I want the radio to sound clean and clear. Plainly enough, I have talked to my spouse on this radio from a distance. It sounds just like her voice, the modulation is clean and clear. I don't have to turn up the volume to hear her. In fact she is louder than most of the other radios that I hear. But her voice isn't distorted into a more bassy sounding voice. Its normal, clear and clean. I try to set most of my radios to that. I have a Royce 620 that people kept tellimg me was "tinty". So I added a D104 hand mic. Then I got reports of more bassy sound and loud. The radio is stock. I also have a 132 xlr and 138 xlr. I want those radios to last and sound clean and clear. I don't want to have them turned up to the point where it shortens the life of these radios, because I am sure that the parts and repair, (due to the age of the radios) is almost impossible. I have purchased three other radios out of the box. An old regency info-cb. mobile out of the box from a shop clearance. On the meter (digital, not saying its completely accurate) it shows dead key of 4.75 and swings into the eights. The TRC 485 dead keys 8.35 and swings up into the 10 to 12. The 138 xlr on side band goes into the 18 to 19 on sideband and 4.35 on am, swings into the 8s. The owner of the radio says he never had it in a shop and in fact only had it in his car a week and his wife made him put it away. So I have a 138 xlr that was used a week, stored in his bedroom closet for over a decade. The 132 xlr, I have owned for over 15 years and have used it alot. I had it tuned by the same tech and he asked the same question. It was tuned to last and sound clean and clear. For the most part, I want to keep the radios that I purchase, not tune them to a level where they burn out after five years or so. Its great to have them put out 20 watts or more. I am sure that some of the radios that have dual finals in them do this with ease. But I would rather keep the old radios that would be very hard to replace running "CLEAR AND CLEAR". I dont' mind burning out a cheap amp that is easy to replace with 40 dollars. I doubt that coppers is going to have any 138 & 132 & 32 xlr radios for sale any time soon. Generally I have found that when I run more wattage. (100 +) I only talk to those people that I hear out there in the distance. I push accouple buttons and then they hear me. I talk for about 30 seconds to those people and then move on. I generally talk to people within 40 to 50 miles. On between 4 to 20 watts with ease with the radios that I have. I live in a town with people that have spent between 300 to 1000 on RCI, Galaxy, modified ham equipment (yes Bruce on am) and they generally don't talk to that many people in the distance than I do. Yes they sound "loud & bassy". When I meet these people in person (thank God rarely) they don't sound anywhere close to their radio voice. But they say, "you sound exactly the way you do on the radio." And thats what I would prefer. I really like reading the advice and opinions on this forum, (excluding the ones from people that seem to post merely to read their own post later). I thank the knowledgable technicians, licensed and unlicensed that are out there. It really inspires me to learn more and be of help to someone years from now when I learn even half what you all know already. Thank you |
Kc0gxz
Advanced Member
Username: Kc0gxz
Post Number: 732
Registered: 3-2003
| | Posted on Tuesday, April 13, 2004 - 3:28 am: |
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Sitm
Inside your Cobra-138 is a verible resistor numbered VR-8. While watching your power meter, key your mic and set this to around 1.5 watts--2 watts at the "VERY" most. This will easily key just about any RF amplifier without over driving it.
The same holds true for your Cobra-132 and 135-XLR by adjusting L-3. And you don't even need a tech to do it.
By the way, I know exactly how you feel about those old Cobras.
Jeff, kc0gxz. |
Sitm
Intermediate Member
Username: Sitm
Post Number: 113
Registered: 1-2004
| | Posted on Friday, April 16, 2004 - 11:04 am: |
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Thank you Jeff, I will do that. Thanks for the technical help |
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