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Message |
    
Bob_p
Intermediate Member
Username: Bob_p
Post Number: 100
Registered: 7-2004
| | Posted on Saturday, August 07, 2004 - 1:48 pm: | 
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Ok I was told that 75 feet of the Belden Super tin and copper shielded RX8 rated at 3000 watts and High Temp would be fine for a base station install. But I would appreciate other opinions out there. I am putting up an I-Max 2000 next week and will be running a tuned Copper 2970DX radio that has over 150 watts AM and who knows what the sideband pep is, but I'm guessing it's higher than 150 watts. ANyway any and all opinions are welcome and thanks
Bob |
Bruce
Senior Member
Username: Bruce
Post Number: 1434
Registered: 9-2003
| | Posted on Saturday, August 07, 2004 - 4:23 pm: |
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BOB at cb RG-58 works fine Coax at 150 watts is not a problem. How ever it is never a BAD idea to go get the GOOD STUFF. |
Bob_p
Intermediate Member
Username: Bob_p
Post Number: 102
Registered: 7-2004
| | Posted on Saturday, August 07, 2004 - 7:09 pm: |
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Thanks Bruce, I'm using what Belden calls Belden Super RX8 mini 8. I don't know if it has special properties, but it looks like all I'm going to need is 50 feet since I was told not to move the antenna when I get the new one, just keep it where it is. The problem was I was coming over the T.V. upstairs at night when my wife went to bed because the antenna mast runs right up against the house with the coax as near as you can get to the upstairs T.V. cable box and stereo... I was thinking that maybe heavier coax would help and moving the antenna and mast about 20 feet from the T.V. and stereo would stop the problem. But like I said I already have the mini 8 and was wondering if the heavier coax would help even though they both say 95% shield.
Thanks again
Bob |
Bob_p
Intermediate Member
Username: Bob_p
Post Number: 103
Registered: 7-2004
| | Posted on Saturday, August 07, 2004 - 9:45 pm: |
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I just added 5 feet of mast to my antenna taking it to about 40 feet. When I did the SWR dropped a little but the power on my PDC meter dropped drom 150 watts on peak SSB to about 100 watts peak. The antenna base is further from a tree branch, but I really do not understand why the power would have dropped by so much.
Does anyone have any ideas?
Thanks in advance
Bob |
Tech548
Moderator
Username: Tech548
Post Number: 206
Registered: 5-2004
| | Posted on Sunday, August 08, 2004 - 3:55 am: |
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Bob_p
What does your power read into your dummyload.
Wow. That 50 watt loss is quite a bit. Did you have to add any coax when you went higher?
Jeff
Tech548 |
Bob_p
Intermediate Member
Username: Bob_p
Post Number: 106
Registered: 7-2004
| | Posted on Sunday, August 08, 2004 - 2:54 pm: |
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Hi Jeff.
Unfortunately I don't have a dummy load, and no I didn’t add any coax. I am beginning to wonder if my PDC 600 meter is working right. When I lowered the SWR on the antenna earlier it showed a 70-watt loss in power when the SWR was under 1.5.1 so I reset the antenna to 1.7.1 to regain the 70 watts. Someone said it sounded like the primary base load? in the antenna was broken and keep the power on the RCI down until I get a new antenna where I can keep the SWR well under 1.5.1. So I don’t know what to think. It seemed to work ok and as long as I kept the QSO’s below a few seconds I wasn’t too worried. But this time I just added a five-foot section of mast pipe and the power dropped. Don’t get it I’ll be glad when I get a new antenna, but in the mean time I’m stuck and wondering if I should use the radio at all. I was also wondering if that branch was causing a false power reading since it was so close to the base of the antenna? Anyway thanks again for responding and if you have any thoughts I would like to hear them.
Bob
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Tech548
Moderator
Username: Tech548
Post Number: 213
Registered: 5-2004
| | Posted on Tuesday, August 10, 2004 - 3:54 am: |
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Bob my friend.
That is one of the reasons to own a "GOOD" dummyload. Only a "GOOD" load will show you your true RF output power because you are reading the power into a perfectly matched 1.1:1 or less SWR. Reading your power into an antenna with a (lets say) 1.8 or more to 1 SWR will usually show you a reading of more power that you actually are using. And you've already proven that to yourself.
Your RF power meter is showing you more power as you tune your antenna to a higher SWR. The higher your SWR is, the more reflected power you will have coming right back down your coax and into your radio. The more reflected power you have, the hotter the radio will run because of this Impedence Mismatch. And sooner or later, those high-power finals in your radio are going to bite the dust because they are being fed into a improper load...better known as a antenna with a high SWR.
Why? Because your radio requires a load of around 52 Ohms. And when you have a impedence of anything above or below that required 52 Ohms, all kinds of weird things begin to happen such as TVI, cracked windshields and the possibility of your kids failing in math-class.
When tuning your antenna for the best possible SWR, "DO NOT USE A HIGH POWERED RADIO"!!! A 3 or 4 watt radio will work just fine. Once you have your antenna tuned to a "almost perfect" SWR of (lets say) 1.1:1, then the RF power reading that you saw when reading it into your dummyload should be very close to the same reading you now see on your antenna.
I'm going to stop here because it's going on 3:00 AM and I will probably end up just confusing the both of us if I continue with this. I do hope some of this made some kind of sense to you. Hopefully when I read this tomorrow, it will make some kind of sense to me also. If not, then we'll start over.
Jeff
Tech548 |
Bob_p
Intermediate Member
Username: Bob_p
Post Number: 142
Registered: 7-2004
| | Posted on Wednesday, August 11, 2004 - 9:11 pm: |
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Jeff thanks again you've been a great help. After I re-tuned the antenna it wouldn't allow me to tune it back down. I set the rings back to where they where but the SWR was way over 3.1. Now I have it back to about 1.8 or so to 1.8 and the radio is heating up just as you explained quickly, even after a few minutes of normal talking at low power it gets warm. So I haven't been using it for more than a few minutes a day. The I-Max will be here Fri. and thank God because this A-99 has a real problem it will not tune back to a usable SWR.
Thanks again bud, BTW I have been looking into a dummy load. The only thing I've seen is the oil can type that will go over 100 watts. Any suggestions would be considered a favor.
Bob
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Actually Bob, the oil-can type of loads are pretty good and can handle more wattage than you'll probably ever put to it.
And in reference to your A-99, if it were mine, I wouldn't even be using it anymore. With the kind of SWR you have been getting with it, you'll just end up destroying the finals in your radion. It's better to wait until you get your I-Max 2K.
You're going to love that I-Max.
Jeff
Tech548 |
Bob_p
Intermediate Member
Username: Bob_p
Post Number: 145
Registered: 7-2004
| | Posted on Thursday, August 12, 2004 - 1:53 am: |
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Thanks Jeff, I'll take your word and save my radio. The I-Max will be here Friday anyway so I can easily live one day without the radio. I haven't been using it much as it is because it makes me nervous when the radio gets warm after a few minutes of use, I'm hoping the new antenna will solve all my concerns. I'm pretty sure it will. But people have said that a 2.0 SWR was usable. But obviously not in this case. |
Bob_p
Intermediate Member
Username: Bob_p
Post Number: 154
Registered: 7-2004
| | Posted on Thursday, August 12, 2004 - 8:56 pm: |
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Jeff I posted this earlier for Lon but wanted you to seee it too.Your not going to believe this, but I took the RCI off line and was using my Cobra 148 GTL, and all of a sudden the meter was showing no power going to the coax, and the person I was talking to said I dropped out. I took the Dosy TC-4001 out of line in a panic because the radio was showing it transmitting, and sure enough after pulling the meter out of line I was transmitting again. Now I have the PDC 600 back in line with the Cobra 148 GTL and where it was getting pretty warm itself before is no running at near or normal temp. I have a feeling the Dosy has a short in it and was pushing power back into the radio. I just hope it's not done any real damage to the radios. I'm still not going to put the RCI back on line until I get the I-Max up, but I feel this could have been a big part of my problem. I think the RCI was just powerful enough to push the signal through the meter and power was coming back was causing the radio to over heat due to some sort of a short. I was really surprised to see that when I took the Dosy TC-4001 out of line the Cobra was transmittting agian, and like I said just hope there is no long term harm done to the radios.
Thanks as always Jeff and I am looking forward to getting that I-Max up.
Bob |
Tech548
Moderator
Username: Tech548
Post Number: 228
Registered: 5-2004
| | Posted on Friday, August 13, 2004 - 1:21 am: |
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Bob
I'm happy to hear that you found the problem. And I hope that you are still going to put up your I-Max when you receive it.
As far as meters go, personally, I've "never" been a fan of the Dosy meters. The meter-face and numbers are too small to suit me. I have other reasons also but I won't go into them here.
Other than that, since you seem to like the "single display" meters, I would opt for one of the big PDC meters (now using the Astatic name I think) that Copper offers. I really like their big displays and easy to read numbers on those meters.
Chech em out at Coppers.
Jeff
Tech548 |
Sanddiegoduner
Junior Member
Username: Sanddiegoduner
Post Number: 27
Registered: 6-2003
| | Posted on Friday, August 13, 2004 - 2:22 am: |
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Jeff have you ever used an MFJ-269 antenna analyzer? What do you think about them for setting up antennas? |
Bob_p
Intermediate Member
Username: Bob_p
Post Number: 156
Registered: 7-2004
| | Posted on Friday, August 13, 2004 - 2:29 am: |
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Jeff I am really excited about the new antenna and am going to get it up asap. The A-99 still won't tune the way it's supposed to and I want the extra band width the I-Max has.
As far as the meter goes I'm going to ask for a refund from Copper and keep my PDC 600. I have a few Rat Shack SWR meters and thats the only place I have a problem with the PDC 600. If they won't refund the Dosy maybe they'll exchange it for a Astatic. I just liked the idea the Dosy read 200 watts and did peak and average RMS. But it's not a big deal
I think my Cobra is smoked by the way, it doesn't put out power anymore. It keys up, but no dead key and power on SSB. I have another Cobra AM WX radio and a Radio Shack 465 SSB radio that's been modified, but that Cobra 148 GTL was my main radio for the last couple of years.
Thanks and wish me luck.
Bob
Bob |
Bob_p
Intermediate Member
Username: Bob_p
Post Number: 161
Registered: 7-2004
| | Posted on Friday, August 13, 2004 - 7:44 pm: |
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I got the I-Max up and it makes all the difference in the world. I called Copper and asked if they would exchange the meter and they said no, and that I needed to contact Dosy. The problem is Dosy tried fixiing it once already and it came back wasted. Well got to go get the the antenna tied down.
Thanks for all the time and patience.
Bob |
Tech548
Moderator
Username: Tech548
Post Number: 235
Registered: 5-2004
| | Posted on Friday, August 13, 2004 - 10:21 pm: |
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Sanddiegoduner
No Sir, I sure haven't.
I have been told however that MFJs antenna analyzers sure are great to have since they take much of the guess work out of antenna building and tuning. Lol. They sure would have been handy back in the 70s.
Jeff. |
Audiomonster
Junior Member
Username: Audiomonster
Post Number: 10
Registered: 9-2004
| | Posted on Thursday, September 02, 2004 - 7:02 pm: |
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Hello gentlemen:
I use the RG8x, (mini 8), and I have not had any problems with it at all, and its better than 200 feet run to my G5RV antenna, sometimes qrm, and lightning crash noise makes comunications rough, and I have to light up the old Ameritron to make the trip through all the noise. So far it has stood up to the Ameritron with no problems at all for over 5 years. |
Tech548
Moderator
Username: Tech548
Post Number: 277
Registered: 5-2004
| | Posted on Friday, September 03, 2004 - 10:55 pm: |
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Audiomonster
For a 200 foot run like yours is, personally, I would be using heavier coax. The mini is great for runs of 100' maximum and under. Beyond that, you start seeing a line-loss. But, your Ameritron can make up for SOME of it.
Look at it this way. If you want to move more RF, get bigger coax. If you want to move more water, get a bigger hose. Pretty much the same principles apply.
Jeff
Tech548 |
Pig040
Advanced Member
Username: Pig040
Post Number: 570
Registered: 7-2003
| | Posted on Wednesday, September 08, 2004 - 9:55 am: |
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I have a 200 ft run of Rg213U to my omni antenna, and it works out well, I am sure I have a substantial loss, but I still make contacts with, and without "help" on a regular basis.
Rich |
Bob_p
Intermediate Member
Username: Bob_p
Post Number: 325
Registered: 7-2004
| | Posted on Wednesday, September 08, 2004 - 3:33 pm: |
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On the mini 8 it's the shorter the better isn't it? I mean if you have a 75 foot coax is it worth it to trim it to 50 feet?
Thanks in advance
Bob |
Tech548
Moderator
Username: Tech548
Post Number: 287
Registered: 5-2004
| | Posted on Friday, September 10, 2004 - 9:40 pm: |
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Bob
If 50' or a bit less is all you need, then yes, cut it down to 50 feet.
The rest won't go wasted. You can always make patch cords from it.
Jeff
Tech548 |
Bob_p
Intermediate Member
Username: Bob_p
Post Number: 334
Registered: 7-2004
| | Posted on Saturday, September 11, 2004 - 7:32 am: |
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Thanks as always Jeff
73
Bob |
Keithinatlanta
Intermediate Member
Username: Keithinatlanta
Post Number: 460
Registered: 3-2003
| | Posted on Friday, January 14, 2005 - 4:17 pm: |
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How come we can't do "new posts" on this page regarding antennas?
Forum Master Note :
We are trying to limit the break down of the subject. That's why we were very specific with the the title of each heading under the installation section. |
Keithinatlanta
Intermediate Member
Username: Keithinatlanta
Post Number: 474
Registered: 3-2003
| | Posted on Saturday, February 05, 2005 - 9:08 pm: |
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10 4!
Keith |
