| Author |
Message |
    
Jay Hobbs (Jayxd)
| | Posted on Wednesday, August 21, 2002 - 10:18 pm: | 
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I've got my SWR meter hooked up to the CB - antenna setup is a 4' firestick II and I've tuned it about as accurate as I think you can get. I've tuned for channels below 20 and on channel 9 I get a 1.1 reading. Here's my question - I've kept the SWR meter in the vehicle to check it at different locations, well, I'm getting different readings. A channel that might read 1.4 on the highway will read well over 2 in a parking lot. What would be causing this? Buildings, power lines, interference? Should I tune the antenna in the environment where it will be used the most or have two, one tuned for road use, one for trail use? |
Al Oliveira (Offroaddisco)
| | Posted on Thursday, August 22, 2002 - 08:36 am: |
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Is the antenna flexing a lot at highway speed? |
Jay Hobbs (Jayxd)
| | Posted on Thursday, August 22, 2002 - 01:40 pm: |
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Probably some, I've got it mounted with a spring base. So I'm sure it moves around at 65 mph. |
Jerry Crawford, 98 D-I
| | Posted on Wednesday, August 28, 2002 - 09:55 pm: |
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This antenna flex or bending at highway speed (called going out of phase) points up a good question: aside from being so cheap why are long wire antenna's so popular? They are inherently unreliable unless you are standing still.
To paraphrase a real antenna guru (who many of you might have read already)"the selection of your antenna is the single most imporatant aspect in determining the quality of your communcations" ...or words to that effect. To me that says if you have a good antenna system you are going to get good communications even with a Radio shack you pick up in a yard sale; if your antenna system is a piece of junk even the best, most costly radio equipment is just so much useless circitry.
Fokes know these long wire antenna's aren't worth squat on the highway, they bend like crazy and that big coil spring on the anchor end just makes it worse. They whip around and pound on your truck parts or roof rack something awful! I've even seen guy's tie strings to them in an unsuccessful attempt to keep them straight up in the air over 20 mph. Nobody can expect to get good consistant SWR under those conditions.....? Well,....maybe some people do.??
A good wire wound fiberglass antenna is stiff enough to hold it's shape in a head wind or at 80 mph. It is strong enough to withstand about any pounding you can give one under most off road conditions, yet they are flexible enough to bend severly if you jam one into a garage overhead door (which I have done on a couple of occasions) and recover to straight without any effect on the condition of SWR. I have never seen one that had shattered from any kind of impact. I parked a popular brand NGP type 48" antenna in my bench vise the other day and bent it well past 90 degrees without failure just to see if it would break or split. Well engineered and well made antenna's are really so inexpensive today using any other kind just doesn't make any sense in my opinion.
I'm not an antenna or electronic engineer and I don't market fiberglass antenna's, but for our purposes it just doesn't make any sence to me to continue to use an item that has proven to be so problematic over the years. It must be sex appeal.
I'll climb down off my soap box now - thank you for listening. I'd appreciate some reasonable opinions to the contrary if they are out there. |
Al Oliveira (Offroaddisco)
| | Posted on Wednesday, August 28, 2002 - 10:34 pm: |
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Jerry you're partially correct. I'm not an antenna guru either but have used enough to say that a wound antenna is not as good as a straight antenna. But it's all a compromise. You will get better performance with a straight antenna over the wound at a standstill but the wound may work better at high speeds. When on the trail I don't think many of us do 80mph much less 30mph. The antenna is another reason my main radio in my rig isn't a CB. I use a UHF service (GMRS) and can talk to any FRS radio on the trail.
Many people I ride with have either CB or FRS and I've ran into a few people with GMRS too. CB just can't cut it despite the fact that in the CB frequency range you can talk half way around the US with 4 watts IF your antenna is good enough (note not mobile) and weather conditions are just right. In the real world you get about 5-7 miles at best in a mobile setup.
In the UHF frequencies I can get 7-15 miles with no repeater and with a repeater I have hit over 45 miles. All this with a 6" antenna. To get the same efficiency on CB as I get with that 6" antenna I would need a 102" straight CB antenna. Just ask the people in OZ what they use and why. Most will use their UHF CB service over the HF (What we have in the US) service. |
Jerry Crawford, 98 D-I
| | Posted on Thursday, August 29, 2002 - 12:26 pm: |
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The antenna is another reason my main radio in my rig isn't a CB. I use a UHF service (GMRS) and can talk to any FRS radio on the trail.
can you jot down a web site for GMRS and FRS? Is this the same as HAM in the VHF UHF applications? |
Jerry Crawford, 98 D-I
| | Posted on Thursday, August 29, 2002 - 04:29 pm: |
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"OZ" ?
...as in the Wizard of...? |
Al Oliveira (Offroaddisco)
| | Posted on Thursday, August 29, 2002 - 04:40 pm: |
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Jerry - try www.gmrsweb.com GMRS is almost like the 70cm Ham band. It's very close but the equiptment is different. Generally it's higher quality but there have been lots of more consumer quality (lower price) radios hitting the stores in the last year. That site also has lots of information on FRS but you may have already seen the FRS radios (motorola talkabout).
OZ, as in Australia |
Jerry Crawford, 98 D-I
| | Posted on Friday, August 30, 2002 - 01:55 pm: |
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Interesting that the issue of transmitting range still comes up. Admittedly CB's are not good when your want to communicate a far piece - but most work with a CB for the off-road community seems to be well within....say 2-4 miles on the trail...and up to 5 in convoy on the highway in Kansas. It would be interesting to do a study and find out what we really use our radios for....rather than what we'd like them to be able to do or think they should be able to do. I'm betting it's well within the expected range envelope of a CB at 4+ watts. If my premis is accurate then a long wire antenna has no advantage over a short wire wound fiberglass antenna. Comment? |
ScottP
| | Posted on Friday, August 30, 2002 - 06:20 pm: |
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I think you should just all get a HAM License, nothing beats 2 meter (VHF) for trail and street. There are also repeaters all over the country free for use by anybody. Having 50 or 70 watts at your disposal is kind of handy too.
ScottP
(aka KF4FHA) |
Al Oliveira (Offroaddisco)
| | Posted on Friday, August 30, 2002 - 08:33 pm: |
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Scott, I agree but getting a HAM ticket is kind of a PITA and then your entire family needs one too if you use your radio to talk to family on trips. There is MURS that's close to 2 meters (151MHz) that works well too and there is no license needed for that but there are few users of MURS and you're limited to 2 watts and can't use a repeater. GMRS lets you talk to FRS users who are all over the place, use 50 watts, access repeaters, use FM (unlike AM CB) and PL tones (no CB style squelch to deal with). The audio quality on CB is about as bad as it gets. There are plenty of mil-spec radios out there that take the abuse off road very well that can be used on GMRS.
Jerry - Just last month I was in a convoy where someone didn't keep an eye on the guy behind them and the group split into two at a fork in the trail. No one could reach the other group via radio but I managed to hit them with my mobile GMRS radio and directed them to the right path. Given the terrain we often drive in on the East coast I think 2 meter ham would be better but there are issues with licensing there. The GMRS has helped my where my CB couldn't often enough but I agree that with the range we *generally* work in it's not needed.
Another bonus for GMRS is that when working with hand helds the GMRS antenna is going to be much more efficient than the CB hand held antenna. I've had a GMRS hand held transmit to a range very close to a mobile CB.
One year ago on 9/11 the phones in the area were down and there were two ways for me to communicate with my family. One was with AIM and the other was on GMRS. Using one of the repeaters in my area I was able to talk to my family within a 50 mile radius.
And my number one reason I like my GMRS radio over my CB is that I can talk trash about Jeeps and they won't hear me on their CB's.  |
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