| Author |
Message |
    
Glassbysam
| | Posted on Friday, January 02, 2004 - 10:16 pm: | 
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has anyone had a channel guard installed in their radio?? I have heard about them for a long time, and while I do not believe that it would be effective in any of my mobile radios , I do have a couple of bases within 2 miles that do bleed my eagle 2000 a few channels...
just wondering if they work and how hard they are to install..
thanks
sam cef 228 |
Dinker1
| | Posted on Friday, January 02, 2004 - 11:01 pm: |
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I understand all they do is cut your recieve back, i've reard, had one in a 2000 cobra and ripped it out! DEAN- |
Crafter
| | Posted on Friday, January 02, 2004 - 11:08 pm: |
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I thought someone had hooked two recieve mixers parallel and had good results, You might ask Bruce. |
Inspector
| | Posted on Saturday, January 03, 2004 - 12:39 am: |
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When properly installed and adjusted the channelguard actually improves the S/N ratio. It narrows the band-pass and then amplifies the signal, giving great adjacent channel rejection while maintaining strong on-frequency receive. It is what is called an active-crystal-filter. |
Bruce
| | Posted on Saturday, January 03, 2004 - 12:57 am: |
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I use them all the time they are easy to install and will give you about 4-5 s units of extra rejection IN ANY RADIO BASE OR OTHERWISE. Dinker that bunk they will not cut back on receive if they do you got them hooked up wrong. Ive run 2 in series very effective but unnessary the first one will kill most bleedover. if anyone needs help or has a question about them ive used them the ( 10.695)mhz one a 2950, a lincoln ( GREAT RESULTS ), a titan 485 the 7.8mhz one in a grant LT and added a 455khz one too VERY SELECTIVE on am with both VERY! also several radio shack moble radios the 455kz ones in a midland 77-115 and several more moble radios with good results.
NOW KNOW NOISEBLANKER PROBLEMS yes on some radios it will cause blanker problems but if your geting clobbred by bleed over what good does that blanker do? Bottom line in most radios its a good $40 investment. |
738
| | Posted on Saturday, January 03, 2004 - 1:03 am: |
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It depends on the radio. I don't know much about the new ones, but in the old days you sure could clean up the single conversion models like the Cobra 142GTL, Washington, etc. I don't think it would help much in a dual conversion radio, but it won't hurt either. What you need to do is find out if your radio is single or dual conversion to start. |
Chillydog
| | Posted on Sunday, January 04, 2004 - 5:23 pm: |
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I have to concur with Bruce's and the Inspector's input; they are right on regarding the Channel Guard. I've installed dozens if not hundreds of them, and consider CGs to be indispensible in urban areas with many users in close proximity. They are very helpful in both base and mobile units.
As far as causing problems with noise blanking, it is possible if the Channel Guard is installed prior to the noise blanking sensing. I don't have my notes with me now, but most noise blankers sample the receive right after the first mixer, and return the blanking bias close to the same point. The CG needs to be installed further down the IF chain. If not, the narrower bandwidth of the filter will "spread out" the noise spikes so the blanker cannot detect them. The instructions Lou Franklin includes with the Channel Guard will indicate the correct place to install the accessory. If you follow his instructions noise blanking will not be affected.
And 738, I can assure you there is plenty of room for improvement in dual conversion radios. The tighter IF bandpass provided by the CG makes a big difference.
The number one thing to realize with the Channel Guard is that it will greatly improve adjacent channel rejection, and will therefore reduce interference from nearby transmitters. It can't clean up spurious signals from improperly tuned transmitters that fall into the channel you're tuned to. It will help somewhat with nasty, limiter clipped •••• radios, but can't clean up the trash they throw into your channel.
A Channel Guard is a great accessory!
Best Regards,
Bob |
Dinker1
| | Posted on Sunday, January 04, 2004 - 10:16 pm: |
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the one i'm talking of Bruce is from the early 70's and was in a cobra 2000-- i think i still have it laying around here some place' rmember this is as old as some of yous are??? DEAN- |
Dinker1
| | Posted on Sunday, January 04, 2004 - 11:51 pm: |
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Tryng again! i'm saying that the radio i had was a cobra 2000 few year on the new fang dinggled ones- and the rejecter was all i know is it cut the recieve as i aND aolder tech came up on when it was removed. i still hAVEA IT AROUND HERE SOME PLACE. Remember the age brackets on this forum, some of you probaley are not as old as the cobra 2000.DEAN- |
Bruce
| | Posted on Monday, January 05, 2004 - 4:20 am: |
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dinker1
The channelguard installed corectly has little effect on reciver gain and at least a 20 db drop in anything outside of the +/- 3khz bandwidth. If you had a problem you either had a bad filter or one installed wrong. |
738
| | Posted on Friday, January 09, 2004 - 8:29 pm: |
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Thanks for the Information Chillydog. I have been away from 11 meters for many years and had never tried one on a Dual conversion radio, but did know for sure how well they used to work on the old 142GTL's I used to run back then. I have always felt TX power is easy and that the RX is the important thing to work on so I think it's a important add-on. |
Keepitreal118
| | Posted on Friday, January 09, 2004 - 9:53 pm: |
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Had one installed in a midland 79-290 and Magnum 257. Works like magic as long as you get a good tech and not a hack shop to do it right. |
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