| Author |
Message |
    
Keithinatlanta
Intermediate Member
Username: Keithinatlanta
Post Number: 265
Registered: 3-2003
| | Posted on Saturday, June 26, 2004 - 7:23 am: | 
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Good morning world. From reading another post, what is a channel guard and its purpose? Thanks.
Keith in Atlanta
CEF 150 |
Tech808
Moderator
Username: Tech808
Post Number: 2788
Registered: 8-2002
| | Posted on Saturday, June 26, 2004 - 7:54 am: |
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Keith,
The CHANNEL GUARD filters are a very effective way to stop one of the biggest problems with CB radios: splash, splatter, or “bleedover” from other channels. Our HF versions use two special high-Q crystals (7.8 MHz or 10.695 MHz) in series on a small PC board, which is installed at the proper circuit point in the receiver’s IF stages. They work by narrowing the “skirt” selectivity around the center of the radio’s IF passband. The filter is generally installed in place of an existing IF coupling capacitor, typically a 2-5pF ceramic disk type.
Interrupting the IF signal path by inserting any extra device can also attenuate the desired RF signal substantially, sometimes as much as 6 dB per filter element. Therefore a single transistor amplifier stage is included on the PC board to compensate for this signal loss. The end result is a filter with zero gain and zero loss, but vastly improved selectivity. There’s no loss in RX sensitivity, and in fact the extra amplification may even improve the S/N ratio. There is also no noticeable effect on the received audio quality of typical AM or SSB transmissions.
NOTE: The CHANNEL GUARD filters may be too sharp for FM-CB reception, if the FM deviation exceeds ±2.5 KHz. If received signals appear to be breaking up, the other station may be overdeviating.
Hope this helps.
Lon
Tech808
|
Hollowpoint445
Junior Member
Username: Hollowpoint445
Post Number: 47
Registered: 6-2004
| | Posted on Saturday, June 26, 2004 - 2:43 pm: |
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Keithinatlanta - they make a HUGE difference when you're very close to someone with a legal radio, or in the general area of someone who's running tons of power cleanly. In both situations your receiver just gets overwhelmed by the strong signal even though it's on a different frequency.
Sometimes it'll just cause your receiver to lose sensitivity, and sometimes you'll hear the guy plain as day on your frequency because the radio can't filter it out.
They'll definitely make a difference in how your radio performs and they're inexpensive. Give one a try. |
Davesmeg
Junior Member
Username: Davesmeg
Post Number: 12
Registered: 3-2004
| | Posted on Saturday, June 26, 2004 - 4:37 pm: |
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I agree with Tech808. They don't work well on FM especially if the opperator you're experiancing bleedover from happens to be using lots of power and splattering 6 channels either side of where they're supposed to be. |
Bruce
Senior Member
Username: Bruce
Post Number: 1307
Registered: 9-2003
| | Posted on Saturday, June 26, 2004 - 7:18 pm: |
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aggred on fm there too narrow but on my grant lt and other radios ive used them on they help cut adjason channel interferance. Now on 10 meters where FM is LEAGAL i have been lucky and not needed to use them in any radio that i use on that mode ( my alinco md-o3 or htx-10 ). Now on other radios i use on SSB and AM the 10.695 works well for both modes and I have used the 455khz one for am .... the 455khz one is VERY sharp! |
Keithinatlanta
Intermediate Member
Username: Keithinatlanta
Post Number: 267
Registered: 3-2003
| | Posted on Saturday, June 26, 2004 - 10:23 pm: |
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Well guys, if I understand you, it would help me get rid of some of the bleedover from the chanel 6 garbage. Remember, I only have the cb radios, not the export radios. So does that mean it still works the same? Thanks for the input. Now is this easy for my tech to do? Any idea what kind of money I would be looking at? My radio is a Uniden Grant XL, the old style, not current or should I say now discontinued one. I also use a Uniden PC 76 XLW with three weather bands. Will this work on this radio as well? Again, many thanks.
Keith in Atlanta
CEF 150 |
Tech808
Moderator
Username: Tech808
Post Number: 2796
Registered: 8-2002
| | Posted on Saturday, June 26, 2004 - 11:34 pm: |
|
Keith,
It makes no difference on weather it is an Export or a Regular CB they will work.
They come with good instructions that if you have done any work before on radios you should be able to do it with no problem.
If not your Tech should not charge that much to install one, off hand I would guess $20.00 to $30.00 should be in the ball park.
The 10.695 MHz Channel Guard should work in both radios you mentioned.
Hope this helps
Lon
Tech808 |
Charliebrown
Junior Member
Username: Charliebrown
Post Number: 35
Registered: 10-2002
| | Posted on Sunday, June 27, 2004 - 8:07 am: |
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mr. tech 808 could you tell me if the channel guard will work in the 2950dx and if so which kit should i use? i think coppers has three to choose from. |
Tech808
Moderator
Username: Tech808
Post Number: 2798
Registered: 8-2002
| | Posted on Sunday, June 27, 2004 - 8:15 am: |
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Charliebrown,
Yes, the Channel Guard Filter will work in your 2950DX Radio.
You will need to use the 10.695 MHz Model.
Please click on the Link below.
COPPER PART # BKS-02004
http://www.copperelectronics.com/cgi-bin/checkitout/checkitout.cgi?catalogSTORE:CKIE:prodBKS-02004+
Hope this helps.
Lon
Tech808
|
Mrhappy
Intermediate Member
Username: Mrhappy
Post Number: 135
Registered: 2-2002
| | Posted on Sunday, June 27, 2004 - 3:34 pm: |
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In my opinion,a waste of money.Didn't see any noticable difference.
Just my two cents. |
Hootyal
Intermediate Member
Username: Hootyal
Post Number: 126
Registered: 9-2002
| | Posted on Sunday, June 27, 2004 - 7:52 pm: |
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Installed one in my Uniden Washington myself and had 8541 install one in my Ranger 2985dx...Great improvement in bleedover reduction!! Reduced some local bleedover from scrambling my receive down to a scratch...barely noticeable. It's not gonna help if your close neighbor is running 2 kw, but in my opinion it was money well spent!! |
Bruce
Senior Member
Username: Bruce
Post Number: 1309
Registered: 9-2003
| | Posted on Sunday, June 27, 2004 - 8:01 pm: |
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Mr happy you did something wrong ....... you must have REPLACED the exsising filter.
On My grant it increased the adj channel rejection by more than 20 db measured on my shop testset. The 455khz filter is SO much sharper than a marata filter there is no contest. |
Triplecguy
Intermediate Member
Username: Triplecguy
Post Number: 165
Registered: 12-2001
| | Posted on Monday, June 28, 2004 - 2:48 pm: |
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Can somebody recommend or tell me the channel guard to put in my Midland 79-290? I think that it is the only hope for it.
Thanx, |
Tech808
Moderator
Username: Tech808
Post Number: 2806
Registered: 8-2002
| | Posted on Monday, June 28, 2004 - 3:13 pm: |
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Triplecguy,
You will need the 10.695 MHz Channel Guard.
http://www.copperelectronics.com/cgi-bin/checkitout/checkitout.cgi?catalogSTORE:CKIE:prodBKS-02004+
You will remove; C57
You will hook the IN wire to T4
You will hook the OUT Wire to; Q-19/R69
Hope this helps.
Lon
Tech808
|
Viking
Intermediate Member
Username: Viking
Post Number: 138
Registered: 2-2002
| | Posted on Monday, June 28, 2004 - 3:22 pm: |
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Midland 79-290
10.695 MHz |
Keithinatlanta
Intermediate Member
Username: Keithinatlanta
Post Number: 268
Registered: 3-2003
| | Posted on Tuesday, June 29, 2004 - 8:27 am: |
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Well, for once it looks like I asked a good question. It has sparked some real good interest, and I am also learning from it. I hope others are too! Thanks for the input guys!!
Keith in Atlanta |
Tech808
Moderator
Username: Tech808
Post Number: 2817
Registered: 8-2002
| | Posted on Tuesday, June 29, 2004 - 9:15 am: |
|
Keith,
You always ask Good Questions. 
And remember there is Never a BAD or DUMB Question!
With life in general and in the radio world it is one constant learning process.
There are so many radios & products & services out there now and new radios & products coming out everyday it is impossible to keep up.
I as well as you and the other Copper Forum Members continue to learn something new everyday.
That is what makes the Copper Forum GREAT!
While one member may have never heard of a product or used it the chances are with the Large Copper Forum Membership that we have, the chances are very good that someone has.
As I have said many times before and will say again, You will never hear me say I know Everything about Anything.
As the Copper Forum Membership continues to grow everyday, we the members have the chance to learn more and more on New & Older Radio Related Products & services that we may never have the chance to own or use.
The Copper Forum has been blessed with Great Techs and Moderators and the Copper Support Staff behind the scenes as well as the Forum Members themselves.
Everyone is always happy and willing to offer help when & where we can.
We are one GIANT FAMILY that continues to grow every day. 
Keep on Posting Keith!
Lon
Tech808 |
Triplecguy
Intermediate Member
Username: Triplecguy
Post Number: 166
Registered: 12-2001
| | Posted on Tuesday, June 29, 2004 - 12:30 pm: |
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Tech 808, you are too darn smart. I don't know how you could possibly now the stuff that you do, except that you must be very old, and very grouchy!!! Thank you very much for the information I must go order the channell guard now. Thanx !!!
DAN |
Tech808
Moderator
Username: Tech808
Post Number: 2821
Registered: 8-2002
| | Posted on Tuesday, June 29, 2004 - 12:43 pm: |
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Triplecguy,
40+ years in the radio hobby and still learning.
30+ years of being in the radio business and still learning.
Been using Lou Franklins products and reading his books for about 25+ Years.
I enjoy reading and learning about any and all old & new products that pertain to the radio hobby.
And I enjoy helping people when & where I can.
Only 53 and I hope Iam Not grouchy 
Semi-Retired now due to medical problems & health.
You are welcome and Thank You for the nice comments.
Lon
Tech808 |
Bruce
Senior Member
Username: Bruce
Post Number: 1315
Registered: 9-2003
| | Posted on Tuesday, June 29, 2004 - 2:23 pm: |
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53??????
Gosh you make me feel OLD! |
Triplecguy
Intermediate Member
Username: Triplecguy
Post Number: 167
Registered: 12-2001
| | Posted on Wednesday, June 30, 2004 - 1:53 pm: |
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Bruce, your age should make you feel old!!!
|
Bruce
Senior Member
Username: Bruce
Post Number: 1319
Registered: 9-2003
| | Posted on Wednesday, June 30, 2004 - 8:17 pm: |
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Yep Sonny ( tripleguy ) I can remember when sex was dirty and the air was clean! |
Hollowpoint445
Member
Username: Hollowpoint445
Post Number: 68
Registered: 6-2004
| | Posted on Thursday, July 01, 2004 - 3:47 pm: |
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Sounds like good times Bruce! |
Bruce
Senior Member
Username: Bruce
Post Number: 1321
Registered: 9-2003
| | Posted on Thursday, July 01, 2004 - 6:47 pm: |
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Hollowpoint .......
My good times are when im on the radio.....
http://www.qrz.com/wa4gch |
Triplecguy
Intermediate Member
Username: Triplecguy
Post Number: 170
Registered: 12-2001
| | Posted on Monday, July 12, 2004 - 11:16 am: |
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UH OH!!! There is no C57 anywhere in my radio!!! I spent over an hour looking at every component trying to find C57 and it isn not there. Unless it is one of the SMT components on the back of the circuit board that isn't marked. Could anybody help me with this? I don't have a schematic for it and I can not tell what any of the SMT components are. Any help would be greatly appreciated, if not I guess I have a channel guard to give away since I don't have anything to put it in.
Thanx, DAN |
Tech808
Moderator
Username: Tech808
Post Number: 2932
Registered: 8-2002
| | Posted on Monday, July 12, 2004 - 11:42 am: |
|
Triplecguy,
It is there probably between two little metal cans. It would be a Very Small/flat ceramic capacitor.
And generally in a very tight spot.
Does the Midland 79-290 use SMT Parts?
If you got schematics with your radio you may have to look at them.
Lon
Tech808 |
Hollowpoint445
Intermediate Member
Username: Hollowpoint445
Post Number: 102
Registered: 6-2004
| | Posted on Monday, July 12, 2004 - 1:39 pm: |
|
I just checked the installation instructions on:
http://www.cbcintl.com/docs/cghookup.htm#10.695 MHz AM/SSB APPLICATIONS LIST
If you're installing it in a Midland 79-290, you should be looking for C51 - not C57. And that page doesn't note it as an SMD, so it's probably not. I did a quick search on the page and the only rig that you would be looking for a C57 is the TRAM D60.
Good luck! |
Triplecguy
Intermediate Member
Username: Triplecguy
Post Number: 171
Registered: 12-2001
| | Posted on Monday, July 12, 2004 - 2:51 pm: |
|
It has a few smt parts on the back side of the circuit board, of which none are marked. And when you talk about 2 little metal cans, are you speaking of the crystals, because there is 4 of them together and then another one by itself. I will look again, thank you for the fast reply!!!
DAN |
Tech808
Moderator
Username: Tech808
Post Number: 2934
Registered: 8-2002
| | Posted on Monday, July 12, 2004 - 4:45 pm: |
|
Now I am stumped.
The printed instructions that come with the Channel Guards says Remove C57 but the web page says Remove C51.
I will give Lou a call and double check on both.
Lon
Tech808 |
Tech808
Moderator
Username: Tech808
Post Number: 2936
Registered: 8-2002
| | Posted on Monday, July 12, 2004 - 5:50 pm: |
|
Hallowpoint445 & Triplecguy,
I just got off the phone with Lou and he said C57 is Correct and Lou has changed the website information.
It may be one of the SMT's and you might need the schematics to find it.
I figured something was wrong as I have been using them since they first came out.
Typos happen on websites too. 
Hope this helps.
Lon
Tech808 |
Hollowpoint445
Intermediate Member
Username: Hollowpoint445
Post Number: 105
Registered: 6-2004
| | Posted on Monday, July 12, 2004 - 6:00 pm: |
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Cool deal. Even though I didn't help Triplecguy, I'm glad Lou got the web page corrected. |
Keithinatlanta
Intermediate Member
Username: Keithinatlanta
Post Number: 291
Registered: 3-2003
| | Posted on Monday, July 12, 2004 - 10:06 pm: |
|
Hey Lon, this post just keeps on going and going and going.......
Keith in Atlanta |
Hollowpoint445
Intermediate Member
Username: Hollowpoint445
Post Number: 107
Registered: 6-2004
| | Posted on Tuesday, July 13, 2004 - 2:58 am: |
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Triplecguy - once you get it installed I'd like to hear how you like the 79-290. I've considered purchasing one, but heard it has issues with adjacent channel rejection. |
handyman (Unregistered Guest)
Unregistered guest
| | Posted on Tuesday, July 13, 2004 - 3:06 am: |
|
I feel the frustration of all the 79-290 owners who can't figure out what's what on the surface mount side. I have a pic with channel guard installation locations as well as mods. For some reason I can't upload it here. |
Tech808
Moderator
Username: Tech808
Post Number: 2938
Registered: 8-2002
| | Posted on Tuesday, July 13, 2004 - 6:28 am: |
|
handyman,
Send me the picture and mods and I will be happy to post them for you.
Lon
Tech808
Tech808@copperelectronics.com |
Tech808
Moderator
Username: Tech808
Post Number: 2947
Registered: 8-2002
| | Posted on Tuesday, July 13, 2004 - 5:43 pm: |
|
Copper Forum Members,
I have added the CORRECT APPLICATIONS LIST for the 10.695 MHz and 7.8 MHz CHANNEL GUARD FILTERS to the:
Ask The Tech
» Installations
» Channel Guard
Area of the Forum to help you determine which CHANNEL GUARD FILTER will fit your radio.
Hope this helps.
Lon
Tech808 |
Mrhappy
Intermediate Member
Username: Mrhappy
Post Number: 136
Registered: 2-2002
| | Posted on Tuesday, July 13, 2004 - 6:14 pm: |
|
Bruce,I didn't do anything wrong..istalled by 8541,one of the best.
I might be expecting to much i guess,but would not waste my money again.... |
Bruce
Senior Member
Username: Bruce
Post Number: 1359
Registered: 9-2003
| | Posted on Tuesday, July 13, 2004 - 7:42 pm: |
|
MrHappy
The channel guard works its been around a LONG time. If 8541 installed it correctly ..... which im sure he did then it WILL improve your radio. Maby he has test results ... I know it always give a radio at least -20 db at +/- one channel and THATS A BUNCH. I realy sorry your not happy i can honestly say never had one that didn't work. |
Hollowpoint445
Intermediate Member
Username: Hollowpoint445
Post Number: 109
Registered: 6-2004
| | Posted on Tuesday, July 13, 2004 - 10:47 pm: |
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Mrhappy - what radio did you have it installed in? |
Triplecguy
Intermediate Member
Username: Triplecguy
Post Number: 172
Registered: 12-2001
| | Posted on Wednesday, July 14, 2004 - 11:22 am: |
|
Is there anyway it could be a variable capacitor? There is a small circuit board with 4 crystals mounted on it which sits on top of the main circuit board. On this small board there is a variable capacitor that almost touches the crystal cans. I was hoping this might be it, there is no labeling by it so I can't tell what number it is. I saw earlier where it should be a very small ceramic capacitor, but maybe they used a variable instead, if not could somebody please try and explain wher it is to me? I am going nuts trying to figure this darn thing out. Thanks to everybody who has tried to help.
DAN |
Hollowpoint445
Intermediate Member
Username: Hollowpoint445
Post Number: 112
Registered: 6-2004
| | Posted on Wednesday, July 14, 2004 - 2:41 pm: |
|
I doubt it would be a trimmer capacitor as the function is basically to couple one stage to another and not to change the signal in some way.
If you didn't get a schematic with the radio I'd suggest you get one now. A service manual wouldn't hurt either as they usually have photos of the finished board that are well labeled. I don't like to fiddle with radios without the service manual in hand.
If you can find a good photo on the net and have a schematic you might be able to hunt down C57 that way too.
Good luck! |
handyman (Unregistered Guest)
Unregistered guest
| | Posted on Wednesday, July 14, 2004 - 10:51 pm: |
|
Okay guys I submitted my 79-290 surface mount pic to Tech 808. Hopefully he'll make it available soon to help everyone with this radio. Hollowpoint, on the 79-290, it is the nicest radio in such a compact size. I needed that because I have little room in my Jeep. Other things I like are:
1:easy conversion-just solder some pads on the faceplate board. Put it back together and hold down some buttons. There! you're done. Also this radio starts out as a CB not a 10 meter rig so there's no need to retune the entire tx/rx for CB. Unless you're power hungry.
2:great looks-Looks like an expensive little ham rig more then the old 70's style cb. Nice to see cb modernized.
3.weather band-just the ability to receive wx on a freeband modded rig speaks for itself. It's rare.
to summerize other things that are good:
modulation-sounds great with a decent microphone. excellent sideband audio.
receive*-very strong.Especially sideband. I have a newer model so the adjacent ch interference wasn't too bad but I added a channel guard anyway and it's even better.
Now the bad stuff:
No ANL/NB button-maybe it has noise blanking all the time but I would like to know it's on and working with a button.
Channel memories don't save without 12v constant. I am still confused about this. I have had a few times that it saves my presets without power for a few mins but most of the time I must do the freeband mod every time i turn on the radio and reset all my memory channels.
No variable power/low maximum output. You must mod the radio for vari-power and the most it will do is about 18 AM and 21 SSB PEP. At least that's what the newer ones do. It's got dual 1969's so it could 40w with some heavy mods.
no real rf gain/mic gain
your mic gain button(mic) is actually an attenuator that cuts back the mic level when pressed (background noise eliminator?) your rf gain button (loc for local) is also an attenuator that's only good for hearing people right beside you. No in betweens for either of these settings without mods. Frustrating!
So there you go. All together it gets a 7 out of 10 for me. |
Tech808
Moderator
Username: Tech808
Post Number: 2958
Registered: 8-2002
| | Posted on Wednesday, July 14, 2004 - 11:02 pm: |
|
handyman,
I received the picture and I am trying to resize it for the forum as it is limited to 100 x 100 size.
If I can't get it I will have the forummaster look to see if he can help.
Lon
Tech808 |
Hollowpoint445
Intermediate Member
Username: Hollowpoint445
Post Number: 113
Registered: 6-2004
| | Posted on Wednesday, July 14, 2004 - 11:33 pm: |
|
handyman - thanks for the review!
You said the adjacent channel rejection wasn't that bad in yours before you installed the Channel Guard, how is it with it installed? Did it make a noticeable difference for you?
Also, you mentioned that when the radio loses power it loses the memories. Do you have contant power to the rig and this happens when you turn it off, or does the radio only get power when your Jeep is running? I read somewhere that you need to pop out the display before the power is cut off to keep the memories. The battery in the display charges while the radio has power and when it doesn't it discharges quickly.
The adjacent channel rejection is the reason I never bothered to get one. Now I guess I can add the lack of an RF gain control. I almost never run the RF gain fully open on my radios and I like to have a control to adjust it to my liking. |
handyman (Unregistered Guest)
Unregistered guest
| | Posted on Thursday, July 15, 2004 - 8:13 pm: |
|
The adjacent channel rejection is much better than average now that I installed the channel guard. Before I did anytime I was on the highway I would receive some kind of bleedover from the big rigs no matter what frequency. Now someone must be within about 4 channels away for any kind of bad bleed to occur.
About the memories-thank you! I finally have it figured out with your help. The manual doesn't say anything about having to remove the faceplace to the radio while there is still power to preserve the memory. That is what the trick to it is. Now I hope I don't wear out the catch mechanism from removing it so much. I think maybe I will hard wire the radio to the battery and not have to worry about it. |
Tech808
Moderator
Username: Tech808
Post Number: 2971
Registered: 8-2002
| | Posted on Thursday, July 15, 2004 - 11:23 pm: |
|
Here is the Picture handyman sent to help out.
Thank you handyman for the picture to help and Thank You Forummaster for getting it for me to post.
Lon
Tech808 |
Hollowpoint445
Intermediate Member
Username: Hollowpoint445
Post Number: 118
Registered: 6-2004
| | Posted on Friday, July 16, 2004 - 7:37 pm: |
|
handyman - Thanks for the report. I'm glad that I could help.
One note on the battery in the faceplate - the article I read says it takes 120 hours to fully charge and once it's fully charged it'll hold the memory for 240 hours. So wiring the radio to constant power is a good idea. It wouldn't hurt to wire the rig directly to the battery anyway. It'll probably help with noise and get better voltage to the rig too. |
Slim1
Member
Username: Slim1
Post Number: 59
Registered: 4-2002
| | Posted on Sunday, July 18, 2004 - 9:26 pm: |
|
I got my 79-290 back when they first came out and at times removed it from my truck. it would sit for 3-months at a time,then I go and hook it back up and BAM,all the memory channels are still there! some will retain it for a very long time and others won't;go figure!
BTW,thanks for the pics on the CG location in the 79-290,much appreciated!
Slim CDX285/RT285 |
Triplecguy
Intermediate Member
Username: Triplecguy
Post Number: 173
Registered: 12-2001
| | Posted on Monday, July 19, 2004 - 10:48 am: |
|
Ok everybody, the channel guard is in. Thank y ou very much to Tech 808 and Handyman for their help as well as all others who have contributed to my adventure. I put a variable resistor in place of the fixed resistor in the amp stage of the CG, and I think it works. Although I have not transmitted yet, the reiver sounds the same with background noise, and I get a very loud clicking or popping noise if I turn the resistor all the way to one side, sounds like a discharge of something every second or so. Can anybody elaborate on this for mw, I would appreciate it. Also, I would appreciate complete alignment instructions for this radio and If someone could tell me how to turn down the sensistivity of the reciever I would greatly appreciate it, I still have full scale noise at all times and I cannot figure out what to adjust to turn that down a bit. Once again, thanks to everyone for all the help!!! |
Tech808
Moderator
Username: Tech808
Post Number: 2995
Registered: 8-2002
| | Posted on Monday, July 19, 2004 - 5:13 pm: |
|
Triplecguy,
Just a Very Silly Question here but Why would you remove the fixed resistor and add a variable resistor.
Lou Frankiln did not design it for a variable resistor or he would of added one.
When you change the design/parts you defeat the function of the channel guard and have problems.
Lou builds every Channel Guard by hand and uses the highest quality parts for many years of Trouble Free use.
Take the Variable resistor Out and replace the STOCK Resistor and see if the problem goes away.
If not you may have already damaged your radio or the Channel Guard.
For Complete Alignment information you may have to contact the Factory for a Service Manual or Schematics of the radio.
Hope this helps.
Lon
Tech808 |
handyman (Unregistered Guest)
Unregistered guest
| | Posted on Monday, July 19, 2004 - 11:18 pm: |
|
Tech808>, I am partially to blame for the variable resistor in his CG. I didn't say to do exactly that but I did tell him he would probably need to replace the stock 560 Ohm with a 1K like the CG instructions say. With the stock resistor I experienced the same symptoms he's describing. The IF stage was overloaded. All my s-bars were lit and there was a constant loud hiss and crackling instead of quiet noise. I tried the 680 Ohm and it got better but the 1K cleaned it up perfectly without any need to realign the radio. Sounds like the VR he installed on the channel guard starts out at less than 560 Ohms and that's not good.
TripleC> Go with the 1K ohm and don't realign the receive inductors unless it is ABSOLUTELY necessary. I sent you a pic of the rig's board with the tuning cans clearly marked "T" for transmit "R" for receive and "W" for WX band. Lets hope the lowered resistance didn't kill your radio's ears. |
Tech808
Moderator
Username: Tech808
Post Number: 3012
Registered: 8-2002
| | Posted on Monday, July 19, 2004 - 11:38 pm: |
|
Ok, Now I understand.
I have also used the 680KW on very few radios as the 1KW has always worked.
The Variable had me thrown off base there.
Lon
Tech808 |
Triplecguy
Intermediate Member
Username: Triplecguy
Post Number: 174
Registered: 12-2001
| | Posted on Tuesday, July 20, 2004 - 10:00 am: |
|
Well that's not what I wanted to hear, but alright I will do it. I still have the resistor and I also have a 1000 ohm as well. But een with the pot turned althe way to 1000 ohm, I still have s9 noise, I just don't see how this will be different with a fixed value but since you guys told me to do it I will. Don't forget, that I have had the S9 noise since the radio was new, it just will not quiet down, that is the last problem I need to fix. I realize that the CG will narrow down my recieve bandwidth on a given channel, but I need to reduce the sensitivity as well. I'll post this evening after I replace the resistor, thank you!!
|
Tech808
Moderator
Username: Tech808
Post Number: 3020
Registered: 8-2002
| | Posted on Tuesday, July 20, 2004 - 10:28 am: |
|
Triplecguy,
The Channel Guard filters were designed to cut down Bleedover from other channels.
Right now I have an S-7 to S-8 Noise level, but I do not hear others talking on other channels above or below the channel I am on.
I would suggest contacting Midland and explain the problems you are having as something just does not seem right with that radio.
An S-9 Noise level is one thing but if you are on Channel 13 and get an S-9 Signal from someone talking on 12 or 14 then they are very close to you and probably using a lot of power.
MIDLAND RADIO CORPORATION
1120 Clay Street
North Kansas City,
MO 64116 USA
Tel: 816-241-8500
Fax: 816-241-5713
Email: mail@midlandradio.com
Let us know what they suggest or have to say.
Lon
Tech808 |
handyman (Unregistered Guest)
Unregistered guest
| | Posted on Tuesday, July 20, 2004 - 8:51 pm: |
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Triple C,
When you say s-9 noise are you saying that when a channel is quiet your meter reads S-9 or are you actually hearing something ( louder than norm hiss,buzz,whine) that shouldn't be there? Maybe your receiver sensitivity is normal but your s- meter is turned up too much? If that's the case there's a VR you can adjust.
The Midland is in a car right? Does the noise go away without the engine on? Without an antenna? I had severe problems with ignition noise and fuel pump whine in my Jeep Cherokee. I took some steps to reduce interference and now I get 3-4 S-units while its running typically. If you are using the radio as a base you could very well have any number of other interference problems that cannot be avoided by de-sensing the receiver. I had numerous bad transformers close by that would arc and pop every few seconds and that kept my base s-meter at about +20dB until it was fixed. Do you have another radio you can put in place of the 79-290 to see if it's really a radio problem? If the radio still is too hot on receive then you can put a slightly greater than 1K resistor (1.3K?) in line with the CG and cut back the IF gain instead of having to mess with the inductors which must be already peaked. That's my suggestion. Midland is a great company but tech support, as nice as they are, will not sit on the phone and tell you the alignment procedure. I don't know how good it is but there is a "service manual" for the 79-290 being offered by a few CB shops. Might just be the same mediocre blurry pics and schematics Midland e-mails for free though. |
Triplecguy
Intermediate Member
Username: Triplecguy
Post Number: 176
Registered: 12-2001
| | Posted on Wednesday, July 21, 2004 - 1:50 pm: |
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I have finally finished the 79-290. Yay!!! I have adjusted the s-meter as suggested and used 2 1000 ohm resistors in parralel to get about 500 ohms for the amp on the CG. It works great now, but yes there is still a lot of noise on receieve. I am talking about white noise, nothing else. It happens no matter what, regardless of location, mobile/base, as long as there is an antenna plugges in, it is noisy. I did adjust the recieve inductors a little to get rid of some of the very high frequency noise, but it made no difference on the s-meter reading. I guess I need to be happy with what I've got. I will be on the air starting tomorrow at 4:00 mst till about 5:00 each weekday. I hope to hear a few of you out there. I will be on ch 13lsb and 38 lsb. Lets make some waves. Thanks to everyone fore their help.
DAN |
Airplane1
Intermediate Member
Username: Airplane1
Post Number: 129
Registered: 5-2004
| | Posted on Friday, September 10, 2004 - 4:21 pm: |
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I have been reading these posts and if I understand right the channel gaurd will fix the problem I have with the bleed over of 4-5 channels from channel 6 when skip is rolling or even other channels like 19 when the truckers bleed up and down channel too?
I wont change the sensitivity of my radio will it?
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Bruce
Senior Member
Username: Bruce
Post Number: 1555
Registered: 9-2003
| | Posted on Friday, September 10, 2004 - 7:20 pm: |
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Airplane ...
No it will have little efect on sensitivity. Where you will THINK your radio is hearing better is the fact you WILL HEAR weak stations that a blabber mouth on a adj channel would have drown out before. Now it WILL NOT help if the other guys radio is a hunk of junk splattering up the band the cure there is a well placed pair of coax cutters ....... |
Airplane1
Intermediate Member
Username: Airplane1
Post Number: 132
Registered: 5-2004
| | Posted on Friday, September 10, 2004 - 8:18 pm: |
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Thanks,
Well I get alot of bleed over at times, What would I need to order for my grant xl.
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Bruce
Senior Member
Username: Bruce
Post Number: 1559
Registered: 9-2003
| | Posted on Friday, September 10, 2004 - 9:09 pm: |
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A 7.8 meg one here is a simple install the black tape is simply to prevent a short.
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Patzerozero
Intermediate Member
Username: Patzerozero
Post Number: 154
Registered: 7-2004
| | Posted on Saturday, October 23, 2004 - 7:50 pm: |
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hey lon, on jun 26 post you told keithinatlanta to use 10.695 ch guard, but lou franklins site says to use 7.8 in grant lt and xl(as does bruce in last post here). can i assume you were mistaken(hey it happens, even i may have been mistaken once. but maybe not) and lou is correct?
i just wanna make sure i order the right stuff the first time! |
Tech808
Moderator
Username: Tech808
Post Number: 3917
Registered: 8-2002
| | Posted on Saturday, October 23, 2004 - 9:52 pm: |
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Patzerozero,
Go to the Ask The Tech Area
Then CLICK on: » Installations
Then CLICK on: Channel Guard
I have all of the Up to Date information from Lou Franklin listed there for the Copper Forum Members to use to find the application they need for their radios.
I very well could have mis-read or posted wrong.
Lon
Tech808 |
