CB Radio

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Dartmoor Navigator said:
The bloke in the shop told me that the antenna come pre SWRed for UK frequencies. I thought this was complete bollox as it would depend on many other factors, so I bought an SWR meter anyway - he was right! Ch20 1:1.1 !!!!
Click to expand...

On a mobile unit???
Surly would depend on mag or side size of car, van or truck as it using that as a ground plate!
 
Hi all me and a mate bought a pair of Midland 77-099 from a well know auction site, it said that they were both in working order if not a little bit worn..
So we set about and fitted them into our Discos to be used whilst out and about green laneing etc.
My set-up is as follows:
Unit up in the roof in the map pocket powered from the interior light supply, then its a short run of RG58 cable with a clamp fit PL259 on either end, to a:

Base-loaded CB Mini Tornado Stinger Antenna
Frequency: 27-28 MHz
Power: 1000W
SWR: 1.5:1
Fitting: standard 3/8
Length: 88cm
When i do a SWR reading i hook up the meter as described in the instructions and carry out the test, turning the "CAL" knob doesn't do anything and when i take readings on different channels the needle move ever so slightly above 1. The SWR meter is:
Moonraker SWR-100 CB meter
Frequency: 26-30MHz; impedance: 50 OHMS; connection: 2 X SO239 sockets
when i turn the Midland on when it is all connected to the antenna and not the SWR i get power and a very faint static noise if i turn the squelch to about half way, but you need to put your ear near the speaker to hear it.
I am now at a loss as to what to do next, i have been told to get the unit tested but i cant find anyone near me to take it to (Kent), can i start testing the unit myself i have a multimeter and access to some other equipment if needed, i just need a place to start really..
Thanks
Rob
 
I take it you are trying to say that the Rig is no longer working,

Is this the case of it was working, and now it an't, the only way to do it is try it with an other rig, see if it transmits/recives, you may even have a duff connection on the PL259, check them first, Crimp commnectors ar fine but if you dont have the right tool then they can be a bugger, dont forget that off roading will rattle anything lose, or is it that cuae the rigs are so old you now got a dry joint somewhere inside.

I tend to stay away from ebay when buying things like this, as some will use it to get rid of things that are begining to play up.

Things like this i tend to buy new rather then repair, as they only cost just over £10, and paying for parts/Labour will only cost you more.
 
Sasha said:
True
What set up you got then
Click to expand...

I got a Midland Alan121 in the map pocket, with a long stinger, for non green lane use, and a short stinger for green laning this is mounted above the Nearside rear door, the SWR meter I keep in the Landy, but its not connected.
 
Side-show-bob said:
Hi all me and a mate bought a pair of Midland 77-099 from a well know auction site, it said that they were both in working order if not a little bit worn..
So we set about and fitted them into our Discos to be used whilst out and about green laneing etc.
My set-up is as follows:
Unit up in the roof in the map pocket powered from the interior light supply, then its a short run of RG58 cable with a clamp fit PL259 on either end, to a:

Base-loaded CB Mini Tornado Stinger Antenna
Frequency: 27-28 MHz
Power: 1000W
SWR: 1.5:1
Fitting: standard 3/8
Length: 88cm
When i do a SWR reading i hook up the meter as described in the instructions and carry out the test, turning the "CAL" knob doesn't do anything and when i take readings on different channels the needle move ever so slightly above 1. The SWR meter is:
Moonraker SWR-100 CB meter
Frequency: 26-30MHz; impedance: 50 OHMS; connection: 2 X SO239 sockets
when i turn the Midland on when it is all connected to the antenna and not the SWR i get power and a very faint static noise if i turn the squelch to about half way, but you need to put your ear near the speaker to hear it.
I am now at a loss as to what to do next, i have been told to get the unit tested but i cant find anyone near me to take it to (Kent), can i start testing the unit myself i have a multimeter and access to some other equipment if needed, i just need a place to start really..
Thanks
Rob
Click to expand...

The factory fitted crimp on PL plugs do work reasonably well, but check for any short circuits in the antennae by using your multi-meter on the PL plug. There should be a totally open circuit on MOST aerials (some home base antennae have a different set-up.) Then check for continuity between the PL plug's centre pin and the antenna's whip also between the PL plug's outer casing and the antenna base.

Bob, the midland 77's were bad for dry joints. First, make sure your power switch is set to norm or high. You cannot SWR a rig on low power.

Another common problem with these rigs is the hi/lo power switch. I've seen a good few which have had the switch damaged by impact from behind and this knackers the inside of the switch. Take off the cover (the one with the speaker mounted on it) and have a looksee at the back of the switch. If this turns out to be the problem, either replace the switch (waste of time no-one ever uses the lo power setting) or bypass it by soldering the centre wire to the hi output wire, off the top of my head I can't remember which was which, but looking at the switch should tell you. If the toggle is set to the HI position, the wire you want is the one diagonally opposite the end of the toggle.

As for the lack of audio, The three main causes of this is either a duff audio amplifier ic (a common fault if connected to reverse polarity - I can look up the right ic if you need it) or a broken wire in the mic, it could be either the earth wire (braided) or the RX wire (again off the top of my head I can't remember the colours for this mic, but can check if you need them.) The third cause could be a bad, or severely dirty, mic switch.

Plug the mic lead in and put power to the rig and switch it on. Turn the Squelch knob fully anti-clockwise and you should hear lots of white noise, with or without an aerial. If you do, then your audio amplifier IC is ok. If you hear nothing, then try a different mic. If you still hear nothing, try plugging in an external speaker.

If you don't have another mic which is known to be working, you can do a simple test by shorting the RX pin of the mic socket to the EARTH pin. Does your rig have a 5-pin din type mic socket or a screw in 4-pin socket?

I think it's the 104 that has the screw in mic and your's probably has the plug in din type. Let me know and I'll tell you which pin is which.
 
Last edited:
i can recommed a radio shop to contact who im sure can talk you through any problems.... you'll find his info at Charlie Bravos
but i would also recommend staying away from ebay when buying cbs due to screwdriver experts...
and i would also recommend a albercht 6890 any day...
an little bit of solder and it modded..
 
Clanforbes said:
The factory fitted crimp on PL plugs do work reasonably well, but check for any short circuits in the antennae by using your multi-meter on the PL plug. There should be a totally open circuit on MOST aerials (some home base antennae have a different set-up.) Then check for continuity between the PL plug's centre pin and the antenna's whip also between the PL plug's outer casing and the antenna base.

Bob, the midland 77's were bad for dry joints. First, make sure your power switch is set to norm or high. You cannot SWR a rig on low power.

Another common problem with these rigs is the hi/lo power switch. I've seen a good few which have had the switch damaged by impact from behind and this knackers the inside of the switch. Take off the cover (the one with the speaker mounted on it) and have a looksee at the back of the switch. If this turns out to be the problem, either replace the switch (waste of time no-one ever uses the lo power setting) or bypass it by soldering the centre wire to the hi output wire, off the top of my head I can't remember which was which, but looking at the switch should tell you. If the toggle is set to the HI position, the wire you want is the one diagonally opposite the end of the toggle.

As for the lack of audio, The three main causes of this is either a duff audio amplifier ic (a common fault if connected to reverse polarity - I can look up the right ic if you need it) or a broken wire in the mic, it could be either the earth wire (braided) or the RX wire (again off the top of my head I can't remember the colours for this mic, but can check if you need them.) The third cause could be a bad, or severely dirty, mic switch.

Plug the mic lead in and put power to the rig and switch it on. Turn the Squelch knob fully anti-clockwise and you should hear lots of white noise, with or without an aerial. If you do, then your audio amplifier IC is ok. If you hear nothing, then try a different mic. If you still hear nothing, try plugging in an external speaker.

If you don't have another mic which is known to be working, you can do a simple test by shorting the RX pin of the mic socket to the EARTH pin. Does your rig have a 5-pin din type mic socket or a screw in 4-pin socket?

I think it's the 104 that has the screw in mic and your's probably has the plug in din type. Let me know and I'll tell you which pin is which.
Click to expand...


Thank you for all the help, i have the 5-pin mic.

i have been searching the Internet for help and circuit diagrams etc (i dint believe they exist), and i have found i may have made a school boy error. I will explain this from a distance so anything hurled at me is less likely to hurt.....

So i made a bracket to hold the antenna on the roof, it is bolted to one of the cross bars on my Disco in the middle of the roof, but i did put a piece of rubber between the bracket and the bar to stop it rattling, this would if i am interrupting what i have read else where correct prevent the antenna from earthing. if this is the case could this be my problem?

Rob
 
Yep. You need a good ground plane. Mag mounts will connect via the magnetic flux lines (or whatever the proper name is) non mag mounts need an electrical connection to ground. Run a wire from the base to the metal, then you can still leave your rubber protector on.

There are a few sites that have diagrams. I'll see if I can find some.
 
Clanforbes said:
Yep. You need a good ground plane. Mag mounts will connect via the magnetic flux lines (or whatever the proper name is) non mag mounts need an electrical connection to ground. Run a wire from the base to the metal, then you can still leave your rubber protector on.

There are a few sites that have diagrams. I'll see if I can find some.
Click to expand...

Thank you

Would it be this that is causing the lack of white noise?
 
Hmmm - I used top have a lot of sites bookmarked for this sort of thing. If you are desperate, I could rig up my scanner and scan the diagrams I have for your rig, but it might not be this week-end.

I suspect the bookmarks might be on my old laptop.
 
Side-show-bob said:
Thank you

Would it be this that is causing the lack of white noise?
Click to expand...
No I wouldn't think so, you will usually get lots of white noise from the speaker with the squelch open even without an aerial attached.

Though, I do know one lad who hates it so much he has had the preset inside his rig set so high that his squelch doesn't open enough to let it through.

Try a set of headphones in the ext speaker socket - don't put them on your head until you've switched on, if it comes through it hurts, even at minimum volume level.
 
Clanforbes said:
Hmmm - I used top have a lot of sites bookmarked for this sort of thing. If you are desperate, I could rig up my scanner and scan the diagrams I have for your rig, but it might not be this week-end.

I suspect the bookmarks might be on my old laptop.
Click to expand...

Thank you i would take a copy of any information you have, and there is no rush we are currently using portable radios it will just be good to get the CBs working eventually.

Thanks for all the help, i am going to go home tonight and rig an earth up to the antenna and see what happens..
 
Typical, so far I've fopund the diagrams for the 77-104 and the 77-1165. I think the 104 and the 99 were the same PCB, but will find the 99 diagrams. Do you want the mic socket pinouts?
 
Clanforbes said:
Typical, so far I've fopund the diagrams for the 77-104 and the 77-1165. I think the 104 and the 99 were the same PCB, but will find the 99 diagrams. Do you want the mic socket pinouts?
Click to expand...


If you have the mic socket pinouts they would be handy


Thank you so much for all the help..
 
yep, I was right, the 099 and the 104D circuits are almost identical but the board layout is a little different.

I'll set up my scanner and scan the booklet for you, though I'm not sure how well it will come across because the print in the booklet is tiny.
 
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