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Modulation meter low bars on radio
- Thread starter Limeybastard
- Start date
Bells CB, and no mods or tunes done to it.
Their price was about the same as everybody else but more importantly. they seem to be the only one that had a 10ft power cable with fuse and Powerpole ready to go plus a few other little odds and ends I needed.
Their price was about the same as everybody else but more importantly. they seem to be the only one that had a 10ft power cable with fuse and Powerpole ready to go plus a few other little odds and ends I needed.
After spending countless attempts of trials and errors ive got 3 of those cables made now lol. Original one is in truck.
Does your PSU show you current draw and volts? Would be interested in seeing some figures .
My PSU does show amperage draw. It shows about 16 amps, a little less on deadkey.
On a slightly different subject, I ordered a 1.5Kw oil filled can type ameritron dummy load, with 19ft coax.
Hello
little late for a post (6 months) but here goes:
I received my 2970N2 couple of days ago and on low power it dead keyed 100 watts , 200 watts high power, I adjusted the high and low power and got it down to 10 watts low 100 watts high dead key,(AM) as I turn up the mic gain will rise to 200 on AM also the bias current was 2.5 amps?? brought it down to 50ma and 100 ma respectively. SSB just doesn't have the power I expected?? unless I over modulate which causes flat topping.
Any suggestions??
little late for a post (6 months) but here goes:
I received my 2970N2 couple of days ago and on low power it dead keyed 100 watts , 200 watts high power, I adjusted the high and low power and got it down to 10 watts low 100 watts high dead key,(AM) as I turn up the mic gain will rise to 200 on AM also the bias current was 2.5 amps?? brought it down to 50ma and 100 ma respectively. SSB just doesn't have the power I expected?? unless I over modulate which causes flat topping.
Any suggestions??
i am wondering if you did the bias adjustment correctly, only because the way you worded it. just to make sure we are on the same page; there are three pots to adjust.
one for the driver, and one for each final.
these are mosfets and don't get adjusted for current, they get adjusted for gate voltage.
set your voltmeter on DC volts, and put the negative lead to PC board ground.
put the positive lead on the gate of the driver, and adjust it for about 3.7 volts.
now put the positive lead on the gate of the first final, and set that for 3.7 volts.
do the same for the other final.
go back and check the first final to make sure there was no interaction from setting the other one.
one other thing that could be just as important is that this radio was aligned on 10 meters from the factory, so go up there and see if the power output is higher there than it is on 11 meters.
if so, you will need to have the transmitter re-aligned for a different center freq.
the circuits in the RCI radios are pretty broadband so this may or may not be necessary, but it should be checked.
LC
one for the driver, and one for each final.
these are mosfets and don't get adjusted for current, they get adjusted for gate voltage.
set your voltmeter on DC volts, and put the negative lead to PC board ground.
put the positive lead on the gate of the driver, and adjust it for about 3.7 volts.
now put the positive lead on the gate of the first final, and set that for 3.7 volts.
do the same for the other final.
go back and check the first final to make sure there was no interaction from setting the other one.
one other thing that could be just as important is that this radio was aligned on 10 meters from the factory, so go up there and see if the power output is higher there than it is on 11 meters.
if so, you will need to have the transmitter re-aligned for a different center freq.
the circuits in the RCI radios are pretty broadband so this may or may not be necessary, but it should be checked.
LC
the gate is the lead on the left if you are looking at the transistor with it right side up.
here is a link to the datasheet that shows the pinout: https://www.vishay.com/docs/91017/91017.pdf
you need to use the PC board ground since you are measuring DC voltage and the chassis is isolated from the PC board through capacitors in most radios.
capacitors will pass AC but will block DC.
this means that you could attach the negative lead of your frequency counter probe to the chassis and it would work fine since it's an AC signal you are trying to read.
the metal body of any of the tuning cans on the board will be connected to PC board ground.
LC
here is a link to the datasheet that shows the pinout: https://www.vishay.com/docs/91017/91017.pdf
you need to use the PC board ground since you are measuring DC voltage and the chassis is isolated from the PC board through capacitors in most radios.
capacitors will pass AC but will block DC.
this means that you could attach the negative lead of your frequency counter probe to the chassis and it would work fine since it's an AC signal you are trying to read.
the metal body of any of the tuning cans on the board will be connected to PC board ground.
LC
LC
Thanks for all the help, setting the mosfets voltage correctly made everything work properly, I was about a volt low. The biggest problem I was having was using the chassis as ground, I was getting a voltage 2.75 that would drop to nothing?? I now know the capacitors were discharging.
I have been looking for a service manual or even a schematic for the 2970n2 do you know of any sources??
Thanks
Plumber-G
Thanks for all the help, setting the mosfets voltage correctly made everything work properly, I was about a volt low. The biggest problem I was having was using the chassis as ground, I was getting a voltage 2.75 that would drop to nothing?? I now know the capacitors were discharging.
I have been looking for a service manual or even a schematic for the 2970n2 do you know of any sources??
Thanks
Plumber-G
glad to help.
the only difference that would matter to you between the DX and the N2 version is that the amplifier now uses 8 mosfets instead of 2 toshiba bipolar transistors.
everything else with regards to the alignment in the service manual should be the same.
honestly i'm not sure if there is an adjustable bias setting on the amplifier board as i can't seem to find a schematic of that new amp module on the RCI site.
here is a link to the service manual and schematics, again, the amp board will be different.
http://www.cbtricks.com/radios/rci/rci_2970dx/index.htm
yes, the manual shows the bias being set using the "current" method, and all i can tell you is that using the voltage method works very well for these mosfet radios.
my guess is that they just forgot to update the manual LOL.
one thing i wanted to mention about these radios is that you don't want to go in there trying to peak the receive and transmit coils if you don't have the right equipment.
these coils are quite broadband and you can turn them quite a ways without noticing a difference, and it can mess you up.
you really want to have a scope and a sinad meter to align this radio.
LC
the only difference that would matter to you between the DX and the N2 version is that the amplifier now uses 8 mosfets instead of 2 toshiba bipolar transistors.
everything else with regards to the alignment in the service manual should be the same.
honestly i'm not sure if there is an adjustable bias setting on the amplifier board as i can't seem to find a schematic of that new amp module on the RCI site.
here is a link to the service manual and schematics, again, the amp board will be different.
http://www.cbtricks.com/radios/rci/rci_2970dx/index.htm
yes, the manual shows the bias being set using the "current" method, and all i can tell you is that using the voltage method works very well for these mosfet radios.
my guess is that they just forgot to update the manual LOL.
one thing i wanted to mention about these radios is that you don't want to go in there trying to peak the receive and transmit coils if you don't have the right equipment.
these coils are quite broadband and you can turn them quite a ways without noticing a difference, and it can mess you up.
you really want to have a scope and a sinad meter to align this radio.
LC
I did peak the transmit section using a watt meter, but do you recommend using the scope instead?
Is there a book, video that explains the best way to tune , peak a radio?? I enjoy working on radios sort of like working on cars when I was younger... make them purr like a kitten and roar like a tiger<GRIN>
Thanks
Plumber-G
I found this on the internet and assume it is correct??
From internet:
I emailed ranger tech support last week. And chip sent me all the info that they had right now regarding the rci2970n2. I hope this info will help others. I will let Jeff put this were he thinks it should go.
Sorry for the delay. They are still working on a service manual for this model.
The 2970DX manual can be used for alignment as it is the same with exception of the driver and final transistor alignment which is as follows.
Turn carrier and mic gain control on front to minimum.
Turn mode switch to SSB
Key transmitter and set the following voltages measured on the gate of each transistor
MAIN BOARD
Driver gate voltage 3.6VDC +-.1VDC
Final gate voltage 3.4VDC +- .1VDC
PA BOARD
Bank 1 VR-2 gate voltage 3.5VDC +-.1VDC
Bank 2 VR-3 gate voltage 3.5VDC +-.1VDC
Please note also same alignment as in service manual except higher wattage listed below.
Carrier should be set to no more than 100 watts at max power AM/FM
SSB should be set to no more than 200 watts PEP at max power SSB
Regards,
Chip
RADIO SHOP SUPPLY
RANGER USA PARTS & SERVICE
1672 Main Street Suite E #228
Ramona, CA 92065
(760) 440-0125
Hours 9am - 5pm PST Mon-Fri
End internet
Is there a book, video that explains the best way to tune , peak a radio?? I enjoy working on radios sort of like working on cars when I was younger... make them purr like a kitten and roar like a tiger<GRIN>
Thanks
Plumber-G
I found this on the internet and assume it is correct??
From internet:
I emailed ranger tech support last week. And chip sent me all the info that they had right now regarding the rci2970n2. I hope this info will help others. I will let Jeff put this were he thinks it should go.
Sorry for the delay. They are still working on a service manual for this model.
The 2970DX manual can be used for alignment as it is the same with exception of the driver and final transistor alignment which is as follows.
Turn carrier and mic gain control on front to minimum.
Turn mode switch to SSB
Key transmitter and set the following voltages measured on the gate of each transistor
MAIN BOARD
Driver gate voltage 3.6VDC +-.1VDC
Final gate voltage 3.4VDC +- .1VDC
PA BOARD
Bank 1 VR-2 gate voltage 3.5VDC +-.1VDC
Bank 2 VR-3 gate voltage 3.5VDC +-.1VDC
Please note also same alignment as in service manual except higher wattage listed below.
Carrier should be set to no more than 100 watts at max power AM/FM
SSB should be set to no more than 200 watts PEP at max power SSB
Regards,
Chip
RADIO SHOP SUPPLY
RANGER USA PARTS & SERVICE
1672 Main Street Suite E #228
Ramona, CA 92065
(760) 440-0125
Hours 9am - 5pm PST Mon-Fri
End internet
yeah that seems right, and thanks for posting it.
If you were able to see a definite peak when tuning the coils, then you are all good.
if however, you turned some of them and they didn't seem to peak, then yes, using a scope on the output of the coil will help.
the only book around that really gets into aligning CB radios is "Understanding and Repairing CB radios" by Lou Franklin.
it's pretty expensive to buy these days, but there is no substitute for owning this book if you want to get into CB repair.
LC
If you were able to see a definite peak when tuning the coils, then you are all good.
if however, you turned some of them and they didn't seem to peak, then yes, using a scope on the output of the coil will help.
the only book around that really gets into aligning CB radios is "Understanding and Repairing CB radios" by Lou Franklin.
it's pretty expensive to buy these days, but there is no substitute for owning this book if you want to get into CB repair.
LC