Radio Crystals for CAB-1 and Command Base

[Neil Poersch]

Hi everyone,

I recently purchased on ebay a CAB-1 and Command Base set for Lionel TMCC. I can not get the two units to talk to each other to control a TMCC locomotive. I notice that the CAB-1 has a radio crystal with a label of 27.225 Mhz and the Command Base, despite having a label on the outside of the case saying also 27.225, actually has a crystal inside it with a label of 26.800 Mhz. It would seem to me that this would prevent the two units from communicating with each other.

Could someone who has this equipment confirm that the crystals in both units should have the same frequency label?

As a further check I have connected the Command Base to my MTH DCS TIU with a DCS/TMCC computer cable and am able to use the command base with my DCS remote control to run TMCC locomotives. So it would appear that the basic control capability of the Command Base is OK.

I would appreciate any advice that you may have on solving this problem

Thanks

Neil

[wrmcclellan]

Hello Neil,

Your CAB-1 and Command Base Crystals are correct.

The CAB-1 directly modulates the 27.225 MHz signal created by the CAB-1 transmitter.

The Command Base receives the 27.225 MHz signal and mixes that signal with a 26.800 MHz local oscillator (LO) to create a 455 kHz Intermediate Frequency which is then filtered and applied to a 455 kHz demodulator chip.

So your issue is if the radio portions of your TMCC command set are working. When the CAB-1 is operated, and the Command Base (CB) is receiving the signal, you will see the red light on the CB flash in time with the commands from the CAB-1 (i.e. spin the red speed dial and you will see the red light flash). If you do not see this you have few options.

Find a friend with a CAB-1/CB set and take your units over there and swap and try each component to see which one is not working. If you can determine which part is defective then call Lionel, get an RMA and send it in for repair.

Good luck!

 

[lionelsoni]

I think those numbers don't add up.  26800 + 455 = 27255, not 27225.  Could you have misread the crystal's label?  Or maybe that 30 kilohertz difference is the problem.

[wrmcclellan]

Bob,

You are correct. Sorry I could not read my own writing. The normal CAB-1 crystal is 27.255 kHz, so if Neil does have 27.225 vs 27.255 MHz in his CAB-1, and the CB crystal is 26.800 MHz (should be 26.770 MHz - recognizing he has a CB crystal cover that says 27.225 MHz), then his system is off by 30 kHz..

I checked Lionel's web site for replacement parts and they still have the crystals for the CAB-1 at 27.255 MHz ($9.00), which should work since the CB has  26.800 MHz crystal.

Lionel years ago offered different crystal sets for TMCC so one could have two independent layouts in the same area. As the years have gone by and now TMCC is discontinued, the selection has dwindled to nothing but a few parts left.

[Neil Poersch]

Thanks Roy. Makes sense. At least I can ignore the difference in crystal frequencies as root cause of my problem. Unfortunately I do not know anyone locally who has this equipment. I will have to keep working with the vendor that I purchased the system from to resolve the problem.

Neil

[Neil Poersch]

Bob, Roy,

Good catch. I did mis-read my label. I do have a 27.255 Mhz crystal.

It seems that 27.255 is Channel 23 on a CB radio so I am going to dig out my old CB radio and see if it will receive a carrier from the CAB-1 or if the Command Base red light will light up with a carrier from the CB radio. Interesting times ahead.

Thanks to both of you for your help.

Neil

[wrmcclellan]

Hi Neil,

The red light on the Command Base (I will call it the Lionel CB - LCB) is after the signal demodulator so a CB carrier into the LCB should not do anything. Now if you could whistle the TMCC digital sequence (it is a Frequency Shift Keying modulation - basically FM)...

A CAB-1 signal into the CB could be interesting? If it works you need to continuously spin the red throttle knob to generate a continuous signal.

[Neil Poersch]

Hi Roy,

I just tested the units with my old CB radio. The CAB-1 does cause a clicking sound on CB Chan 23 when I press any button on the remote and I can see the carrier signal strength indicators light up on the CB radio. Turning the throttle knob generates a series of clicks reminiscent of an old rotary dial telephone. So I am operating under the assumption that the CAB-1 is transmitting as it should.

As you predicted, when I keyed the microphone on the CB I did not see any flicker of the red light on the LCB..being unable to whistle FSK I stopped at that point.

So I can get the LCB to control a TMCC locomotive when the LCB is hardwired into the MTH DCS system and the CAB-1 remote generates RF signals and the LCB red light doesn't flicker at all so I have to conclude that the LCB RF receiver circuitry is not working properly.

Neil

[wrmcclellan]

Neil,

Unfortunately it sounds like your description is indeed the case.

I will do some additional poking around to see if I can come up with any other ideas.

[Neil Poersch]

Thanks Roy. Any help is appreciated.

Neil

[wrmcclellan]

Neil,

Tried to start an off-line conversation with you using the Forum "Start Conversation" feature. Let me know if it works and you get the message.

[Neil Poersch]

Hi Roy,

Sorry but I was offline until now. Thanks for your additional comments. I just read your message to me. I don't think my problem is one of a minor tuning adjustment but rather one of a major failure of a component. I think that I have done everything correctly to set up the TMCC system and have done a reasonable amount of troubleshooting so I have initiated a conversation with the vendor who sold the system to me to either get a replacement system or a refund. time will tell how well that turns out.

Thanks for all your help though.

Neil