[Coco] COCO 3 for LowFER transmitter?

[jdaggett at gate.net]

All

To lower the frequncy of the TV out down to 160 KHz is insane. 

The neatest way to get the carier frequency needed is to divide the E clock 
freqency with an external divider. 

There are routines in the cassette output section of the basic roms that will 
generate the audio to modulate the carrier. 

To store data on the cassette the Coco outputs AFSK baseband signal. I am not 
sure if AFSK is permitted on that segment. 

The filtering from the divider can be done with opamps or standard LC filter 
network. 

The final stage is a cascode amplifier where the audio is fed to the base of the 
top transistor and the carrier to the bawse of the bottom transistor. The output is 
taken from the collecter emmiter junction of the two transistors and fed through 
and LC filter.  

I can supply a basic simple schematic of the ext0ernal hardware if needed. 

james


On 10 Dec 2003 at 12:21, Jones, Orville CPT wrote:

> Hi James,
> Sorry I took so long to reply to your message. I believe you could use
> the CoCo to key a CW signal no problem, but I don't think you could
> convert the rf modulator to transmit a A.M. signal. I am not an expert
> on the rf modulator, but I would think it would have to be at a VHF
> frequency and "frequency modulated" not "AM", but I could be wrong. I
> would have to look at the service manual which I don't have a copy of
> here. What kind of HF gear do you own? If you are only going to have a
> beacon on one frequency then you could build your AM transmitter from
> a kit and save a lot of money, then let the CoCo do the beacon stuff
> using the cassette port relay as a keyer.
> 
> Chaplain (CPT) O. Alan Jones
> AA4ZI - Amateur Radio Station
> AEM3AK - Military Affiliate Radio System (MARS)
> 
> 
> 
> -----Original Message----- 
> From: "Rev. James E. Smith" 
> Sent: Dec 7, 2003 2:14 AM 
> To: chaplainjones at earthlink.net 
> Subject: COCO 3 for LowFER transmitter? 
> 
> 
> Dear Alan Jones,
> I have a COCO 3 that is still in great shape. I would like to know if
> I can use it as a LowFER home-brew beacon transmitter for operation at
> 160 to 190 kHz 1750 meters? As to send Morse code, AM, and use it as a
> transmitter all in one. Since it has a output of Ch, 3 and Ch, 4 wide
> band how could I drop the frequency and narrow the bandwidth to less
> than 100 Hz without opening her up? I will be using FCC Part 15 rules.
> Any info you can send would be welcomed.
> 
> 73
> 
> Rev. James E. Smith
> 
> 
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