Hello all, I am new to this forum and hope to be of service to others on this forum board.
In the meantime, I have the older Ramsey FM100 unit (the one with the BA1404 FM stereo generator chip) and I am curious if anyone here has owned this unit with the version 1.1 circuit board and if so, what mods were successfully done to this unit.
First off this is the Ramsey FM100 Transmitter kit, do not confuse it with the currently available FM100B unit. This is the FM100 circuit board version 1.1
Audio mods are my biggest interest, I have seen one such mod listed under alt.radio.pirate where parts were replaced with different parts or parts were placed in parallel with existing parts. My only concern is part numbers mentioned in some parts of the text do not relate to the actual part values in the kit I have, or the part numbers don't match.
So basically, I am not willing to try a mod if things don't match up to what my unit has.
Can anyone respond who owns or has owned this kit and tell me if there are any seccessful and useful mods for this unit to clean up the audio of distortion and unwanted harmonics in the audio chain? Please keep in mind, some of the parts for this kit are no longer available, so trial or error could render this kit a boat anchor if a mod happens to damage anything.
I do not own this particular transmitter but being as it uses the BA1404 is where the trouble begins. The chip itself has limitations and no matter how well you filter the audio going into it there is going to be a point of diminishing returns. I own a FM10c that uses the same chip and the best that I found which can be done is to RF choke the audio inputs by both bypass capacitors and RFCs which can help a bit with RF getting back into the audio. I also removed the pre-emphasis on mine as my audio processor itself handles the pre-emphasis in a more proper way and that alone makes a huge difference in audio quality as I can achieve full modulation without any distortion whereas the transmitter in its original form had to have audio levels down far below other radio stations in order to sound good. When the BA1404 is used only for its MPX output and not its built in FM oscillator it can produce good results but it requires a radically different approach than Ramsey has designed their kits to utilize for cost saving reasons to keep it within the budget of hobbyist.
Here is something interesting I just found out. It appears that the left/right channel circuit design is incorrect.
The LEFT audio circuit is designed on the circuit board to go to pin 1 of the BA1404 chip which is the RIGHT channel input pin and the RIGHT channel is designed to go to pin 18 of the BA1404 which is the LEFT channel input.
I was wondering why when I used the balance control on my mixer and set the balance to full LEFT, the audio on my FM stereo receiver played out of the RIGHT speaker. I rechecked this on 4 different FM stereo receivers and the results were the same. The balance was backwards.
Close inspection of the schematic diagram and close inspection of the circuit board road map indicated that the RIGHT channel circuit was going to pin 18, which is the left channel input and the LEFT channel circuitry was going to pin 1 which is the RIGHT channel input.
Go figure huh? I wonder how many other people who bought this kit noticed this mistake. I am fortunate that this kit was given to me for free from a friend, who actually built the kit. They failed to get it working because he put a part in backwards in the audio circuit and forgot which one it was upon giving it to me. However he claimed he corrected the mistake. So it was a pain for me to get it working because I had to figure out what part that was and replace it.
So now I have to take the kit apart and figure out a way to cross the audio circuits so the RIGHT channel goes to the RIGHT channel input and the same for the LEFT channel.
This includes cutting the circuit board traces at the BA1404 inputs and using jumpers to cross the circuits to the correct pins.
I am still open to any audio MODS for this unit though.
Are you serious!?!? My FM10c had the same stupid design flaw in that the right/left channels were reversed. I noticed right away in the same exact way as you did by using my computers digital balance control and it was the opposite on the radio of what it was supposed to be. I wonder why Ramsey built them like this? I thought the FM10c was the only one they made that mistake with.
Hrmmmm, are those kits designed in China? Because for example our headphones are tip = left, middle ring = right .... EVERY Asian-except-Korea-and-Japan made headphone I've had not intended for an American reseller (or those cheapy "add your company name here" ones they give away on planes) are reversed.
Here is something interesting I just found out. It appears that the left/right channel circuit design is incorrect.
The LEFT audio circuit is designed on the circuit board to go to pin 1 of the BA1404 chip which is the RIGHT channel input pin and the RIGHT channel is designed to go to pin 18 of the BA1404 which is the LEFT channel input.
I was wondering why when I used the balance control on my mixer and set the balance to full LEFT, the audio on my FM stereo receiver played out of the RIGHT speaker. I rechecked this on 4 different FM stereo receivers and the results were the same. The balance was backwards.
Close inspection of the schematic diagram and close inspection of the circuit board road map indicated that the RIGHT channel circuit was going to pin 18, which is the left channel input and the LEFT channel circuitry was going to pin 1 which is the RIGHT channel input.
Go figure huh? I wonder how many other people who bought this kit noticed this mistake. I am fortunate that this kit was given to me for free from a friend, who actually built the kit. They failed to get it working because he put a part in backwards in the audio circuit and forgot which one it was upon giving it to me. However he claimed he corrected the mistake. So it was a pain for me to get it working because I had to figure out what part that was and replace it.
So now I have to take the kit apart and figure out a way to cross the audio circuits so the RIGHT channel goes to the RIGHT channel input and the same for the LEFT channel.
This includes cutting the circuit board traces at the BA1404 inputs and using jumpers to cross the circuits to the correct pins.
I am still open to any audio MODS for this unit though.
I know this is an older thread but it should be noted that Ramsey Electronics, LLC has made numerious revisions over time to their transmitters. The FM10 series in particular originally had the left and right channels reversed. Revision levels less than 2.0 were reversed The current revision is the FM10B and revision level 2.1 is correct since at least 2006. I am currently looking at the actual design files and you can believe this to be factual. The FM25 series also have had numerious revisions over the years.
Please do not expect me to monitor this forum on a regular basis. I came across it while researching a customer question. I thought it would be good information to post.
Some one stated that Ramsey products are designed and built in Victor NY and this is also true. We do resell a number of kits and other products but all true Ramsey Electronics kits are designed and produced in the USA in Victor, NY.
Some one stated that Ramsey products are designed and built in Victor NY and this is also true. We do resell a number of kits and other products but all true Ramsey Electronics kits are designed and produced in the USA in Victor, NY.
Will Ramsey ever respond to the flood of requests made some years ago for an AM CQUAM kit?
K-ROCKS RadioOne
ZeroPointRadio
AM Stereo 1670
FM Stereo 92.1
I asked a few times on their forum if they would ever consider a part 15 longwave transmitter and receiver kit. Of course I expected they never would from the lack of interest in longwave but I thought it would be cool if some kit existed for the experimental band.
I have a Ramsey PA-100 amplifier for sale if any one is interested. 40 watt output... I also have a Ramsey transmitter if needed as well to make a complete package.... you can email me at k4kak@hotmail.com