Fortune recently favored me when I picked up a box of electronics ‘stuff’ from a friend (to replenish my own ‘junk box’.)
I was looking for a case for a project and when I opened up one of what I thought were project boxes, I discovered that it was a Ramsey FM-25. I did some googling and and have concluded that this is not a 25b or a 25a, but in fact a plain ‘25’. I’m rather excited as I always wanted to work with this little transmitter, but never the time, or inclination to throw money down on what I unfairly considered a lark. That has obviously changed with this discovery.
Despite several days of searches and looking at A LOT of links, I have been unable to find a manual or any information about the transmitter as it seems pretty much everything is for the 25a and the 25b. The couple of questions I had were 1) does anyone have source for the manual? And 2) does anyone have an idea of what differences there are between the 25 and the 25a? They look rather similar from looking at the manual, but are clearly not the same device.
Thanks in advance for any links or helpful information.
Regards,
Grant
I was curious about the differences between the FM-25 and the FM-25A as raised by your post so I did a web search and found this:
http://senderbau.egyptportal.ch/ramseyfm25.htm
The schematic in this link is not the same as the one in my FM-25A manual so it may be the one for the FM-25. A quick look at the schematics shows the main differences are the power input circuitry is different from the A, the output network to the antenna is different from the A, this one uses a 4 MHz crystal where the A uses a 6 MHz crystal. This is probably the info which applies to your unit. Check if the schematic matches what you have.
Neil
Might want to check this out http://www.part15.us/forum/part15-forums/transmitter-talk/ramsey-fm25-and-fm25b
Neil, thanks for taking the time to look and to answer. I found that site and schematic in my initial searches but kept looking (and asked here) because it was just the schematic and not the whole manual.
The version I have is marked "Model FM-25 Rev.1.2" (exactly like the 'x-ray view') and indeed uses the 4000.00 Hz crystal so I was pretty sure it's the same one.
Frequency is set with some hex switches. I was hoping to avoid having to build a truth table to figure out programming. I also noticed that there is no stud on the board to mount an antenna, just a spot marked ANT1. Q1, C6, and R1 and R2 are not populated. Hoped a manual would explain that. No mention of power requirements either and while I assume it's 12v with some modest current level, that was another datapoint I was hoping to collect from a manual.
If you do have any ideas about hunting down the rest of the manual, I'm all ears, and thank you again for the time you spent helping me.
Regards,
Grant
Rich,
Thaks for taking the time to post that link. I did read that whole thread as part of my initial searches.
Unfortunately there was no link to a manual, and there seemed to be several places where the posters descriptions differed from what I have in front of me. One example was that the frequency was set with dip switches (this one has binary coded hexidecmal pushbutton switches.) another was the power level discussion, and in the end, that post drifted far away from the original topic.
If you are aware of any repositiories for Ramsey manuals besides the pay sites (that seem to have only the 25B anyway) and mods.dk, I'd be greatful for the pointer.
Thank you again for taking the time to read and reply.
Regards,
Grant
So far as we know...
No one has ever written a detailed description of what the differences are between the several versions of Ramsey FM25 Series Transmitterrs.
Up above the number of versions appears to be three, with FM25, FM25A and FM25B.
I have an FM30B which the manual says is built around the fundamental features of the FM25B with LED readout and button control over such variables as volume, frequency, power and so on.
If FM25B is an improvement over earlier versions perhaps there are upgrades one can do to his FM25?
It had been in the back of my mind, mostly due to the searches and finding info about the FM25B and the FM25A being referred to as both a 25A and just "FM25" (but it clearly wasn't THE original FM25), that If I could find a manual, I should sort out the differences and share what I found.
As I have some time, I plan to do just that. I'm finding that there are some similarities between the original and the 'A' version, but several board layout things changed. Of course I expect that, not just because the circuit board version differed, but also due to the fact that Ramesy promoted improvements.
As a side note, I did email them asking if there was a source for the old manuals and heard nothing back. 🙁
Regards,
Grant