Ramsey FM-30 or FM-35?

[chanito]

Bought two of the FM-30's, fully assembled, several years ago. Opened the case on one, and found the circuit board marked FM-35.


The FM-30 was sold as a kit or assembled, with 25mw out, and the FM-35 was only for export and available assembled only. Does anyone have a FM-35 or know of a pic somewhere showing the board? Here's the board in my FM-30:

[Pigmeat]

I don't think there was much difference between the two. You connected a jumper to get a full watt out of the 35. There are enough guys on here who owned those things, I'm sure someone can clue you in on how to do it.

[chanito]

Guessing it might be that open spot up there at the output transistor marked "C64" but since there is no schematic available with these, hard to tell.


I did verify this is an oddity. It is the "FM35B" circuit board, but in a case marked "FM30".  The other giveaway is that the FM30 product was a through the hole component board, while the FM35 was all SMD. Parts placement on the FM30 layout diagram from the construction manual, which, btw, has no real schematic, is completely different from this FM35 board. The only real similarity is the curly stub.


I suspect the deal is that if someone ordered a "fully assembled" FM30, they changed the front panel on the FM35B and omitted the jumper to keep it at the preamplifier power output. Or, maybe at the time they just had a bunch of spare FM35B's to get rid of.

[CoolAM Radio]

Check

https://sourcefmtransmitter.com/wp-content/uploads/2017/07/FM30-manual.pdf

Google  >  "ramsey fm 30 output power modifications"

André
CoolAM Radio - Shortwave

[ThaDood]

One MOD that you may want to consider with the FM-30 / 35 is one that helps drain an ESD (Electro Static Discharge.), to chassis ground, since the RF Final is extremely static sensitive. A 200uH choke across the RF OUT and GND seems quite effective for that. (So I have read.) Years ago, that happened to my FM-30 TX from a close lightning strike, so I wish that I'd come across that MOD back then. 

[chanito]

Found the schematic for the FM35. There is a MRF557 following the "U8" amplifier, before all the final filtering and tuning mentioned in the FM30 manual, and is what makes the 1 watt in theory. Mine don't make anywhere near 1 watt. Hard to tell what the actual output is on the two units because I don't have a VHF watt meter that will go down to mw range. It is, however, enough to barely lift the needle off the peg on a Daiwa meter set to the 20w scale. SO.... either the final is blown or it is disabled. Either way, it's enough output to cover the typical 25mw expected range of about 100-200ft. with a crappy antenna. Christmas music neighborhood station level.

[chanito]

Built a bazooka dipole and it quadrupled the range. Had to turn it down.