FM100B Comments?

druidhillsradio · #1 08-02-2012, 07:42 AM

I just took delivery of the FM100B. Wanted know what others thought about it. Also, any mods that one could recommend. Currently using a vertical wire dipole inside and tuned with a MFJ analyzer. Audio is from a pc using the latest version of Stereo Tool set for FM. So far I am very impressed.

joseph363 · #2 08-04-2012, 10:08 AM

Hi to you. I just finished building a FM 100 B kit with the Hi-Power option. I also purchased the TM100 antenna kit. Here are my initial observations but I plan another review later on when I get more time to help other kit builders. It took me nearly a month to build the FM100 as I took extra time to verify part correctness, placement and soldering. Sure, it can be done quicker but I wanted it to work the first time, which it did NOT. Constructing the kit went fairly well with only a few questions but a few phone calls to Ramsey solved everything. I had one part missing, one part of the wrong value and a bad line cord. Again, Ramsey solved everything just fine. My only start-up problem was a misplaced connector on the main board which was my fault. I had no indications on the front panel board due to this error. The FM100B replaces an FM25B that was in service for over 2 years and worked great. I was using a "home built" vertical dipole with the FM25 but thought the TM100 would be a better antenna. Right now, I can only operate the FM100 at minimum power due to higher SWR of the TM100 and its placement outdoors next to other antennas. The home built dipole shows a better SWR so I need to look into that problem or put it back in service instead of the TM100. Any power setting higher than minimum locks up my scanner radio on various VHF frequencies but I attribute this to antenna placement. Another 2 Meter radio also "locks up" on certain frequencies. I really do not expect to operate the FM100B at maximum power as it is illegal but should be able to set the power level half way in my opinion. The sound quality of the FM100 is good but sounds a bit off frequency. There is no way to adjust or "tweak" the frequency output that I know of but am still looking into that problem. Recall that when you set an Analog tuned FM radio receiver not quite on frequency of what it sounds like? That's what my FM100 sounds like. This presents a problem when using a digitally tuned FM receiver as it only tunes "right on" frequency. Again, I am thinking this might be antenna placement or a problem with my TM100 antenna. My audio source cannot vary the left or right channel output as its a fixed balanced output. I see this on the LED barmeters of the FM100 in that the left channel shows quite a bit higher than the right channel. How to adjust that? Don't know right now but I am looking into that. All in all, I like the FM100B and think that if I did not have all the other antennas and radios nearby, I would not see some of the problems I now have. I have a few photos and construction tips that I will pass on in the future. The FM100B is a very good transmitter but so is the FM25B.

druidhillsradio · #3 08-06-2012, 09:55 AM

Hi Joseph. Thanks for the detailed description of your experiences. My FM100B sounds great. I am using the latest version of Stereo Tool (FREE VERSION) as a plugin for WinAmp. I selected the 75us US FM and the processing sound as good or better than any of the local FM's around here. As far as the left VU meter goes, mine is slightly higher as well. So I ignore it. :-) I too have the 1 watt option installedm but I am running a home-brew vertical dipole inside near a window. I am running it a 1/2 watt or thereabouts. I tuned the dipole with a MFJ analyzer. I covers my small neighborhood with a little bit of flup when you drive around. Signals drops off very quickly when leaving the neighborhood. Why not check the output with a frequency counter with regard to the off-freq sound? Also, make sure that if you are using any processing with pre-emphasis, that the pre-emphasis is turned off. What are you driving the transmitter with? CD? PC?

73, John

josephjnx · #4 08-26-2012, 10:45 AM

Hello John. Earlier this week, I removed the TM100 antenna from service and re-installed my homebrew dipole antenna. I did move it to a different location, higher than before and farther away from my other antennas. My scanner now does not lock up on any frequency and better than that, the FM100B now sounds right on frequency. I’m not sure why that corrected my “off frequency” report of the FM100B but it sounds great now. My 2 meter radio still locks up on 146.520 MHZ but not when I listen to that frequency in my truck in the driveway. I’m sure it’s due to the 2 Meter antenna still being about 15 feet away from the FM100B’s dipole antenna. This happens even with the FM100B set to ¼ power or greater. I’m planning on getting a MFJ 259B anyway for other uses so CAN I use its internal frequency counter to check the FM100B’s output? I plan on a major change to the location of 2 of my antennas so that will help the FM100B.
As far as the audio being unequal on the bar graphs, I am temporarily using an XM radio to drive the FM100B. I’m not sure about the legality of rebroadcasting my XM audio so I probably will not use it long term as my audio source. The XM has no way to adjust the balance of the audio output. This unequal audio can be heard on any portable radio I use for testing so that’s one item I need to get fixed. 73’s Joe

XRQKFM · #5 08-27-2012, 02:19 PM

I have an older XM radio, that broadcast a block on its own! XM Radio really needs to be processed, so you need an external transmitter. Be careful not to rebroadcast the channels with the four letter words, it won't be XM; you will have to worry about!

I have had good feedback, from users of the FM100b. Using a well tuned outdoor antenna and some distance from other antennas, will eliminate many problems you are encountering with images on 146.520; often caused by overload.

Make sure you use quality RF cable, poor quality cable from China can cause high SWR. I got some fake Belden from a reputable business, on some frequencies; I would get 2.1 to 3.1 into a dummy load, but that was only after spending hours trying to tune an antenna.

Poor processing, can cause that off frequency sound. FM, is very sensitive to excessive highs; even with a good LPF.

Steve
www.radiobrandy.com