There is also a Ramsey FM-100 unit with the various modifications for improvement around the BA1404. I also added a 2nd output stage prior to the final filter for better performance from that filter. Running a cool 50mW, it drives a home built 25 watt amp. This unit serves as a hot stand-by. I purchased this kit back in "97" and it still runs as perfect as it did the first flip of the switch after assembly.
RFBurns, I own the FM100 (Not to be confused with the FM100B) I have found a few goofs made to my unit such as two electrolytic capacitors C58 and C72 being installed backwards per the instruction manual. I am not sure if you had turned those caps around in your unit so the + sides pointed towards the MAX291 IC chips.
I realize your post is rather old, but I am curious what modifications you made to your Ramsey FM100.
I have a CRF-T01A fm transmitter which is better quality than other Chinese transmitters and is power adjustable from 0-1 watt with actual transmitting power displayed on screen as compared to the actual power setting which is great for antenna matching without a meter. Sound quality is fantastic on this unit and pre-emphisis is selectable. Can "almost" get to the volume of the other stations without distortion. These are on Ebay too and can be purchased directly from Elecsky in China for about $100 DHL shipping. Alot less than a Ramsey FM 35B. Sounds better than commercial stations and very low background noise...none at normal volume, and no hum at all with block style laptop power supply(12V).
K-ROCKS has both FM and AM facilities as well as online streams.
The AM consists of two LPB AM-30 transmitters modified for C-QUAM AM stereo using the Chris Cuff (Alfredo) C-QUAM exciter boards. One transmitter is on a hot-standby state and the other is on air. Both are fed into LPB's TCU-30 line couplers feeding the neutral wire. Coverage is 4 solid miles and on rainy days, extends to well over 8 miles.
The LPB units were second to none in craftsmanship and long term dependability. The design is simple and easily field serviceable. Even years later after the LPB company has all but disappeared, replacement parts are still available, making any one of the solid state LPB units well worth their weight in gold. My avatar picture shows one of the LPB units on air with the C-Cuff C-QUAM exciter board installed.
There was only one drawback to these particular units. The factory exciter board, though well designed and excellent component layout, they suffered from nearby inductance influences near the exciter RF power adjustment pot, making the power adjustments a real nightmare, and often at times blowing the finals due to the inductance effects causing the power level to swing wildly. LPB used a stand-up potentiometer mounted on the PC board, basically turning that adjustment pot into a little radiator and anything within a 4 inch range such as a hand or even a screwdriver would throw off the circuit impedance, thus shifting the power level.
The solution to this was to replace that pot with a trimmer pot that mounts flat and flush with the PC board so that a non-conductive tuning tool could be used to adjust the pot. It would take a direct contact with a finger or metal object to the top of that pot to make it go crazy, compared to just moving your hand within 4 inches with the older style pot.
On the collection shelf I have the Panaxis AM-100 and AM-5000 amp, a much older LPB AM-6 tube unit, and a Harris STX-1C C-QUAM exciter, plus various other home built units of tube and solid state designs and linear amps.
The FM side..several tx's over the years. Out of all that, probably only two really worth mentioning.
First is the Panaxis FM 10 watt unit with the ENC-1 case. It has the SG module, the FM-10 10 watt amp and PS. After including a small 1 inch 12vdc fan, it has stood up to the test of time and on air endurance. Spare parts are still available including the PLL chip which is a DS8907 available from UTSource. This unit serves as the full time on air tx.
There is also a Ramsey FM-100 unit with the various modifications for improvement around the BA1404. I also added a 2nd output stage prior to the final filter for better performance from that filter. Running a cool 50mW, it drives a home built 25 watt amp. This unit serves as a hot stand-by. I purchased this kit back in "97" and it still runs as perfect as it did the first flip of the switch after assembly.
I also have 3 of the CZH units from China. These are more for collecting purposes than on air use, however they have proven to be highly reliable and clean with some minor adjustments of their final filters. I have the 1/2 watt, the 1-7 watt and the 1-25 watt units.
Along with the CZH units sitting on the collection shelf are several home built FM units and amps.
At my station's forum is a section about AM Carrier Current with a few detailed photos of the setup and short article about Carrier Current broadcasting.
Peace!
just love this review so much, can you add some pictures?
I used to use two CZH clones from FMuser, one 7-watt, and the other a 15 watt. As others have mentioned, the harmonic were horrible, the output wasn't much better: My processor had to be turned down as if I used my loudness settings, it would create distortion in the 7-watt. The 15-watt handled this slightly better, but among many issues, it lacked a dedicated power switch (It turned on when yoiu plugged it in and...well, turned off when you unplugged it).
Now I have a BladeRF Software-defined radio. I broadcast both FM Stereo with RDS, as well as a neat little digital system I put together. Being an SDR, none of the output issues exist, the signal is clean and constant. The catch? I don't yet have the VHF downconverter, nor do I have an amplifier so unlike the previous two, it is closed-circuit testing for now.
My processor is Stereo Tool. I used Breakaway but did not like its limited options.
I'm going to try putting in a 15 watt transistor after it comes in, see if that helps it.
Please let me know how you make out after you change the final output transistor to the real McCoy ! I have two similar units rated at 5-15 watts model ST-15B, silver aluminum case.. Best I can muster from it is 12 watts. I'd be very interested how you can tell if the final output transistor is bogus ? Thanks, Spooky..
"Knowledge Is Always Made More Valuable By Sharing It With Others !" Always Remember To Be Kind ! True Greatness Often Has Very Humble Beginnings ! Help A Kid Out Today ! *** High Mountain Radio *** "Broadcasting From Somewhere High In The Remote Appalachian Mountains"
Post by HighMountainRadio on Jan 3, 2018 4:15:04 GMT -6
Greetings From High Mountain Radio 99.9 FM Stereo !
Good morning to all ! Here I am using a Chinese imported Model ST-15B, 5/15 Watts. I like this unit for the mere $55.00 U.S. that I paid for it on EBay. It is very well built with aluminum housing with internal cooling fan. The fan isn't really 'top shelf' but it does work, and work very well ! Pictures of both transmitters can be viewed by clicking on the links provided. My second backup and mobile FM broadcast transmitter is VERY well constructed and is sold from an EBay seller in Hong Kong. A very good friend gave me the Hong Kong transmitter recently. The same transmitter is selling on EBay for a mere $35.49 plus $5.00 for shipping from Hong Kong. Don't let the price dissuade you from purchasing one, this is the best deal for a very good low power FM broadcast transmitter that you will likely find anywhere ! This unit is an excellent performer and has the ability to be used in your vehicle since it requires 12 VDC @ 6 Amps and can be simply plugged into your cigarette lighter (assuming the car manufacturers still put these in cars these days). It is a terrific 'tactical' transmitter and puts out a solid 5 watts of power ! I can't praise this little unit enough !
"Knowledge Is Always Made More Valuable By Sharing It With Others !" Always Remember To Be Kind ! True Greatness Often Has Very Humble Beginnings ! Help A Kid Out Today ! *** High Mountain Radio *** "Broadcasting From Somewhere High In The Remote Appalachian Mountains"
Post by HighMountainRadio on Jan 14, 2018 9:26:23 GMT -6
Do any of you have and use a HLLY Model TX30S transmitter ? In it's specifications it states that it has a user selectable pre-emphasis, 50us or 75us. Can anyone having one of these verify if this is true ?
Also, if there is someone out there using one of these units tell me what the correct procedure is for setting the pre-emphasis as a user selectable variable ?
It appears that the board being used in the HLLY TX-30S is exactly that same internal boards being used in the ST-15B(V1),(V2) and (V3) versions fm transmitter. In fact just doing a visual inspection without a schematic diagram it appears to be identical !
I was thinking that perhaps, since the internal components appear to match exactly, I MAY be able to utilize the procedure for the HLLY TX30S for setting the pre-emphasis on my two ST-15B's.. It would be nice !
One final note, I have two ST-15B 5/15 Watt transmitters and both sound excellent using a wide variety of radio receivers from very old to very new, very cheap to quite expensive and on every one the signal sounds very clean, good frequency response, excellent sounding transmitter ! I use a Xenyx Model 1002FX Stereo Effects Processor with adjustable EQ ahead of it in conjunction with an old Tascam Model M-06ST Stereo Mixer. I use a PC as my sound source with outstanding results. If, in fact, this transmitter is set to 50us pre-emphasis, it certainly doesn't present any serious degradation in audio quality !
"Knowledge Is Always Made More Valuable By Sharing It With Others !" Always Remember To Be Kind ! True Greatness Often Has Very Humble Beginnings ! Help A Kid Out Today ! *** High Mountain Radio *** "Broadcasting From Somewhere High In The Remote Appalachian Mountains"
Post by ogrevorbis on Jan 29, 2018 19:04:36 GMT -6
BTW: "Somewhere High In The Remote Appalachian Mountains" - So am I! Maybe I can hear your station around here. Can you give me an idea of the general location. I am in NH. I am interested in getting my station up onto a mountain using a solar panel right now.
If you're interested in changing the pre-emphasis on the ST-15B, there is a mod you can do to the board to make it work. You need to replace two caps. When you look at the BH1415F datasheet, you will see two pins for the pre-emphasis (pins 2, 21). There should be some 2.2nF caps on there. You can replace those to change the pre-emphasis. I don't know what value to change it to for 75uS because it doesn't say in the datasheet, but you can probably find it somewhere and if not, just do some experimentation.
Post by dave radio on Oct 14, 2022 14:21:08 GMT -6
Add to/resurrect an old thread here. Owner of an ST-7b. Probably a couple years now on this xmtr going 24/7. The very first thing I did was replace the fan as the original was really really loud. Replacement much quieter. However, old or new fan, unit always ran quite warm to the touch on high power.
Over time I've become increasingly disappointed with the quality of audio. Fiddling around and jiggling the dc cord going in, found that the unit would cut off/on. First thought was "bad power supply" so replaced with comparable PS, no change.
Opened up ST-7b and re-soldered PS connectors on the motherboard. Works fine now and I can't believe how much insanely cooler this thing runs now. Also, a better sounding signal.
I'm glad a little checking around with this saved me a replacement cost, but I've ordered a CZE-15b which seems to have a better chip so I'll have a backup down the line. Happy broadcasting!