The Compact Synthesized PLL FM Kit -10mW and 100mW versions

scwis's picture
From our old site There has been new FM PLL Kit showing up on ebay these days, so I grabbed one and gave it a try. The product web page is Overall impression - great to play with, might be frustrating for a beginner. The version without a case or power supply needs both and should be considered a kit. Be prepared to do some assembly.

Compact size
Microprocessor Controlled
Easy Frequency Programming
Digital Frequency Readout with 7-segment LED display
Non-Volatile Memory
Transmissions from this unit can be received on any reasonable FM radio MONO or STEREO between 87.7 ? 107.9MHz

You must be able to find a fairly quiet spot in this band to operate the unit otherwise range and stereo quality will be affected.

When assembled, this kit is a digital synthesized unit (meaning no frequency drift, tuning or fiddling). Frequency is phase-locked against a accurate and stable quartz crystal (similar to the one in watches) This unit's frequency is programmed by means of a CMOS microprocessor without any DIP switches and complicated look-up tables. Pressing the UP or DOWN buttons makes it very easy to set the frequency. Transmit frequency is clearly indicated on a 3 digit, 7 segment LED display.

Frequency response: 20Hz - 15kHz
Level: Line-level input via RCA type sockets
Stereo Separation:
Typically about 40dB
Operating Power Requirement:
Needs a clean regulated 12v DC source with current capacity of 150mA for the standard power and 250mA for the high power option.

Operating the unit with an un-regulated wall wart type transformer will introduce mains hum into your transmissions.

I set up an "instant OTR outlet" using a completed 10 mW PLL XMTR kit, a guitar compressor for a little punch and a CD player for program input. I pushed it all out through a simple dipole.

Total cost was $100.00, $70 for the transmitter kit, $20.00 for the compressor and $10.00 for the CD player.

The primary problem in setting up this system was that the transmitter kit needs extensive post purchase work to be useful. That's not a criticism, per se, as it is only $70.00 and it's and otherwise nice unit - just be aware it's a kit and not plug and play.

First, it must be mounted in a metal box, as the circuitry has no protection from stray signals.

Second, you need a real clean power supply or you will be slammed with ripple. I've been using Eveready lantern batteries until I could build a clean enough PS.

Range is a bit too much for comfortable Part 15 use, I'd probably add an antenna attenuator to knock the range down a bit if I was going 24/7. I was getting a car radio range of about 3000 feet north-south, and 2000 feet east-west. Portable radios couldn't pick me out of the cross talk on the band as well, and I got about half that on the portables.

This transmitter is also available in a 100 mW kit unit for $100.00 - Probably a guaranteed bust if left running for any period of time

UPDATE: EDM Designs FM 100 Mw Transmitter Kit with case.

The New 100 Mw kit, completed and mounted in its case

I ordered this thing on Friday last week. Wednesday the following week I got the kit in the mail. Nicely packed, easy to assemble, easy to get the transmitter installed in the case, included a power supply to use after assembly.

I got the whole kaboodle to avoid blowing the thing up by plugging in the wrong kind of AC adapter by mistake (it's happened).

I immediately sorted through the FM dial to find 3 adjacent channels that were clear - remarkably, I found them.

I plugged in the long wire they include with it, and away I went. A short time after opening the box my kit was assembled and I was listening to my radio.

The design is rugged. The box has mounting ears and 4 screw holes.

There is an RCA jack for the antenna, 2 for the stereo input, and the power supply plug.

I don't know what else to say other than : Wow. VERY nice.

And for people who are wary of buying from overseas: this was shipped from the EDM affiliate in California.

I most definitely give this bad boy 2 thumbs up.

Kit Assembly Instructions from EDM

Basic summary of assembly steps

We are often asked about the skill level needed to get a unit completed and operational. Below is a quick summary of the steps to be performed by the buyer to get the unit functional. More detailed instructions and precautions about static sensitive devices, polarity etc. will be provided in the manual.

Remove microprocessor from protective foil and insert into socket holder on PCB

Insert digital displays into respective sockets on PCB

Connect the power wires to a suitable 12VDC source.

With the EP versions, install the supplied power connector and fasten with screws

Solder the power wires, Red and Black to power terminals on the power connector

For versions without enclosures, you may construct your own enclosure or purchase from another supplier

For versions without power units, you may construct your own or purchase from another supplier

Follow operating instructions supplied for specific model series in manual

More Images Here

Operating Manual Here
I give it HIGH marks!

Just got this transmitter, and have been pleased. Got it in the mail while on vacation (had it sent to where I was staying) so had time to play around with it. There was a FM channel not in use (an FM station went dark in Columbia, MO at 98.3FM for reasons I won't go into) so I used it, and here are the results. At 10mW, with included antenna, transmitting at ground level, was able to get the signal about 3 to 4 blocks. At 100mW, it was about 9 blocks. Needless to say, I'll be operating in the 10mW setting.

It was in a kit form as stated before, but it was easy to put together. The IC Chip was wrapped in foil. Care must be used with the chip, and the chip will sit in it's socket in the transmitter, no solder required. 2. Some very basic soldering is needed for the power terminal. 3. Place the antenna on the unit. BE WARNED: Unit will power up on 87.7FM, so move it off that channel right away. The nice thing is that it remembers the last channel you were on when it powers down, so you need not worry about it reverting to 87.7 again. When you do power down, and power back up, it may take a second or two for it to start transmitting again, more true for higher channels.

Audio out is as good as the other broadcasters when using a good audio source. Stereo is quite nice. Both right and left channels can be adjusted using pots inside the transmitter. Your listeners will be pleased with it's performance, and so will you.

As a added extra, one that has no impact on performance is the color of the LED display readout. You have a choice of red or green. This is up to the user, I don't think the listeners care about it. Mine is green.

All and all, I would say choose this FM transmitter. You won't go wrong!

Not taking orders "at the moment"

When I checked the web site, the order page links are shut down. No ordering. The exciter looks great and people obviously love the rig. I hope they get their updates or whatever ironed out soon. It would be fun to experiment with this one.

Marshall Johnson, Sr.
Senior Pastor, President
Rhema Christian Fellowship, Inc.

Rhema Radio - The Word In Worship
AM 1660 - FM 93.5

Marsh Johnson, Sr. - North Bend, Oregon, USA

Back in stock and taking orders
EDM is back with several new products.

Experimental broadcasting for a better tomorrow!

10 thumbs up!!!

About 6 months ago, I purchased the model EDM-TX-LCD-EP that has the LCD display and comes with everything. Price was a little less then. I had it up and running a half hour after I opened the box. I put it on a shelf in the basement and just let the fairly short antenna wire dangle down. Set at 10mW, it covers my whole house with a strong, clear signal. Using it inside the house was my only intent. The received signal is fabulous. You wouldn't know it isn't a commercial broadcast station if you didn't know better.

I bought it because it had good reviews and I didn't want to fuss around with any of the cheap little iPod-type FM transmitters. I rate it at 10 thumbs up because I think even people with all thumbs can put this great transmitter together.

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