C. Crane FM Transmitter 2continued
Testing In The Lab:
The audio test files used on our audio player typically cover two categories. One set of files are standard audio files as sourced from their parent compact discs transferred at 256K or 320K. Another set of files have aggressive audio processing applied to them with reasonable high compression and loudness applied, simulating processing commonly utilized in commercial radio broadcasting. These audio files were transferred to our test audio player at 320K as well.
For the first battery of tests we used the non-processed audio files feeding the transmitter. The audio was quite clear and no signs of distortion were noted. The on-board LED audio indicator serves to alert the user of audio levels feeding the transmitter, illuminating green to indicate normal input levels and red indicating excessing audio input.
Thanks to the on-board audio dynamic range control in addition to a built-in digital audio limiter, we found it impossible to grossly overmodulate the transmitter as observed on the Belar FMM-2/FMS-2 broadcast modulation monitors. With a very hot audio input you can hear some pumping from the built-in processor when the audio input is pushed. This appears to be paired with the LED modulation indicator as keeping it in the green we did not notice any pumping. For those of you seeking in-depth information regarding the on-board audio processing page 24 of the SI4710 datasheet (PDF file) is very interesting to read.
We repeated the audio test using audio source files that were pre-processed using a popular broadcast audio processor set for a very aggressive (i.e., loud) sound signature. The audio was quite loud and rarely overmodulated the transmitter while set with the green LED indicator.
A major improvement from the original generation of this transmitter is that the last transmit frequency setting is retained when the transmitter is powered off or power is removed from the unit. This could prove useful if the transmitter is located in a difficult to reach or remote location.The Test Range:
Tests were conducted in an open field with the transmitters elevated 8 feet above the ground. For equal comparisons the transmitters were powered from their supplied AC power adapters. Our field strength readings were measured with several different instruments including the Potomac FIM-71 field intensity meter. We averaged the measurements across all measurement devices. We also measured the field strength across the band using three different frequencies.
Our factory fresh original version FM Transmitter was right at the maximum allowable level while the FM Transmitter 2 measured lower than expected. Outdoor coverage evaluated in several different ways. Besides measuring the field strength with our field strength meters we tested unobstructed outdoor coverage utilizing various portable and automobile radio receivers.
We reviewed the technical documentation that was submitted for the Part 15 certification of FM Transmitter 2. It appears the transmitter has no problem reaching the proper field strength so we assume our test sample is not necessarily representative of all transmitters off the manufacturing line calibration process. We followed up with the folks at C. Crane.Excellent Customer Service:
All the people we've dealt with, directly and indirectly, were super to work with. Customer Support Specialist Jessyca Rosson and C. Crane's President Bob Crane worked with us to provide us the units to be used not only in this and long-term product evaluation but in our soon to be published FM transmitter competition.
Our technical queries were expertly handled by Jarl Johansen, C. Crane's Electronics Research and Testing Specialist. He was able to provide the technical information we were looking for and even offered to send us additional units if we needed other samples to complete our lab measurements.
C. Crane backs their products with a 60 day satisfaction guarantee to make certain every customer is pleased with their purchase.The Verdict:
The C. Crane FM Transmitter 2 has to be one of if not the very best transmitter for its price range. Small, portable and very good audio quality makes this a winner in our book. The transmitter would work quite well for the casual user wanting to play their audio sources through their radios as well as the Part 15 enthusiast wishing to experiment with FM radio on a budget. We also note that as of this writing the FM Transmitter 2 is $10 less expensive than the unit it replaces.
HobbyBroadcaster.net would like to take this opportunity to extend thanks to Customer Support Specialist and Purchasing Assistant Jessyca Rosson, Company President Robert Crane and Electronics Research and Testing Specialist Jarl Johansen for their assistance in making this product review possible.September 8, 2011 Update
After an excellent information exchange with Jarl Johansen the problem with our test specimen was discovered and corrected. There's a ring connector that attaches the output lead of the transmitter to the antenna and under close inspection with a jeweler's loop we found and confirmed the existence of a cold solder joint. Cleaning and re-soldering the wire to the antenna connector successfully corrected the transmitter's power output.
C. Crane's quality assurance team is working with their manufacturing partner to make certain any future occurrence of an anomaly is minimized. While the typical purchaser would request an exchange in the unlikely event of receiving a defective product, our lab crew's curiosity prompted a more in-depth examination which resulted in returning the transmitter to proper operation.
Since our field intensity meter has been sent back for factory recalibration we plan to revisit our test results once our meter has returned from its visit to the factory.
C. Crane Part 15 FM Transmitter 2
- Thumbs Up
- FCC Part 15 Certified
- Compact Size
- Integrated Antenna
- Built-in Over-modulation Protection
- Retains Last Transmit Frequency When Powered Off or Power Loss
- Thumbs Down
- Does not cover entire FM band (88.3 - 107.7 MHz only)
- Non-weatherproof enclosure
FCC Certification ID: YXEFT007
CONTACT: Visit C. Crane Company
Date of Review: September 5, 2011