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A very small TCXO (Temperature Compensated Crystal Oscillator) based synthesizer unit for many YAESU and ICOM transceivers, but virtually compatible with many other radios.
Based on a Si5351 CMOS synthesizer with a high stability TCXO as reference clock, the CRuni-NG is a programmable synthesizer designed as a replacement for many oscillators with “exotic” output frequencies or hard to find as standard TCXO’s, especially the YAESU TCXO-1, TCXO-4 and TCXO-6 crystal units:
The CRuni-NG has the same mounting holes and pin assignment as the TCXO-1, TCXO-4 and TCXO-6, so it can replace both devices 1:1. Even the fine frequency calibration by the transceiver is still possible with the CRuni-NG.
A list of transceivers, where the CRuni-NG can be installed instead of a TCXO-1, TCXO-4 or TCXO-6 (frequency=10,48576MHz):
- FT-1000MP (MK-V)
Furthermore the programmable output frequency up to 160MHz, the small size, wide supply voltage range and standard pinout (4 pins with the same footprint of a DIL14 socket) allows the flexible use of CRuni-NG as high stability reference clock source for many other radios where “exotic” reference clock frequencies are used.
The CRuni-NG was designed for a improvement of the frequency stability and accuracy of many Icom rigs. If you looking for a solution to keep the frequency of your rig stable over a wide temperature range, then a CRuni-NG is the right choise!
How it work the CRuni-NG ?
It was designed around a Si5351 CMOS synthesizer with a high stability TCXO as reference clock source. The supply for the Si5351 and reference clock are provided from a active denoiser circuit, which permit to achiev a low level of in-band phase noise of the synthesized output signal. The TCXO module from Murata providing a high degree of frequency stability of ±0,28ppm over a wide temperature range. Optionally is possible to use for example, a SiTime Precision Super-TCXO with an amazing stability of ±0,1ppm. The microcontroller configure the synthesizer very fast at power on, to avoid critical startup locks on some ICOM transceivers. The initial firmware programming are provided through ISP-interface on a 6 pin header.
There are 4 user-selectable startup frequencies (defaults: 30Mhz, 30.2MHz, 32MHz and 10.48576MHz) in the firmware, but these values can be replaced with any value between 8kHz and 160Mhz. The frequency selection can be done through two solder jumpers on the upper board:
- SJ1+SJ3 open: 32MHz (ICOM CR338-mode)
- SJ3 close: 30MHz (ICOM CR282-mode)
- SJ1 close: 30.2MHz (ICOM CR293-mode)
- SJ1+SJ3 close: 10.48576MHz (YAESU-mode)
Another important feature of the CRuni-NG is the high quality multiturn trimmer, which permit a fine frequency alignment from the top without removing the unit from the transceiver.
The fine frequency calibration trimmer position:
- Output frequency: 30MHz, 30.2MHz, 32MHz or 10.48576MHz (programmable for any value from 8kHz up to 160 MHz)
- Output level: 350 mVpp at 50 Ohm
- Reference TCXO Frequency stability: ±0,28ppm@20MHz (or with extra high stability option: ±0,1ppm)
- Output Frequency stability: ±0,14ppm@10,48576MHz (or ±0,05ppm@10,48576MHz with extra high stability option)
- Operating Temperature Range: -20 to 70°C
- power supply requirements: 5,5 to 24 VDC, max. 36mA (or with extra high stability option: 10,5 to 16 VDC, max. 90mA)
- Frequency fine adjustment range: 90Hz (±5ppm) (or with extra high stability option: 100Hz)
- Module size (LxWxH): 25x15x13mm
The CRuni-NG phase noise measurement (pink), compared to a YAESU TCXO-4 (blue):
Performance test on a FT-1000MP:
These tests was done on a YEASU FT-1000MP and a HP 8648C signal generator (output frequency = 29.300MHz) with a external high precision 10MHz Rubidium reference clock, and the radio tuned on 29.299 MHz USB. I have choose the highest HF band because the frequency drift of a transceiver are more noticable at the highest frequency band. The audio output from the FT-1000MP is sampled with a TinyGate USB interface on a pc where running Spectrum Lab.
If have made a comparison test between three different reference clock sources on a YEASU FT-1000MP:
- Stock crystal
- YAESU TCXO-4 high stability crystal option
- CRuni-NG (with a 0,28ppm reference TCXO)
1) FT-1000MP – Test with stock crystal:
I put the crystal unit in a freezer to bring the temperature down to aprox. -15°C. The graph below with a horizontal scale grid of 10Hz shows the HP 8648C carrier received while the crystal unit is warming up (at the ambient temperature of about 23°C). The resulting frequency drift at 29.3MHz is about 59Hz:
2) FT-1000MP – Test with YAESU TCXO-4 high stability crystal option:
I put the TCXO-4 unit in a freezer to bring the temperature down to aprox. -15°C. The graph below with a horizontal scale grid of 10Hz shows the HP 8648C carrier received while the TCXO-4 is warming up (at the ambient temperature of about 23°C) with the high stability crystal option TCXO-4 installed.
The resulting frequency drift at 29.3MHz is (after initial warming up drift) about 46Hz:
3) FT-1000MP – Test with CRuni-NG:
I put the CRuni-NG unit in a freezer to bring the temperature down to aprox. -15°C. The graph below with a horizontal scale grid of 10Hz shows the HP 8648C carrier received while the radio with the CRuni-NGis warming up (at the ambient temperature of about 23°C).
The resulting frequency drift at 29.3MHz is about 2.5Hz:
4) FT-1000MP – Long term frequency stability test:
This test analyze the behavior of the frequency drift over long period. There are minor swings to notice, maybe a supply voltage sensivity due the periodical power-on and -off of internal fan:
As comparision here the resulting frequency drift with a CRuni-NG, where are lower swings noticable:
Installation example of a CRuni-NG in a YEASUE FT-1000MP:
Remove the stock crystal board located on the right side, next to the RX2-unit:
2. Mount the CRuni-NG with two screws and connect the 3 pin connector. Done!
The CRuni-NG is available from RF-SYSTEM‘s webshop.
For other questions please send me an email.