项目负责人是 Graham, KE9H。他同时负责 PCB 的设计。设计是和 Phil, VK6APH 共同承当的。
作为接收机的预选器，Alex 模块的目的是抑制接收机输入的带外信号；尤其是抑制镜频和防混叠频率（sampling image or alias frequencies）时的信号。参阅 Anie了解可调预选器的概念。
作为发射机的低通滤波器，Alex 一般用来抑制 RF 功率放大器的谐波能量。特别在采样频率(122.8 MHz)加减工作频率时产生的镜像或防混叠信号。发射链路的低通滤波器也可以用作 MERCURY 模块的额外接收输入带通的限幅。
You will normally "pair" one of the low pass filters on the transmit board with one of the high pass filters on the receiver board. There is an additional 33 or 55 MHz low pass filter on the receiver board, plus the 6 Meter transmit low pass filter that are in-line at all times to help suppress VHF images.
There are at least three major issues to consider with a preselector for a data converter type receiver such as MERCURY.
There is a similar issue with the Penelope transmitter. In addition to the desired HF signal at the operating frequency, the D->A converter also puts out images or aliases at the sampling frequency (122.8 MHz) plus or minus the operating frequency. This means that "flyback" in the stopband of a transmit harmonic filter in the 90 to 160 MHz range that might not be a problem in a traditional HF transmitter must be addressed in ALEX.
The primary purpose of ALEX is to be a preselector for MERCURY, and should not materially degrade MERCURY's native performance. There should not be any restrictions that would prevent ALEX from being used with any other receiver that required a similar preselector.
MERCURY is an extremely robust receiver in its native performance.
Measured MERCURY Prototype Specs:
The first PC board is the Receiver/HPF board. It has a 33 or 55 MHz 7th order Low Pass Filter that is always in line with the receiver. If the user is going to operate on 6 meters, the 55 MHz version should be used, otherwise, the 33 MHz version is recommended (for better VHF image suppression.)
There is a 6 meter low noise preamp; selectable 20 MHz, 13 MHz, 9.5 MHz, 6.5 MHz and 1.6 MHz high pass filters, plus a bypass function. It has five external BNC connectors, described below.
The receiver board also contains a switchable front end attenuator, configurable for 0 dB, 10 dB, 20 dB or 30 dB loss.
The second PC board is the Transmitter/LPF board. It consists of seven relay switched low pass filters for transmitter harmonic suppression, that are also used in conjunction with the receiver high pass filters to provide a flexible variable bandwidth receiver input filter function. It has four external BNC connectors, described below.
Each active board contains three LEDs, so that an indication of power and proper control and SPI bus operation can be seen.
ALEX is controlled by an SPI bus. This SPI bus should NOT be shared with other devices, in that it is intended that the data and clock lines should not be transitioning except when a command is being sent to one of the ALEX boards. There are two analog voltage outputs providing an indication of transmit forward and reverse power. There are no oscillators or continuously running clocks anywhere inside of ALEX.
Power handling capability - The transmit harmonic filter banks and associated relay switches are intended to handle up to 100 watts, peak power with a CW or SSB duty cycle.
Contribution to Receiver IP3 performance - Measured in the Alpha versions as approximately +50 dBm. That is, there is no measurable degradation of native Mercury IP3 performance.
Total power consumption for ALEX can vary over a range of 90 to 180 mA., all from the +12 volt supply. 90 mA is with 12.0 Volt supply, minimum number of relays active. 180 mA is with 13.8 Volt supply, 50 MHz transmit, 50 MHz preamp. on, all LEDs on, and both receive attenuators active. The +5 Volt and -12 Volt supplies are not used.
Thanks to John, N8UR, for testing and documenting the performance of the ALEX filters. This is ongoing testing in preparation for manufacturing, and the latest results can be viewed on his website at http://www.febo.com/pages/alex.
Bill, KD5TFD, has built and tested one of the Alpha-3 filter sets. See http://tracey.org/wjt/hpsdr/Alex/sa0630/
August 3, 2008 - The production release information package for ALEX has been sent to TAPR for review and approval.
June 28, 2008 - Phil did show Alex, along with Mercury and Penelope at Dayton. Three sets of Alpha-3 boards are built and in test. A few "tweaks" to capacitor values have been made, and the design is getting close to being frozen.
April 26, 2008 - Phil, VK6APH reports having finished building a set of Alpha-3 PC boards. Testing should start soon, and hopefully will be demonstrated at Dayton with a Mercury-Penelope receiver-transmitter.
March 14, 2008 - Alpha-2 boards were laid out, and one set built up for measurements. All of the Hittite switches in the Alpha-1 design were replaced by relays on the receiver board. The transmitter board was already using relays due to the 100 watt power levels. All changes look good. There is one nagging problem with PCB parasitics detuning the 6 Meter transmit Low Pass Filter, but an alternate filter design recognizing the board parasitics should resolve the problem. TAPR manufacturing has requested a change to a mass termination (ribbon cable) control cable and connector to lower costs and eliminate the board to board control jumper, so there will be an Alpha-3 version of the boards before we go final. Phil has been using the Alpha-1 version continuously for Mercury-Penelope testing, including on-the-air contacts, and has not found any new problems.
December 11, 2007 - Phil has completed the evaluation of the Alpha version of the ALEX receiver board. The main issue is that the losses of the Hittite solid state switches are too high for them to be used in most locations, so we will go back to relays for much of the 50 Ohm switching. A few other tweaks are necessary for packaging reasons, so the Alpha-2 version layout is underway. Using this high-pass/low-pass switchable filter approach results in no measurable degradation to the IP3 performance of Mercury.
November 11, 2007 - The Alpha-1 version of the ALEX receiver board is built and ready to start testing. A picture has been posted on the Wiki page. Phil, VK6APH has completed testing of the ALEX transmitter board, and reports good results for the directional coupler, no measurable degradation of receive IP3, and that the LP filters work well at 100 watts with SSB and CW duty cycles.
October 8, 2007 - The Alpha-1 version of the ALEX transmitter filter board is complete, through initial testing and a unit shipped to Phil, VK6APH for further evaluation. The companion receiver filter is in layout. Pictures of the board and the proposed housing have been added to the Wiki page.
August 5, 2007 - After the call for comments, changes and revisions to the ALEX concept and description have been incorporated into the Wiki page.
July 24, 2007 - Phil, VK6APH released measured performance for prototype MERCURY in an email to the group dated June 18. A preliminary design for ALEX is being released for review and comment before first pass PC board layouts are completed. The information released for comment on July 24 is at revision level 6-2.
Alexiares and his twin brother Anicetus - were the Greek Gods of Defense, in particular the defense of fortified towns and citadels.
Both were sons of Hercules (Herakles), born after the Hercules' ascension to Olympus and his marriage to the goddess Hebe. Alexiares and Anicetus helped serve as the gatekeepers of Olympus, assisting their father in a role which was commonly assigned to him.
The Schematics and Bill of Materials are in this ".pdf" file. Media:ALEX_P1_Binder.pdf
Hammond Euroboard Instrument Case: Mouser # 546-1455N1601, or Hammond # 1455N1601
The original design of these filters were done in ELSIE. Jim Tonne, WB6BLD, Tonne Software, just revised his product offering. I would recommend his "Pro-Lite" version as the minimum version to implement or modify one of the filters. This is a good tool for this kind of filter design. http://tonnesoftware.com/elsie.html