The newest apolLO I boards have two new jumpers on them, SJ3 and SJ4, which have not made it into the documentation yet. I’ve received a few questions about these and wanted to explain their purpose.
SJ3 should be fairly self-explanatory — it is marked as EXTREF and TCXO so that you can select between an on-board TCXO and an external 10MHz reference. Just jumper the center to the marked side for where your 10MHz (or other 2-26MHz reference) lives.
SJ4 allows the output to be shifted from the RF synthesizers in the Si41x3 to the IF synthesizer. I have not yet implemented the IF synthesizer in software, but I am working on this so this run of boards has this as an option. Connect the center to the (H) side for RF use (700-1700MHz) or to the (L) side for IF use (62-1000 MHz). Again, at the time of this writing, the software only supports the RF side so jumper to (H).
The “C” revision of apolLO-32 is now shipping and has a few enhancements over the “B” version. Specifically, SMA lanuches are provided on both the RF Reference Input and the RF output so if you would like to connectorize the board, it is now easy. Of course the board can still be used in a DEMI transverter by just soldering to the connection points. The 10MHz LPF is now integrated on the board as part of the production process to supress noise from harmonics on a 10MHz reference. The board also has expanded room for additional frequencies. If you have a frequency between 800-1700MHz you would like to see on the board, let me know and I’ll see if I can get it added for you.
Also by popular demand, the board has space for an on-board TCXO just as the apolLO-I does. If you would like to use a TCXO instead of an external 10MHz reference, just add the TCXO and a couple of resistors and a pot and you are in business. You may order the TCXO kit directly from the website under “products” (order the same kit as for the apolLO-I). Note that only the larger footprint TCXO is available on the board (for the ECS/FOX TCXOs). If you choose to place the FOX oscillator on the board, be sure that you have a 3.0V regulator on the board and not a 3.3V regulator. Just measure the voltage on the back of the board where it is marked “3.3.” If you need a replacement regulator for 3.0V, just let me know and I’ll drop you one in the mail.
As I add frequencies to the board, I will increment a number after the “C” to indicate which frequencies are in the board. The intent is to never remove a frequency. So you will see a minimum rev level for each frequency and if your board has this rev or later, it will support the frequency. Again, if you need a specific frequency, let me or Steve, N2CEI, know and we’ll try to get it added for you.