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<blockquote data-quote="s-band" data-source="post: 967777" data-attributes="member: 407744">Modifications to a C1W PLL LitePolarisation SwitchingAs received, the C1W Lite switched to H at 14.07V and back to V at 13.86V. Since the TBS6983 switches at 14.2V it will only switch polarisation if the cable is long enough to drop the voltage a bit. Adding a 2k7 resistor (circled red) moves the switching points to 14.6 and 14.3 which fixed the problem for me.TCXOI used one from an Ebay seller, Item 121096363971. There is no specification that I can find but it I guess it is 1-2ppm. It has the advantage that it has a trimmer built in so there’s no need to add anything. I used a Dremel to cut tracks on a bit of PCB to mount the TCXO. The PCB is grounded to the main board with some copper tape.I removed 2 capacitors (yellow circles) and fed the 25MHz via thin co-ax as shown (magenta connection). It may not look like it but the coax is well clear of the filter on the main board. The TCXO o/p is capacitively coupled so there’s no need for an external capacitor. The drive to the IC is more critical than expected and there is a 510R resistor in series at the TCXO end. This forms a low pass filter with the coax capacitance and drops the level slightly. It’s a bodge but it works. The synthesiser gets very messy if the reference level is wrong so it is necessary to keep an eye on its spectrum. Unfortunately this could be hard if you don’t have any test gear.The TCXO should run from 5V but I was too lazy to add another regulator so it is fed from the 6V line via a 120R resistor and decoupled with a 100n chip. It’s running from ~5.5V but seems ok.[ATTACH]92246[/ATTACH]</blockquote>

[QUOTE="s-band, post: 967777, member: 407744"] [B]Modifications to a C1W PLL Lite Polarisation Switching[/B] As received, the C1W Lite switched to H at 14.07V and back to V at 13.86V. Since the TBS6983 switches at 14.2V it will only switch polarisation if the cable is long enough to drop the voltage a bit. Adding a 2k7 resistor (circled red) moves the switching points to 14.6 and 14.3 which fixed the problem for me. [B]TCXO[/B] I used one from an Ebay seller, Item 121096363971. There is no specification that I can find but it I guess it is 1-2ppm. It has the advantage that it has a trimmer built in so there’s no need to add anything. I used a Dremel to cut tracks on a bit of PCB to mount the TCXO. The PCB is grounded to the main board with some copper tape. I removed 2 capacitors (yellow circles) and fed the 25MHz via thin co-ax as shown (magenta connection). It may not look like it but the coax is well clear of the filter on the main board. The TCXO o/p is capacitively coupled so there’s no need for an external capacitor. The drive to the IC is more critical than expected and there is a 510R resistor in series at the TCXO end. This forms a low pass filter with the coax capacitance and drops the level slightly. It’s a bodge but it works. The synthesiser gets very messy if the reference level is wrong so it is necessary to keep an eye on its spectrum. Unfortunately this could be hard if you don’t have any test gear. The TCXO should run from 5V but I was too lazy to add another regulator so it is fed from the 6V line via a 120R resistor and decoupled with a 100n chip. It’s running from ~5.5V but seems ok. [ATTACH]92246[/ATTACH] [/QUOTE]

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