Unterschiede

Hier werden die Unterschiede zwischen zwei Versionen angezeigt.

--- alphapocwatchdescription [2023/02/09 15:39]
on6rf
+++ alphapocwatchdescription [2023/02/09 15:43]
on6rf
@@ Zeile 15: / Zeile 15: @@
   * Soldering iron
   * RF tuning screwdriver (or anything not metal to turn the trimmers)
-{{ ::alphapoc:alphapoc801w_ham_mod.jpg?direct&600 |Image of Alphapoc 801W, next to the 602 and a Swissphone pager. }}
+{{ ::alphapoc:alphapoc801w_ham_mod.jpg?direct&600 |Image of Alphapoc 801W open, showing all relevant points for the mod }}
+  - Program the pager on 439.98750MHz.
+  - Replace capacitor marked 1 with a 6.8pF one.
+  - Turn the pager on.
+  - Place a probe on 2 (I used an 80MHz oscilloscope probe, ground on the USB connector) connected to a spectrum analyser, central freq 21.4MHz, span 30kHz. An SDR might just do the trick, careful about the input protection though!
+  - Key in a POCSAG transmitter to a 600Hz tone (the test button is quite handy on unipager). Lowering the power might also be a good idea to avoid saturating the receiver.
+  - The two POCSAG peaks should show up. Adjust trimmer numbered 3 for maximum signal strength. I really recommend a plastic screwdriver as a metal one will always detune the Rx antenna.
+  - Optionally, adjust trimmer 4 if the frequency is a bit off.
+IF and ONLY IF there is absolutely no signal being received, the PLL might not be locking. I found adjusting trimmer 5 helps, but it's very sensitive and can sometimes make matters worse!

DAPNET DokuWiki