OperatingFreq + 0.650 = MarkedCrystalFreq<\/p>\n
91.3 + 0.650 = 91.95<\/p><\/blockquote>\n
I was able to pick up a strong carrier at 91.95 using a pick-up coil in proximity to the oscillator board.<\/p>\n
I don’t think there are many crystals (if any) that are made on a fundamental frequency of 90+ MHz.\u00a0 Such things are done by taking a lower frequency crystal and operating it on a multiple or over-tone.\u00a0 I was able to do some measurements of the as-delivered crystal and came up with a figure of 18.390 MHz which is 1\/5th of the marked frequency.<\/p>\n
CrystalFundamentalFreq = MarkedFreq \/ 5<\/p>\n
18.39 = 91.95 \/ 5<\/p><\/blockquote>\n
I used an AD9850-based frequency source and replaced the crystal with a direct injection of 18.39 MHz and I then attempted to detect the 91.95, which was successful.\u00a0 Below is a picture of my wire-and-hot-melt-glue crystal replacement plug.<\/p>\n
I then calculated the needed injection frequency for use of the unit on my operating frequency of 95.5 MHz<\/p>\n
95.5 + 0.650 = 96.15<\/p>\n
96.15 \/ 5 = 19.23<\/strong><\/p><\/blockquote>\n
I then changed my frequency injection to 19.23, adjusted the oscillator coil as instructed in the manual for crystal changing, and detected a strong carrier at 96.15 MHz.<\/p>\n
I have to leave the project for a little while.\u00a0 I think my next step is to get the off-air signal into the RF port of the modulation monitor.\u00a0 I would rather get the signal off of the air than use a tap on the transmission line.\u00a0 I probably will need to use a pre-amplifier to get the off-air signal up to the right voltage level.<\/p>\n
![\"\"](\"http:\/\/w0ep.us\/OM\/wp-content\/uploads\/2018\/10\/signalsource.jpg\")
<\/a><\/p>\n![\"\"](\"http:\/\/w0ep.us\/OM\/wp-content\/uploads\/2018\/10\/homeMadeCrystalPlug.jpg\")
<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"