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LC,
The two series caps in parallel with the load capacitor are there to lower the capacitance of the variable load capacitor since with them in circuit you effectively have two parallel capacitors of 400pF and 60pF giving a total of 52pF.

How that will change the total value of the circuit(coil) I cannot calculate. A 14 hour work day has sapped my brain.

Your input tune may be helped with a 4-6 turn coil in series with the cathode of the driver tube (if it doesn't already have one). My Hygain Afterburner+ and the Skipper 300 I refurbbed for a friend did not have one. After installing one and pruning a'la the "cut and try" method, it was tuning pretty flat.

Pretty sure nomadradio has the answer to the loading/tuning coil issue. Stay with it! The oldies need to be saved!!!

73
David

<blockquote data-quote="Dmans" data-source="post: 752885" data-attributes="member: 49046">LC,The two series caps in parallel with the load capacitor are there to lower the capacitance of the variable load capacitor since with them in circuit you effectively have two parallel capacitors of 400pF and 60pF giving a total of 52pF.How that will change the total value of the circuit(coil) I cannot calculate. A 14 hour work day has sapped my brain. <img src="https://cdn.jsdelivr.net/joypixels/assets/8.0/png/unicode/64/1f641.png" class="smilie smilie--emoji" loading="lazy" width="64" height="64" alt=":(" title="Frown&nbsp; &nbsp; :("&nbsp; data-smilie="3"data-shortname=":(" />Your input tune may be helped with a 4-6 turn coil in series with the cathode of the driver tube (if it doesn&#039;t already have one). My Hygain Afterburner+ and the Skipper 300 I refurbbed for a friend&nbsp; did not have one. After installing one and pruning a&#039;la the &quot;cut and try&quot; method, it was tuning pretty flat.Pretty sure nomadradio has the answer to the loading/tuning coil issue. Stay with it! The oldies need to be saved!!!73David</blockquote>

[QUOTE="Dmans, post: 752885, member: 49046"] LC, The two series caps in parallel with the load capacitor are there to lower the capacitance of the variable load capacitor since with them in circuit you effectively have two parallel capacitors of 400pF and 60pF giving a total of 52pF. How that will change the total value of the circuit(coil) I cannot calculate. A 14 hour work day has sapped my brain. :( Your input tune may be helped with a 4-6 turn coil in series with the cathode of the driver tube (if it doesn't already have one). My Hygain Afterburner+ and the Skipper 300 I refurbbed for a friend did not have one. After installing one and pruning a'la the "cut and try" method, it was tuning pretty flat. Pretty sure nomadradio has the answer to the loading/tuning coil issue. Stay with it! The oldies need to be saved!!! 73 David [/QUOTE]

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