> through D30, and replaced each of Ten Tec's 'cheap' pin-diodes with the
> more expensive and 'better' (and Mr. Rhode's recommended) HP-5082-3081
> pin-diodes. Since the best operating point of the HP diodes occurred
> with about 100ma flowing through them, I had to decrease the value of
> R14, R15, R25, and R26. Took several hours and very careful soldering,
> but I knew it would be better!
Yes, the milage truly does vary! I replaced all BP board diodes with the HP
5082 types as suggested by U. Rhode and had very
satisfactory results. Like you, I had to re-bias the diodes in order to place
them into a linear operating region. The work was
so invasive that I would not recommend it for the minimal benefit derived.
One of the most dramatic changes I performed was replacing the three 1N4007 T/R
diodes with Microsemi UM-2110 types. These are 1KW
F.F. PIN diodes that improved the main-to aux receive antenna isolation to
better than 70 dB. Now, an extrmemely strong 40M BC
station is barely audible when the aux Rx antenna is slected into a dummy load.
Prior to that, perhaps only 40 dB of isolation was
achieved with the stock diodes. With the same 40M BC signal, the S meter would
often read S9 or more on the aux RX antenna with the
dummy load attached.
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