FW: [BITX20] RD16HHF1 power curve flattening...some
|
Ashhar¡ see this result too.? The PA output transformer is sub-optimal so some of us have found.? Needs to be 2T:3T and frequency compensated by a cap across the primary.? My simulations show something in the 330-450pf range as optimal for this configuration, but that is through simulations. ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton ¨C J68HZ Soufriere, St. Lucia W.I. Rent it: Like us on Facebook! ? Moderator ¨C North American QRO Group at Groups.IO. ? email:? bill@... ? ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of John
Sent: Wednesday, March 21, 2018 6:42 AM
To: [email protected]
Subject: Re: [BITX20] RD16HHF1 power curve flattening...some ? Hello Nik,
How did you go with the feedback issue?
My power amp mods in summary:? finals as RD16HHF1s, feedback resistors R261/R262 as 820 Ohms, Transformer 2T primary / 3T secondary on BN43-202, 180pF across the output transformer primary and 330pf across R87/R88. That's all...in a way.
Heavily inspired by Erhard's (DF3FY) information as displayed on uBitx.net.
Results per band at 14V supply, RV1 at %60, RD16's biased at 250mA each:
Band? ? ? output power? ?Total current
80M? ? ? ? 22W? ? ? ? ? ? ? ? ? ? ? ? ?2.9A
40M? ? ? ? 20W? ? ? ? ? ? ? ? ? ? ? ? ?3.2A
30M? ? ? ? 16W? ? ? ? ? ? ? ? ? ? ? ? ?2.3A
20M? ? ? ? ?16W? ? ? ? ? ? ? ? ? ? ? ? 2.7A
17M? ? ? ? ?15W? ? ? ? ? ? ? ? ? ? ? ? 2.4A
15M? ? ? ? ?12W? ? ? ? ? ? ? ? ? ? ? ? 1.6A
12M? ? ? ? ?12W? ? ? ? ? ? ? ? ? ? not measured
10M? ? ? ? ?12W? ? ? ? ? ? ? ? ? ? ? ? 1.7A
At 22W the output transformer does get warm but not the LPFs.
Wound back RV1 to get 9-10W on the high frequency bands and 16-18W on the lower ones.
All the best,
73, John (VK2ETA)
|
K9HZ