On Tue, Jul 11, 2023 at 01:14 PM, ajparent1/kb1gmx wrote:
In the industry everyone know the 2n2222 as the roach as it
just doesn't die.
Roaches that don't die..hmm lets make a list for some fun.
2N2222
BS170
741's
555's
BC108's
IRF510's and similar.
RF power trannies are a bit fickle though.
MRF series and some old 5-10w chicken band stuff etc.
RF PA devices appear to follow the trend of whatever has been used in the professional
user world.
But that stuff has fades quite a bit.
No one cares? about QRO VHF /UHF land mobile stuff for example because cell phones
have replaced the RF services.
No taxi / police / courier rigs needed so the devices that could be used a few Mhz either
side for ham service eventually die :-(
10-20w chicken band stuff is dead, so those parts adopted for ham usage have gone too.
Dual gate mosfets, almost dead now thanks to SDR, not good.
The only decent RF PA parts come from Mitsubishi, and how? long will they last.
The overriding thing about have an *RF* part is that they are designed to have a constant
input / output impedance across their freq range, as well as a constant Gate bias voltage.
Something a crappy IRF device and others simply cannot offer since they vary too much.
Non RF parts can be good, not disputing that, but real RF parts are still superior.
At least with something like an RD06HHF1 you can guarantee 6 watts into ANY load forever,
have a constant input / output RF impedance, use the same Gate bias voltage in production,
and with reasonable heatsinking and a good load push them to 15-20w with 100% duty cycle
for years, just like a broadcast TX. (Same for other RD series stuff).
Or RD16's. 16 watts guaranteed to any load 100% duty cycle, just a different input / output Z
and a slightly higher input drive required for max output.
(Use a 1:9 un-un in the output instead of a 1:4 to bring the lower output Z to 50R)
Bullet, manual ATU proof and idiot proof.
Shove about 2.5 volts on the GATE and make a Class A amp, perfect.
Standing current about 50ma, does everything you want, works perfect even on AM with about 400mw
of drive.
--
- 73 de Andy -
