Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while tying up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
All trademarks, copyrights, patents, and other rights of ownership to images
and text used on the RF Cafe website are hereby acknowledged.
My Hobby Website:
High IP3 VHF LNA - RF Cafe Forums
RF Cafe Forums closed its virtual doors in 2012 mainly due to other social media
platforms dominating public commenting venues. RF Cafe Forums began sometime around
August of 2003 and was quite well-attended for many years. By 2010, Facebook and
Twitter were overwhelmingly dominating online personal interaction, and RF Cafe
Forums activity dropped off precipitously. If the folks at
phpBB would release a version with integrated
sign-in from the major social media platforms, I would resurrect the RF Cafe Forums,
but until then it is probably not worth the effort. Regardless, there are still
lots of great posts in the archive that ware worth looking at.
Below are the old forum threads, including responses to the original posts.
|-- Amateur Radio
Gripes & Humor
-- CAE, CAD, &
Test & Measurement
Post subject: High IP3 VHF LNA Posted: Tue Feb 26, 2008 11:33
Joined: Mon Sep 24, 2007 8:34 am
I am looking for a high dynamic range VHF LNA. The
data should be around:
This is not an easy task. (Perhaps it was easier 30 years ago,
when VHF were a "popular" frequency?) The pHEMTs are great, but have
too much gain at VHF frequencies. Do anyone know if there exist any
chips designed for VHF/UHF, rather than 6GHz - that has good NF and
high OIP3? The most likely solution for me is perhaps to try to make
some kind of transformer feedback configuration in order too meet my
demands. Yet I wonder if that is easier said than done!
Post subject: Posted: Thu Feb 28, 2008 3:48 pm
Joined: Mon Sep 25, 2006 5:52 pm
SPF-5122Z from Sirenza (now RFMD) may have a too much gain, but
it has a high IP3, low noise figure and is already matched in a small
It has >>+30 IP3, so maybe a pad on the output to
get rid of some gain.
Update: Looking at the spec sheet,
it looks pretty bad at VHF. Gain is way too high and OIP3 falls off.