EMRFD Message Archive 2
Message Date From Subject 2 2006-07-05 16:12:13 Rick New EMRFD related projects Hi Group,
Thank you Roger for starting this. Here's a quick post describing
some new EMRFD related projects on my bench.
After some discussions with Wes and a thorough review of chapters 8
and 9, I decided it was time to do another little pc board receiver
last fall. It's a simplified miniR2 circuit with a VFO and LNA all
on one small PC board. I've now built half a dozen of them, and
it's available as a kit (the microR2) from Kanga US. Bill Kelsey is
sailing on Lake's Huron and Superior this summer, so Kanga is closed
until September. This is bit off topic, since the whole point of
EMRFD is to design, experiment and build, not buy a kit and stuff
parts--except for the very important fact that EMRFD was my only
reference for designing this new receiver. If you are interested--
start by reading chapters 8 and 9.
Why did I need another receiver? First, as a companion to Wes's
MKII transmitter in April QST, and second, as a tunable IF for some
simple weak-signal VHF gear I'm working on. If I were just going to
use it on 7 MHz, I would have done the whole thing ugly--maybe a
superhet like the S7C in chapter 12--but I needed more than one so I
went ahead and designed a clean image-reject DC receiver and did a
board layout. A crystal controlled converter in front of a tunable
DC IF is a super clean receiver topology.
Apparently my rule of thumb is that if a project has more than about
50 parts and I'm going to need more than one of them, I design a pc
board. Anything I only need one of I build ugly style in a die-cast
Over the summer I'll be working the bugs out of a companion SSB
exciter, the microT2. Then I'll have simple tunable IFs for both
transmit and receive. As soon as those are done, I'll start messing
with simple-clean crystal controlled frequency converters. I'll do
those ugly style, in die-cast boxes, so they'll be really clean.
Then I'll reread all of Wes's chapters on amplifier design and come
up with a good linear.
Speaking of--the latest QEX has a delightful article on a 1500 watt
linear using a hybrid EER (envelope elimination and restoration)
technique. I've done that on the bench at 2m with low power (<1
watt)and it really does work.
3 2006-07-07 11:09:43 S. Cash Olsen New EMRFD related projects Hi group,
I appreciated that Rick outlined his projects and thought I'd give you some
information on my projects and the kits that are available.
This week a Compact Spectrum Analyzer was authored by Neal Martini and
published in Circuit Cellar July 2006 addition. I've been in touch with Neal
about the availability of printed circuit boards and while he had made one
or two he had no intention of having any more built for sale.
I have made arrangements to get his artwork and to get boards made for sale,
kits and finished boards will also be available. It's a little early to
quote a price but the boards will be in the ~$20 range I believe, the kit in
the <$300 range and the finished and tested boards in the <$500 range. Board
availability Mid August. Kits about the same time frame.
This board uses a TV tuner chip by Maxim and covers the range of 50MHz
greater than 900MHz. It uses three conversions and has a final IF of 10.7MHz
and two resolution filters. The firmware offers an on board keyboard and LCD
display, an analog interface to an oscilloscope and to the PC. Can be
contolled by the PC with display. This should be a great project for the
serious RF tinker and some semiprofessional applications.
I also offer the kits for the Scotty's Spectrum Analyzer which is a much
more serious tool. It is also available in board and kit form, the details
of the SSA can be found on the URLs in my signature line. Some of you may
already be building the SSA.
I also really enjoy teaching the techinques I've learned for building
surface mount projects. I have a complete turorial on Hot Air Reflow
soldering which can be accessed by going to
www.zianet.com/erg/kisses_and_pies.html . There are pointers for a short and
long version of a movie that you can actually see the solder paste melt and
solder the parts in place.
These projects have tought me a lot and I continue to learn more and more
about every phase of electronics and programming.
My interests are primary in the VHF / UHF and microwave frequencies.
Cash Olsen, KD5SSJ
Kits to build Scotty's Spectrum Analyzer http://www.zianet.com/erg
Scotty's Spectrum Analyzer website http://users4.ev1.net/%7Ewsprowls/
Yahoo Builders Group http://groups.yahoo.com/group/spectrumanalyzer/