Microwave Projects?
 

I like to build simple receivers from 1 to 2.4GHz.
Any recommendations for oscillators?
What schottky diode works to make a signal strength meter?

Thanks

JJ

Microwave Projects?
 

"JJ" wrote in message
...
I like to build simple receivers from 1 to 2.4GHz.
Any recommendations for oscillators?
What schottky diode works to make a signal strength meter?

Thanks

JJ

Oscillator construction seems a big problem up there. Was trying something
similar the other week. Turned out 99% art 1% science, so packed it in and
now awaiting a sample of an interesting satelite downconverter chip.
http://www.semiconductors.philips.com/pip/TDA8261.html , digitally covers
950 to 2175MHz using a VCO/synthesiser running at a quarter of it's mixer
input frequency. VCO simply consists of a Varicap, 2 caps and a 18nH
inductor. Chip is 'direct conversion'(with quadrature outputs!) and would
make a wonderful 0-1GHz spectrum analyser if it's mixer ran down to a few
megs. Sadly, no mention of this spec' in the datasheet, so must assume
response tails off badly at the low end.
john

Microwave Projects?
 

Very interesting receiver chip. I see Maxim makes those too.
Any other manufacturers that would interest microwave experimenters?

JJ

Microwave Projects?
 

"JJ" wrote in message
...
Very interesting receiver chip. I see Maxim makes those too.
Any other manufacturers that would interest microwave experimenters?

JJ

Also hoping the RF guys could throw in a couple of tasty pointers. Seems
plenty of amps and mixers out there but if it's not cellphone stuff then
seemingly very little else.
john

Microwave Projects?
 

What do you mean by simple receivers ? What are you trying to receive,
with what stability and sensitivity ? Amateurs have traditionally used
crystal-controlled downconverters in front of lower frequency
receivers, but this is generally suited only for receiving small
segments of spectrum and doesn't usually have a very small parts count.
The local oscillator usually involves several multiplier stages and
tunable filters. The performance can be very good though.

For example there are lots of technical articles at

http://dpmc.unige.ch/dubus/index.html

The 1N5711 schottky diode works well in the lower microwave range and
is quite widely available and cheap.

Steve VE3SMA

Microwave Projects?
 

JJ wrote:
....
What schottky diode works to make a signal strength meter?


Schottky diodes are soooo 20th Century,
http://www.analog.com/en/prod/0%2C28...8313%2C00.html

-W8LNA

Microwave Projects?
 

Seems you could take advantage of all the old Ku & C band
receivers,lnbs and other big dish stuff that people are throwing away,
i
remember the reciever tunes a 950-1400 mhz input span or somewhere
close, from the lnb. Should be alot easier to convert one of
these yardsale items than start from scratch. Ive got a bunch of these
setting around & wanted to put one on the 33cm 902-928mhz
amateur tv band, but the satellite starts alittle higher than that so i
put it on hold for now.

Microwave Projects?
 

Microwave Projects?
 

" wrote in
oups.com:

Seems you could take advantage of all the old Ku & C band
receivers,lnbs and other big dish stuff that people are throwing away,
i
remember the reciever tunes a 950-1400 mhz input span or somewhere
close, from the lnb. Should be alot easier to convert one of
these yardsale items than start from scratch. Ive got a bunch of these
setting around & wanted to put one on the 33cm 902-928mhz
amateur tv band, but the satellite starts alittle higher than that so i
put it on hold for now.
Cool, how much are these cheap receivers?
Can you use them for a radio telescope @1420MHz?
These would need to recieve AM mode.

JJ

Microwave Projects?
 

"JJ" wrote in message
...
wrote in news:1145727069.586990.95580
From what I read, regular fiberglass boards don't work well above 1 GHz.

That's a bit of an overgeneralization. We routinely use "generic" FR-4 to
3GHz, and you'll find that many wireless routers at 2.4GHz do as well. As
long as the paths are relatively short and you're just using the board to get
a signal from point A to point B, it works pretty well.

The folks who suggest you use Teflon or other high-quality board materials are
probably thinking of building distributed circuits on it -- stuff like
filters, where the board's loss (its Q) significantly impact how good your
filter's response is. (Building something like a bandpass WiFi filter --
~25MHz wide at ~2.45GHz -- on FR-4 using coupled lines is probably not such a
hot idea -- this would be a good test case to simulate.)

Where do you get teflon boards?

All the decent-sized board houses (e.g., Advanced Circuits, DDI, etc.) have
low-loss board materials available. Nelco (http://www.parknelco.com/) and
Rogers (http://www.rogers-corp.com/acm/index.htm) are two of the big players
here. We have many boards done in Nelco 4000-13, which is a "mid-loss"
material... only somewhat better than FR-4 when it comes to absolute loss, but
considerably better when it comes to the specs not drifting over process,
temperature, etc., all at a relatively small pricing premium.

If you can afford it, by all means, get low-loss boards. However, in many
cases in the low-GHz area you end up with more loss from items such as coax
cable, connectors, impedances mismatches, etc. than the PCB material itself.

---Joel Kolstad