Forgive me for being "outrageous" : but why not, just for the sake of it, try a 4-5 transistor 2m AM tcvr with Super-regen Rx for the bang of it? Oodles of sensitivity, horrible selectivity: I used a BF200 preamp + BF194 super regen detector + LM386 (oops Raj) for airband monitoring with a tuner varactor back to back for tuning back in 90s. The BF200 booster transistor at 9V 2mA prevented the reradiation. A simple 2 stage overtone oscillator BF194 + 2SC3355/2570 running class C and a series modulator makes the 20mw Tx...Could cover half a mile I guess. In the sixties, I guess this scheme with miniature 90V tubes was a popular project, no? Somewhat improved selectivity was achievable using a 3 pole helical LC filter in a copper foil enclosure, but for a single channel only. The only crittical thing was starting the quench: the super regen stage emitter RFC and the base decoupling caps are the tricks!!!!
--- On Wed, 6/1/11, rahul srivastava <lkorahul@yahoo.com> wrote: From: rahul srivastava <lkorahul@yahoo.com> Subject: Re: [HamBrewers] 144 - 146 Mhz (2M) Rx thoughts To: HamBrewers@yahoogroups.com Date: Wednesday, June 1, 2011, 1:53 PM
Great Raj, For those interested the chip has some very interesting applications. To start with with one of this single chip you can homebrew a complete HF SSB rig, but now if that you are a true Hambrewer...!!! 73's Rahul VU3WJM
--- On Wed, 1/6/11, Raj <vu2zap@gmail.com> wrote:
From: Raj <vu2zap@gmail.com> Subject: Re: [HamBrewers] 144 - 146 Mhz (2M) Rx thoughts [2 Attachments] To: HamBrewers@yahoogroups.com Date: Wednesday, 1 June, 2011, 9:51 AM
Some data sheets attached. At 01-06-2011, you wrote: Hi! Raj, MC13135 and its earlier variant MC3362 is still available at Delhi if anyone interested. Lately I stopped going in for complete discreet ones cause found it easier modify surplus items, but that barely scrathes the itch of a totaly homebrewed project. 73's Rahul VU3WJM
--- On Wed, 1/6/11, Raj <vu2zap@gmail.com> wrote: - From: Raj <vu2zap@gmail.com>
- Subject: [HamBrewers] 144 - 146 Mhz (2M) Rx thoughts
- To: HamBrewers@yahoogroups.com
- Date: Wednesday, 1 June, 2011, 9:08 AM
-
- For two meters I would suggest the obvious "kiss" mode.
- I will leave out the PLL/DDS part out of discussion for now. We have others who can suggest.
- One chip of the series MC3357, 3359 and so forth.. will do the major task of conversion, limiting & detection! These devices are designed for cordless phones and are for NBFM.
- Some thoughts:
- You have the front end built in the later chips. Others require the first mixer e.g. 3357
- Some chips require a discriminator coil/cap and others resonator.
- 10.7 or 21.4 Mhz & first IF 455 second IF (first IF depends on your junk box xtals)
- Audio stage:
- No more LM386 please. It took many years to get out of the clutches of LM380!
- Now I suggest the TDA2822 stereo amp in push pull mode. I found this chip very
- stable and took a lot of abuse. I got a great sound in my RX project. Cheap!
-
- Hi,
- I am also interested in this project.
- I am also requesting VU2ZAP to give his thought in this regard.
-
- with 73's
- de VU2GAQ
- Kumar Gautam
- Ex- VU3KGL
- --
- Raj, VU2ZAP
- Bangalore, India.
-- Raj, VU2ZAP Bangalore, India.
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