Clublog

Monday, 5 January 2009

TCVR project (80m, 40m, 20m, 15m and 10m)




Starting from an original design from VU2HMY using the TA7358 here:




The design uses components that are put to use in India as the alternatives we have in UK are just not available there. However after having a lot of fun and frustraition tracking down suitable toroids when building the BITX20 using the original design (I also built one of Doug Hendricks BITX20A kits http://www.qrpkits.com/) and finding 'tap washers' and 'TV baluns' a bit hard to come by I will rework this with a few 'western components' such as TOKO coils, T37/T50 toroids and BN2402 cores. I will also build the band pass filters according to the GQRP designs here http://www.interalia.plus.com/bandpass_filters.pdf





Bag of the TA7358 SIL IC from Peter at JABDOG, just arrived this morning. A number will go out to others this morning.


GQRP/Graham G3MFJ sold me a matching pair of carrier crystals for SSB @ 9MHz +/-1.5kHz at the last GQRP rally so I will shift the IF to 9MHz from 10MHz so I can use them.



In addition I may add a second switchable cw/ssb filter so that I have a narrow (CW) and wide (SSB) filter of the same design. Or I might finally find a use for a pair of GQRP club CW and SSB filters.



For the VFO I will either use a simple colpitt VFO or roll a new DDS AD9851/PIC controlled or similar based DDS. Although I also have already built an FCC-1 and FCC-2 DDS VFO and Frequency counter that could be employed immediately.



Adding an AF based S meter, a cw keyer (KD1JV simple keyer), a battery power meter (see http://m1kta-qrp.blogspot.com/2008/12/kd1jv-and-n7ve-battery-monitors.html), a SMT AF filter (see http://m1kta-qrp.blogspot.com/2008/10/what-to-do-with-some-free-max-74xx.html) and a AD8307 based pwr/vswr meter should round the project off.

The project doesn't include a PCB mask but there is a layout but as I will modify a few things as per usual will create a PCB with ExpressPCB and blue Press N'Peel film.

Initial layout the board is approximately 8" x 3".
Using TOKO coils and I have left the 6 crystal filter on the board for now but I expect I will change the layout to add the GQRP CW and the SSB filters. The transistors on the design layout appear to be TO18 varieties. Those I have are either TO92 or the TO220 (three on left hand side).