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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 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

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, a SMT AF filter (see 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).