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Re: Substitutions
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Timothy You are talking about a 10+ year old design in that original BITX20 board from Far Circuits.? We have come a long way since then.? That old circuit will work, but there are better BITX designs available now.? <<arghhrgh ARV.. this maybe:??? ? (cut and paste from Far Circuits site).>> Steve's KD1VJ SSB transceiver is not a BITX.? The Bingo series from France and the MKARS-80 from the UK were the first BITX clones.? After that came the BITX20A and BITX17A from QRPKits (Doug Hendricks KI6DS). <<What I was pointing out that this PCB plus the old Farhan PCB were available from Far Circuits in Chicag for those who? wanted to scratch build a BIT x .."almost the same"..? Fred also has the old A Farhan analogue PCBs listed.>> Most who are scratch-building their own? versions of the BITX and uBITX are doing so in modular fashion.? This lets them build and test each section before progressing on to the next stage.? It is much easier that way.? <<This Bitx might be a bit deaf on receive. I'd be changing the 51R resistor ahead of the LC circuit/transformer on the receive front end. As in increasing it unless the circuit started ringing. Especially for use on 40 and 20 m.>> That old BITX20 board would be quite difficult to bring up to the present state of things.? The discussion group has numerous conversations in the archives that talk about modifying BITX designs for other bands.? It is quite easy with the older single-band units like the BITX-xxA series from QRPKits (QRPKits is now Pacific Antenna and they are not continuing the BITX product line). <<The IFT 10,7 Meg cans shown , three off from old style FM radio designs are very hard to get as new items now.>> As far as I know, the only BITX boards that used 10.7 MHz IF transformers were those sold by Sunil VU3SUA via his web site. <>. ? I just checked his storefront and he does still sell the BITX-3C for 20 meters and a components pack to populate that board.??? If you go that route the necessary transformers should be included in the parts kit. Farhan`s original design used rubber fawcett washers (tap washers) as the formers for toroidal transformers.? Wes W7ZOI performed some tests that indicated these had lower Q than more traditional toroid cores. Since then most BITX builders have used conventional toroid cores in place of the tap washers.? <<74HC4053 analogue switch as used by Weber on RF? may be of great interest for those designing BP? filter banks as a relay replacement ??? Yall Heard it here first !!>> CMOS switches like the 74HC4053 might be used in receiving circuits, but probably not suitable as switches for filter banks where the RF voltages can exceed 30 to 50V.? I doubt that the 74HC devices would survive that environment. Arv _._ On Mon, Aug 13, 2018 at 5:33 PM Timothy Fidler <engstr@...> wrote: arghhrgh ARV.. this maybe:??? ? (cut and paste from Far Circuits site). |
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