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Timothy Fidler
DS as per my reply to GY3rp you can get pre etched boards for he old Bitx frm Fred at Far Circuits . He also does the 75m? SSB board by Weber which is essentially a Bitx but using? CMOS analogue switch switching.? Latter board is eight USD. BEWaRE you have to source the IF cans for the post mixer filter.? Now hard to get. This latter board can be moved over to 40m I have had that in writing from Weber. Ditch the 9M IF frequency if you use it. Use 10M , much more practical. Maybe 9M IF crystals cab be had in India but try finding them at Reas price in US or Australia.? The Weber PTO VFO.design ie permeabilty tuned . .. I would not go there it looks the work of the devil mechanically . There are much better buffered VFO designs from Ashan? Farhan for example.? On the Weber board the power amp is integrated.? An 2n3866 subs on the driver would make a world of difference to power output.? have a fish around on my other replies as to where to get this cheap (and not fake). Diz the toroid king, or Fred at Far Circuits can supply.? Without this as the driver , the IRF can barely make 2 Watts.? With it it will go closer to 5 W.? before you try to juice up this PCB with more volts than say 13 CHECK ALL the component specs.? I can't remember if Fred splits out the power rail to the IRF510.. if he does then you can do more things. Remember an anti stuff up 2A (say) schottky diode on the power rail. You don't want 12hrs' work down the drain by some fool hooking it up back Ass-wards.
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Timothy Fidler
arghhrgh ARV.. this maybe:??? ? (cut and paste from Far Circuits site).
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.? 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. The IFT 10,7 Meg cans shown , three off from old style FM radio designs are very hard to get as new items now. 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 !! |
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Well as it stands now 10.7MHz IF coils are long gone from Indian mkt. My guess Sunil VU3SUA bought them all... I have not seen 9MHz xtals available anywhere in India, 27MHz 3rd OT is still available as it is used in DTH Rx.. Rahul VU3WJM
On Tuesday, 14 August, 2018, 6:32:30 AM IST, ajparent1/KB1GMX <kb1gmx@...> wrote:
Timothy, You have restarted a 14 year old topic! Its dead, need a shovel? Allison |
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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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Timothy Fidler
There were a few misunderstandings and misreadings in the reply to me that was well intentioned. I have send a direct post to AE.
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CMOS HCT4051 for example can withstand a full range of 10V offset 5V? sinusoid with no degradation of through RF up to 100Mhz. I was advocating this type of chip as a possible fix in relation to BP filter only not LP Filter..... etc.? I agree Weber 75m SSB design is? not a true Bit x (no bidirectional RF amps with voltage switching ) but it reuses all the? IF filter and so on via cunning signal switching using HC Cmos and has only one Relay in the whole business..and would still have only 2n+1 relays in it, if it were a n band design. regards, Timothy E. Fidler : Engineer BE Mech(1) Auckland , NDT specialist AINDT UT /RT3 , MT2? Telephone Whangarei?? 022? 691 8405
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