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New member intro

John
 

Hi All! I'm John G4EDX and I live in Nottingham, England. I've been licenced since June 1975 and I'm a keen homebrewer.

A friend at our local radio club asked me for advice on choosing a kit to build a 20 metre transceiver and I suggested he build a BITX20 from parts, not a kit, as this will be less costly and he'll learn more. Now I've started building one too.?

We're building them on 50mm (two inch, actually) square pieces of copper-clad board along the lines of PA1ED's build. I've cut some boards and built the AF amplifer. I'll do the BFO stage next.?

I see that there are variants of the BITX20 on the web so I wonder whether anyone can recommend a particular circuit to follow. I have a good supply of iron dust toroids, 2N3904s and 2N2222s. I have a few SBL1s recovered from old boards. Are these much better than rings of 1N4148s?

I'll let you know of our progress and no doubt be asking more questions as we progress with the build.

73,

John G4EDX
 

Hi John,?

Welcome. ?I'm a newer member but I wanted to say hi and that it sounds like a fun project. ?Glad to see people who like to build stuff. ?Someone with more experience with Bitx20 will likely respond eventually. ?Good luck.?

73

Jamie VA3RLF?
 

The BitX40 schematics up on hfsigs.com are probably a good place to start, adjustments for 20m would be restricted to the BPF, the transit LPF, and the VFO.
You need to decide if you are going with an analog VFO, I'd suggest using an Si5351 for both VFO and BFO as is done on the uBitx: ?
In fact, not a bad idea to just go with the uBitx schematics, has a number of improvements over the Bitx.
The SBL-1's should work fine, though it's possible that building up from torroids and diodes could work slighty better as they don't need to work at 500mhz.
The 1n4148's should probably have more drive than they get on the Bitx.
The Bat54 schottky diodes on the uBitx have lower drive requirements, same as the SBL-1's at 7dBm into 50 ohms.
?


On Fri, May 26, 2017 at 11:39 am, John wrote:
I see that there are variants of the BITX20 on the web so I wonder whether anyone can recommend a particular circuit to follow. I have a good supply of iron dust toroids, 2N3904s and 2N2222s. I have a few SBL1s recovered from old boards. Are these much better than rings of 1N4148s?
?
?

?
John
 

Thanks for the replies Jamie and Jerry. I'll look at the links you provided. This is my friend's first radio construction project although he's built electronic circuits before. I thought modular construction would be instructive, debugging stage-by-stage (if necessary) and we can always upgrade modules when the whole thing is working. I have a couple of Si5351 breakout boards bought at a rally and doing nothing. Using them we wouldn't have to worry about drift, and a digital display will be easy too.

I'll keep you informed of my (our) progress.

73,

John G4EDX

On 27 May 2017 at 15:23, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
The BitX40 schematics up on are probably a good place to start, adjustments for 20m would be restricted to the BPF, the transit LPF, and the VFO.
You need to decide if you are going with an analog VFO, I'd suggest using an Si5351 for both VFO and BFO as is done on the uBitx: ?
In fact, not a bad idea to just go with the uBitx schematics, has a number of improvements over the Bitx.
The SBL-1's should work fine, though it's possible that building up from torroids and diodes could work slighty better as they don't need to work at 500mhz.
The 1n4148's should probably have more drive than they get on the Bitx.
The Bat54 schottky diodes on the uBitx have lower drive requirements, same as the SBL-1's at 7dBm into 50 ohms.
?


On Fri, May 26, 2017 at 11:39 am, John wrote:
I see that there are variants of the BITX20 on the web so I wonder whether anyone can recommend a particular circuit to follow. I have a good supply of iron dust toroids, 2N3904s and 2N2222s. I have a few SBL1s recovered from old boards. Are these much better than rings of 1N4148s?
?
?

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