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Don't forget, guys,that EVERY transmitter must meet the rules of operation and emission for your country, no matter how it is originally set up or modified.

In the USA, that means meeting the Part 97 FCC Rules. Note that ALL spurious emissions must be at least 43 dB below the transmitting frequency. The responsibility for measuring and verifying this lies with the operator -- that's you, the builder of the rig. You shouldn't rely on any given design. You must verify that it is within limits.

"(d) For transmitters installed after January 1, 2003, the mean power of any spurious emission from a station transmitter or external RF power amplifier transmitting on a frequency below 30 MHz must be at least 43 dB below the mean power of the fundamental emission. For transmitters installed on or before January 1, 2003, the mean power of any spurious emission from a station transmitter or external RF power amplifier transmitting on a frequency below 30 MHz must not exceed 50 mW and must be at least 40 dB below the mean power of the fundamental emission. For a transmitter of mean power less than 5 W installed on or before January 1, 2003, the attenuation must be at least 30 dB. A transmitter built before April 15, 1977, or first marketed before January 1, 1978, is exempt from this requirement."

john

AD5YE

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Thanks Arv,

Are they SMD resistors? If so, what size are they? Physical size. I don’t work with SMD enough to tell by looking.

I have a multiturn pot on the way. My tuning is super touchy. It takes quite a while to tune a signal in correctly. I literally have to tap the shaft to fine tune.

Thanks for the info

Mark

K3MRK

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From: BITX20@... [mailto:BITX20@...]
Sent: Saturday, November 26, 2016 11:24 PM
To: BITX20@...
Subject: Re: [BITX20] Bitx 40 board.

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Mark. K3MRK

Either 10K or 100K, or anything in between, will work fine for the

tuning pot.? A 10-turn type pot makes tuning much easier if you

have one available.?

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Resistors for decreasing heat generation are 220 ohms.

Arv? K7HKL
_._

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On Sat, Nov 26, 2016 at 8:56 PM, 'Mark W' k3mrk1@... [BITX20] <BITX20@...> wrote:

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No I did not receive any resistors. What size are they? I’ll try to find some. I also noticed that my tuning pot is 10k. The board info on the website says it should be 100k. Which is correct?

I have received my enclosure and am almost done installing.

Mark

K3MRK

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From: BITX20@... [mailto:BITX20@...]
Sent: Thursday, November 24, 2016 8:48 PM
To: BITX20@...
Subject: Re: [BITX20] Bitx 40 board.

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mark,
you must have received a strip of 220 ohm resistors in the pack. if you replace the 100 ohm emitter resistors of the six amps with these, the drift will drastically reduce. the details are on the blog.
- f

On 25-Nov-2016 4:58 am, "Mark Walton k3mrk1@... [BITX20]" <BITX20@...> wrote:

>?

> ?
>
> It might be worse since there is no enclosure at all. Maybe not really warming up at all. I'm hoping the enclosure itself will have some heat retention. There are some transistors that can be used as heaters. I'll wait till I get the enclosure and see how it is. I realize that this circuit is prone to some drift on warm-up, but I think mine may be excessive. Bad cap? I haven't really started digging in yet. I have all the parts for a DDS and may just go that way from the start. I'm no engineer and will have to figure out how that is done as well.
> Mark
> K3MRK
>
>
> On Nov 24, 2016 4:21 PM, "Thomas Noel tnoel@... [BITX20]" <BITX20@...> wrote:

>>?

>> ?
>>
>> What would happen if you added an intentional heater to the enclosure? I'm thinking of something like the flat stick-on pads used to warm reptile tanks, stuck on the underside of the radio enclosure? Thinking a giant version of an oven controlled crystal oscillator?
>>
>> Tom
>> KF7RSF
>>
>> Sent from my iPhone
>>
>> On Nov 24, 2016, at 12:53, Mark Walton k3mrk1@... [BITX20] <BITX20@...> wrote:
>>

>>> ?

>>>
>>> I recently received my BitX-40 board. Until I get the enclosure, I only hooked it up for receive. Worked right out of the box. The only issues I've found is the drift is pretty bad even after being powered up for an hour. What should I be looking at to try to improve the stability? I do plan to build a DDS VFO for it over the winter.
>>> The only other issue is the running is very touchy. I have coming a multiturn pot to fix that.
>>> Any ideas on the drift?
>>> Other than that , I'm very happy with the board and look forward to building onto it in the near future.
>>> Thanks
>>> Mark. K3MRK
>
>
>

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A buddy bought a SMD pre-assembled board and says it's completely deaf, while he can hear lots of band activity with his FT-817ND. I volunteered to go over it with my scope and diagnose it.

First things first: What's the typical approximate current draw in milliamps for these boards on a 12.0 volt power supply in receive mode? (Knowing the expected current draw will allow me a rough determination of any gross circuit faults before I start tracing and probing.)

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Thanks for answering John. I didn't know as much about the history.?

I have Ashar's SMD version, and it works great, but I wouldn't mind a through-hole version in case I needed or wanted to replace a component. Replacing those teeny tiny SMD parts can be quite a challenge. :-)

On Sun, Nov 27, 2016 at 5:26 PM, iam74@... [BITX20] <BITX20@...> wrote:

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Mark, Sunil Lakhani and Asher Farhan are in completely different companies.

Sunil brought out the BITX20 v.3 some years ago (with Farhan's blessing). He has since expanded the line considerably; parts are available from only circuit boards to complete rigs as kits. Sunil has a long and respected tradition in the BITX arena, but he has no smd kits as far as I know. I have bought several kits from him over the years and have always been treated well. They have become more expensive over time.

Farhan invented the BITX and has been involved with the various permutations over the years from start-up.
He has decided to market the smd BITX40 partly (or mainly) as an aid to a womens' group in India. At first, the kit was available only in India, but has recently become available internationally. It is only the second smd version that I know of; the first was by eliamady back in 2009. I have the BITX40 and also the eliamady smd version of the rig. (I will probably post pictures of both for comparison to the group shortly).

As to which one to use...that is kind of a personal question -- it depends...

Sunil's rigs are through-the-hole construction and are designed more or less for complete assemblage by the user, except for making the pcb. Their principal advantage is that missing or different parts are commonly available most everywhere -- including where you live. Asher's rig is pre-assembled and smd, but one has to figure out how to put it in a box and make it work without assembling the main board (or boards). Both are essentially the same design.The one radically different BITX was probably the BITX20A with its push-pull dual output PA. That also is still available.

Every single BITX has been tweaked and modified over the years for one purpose or another. Both Sunil and Asher (as well as everybody else) encourage innovation to make things more to the user's liking. The best general summary I know of for the circuit is that of F8VOA, which has all the good mods in it. It is an excellent reference. The next best reference is this list. Search for any topic and you will probably find it discussed somewhere on this list.

Hope this helps.

john
AD5YE

---In BITX20@..., wrote :

Thanks Mike!

I have a few questions:

1. What is story behind the two different sellers?

There's like you mentioned, and then what I was referring to:

Sunil Lakhani VU3SUA at

and he's selling his kits on eBay as sunillakhani

The kit I was thinking I wanted to buy was:

2.?Would I want the through-hole version referenced or the SMD version you linked to?

Which would be better for experimenting or modifying for other bands?

I also see that the SMD version is already assembled, and cheaper! $45?

I appreciate the input.

Thanks!

Mark, KC9DZT

--

Mike Haynes

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--- wrote :

We starting including the resistors after the reports of the drift. the pads are big enough for you to solder regular 1/4 watt in place of wthe smd resistors (in manhattan style). if you do really want them, drop a mail to and they will post a 'pinch' of them to you for free, though the cost of postage is prohibitive but they have agreed to bear it.? - f

That is indeed very generous, but I hope no North American or European takes advantage of the offer. 1/4 watt resistors are ***far too easy*** to come by on both continents for any sense to be made of sending a "pinch" of them all the way from India! Moreover, it's my understanding that this effort by RF Signals is part of a community fund-raising and money *earning* (as opposed to money *making*) project. That was one of my reasons for buying one of the boards. I'd like to see as much of that money stay in India as possible.

I think there's another issue involved here that bears some thought and discussion. So the BitX40 VFO has some drift? BFD (Big Fat Deal)! I hope I never get to the point either physically or psychologically when having to touch a VFO knob to sharpen the tuning up a bit now and then becomes burdensome or somehow unacceptable. And God forbid I would ever become such a jerk as to mar an otherwise pleasant QSO by pointing out to the other guy--more often than not a total stranger--that he's drifting (or exhibiting some other meaningless "flaw" in his signal) unless I'm **asked** for a detailed signal report.

This ongoing inflation of features and expectations needs some serious reconsideration, reflection, and soul searching. It's made possible by **store-bought** DDS and SDR technology, along with all the feature bloat that goes along with much of it: waterfalls and spectral displays and other means of finding fault with the other-guys transmission.

Sure, lower the bias current by putting in 220 ohm resistors to minimize heating. Take any other reasonable route to maximize the VFO's stablility. Figuring all that out is part of the fun. But if you can't get around to any of that, stick an antenna on the thing and get on the air anyway! If you end up offending the spectrum police, too bad for them!

73,

Todd K7TFC ?

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Mark, Sunil Lakhani and Asher Farhan are in completely different companies.

Sunil brought out the BITX20 v.3 some years ago (with Farhan's blessing). He has since expanded the line considerably; parts are available from only circuit boards to complete rigs as kits. Sunil has a long and respected tradition in the BITX arena, but he has no smd kits as far as I know. I have bought several kits from him over the years and have always been treated well. They have become more expensive over time.

Farhan invented the BITX and has been involved with the various permutations over the years from start-up.
He has decided to market the smd BITX40 partly (or mainly) as an aid to a womens' group in India. At first, the kit was available only in India, but has recently become available internationally. It is only the second smd version that I know of; the first was by eliamady back in 2009. I have the BITX40 and also the eliamady smd version of the rig. (I will probably post pictures of both for comparison to the group shortly).

As to which one to use...that is kind of a personal question -- it depends...

Sunil's rigs are through-the-hole construction and are designed more or less for complete assemblage by the user, except for making the pcb. Their principal advantage is that missing or different parts are commonly available most everywhere -- including where you live. Asher's rig is pre-assembled and smd, but one has to figure out how to put it in a box and make it work without assembling the main board (or boards). Both are essentially the same design.The one radically different BITX was probably the BITX20A with its push-pull dual output PA. That also is still available.

Every single BITX has been tweaked and modified over the years for one purpose or another. Both Sunil and Asher (as well as everybody else) encourage innovation to make things more to the user's liking. The best general summary I know of for the circuit is that of F8VOA, which has all the good mods in it. It is an excellent reference. The next best reference is this list. Search for any topic and you will probably find it discussed somewhere on this list.

Hope this helps.

john
AD5YE

---In BITX20@..., wrote :

Thanks Mike!

I have a few questions:

1. What is story behind the two different sellers?

There's like you mentioned, and then what I was referring to:

Sunil Lakhani VU3SUA at

and he's selling his kits on eBay as sunillakhani

The kit I was thinking I wanted to buy was:

2.?Would I want the through-hole version referenced or the SMD version you linked to?

Which would be better for experimenting or modifying for other bands?

I also see that the SMD version is already assembled, and cheaper! $45?

I appreciate the input.

Thanks!

Mark, KC9DZT

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Try ordering direct from India. It takes a few weeks, but that's how I got mine.

- Mike
KE0KRY

On Sun, Nov 27, 2016 at 2:58 PM, Mark Baldridge marktbaldridge@... [BITX20] <BITX20@...> wrote:

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I was looking at finally ordering a kit, and now they all seem to have disappeared. Only the PCBs are left.

Do we know if/when they will be available again?

Thanks all!

--Mark

--

Mike Haynes

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I was looking at finally ordering a kit, and now they all seem to have disappeared. Only the PCBs are left.

Do we know if/when they will be available again?

Thanks all!

--Mark