Wow, user error on my part, I was measuring total current. ?I just inserted meter in just the PA line and all is OK now, 100ma.

I guess the excitement to get the BITX connected quickly, I was too quick on the trigger to read the setup slowly, ?Thanks so much for the quick response.?

I know there's no AGC but has anyone been looking to modify so as to add an S-Meter based on RF signal level, not tapping off Volume control.

Thanks so much for the quick response....lesson learned, read twice and slowly.

Tnx,

Faris

Hi,

I just got my license a month ago and have been sitting on my bitx40 until I got it. I also ordered a PLJ6-LED frequency counter off of ebay to mess around with, as seen Is there any way to keep the analog VFO on the bitx40 and use a frequency counter to display the VFO frequency? From what I understand I would have to find a way to measure the frequency of the crystals on the board then add or subtract the offset and put that into the frequency counter. Is that correct? Has anyone here done this with their bitx40 yet? I apologize in advance for such a noob question, I'm slowly but surely modifying my bitx40 and it has been a great introduction to electronics!

If you are seeing 7 watts out, sounds like it is working. ? ?However:

Setting RV1 to the top of its range (5.4v?) could easily blow the IRF510. ? Just slowly bring it up to 100ma of drain current into the IRF510.

There is no zener, perhaps you are referring to the LM78L05 3 pin regulator? ?Should be 5.0 volts, within a tenth of a volt or so.

Jerry

Where are you measuring the 310ma? ?You should be measuring just the current through the PA 12v line into the IRF510 when setting the bias.

> ?The alignment section says when RV1 is fully clockwise (PTT keyed) current should be zero, I see 310ma.

Hi,

Just received my BITX this week and put it together..... receiver & display works fine. ? Receive current is 130ma.

-The alignment section says when RV1 is fully clockwise (PTT keyed) current should be zero, I see 310ma.

- Next it says key Mic without talking and adjust RV1 for 100ma, the lowest I can get by adjusting RV1 is 310ma. ?When transmitting into a dummy load and speaking (constant) into the Mic & adjusting RVI for 7watts out, the current is 1.1 amps. ?I can hear myself fine out of another receiver nearby.

- Voltage at Zener is 5.4v, voltage at IRF gate is 0 to 5.4v (when adjusting RV1)

Not sure if IRF-510 is slightly bad ??

Appreciate any help or comments.

40meters totally dead last few hours here in NJ, hopfully looking forward to making some contacts tomorrow.

Tnx,

Faris N2FH

Not weird. ?Especially if there's a lot of copper on that ground pin sucking away the heat. ?Everybody has trouble cleaning solder out of through-holes, the surface tension of the solder does a good job of holding it down in the hole. ?A really hot soldering iron, the right kind of soldering flux, and some solder wick are about as good as you can do. ?If the flux is corrosive, make sure to wash it off good. ?

You can clip the pins, put a soldering iron on each one in turn, and use your third hand to pull the clipped pin out of the board with a needle nose pliers. ?

Easier still, just clip them back and leave them be. ?Bend the pins on the new part till they are doubled back (gives more surface area to solder to), tin them good with solder, then solder them to the old pins with a glob of yet more solder. ?Will be trivial to replace the next time you blow the part. ?And you're in far less danger of damaging the board.

Five watts and less is pretty marginal for SSB, much easier to make CW contacts at QRP power levels. ?How far away are those guys listening from? ?Are they pretty much line of sight? ?Depending on terrain, could be that a couple dozen miles away is out of your ground wave.

I tried tracking on the web, could see it was handed off to MumbaiAir on Dec 31. ?The USPS website claimed it didn't know about any IndiaPost tracking number. ?I checked at a local post office (small town, clerks have time to help), and the clerk found that it had been scanned in Eugene Oregon on Jan 16. ?And thence apparently on to something called the ACS (Address Coding System) in Seattle, which I assume could be called the dead letter office. ?She tried but failed to get an image of the scanned label from Eugene, and made an inquiry. ?I've got my own inquiry into the USPS via their website. ?(Go to usps.com, ?help, contact us). ?We'll see if they can find it. ?

I had an email exchange with hfsignals at gmail dot com. ?They said if deemed not deliverable, it should come back to them. ?And that the package labels are directly printed from the PayPal system and covered with clear protective tape. ?I've verified that the address is correct in the email I got from PayPal. ?And ordered a second Bitx40 (I can use two).

So anyways, I think hfsigs did their thing, and that the USPS ate it. ?Or maybe Jack bought one of these: ?/g/BITX20/message/20575? ? and it happened to be in the same mailbag.

Jerry

Funny you should ask about the adequate antenna. My elmer is extra class and I am a general. He gave me a homemade G5RV jr. for Christmas and I had to figure out a choke balun to get a low swr with my chinese qrp kit antenna tuner and MFJ qrp swr/watt meter. Before this, I had my homemade dipole that had a perfect swr in the cw range without tuner. I made contacts with it and could hear my signal a few states away with a webSDR station. The G5RV jr. is unproven, but is a good multiband receive antenna. The BITX 40 is a good receiver too. But I have to tune up a hundred hertz to make ssb sound natural. The fourth number to the right of the decimal on the raduino display is a hundred hertz right?

Okay Jerry, I'll try the voltage test and resistor thing. I orderd 2 replacement PA's when I orderd the BITX 40 and china sent me 10 of them. I don't like desoldering components unless it's really necessary because of eventual damage to the pads. And with plated through hole boards I sometimes have trouble getting solder out of the hole. It's weird.

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And a minimalist RF probe, such as that N5ESE circuit. ?And a low pass RC filter to measure the quiescent DC voltage. ?I'm willing to assume they have a voltmeter, that costs a buck here in the USA if you show up at Harbor Freight on the right day. ?But the rest of this stuff should be on the main Bitx40 board.

First off, you are really close to having this thing work properly. ?And I suspect you are learning quite a lot.

I assume you have an adequate antenna. ?Can they hear your 6 or 7W CW transmitter?

Turning the bias control up all the way should be putting like 10 Amps through that IRF510, enough to blow it across the room. ?Especially if you are feeding the IRF510 from 20V. ?Are you sure your IRF510 power supply is capable of giving at least a couple Amps? ?Monitor the power supply voltage with a voltmeter when transmitting. ? Yes, I think that when your 10A max digital meter says 0.1 that means it sees 100ma. ? I have no idea why your meter would show 2.4 when watching DC current into the final with the meter set for a maximum range of 200ma, that might be a question for whoever sold you the meter. ?Better yet, take the whole thing to the next club meeting or over to your Elmer, see if they can figure this out.

If you don't trust your wattmeter, here's a sanity check. ?Get a 50 ohm carbon resistor rated for 1 or 2 watts. ?Put it across the transmitter output for a dummy load. ?Put something like a tone generator or even some loud music in front of the microphone. ?Hold down the PTT (while monitoring IRF510 current, and making sure the IRF510 doesn't get hotter than you want to touch) and see how hot that 50 ohm resistor is getting. ? Let it cool down, then put the same 50 ohm resistor across a 12 volt battery or power supply, compare how long it takes to get as hot as it did with your transmitter. ?With 12v across 50 ohms, that's 12/50 = 0.24 Amps. ?Amps times Volts is power, so the 12 volt supply is heating the resistor with 0.24*12 = 2.88 Watts. ?When your transmitter is working correctly with 12v into the IRF510, it should heat that resistor about twice as fast as the 12v power supply did.

I ordered a Bitx40 on Dec 23, it hasn't shown up yet, apparently the USPS has eaten it. ?So I can't measure a real rig. ?But I did simulate what the voltages should be with LTSpice as documented in the following post: ?/g/BITX20/topic/ltspice_simulation_of/4260835? ? ? That might be of some help to figuring out how well the IRF510 is doing, especially if you can find somebody with a scope who knows how to use it. ? LTSpice is very easy to use, and makes it easy to see exactly what is going on in these circuits using nothing more than a computer.

Don't feed the IRF510 20v until you are sure it is working correctly at 12v. ?Easy enough to blow it at 12v. ?Possible that it is somewhat damaged now, and that's the problem? ?Though usually they fail catastrophically, and if you can still adjust the bias control for 100ma, it's likely working well enough. ?When you do get around to blowing the IRF510, you will find that they are very cheap online. ?I'd recommend getting either the InternationalRectifier or Vishay brand.

And to the rest of the group here, we clearly need a standard way of driving the final amp with a known signal source. ?Perhaps one of the Si5351 outputs gets used as a signal generator, goes through a resistive attenuator, the output of which gets shorted into the final amp side of the LPF. ?And/Or perhaps a Raduino digital output drives a resistive attenuator with a 1khz square wave from a counter-timer, gets applied to the microphone input. ?The only additional parts required are a few one cent resistors.

Jerry, KE7ER

Hi Noel!

You can sure try. Depending on the DC/DC converter you have it might work.

In my case the model I had on hand (for which I've posted the link in my previous post) generates a lot of switching noise on the 12V power line. That increases the receiver noise which is quite high from the start.

For the PA the current requirements are only 1.5A to 2 A. If it is for desk use I would use a second linear power supply for PA. If you have a 120V to 24V transformer that can deliver 2A I would make a power supply just for that.

A good option is this:

or this:

Second option has higher output current capability but you cannot adjust the current limit and the voltage is set using a multi turn trim pot.

You need to find a good heat sink for the power transistor.

--
Ion

VA3NOI

I haven't been able to make a contact yet, and I think my PA isn't putting out enough power. Awhile back on the subject of bad audio, Farhan suggested I ask someone for a signal report. No one I asked at the club could hear my Bitx 40.

I am going to cut and paste an Email I sent to my elmer. Perhaps some of you already know about this one.