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Hi Raj, You may not have had a big enough heat sink for the 317T or another stability problem if it starts to limit current at 0.5A. My experience with about 31V input and 18V to 25V output has shown

Gary, The carrier burst on PTT is due to the C122 charging up through D15 or 16 unbalancing it and allowing a leak. Quick fix is put a 0.68uF cap from the common of D15/16 to the atten pad R39. A

i.e LM338 - my choice over a LM317 series. 317 starts limiting current quite early even with minimum rise in temperature. I don't recommend it for anything over 0.5A unless the in-out voltage

I tried the relay idea Brent, and it did nothing, so don't go hacking your board on the hope this is going to fix your problem. I still see a burst of full carrier for ~ 6 ms immediately after PTT is

A 10-T pot is not strictly required but highly recommended. The code will still work with a standard pot. 73 Allard PE1NWL

If you are going to build a linear regulator to power the drain of the IRF510, why not use a LM336? It is good to 5A throughput at those voltages. A smaller one would do for powering the board

Do I also need to install a 10 turn pot? ? Paul

Hi Brent; ? ? ?Gotta say; I share your glee with this radio. I’ve been heads down on “fixing some of the more serious woes of this rig the past couple of weeks, while resisting the urge to

I've got a SOTABEAMS mountain tuner and a couple pico tuners that I'm using to get into EFHW antennas. I'd like to build one that I can use with a bitx40 with a full 20w output, but I can't seem to

The 5W out is at 28MHz, where the IRF510 efficiency is worse than awful...I'll try a LM317T supply on my BITX40 and report the results. The 317T can provide up to about 1.5A.

even LT1083CP can well be managed upto 7amps of load. being a low drop regulator one can manage a trafo with 24V secondary regards Sarma jgaffke@...> wrote:

5w out powered from an LM317 sounds fine. And yes, the current limiting would be very handy. 20w out of the bitx40 with the irf510 at 24v would not work quite so well.

An LM317 is a "bullet-proof" choice for powering an IRF-510, in my experience. I use this solution for beacon transmitters and they tolerate about anything (except lightning!). Since the LM317

Yes, around 150ma. 0.5v sounds high, perhaps more like 0.1v rms for the microphone input? Laptop supplies are usually spec'd conservatively and are well designed.?

?I think the main board is about 100-150 ma? Droppng 12V (from 24--> 12) would be about 1.2 - 2 watts, could be done with a small heatsink. I don't yet know about the noiselevel of laptop supplies.

However, something like an LM317 with heatsink might be about right for powering the main bitx40 board from the same 19-24v. that you feed the irf510 with. Then you could get by with a single old

Powering the BItx40 at 24v will require on the order of 50w, A load like that would turn those ebay LM317 regulators into smoking ash. That stuff gets spec'd as aggressively as they can sneak by with.

Have you considered trying laptop powr supply? I found a 19V one in a thrift shop for $5 and it seems to work so far; I added a 50 microfarad cap and a 0.01 at the output; here is one from walmart at

The LM317 version of the DC converter would be my choice. You'd need a 15-24 volt AC power transformer for it's input. The Lab supply would be a bit of overkill, but if you're building circuits, it

for powering the bitX40? final to 24v? Just add the appropriate power transformer, fuse, etc, seems reasonable.?