Note that this fix is not compatible with Allard's instructions for using the rig on CW.
Also, note that there are two PTT bursts. ?
Raj's fix is for the carrier burst that transmits out over the air.
There's also a kerchunk you hear in the headphones.
Jerry, KE7ER
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On Thu, Oct 19, 2017 at 01:31 am, Raj vu2zap wrote:
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 track has to be cut.
If your board has a trimpot there then you can tombstone the pot and add the cap.
A 1K resistor across C107 helps.
The leak is almost eliminated.
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? ? ? Hello everyone, anyone ever thought of replacing the relay by switching to transistor? I made some hopes with this but did not measure the delay of the two switches, it's just an idea!? ? ?Jorge PY2PVT _._
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 applied. I see the same result in CW mode, except there's a pause after the burst before the carrier comes on for the first code element is transmitted. The timing is almost precise on this, but I haven't found anything in the code that seems to correlate with it. The 6 ms does correlate with the relay switching speed, but it seems I'm puzzled on this issue again. Either I'm still overlooking something, or I botched the hack on my board.
Sorry about that.
Gary, N3GO
-- ? 73 de Jorge PY2PVT
? Campinas SP
? GG67MD
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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 1.5A output reliably,
with stable voltage regulation. For a typical datasheet, see the
"Figure 8. Current Limit" graph on page 5 of this PDF:
...As with all ancient regular ICs, the 317T has been cloned by everyone
and specs may vary. The exact parts I'm using came from National
Semiconductor many years ago.
Why I originally chose the 317T for my project is that it seemed an almost
perfect match for the IRF-510---meaning keeping the 510 within maximum
specs under all load conditions...Again, with a big enough heat sink on
the 510, too! ....And, over the last 5+ years of continuous beacon
operation, I've found this premise to be true.
Anyhow, there are plenty of regulator choices out there! ...Have fun and
homebrew!
73, David KB4FXC
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On Thu, 19 Oct 2017, Raj vu2zap wrote: 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 difference is a few
volts!
Raj
At 19/10/2017, you wrote:
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
directly, even a LM7805 if the voltage drop is not too great.
Don't forget the reverse voltage protection!
john
AD5YE
|
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 track has to be cut.
If your board has a trimpot there then you can tombstone the pot and add the cap.
A 1K resistor across C107 helps.
The leak is almost eliminated.
Raj
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Show quoted text
At 19/10/2017, you wrote: 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 applied. I see the same result in CW mode, except there's a pause after the burst before the carrier comes on for the first code element is transmitted. The timing is almost precise on this, but I haven't found anything in the code that seems to correlate with it. The 6 ms does correlate with the relay switching speed, but it seems I'm puzzled on this issue again. Either I'm still overlooking something, or I botched the hack on my board.
Sorry about that.
Gary, N3GO
|
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 difference is a few
volts!
Raj
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Show quoted text
At 19/10/2017, you wrote: 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
directly, even a LM7805 if the voltage drop is not too great.
Don't forget the reverse voltage protection!
john
AD5YE
|
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 applied. I see the same result in CW mode, except there's a pause after the burst before the carrier comes on for the first code element is transmitted. The timing is almost precise on this, but I haven't found anything in the code that seems to correlate with it. The 6 ms does correlate with the relay switching speed, but it seems I'm puzzled on this issue again. Either I'm still overlooking something, or I botched the hack on my board.
Sorry about that.
Gary, N3GO
|
A 10-T pot is not strictly required but highly recommended.
The code will still work with a standard pot.
73 Allard PE1NWL
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On Wed, October 18, 2017 20:38, Paul Avona via Groups.Io wrote: Do I also need to install a 10 turn pot? ??
Paul
|
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
directly, even a LM7805 if the voltage drop is not too great.
Don't forget the reverse voltage protection!
john
AD5YE
|
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 alter the as-is configuration. ?It¡¯s not useful to others to do otherwise. I need to spend some time documenting my findings though; both to defend them, as well as my fix recommendations.
? ? ?It¡¯s been helpful that this radio is so simple to simulate and analyze. The fate and fixes almost jump out at you. :-) I¡¯m still new to this project and list though, and I haven¡¯t yet found the repository of sanctioned upgrades and fixes. Much of what I¡¯ve discovered and conquered has likely already been addressed; so my apologies in advance for not doing the research to find them.
? ? ?The issue you describe is related to the PTT pop issue. The hard answer is that it¡¯s inherent in the current design. DC Xmt power is applied in advance of the decay in the Rcv DC supply. Hence; both are simultaneously enabled for the duration that the Rcv DC supply holds up. This is exacerbated by D10, and the sequential switching of K1 followed by K2 which keeps the audio preamp connected to the PA... albeit briefly (up to ~ 7 ms) following enabling of the mic amp.?
? ? ? I¡¯ve conquered the transmit pop, but in full disclosure, I¡¯ve not yet implemented the following ?receive side fix that I have in mind. ?It should address your problem nicely, but you¡¯ll be on your own, as there¡¯s always the risk of a snafu I failed to spot. If you wish to stick your neck out though, give this a try:
? ? Observe that the right side of K2 does the T/R antenna ?switching, While the top section of K1 grounds the now disconnected wire, and thus serves no purpose. Sever the connections at K1 pins 12, 14. Jumper K1 pins 12 and 3 and your done. The keying of K1, now dumps the receive supply to ground before the transmitter circuits become enabled.?
? ? ? I¡¯m guessing that it¡¯s not easy to sever the connection at K1 pin 16; otherwise the top portion of relay K1could be used to dump transmit power to ground when switching to receive as well by simply grounding pin 12. That would be the preferred fix.?
? ? ? While at K1, shunt the coil with a diode. D7 does nothing as wired.?
? ??
? ? ? Swap D18, and R127, or simply jumper across the old D7 location. A diode in lieu of R127 greatly accelerates the power-up of the mic amp. Also add 20 to 100uF from the top of C-123 to the top of C-124... plus side to C-124. Together, these changes nullify the PTT carrier spike (pop!) at the beginning of a SSB transmission.
? ? ?Finally; place a short jumper between the VFO input side of L4 and the emitter of Q8. This bypasses the first two VFO Impedance buffers that band limit the Raduino clock and starves the first LO in USB mode. No need to remove the unused buffers, as they don¡¯t interfere. This fix yields +6 to +7 dBm into the first mixer at both 5 and 19 MHz, and results in full transmit power out, good sensitivity (0.1uV) and RF dynamic range to +25 dB over S9 in all modes.?
? ? ?All but the relay wiring fix and miswired D7 were derived via simulation, and verified on my BITX-40. I also added a 1uF ceramic cap across the PTT to suppress switch bounce noise from chattering the relays.
? ? ?I zapped the SPOT port of the Rudino¡¯s Nano, so I¡¯m limping along until I can get it replaced. I always seem to fat probe stuff when I¡¯m eager to get stuff done. <sigh>
? ? ?Good luck with the mods. I hope you¡¯re having as much fun as I am having.
72 es 73
Gary, ?N3GO
? ? ?
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toroid and capacitor power handling (EFHW tuner question for bitx40)
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 find info on the breakdown voltage on the caps used in these 6-10w tuners, so I can't seem to figure out just how heavy-duty my cap needs to be.
Also, what's the deal with toroids and power handling? ?How do I determine how much power a given wound toroid can handle at RF?
I plan on building a Match-22 tuner as described in "Hand Carried QRP Antennas," but I'd love for it to be able to take a full 20W so I can use my bitx or my TJ5A with it.
Thanks,
Jake
KE0GYC
|
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.
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On Wed, 18 Oct 2017, Jerry Gaffke via Groups.Io 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.
On Wed, Oct 18, 2017 at 08:04 am, David McGough wrote:
Output power after the LP filter is about 5W (+/-).
|
even LT1083CP can well be managed upto 7amps of load. being a low drop regulator
?one can manage a trafo with 24V secondary ?
On Wed, Oct 18, 2017 at 8:55 PM, Jerry Gaffke via Groups.Io <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.
On Wed, Oct 18, 2017 at 08:04 am, David McGough wrote:
Output power after the LP filter is about 5W (+/-).
|
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.
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On Wed, Oct 18, 2017 at 08:04 am, David McGough wrote:
Output power after the LP filter is about 5W (+/-).
|
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 provides fast-acting
current limiting, this has saved my IRF-510 on many occasions when various
antenna system failures occurred. I power the LM317's from surplus HP
deskjet switchers. Works GREAT and been on-line 24/7 for years now! The
CW note is very clean, no detectable clicks, etc., with very low spurious
noise--there are several very active hams on 10M within line-of-sight to
the beacon antenna and less than 1 mile away! Here are some links:
Here is a schematic of the beacon. It's simple and brute-force. Note that
the output low-pass filter isn't shown. This schematic also pre-dates a
better output matching solution. Like I mentioned, it has been on-line
continuously for years now, through antenna/feedline failures and all;
sometimes with very bad SWR for days at the time! Output power after the
LP filter is about 5W (+/-).
73, David KB4FXC
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On Wed, 18 Oct 2017, Gordon Gibby wrote: ?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. While rated often for 2A, some of mine get pretty warm when chargeing AND running a dead laptop; the one on my Lenova is rated 20V @ 2.5 A and for medium dutycycle 50% it is probaby fine. Since they are produced in such large quantity, they are quite cheap. I have one running an LDG auto tuner right now (a 12V laptop supply).
My next project is to build an itty bitty 10X preamp for the mic input; I've read the bitx needs 0.5V --- holy cow!! Had to turn a signalink nearly halfway up, farther than I've ever had to turn one, and screaming into a powered mic was necessry.....that should be easy to fix with a tiny 1-transistor preamp. I'm using this for psk31 and WINLINK. Hit four winlink gateways the other evening. Cool rig.
________________________________
From: [email protected] <[email protected]> on behalf of Jerry Gaffke via Groups.Io <jgaffke@...>
Sent: Wednesday, October 18, 2017 9:50 AM
To: [email protected]
Subject: Re: [BITX20] Would this P/S work?
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 laptop power supply if it's not too noisy.
On Wed, Oct 18, 2017 at 06:44 am, Jerry Gaffke wrote:
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.
And then a little bit more.
|
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.?
Lenovo/Dell/Asus/Acer/HP/Samsung/Apple can't afford the headlines.
A large cap will help on voice peaks if performance on current transients is marginal.?
RF filtering using toroids and caps could be used to cut the noise if necessary,
on both dc out and ac in cords. ?
And maybe enclose it in something RF tight, though watch out for overheating.
But I think some folks are using laptop supplies on the bitx40 without any such measures.
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On Wed, Oct 18, 2017 at 07:22 am, Gordon Gibby wrote:
?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.? ?While rated often for 2A, some of mine get pretty warm when chargeing AND running a dead laptop;? ?the one on my Lenova is rated 20V @ 2.5 A and for medium dutycycle 50% it is probaby fine.? ?Since they are produced in such large quantity, they are quite cheap.? ? I have one running an LDG auto tuner right now (a 12V laptop supply).? ??
My next project is to build an itty bitty 10X preamp for the mic input; I've read the bitx needs 0.5V? --- holy cow!!? ?Had to turn a signalink nearly halfway up, farther than I've ever had to turn one, and screaming into a powered mic was necessry.....that should be easy to fix with a tiny 1-transistor preamp.? ? I'm using this for psk31 and WINLINK.? ?Hit four winlink gateways the other evening.? ?Cool rig.
?
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?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.? ?While rated often for 2A, some of mine get pretty warm when chargeing AND running a dead laptop;? ?the one on my Lenova is rated 20V @ 2.5 A and for medium dutycycle 50% it is probaby fine.? ?Since
they are produced in such large quantity, they are quite cheap.? ? I have one running an LDG auto tuner right now (a 12V laptop supply).? ??
My next project is to build an itty bitty 10X preamp for the mic input; I've read the bitx needs 0.5V? --- holy cow!!? ?Had to turn a signalink nearly halfway up, farther than I've ever had to turn one, and screaming into a powered mic was necessry.....that
should be easy to fix with a tiny 1-transistor preamp.? ? I'm using this for psk31 and WINLINK.? ?Hit four winlink gateways the other evening.? ?Cool rig.
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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 laptop power supply if it's not too noisy.
On Wed, Oct 18, 2017 at 06:44 am, Jerry Gaffke wrote:
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.
And then a little bit more.
|
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 laptop power supply if it's not too noisy.
toggle quoted message
Show quoted text
On Wed, Oct 18, 2017 at 06:44 am, Jerry Gaffke wrote:
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.
And then a little bit more.
|
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.
And then a little bit more.
toggle quoted message
Show quoted text
On Wed, Oct 18, 2017 at 03:53 am, Thomas Sharka wrote:
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.
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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 24VDC? for $10
?
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for powering the bitX40? final to 24v? Just add the appropriate power transformer, fuse, etc, seems reasonable.?
Would a LAB adjustable power supply be a good choice for powering the bitX40? This one is linear not switching.
Dave
k4em
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Raj vu2zap
Allard PE1NWL