Date   

5V to 12V converter to power a QRP Tramsceiver

Bob - K2KI
 

Hi all,
Well, as the subject line sez.... I have several high capacity 5V USB charging bricks that have good long lasting time between chargers. And, I would love to power a QRP Transceiver with them. I have a QCX-Mini on the bench now and would love to be able to power this off of one of the chargers I have (Plus a 1watter & 5watter).

I have seen Buck Boost converters of all kinds and those that plug directly into a USB port look very desirable as they would fit nicely into my Go-Bag.

Does anyone have recommendations on which would be the best course of action? For obvious reasons, I like the ability to see the voltage and current draw. but the rectangular kind that look like they should be mounted on a panel seem rather bulky but... If that is what I should be using, then that is what I will have to live with!

Thoughts??? I look forward to any and all replies!
Many thanks!

-- 
"Of all the things I've lost in life, I miss my mind the most!"
Very best 72/73 from Vermont. .
Bob de k2ki
k2ki@... (Primary Email)
k2ki.bb@... (Secondary: Goes to my cell)
Grid: FN34LW
NEQRP#: 911
4SQRP#: 2292
FP#: 4214
SKCC#: 12195
NAQCC#: 2337
Sasquatch#: 769
30CW#: 190
100WattsID#: 4675
SOC#: 1312

Virus-free. www.avast.com


Re: Oscillation with Hycas AGC Amplifier

Richie Chambless
 

Hi All,

I have good news. I took the Hycas module out of my test receiver and powered it directly (with short leads) with a 13 volt battery. With two 40db attenuators (one on input, other on output), it does not oscillate when connected to my nanovna. I measured around 50db of gain, and the agc action was working to reduce the control voltage down around 4.75 volts, so I know everything is working. I'm thinking I had a ground loop in my receiver, so I will need to change the power connection and build an RF shield for it. Thanks for all of your help!

Rich KM4TLR


Re: Oscillation with Hycas AGC Amplifier

Larry Acklin
 

Diz is a fan of gimmick capacitors- 1 inch of enameled wires twisted tightly, cut off to suit.  Maybe that across R2?

On Fri, Aug 13, 2021 at 9:42 PM Larry Acklin via groups.io <acklin=gmail.com@groups.io> wrote:
have you looked here?

oscillation was apparently an issue. 

73
Larry
KB3CUF 

On Fri, Aug 13, 2021 at 7:50 PM Richie Chambless <rchambless7@...> wrote:
I thought it was the LM386, so I tried two other amps but got the same result. I swapped the Hycas with another IF amp (around 20 db gain) and it worked fine. So, I know the problem is in the Hycas. My next step was to terminate the input and output with 50 ohms and test the AGC voltage. Sure enough, it was only 1.5 volts, meaning something was oscillating internally and driving the control voltage low. I then changed R4 and R8 to 100 ohms, no luck. But when I held a 4.7k resistor across R2, the oscillation stopped! While holding this resistor in place, I put the volt meter on the AGC pin. It had around 5 volts the reduced with incoming signals. So, I soldered the 4.7k resistor in place on top of R2, but the oscillation came back! It's something about my hand capacitance that calms the instability. I think I may experiment with higher R4 and R8 values, along with a transformer impedance match in lieu of the L match. Maybe something will work!


Re: Oscillation with Hycas AGC Amplifier

Larry Acklin
 

have you looked here?

oscillation was apparently an issue. 

73
Larry
KB3CUF 

On Fri, Aug 13, 2021 at 7:50 PM Richie Chambless <rchambless7@...> wrote:
I thought it was the LM386, so I tried two other amps but got the same result. I swapped the Hycas with another IF amp (around 20 db gain) and it worked fine. So, I know the problem is in the Hycas. My next step was to terminate the input and output with 50 ohms and test the AGC voltage. Sure enough, it was only 1.5 volts, meaning something was oscillating internally and driving the control voltage low. I then changed R4 and R8 to 100 ohms, no luck. But when I held a 4.7k resistor across R2, the oscillation stopped! While holding this resistor in place, I put the volt meter on the AGC pin. It had around 5 volts the reduced with incoming signals. So, I soldered the 4.7k resistor in place on top of R2, but the oscillation came back! It's something about my hand capacitance that calms the instability. I think I may experiment with higher R4 and R8 values, along with a transformer impedance match in lieu of the L match. Maybe something will work!


Re: Oscillation with Hycas AGC Amplifier

Richie Chambless
 

I thought it was the LM386, so I tried two other amps but got the same result. I swapped the Hycas with another IF amp (around 20 db gain) and it worked fine. So, I know the problem is in the Hycas. My next step was to terminate the input and output with 50 ohms and test the AGC voltage. Sure enough, it was only 1.5 volts, meaning something was oscillating internally and driving the control voltage low. I then changed R4 and R8 to 100 ohms, no luck. But when I held a 4.7k resistor across R2, the oscillation stopped! While holding this resistor in place, I put the volt meter on the AGC pin. It had around 5 volts the reduced with incoming signals. So, I soldered the 4.7k resistor in place on top of R2, but the oscillation came back! It's something about my hand capacitance that calms the instability. I think I may experiment with higher R4 and R8 values, along with a transformer impedance match in lieu of the L match. Maybe something will work!


Re: Oscillation with Hycas AGC Amplifier

ken WA2MZE
 

The LM386 has a single ended output.  It MUST be coupled to the load through a capacitor (value depends on load impedance, 100-250uf is fine).  One end of speaker or headphone to ground is OK if capacitor is present at '386 output.

On 8/12/21 9:24 AM, Larry Acklin wrote:
I second that LM386 thought.

cribbed from Stackexchange.com-

  • GAIN CONTROL To make the LM386 a more versatile amplifier, two pins (1 and 8) are provided for gain control. With pins 1 and 8 open the 1.35 kΩ resistor sets the gain at 20 (26 dB). If a capacitor is put from pin 1 to 8, bypassing the 1.35 kΩ resistor, the gain will go up to 200 (46 dB). If a resistor is placed in series with the capacitor, the gain can be set to any value from 20 to 200. Gain control can also be done by capacitively coupling a resistor (or FET) from pin 1 to ground.

Gain = 15,000 x 2 / (Ra + Rb)
Initially Ra + Rb = 0.150 k + 1.350 k = 1.5k
So gain = 2 x 15,000 / 1.500 = 20.
Shorting the 1.35K FOR AC increases gain to 2 x 15k/.15k = 200

Try reducing gain by pulling out the cap if it is there.

If an lm386 is overdriven, it will oscillate too.  And be careful- I seem to remember that you can't ground either of the outputs- like a headphone jack would ground one side.


73

Larry

KB3CUF


On Thu, Aug 12, 2021 at 1:57 AM Alan Jones <oalanjones@...> wrote:
Hi Rich,
I would take a look at the preamp circuit first and then the gain on the LM386
This is just a guess since I don't have your schematic in front of me.

Kind Regards,
Alan, N8WQ

On Wed, 11 Aug 2021 21:25:37 -0400, Richie Chambless <rchambless7@...> wrote:

Hi,

I've recently built a receiver using the Hycas amplifier and I am have some oscillation issues. First, here is the basic layout of my test receiver:

Antenna > 40 Meter BPF > SBL-1 > TIA Amp (copied from uBitx) > 12 Mhz SSB filter > Hycas amp (L match retuned for 12 Mhz) > SBL-1 > LM386 AF Amp with 2N3904 preamp

When I power up the Hycas amp and AF section (with no TIA, LO, or BFO running), I get a loud motorboating sound. When I jumper across the AGC off pins, the motorboating stops. When I turn the rest of the receiver on, I get a high pitched oscillation with a frequency that varies with turning C2. I can null out the squeal and here some stations, but the noise floor (hiss) is very high. But, when I jumper the Mute pins, the gain is reduced and I am able to hear stations at a comfortable level. Now, I know this module wasn't designed to be used on mute, so I know I have something wrong. Any suggestions on where to start? Is there any particular thing I need to do, such as decoupling caps or shielding? I appreciate any help you can give.

Thank you,

Rich

KM4TLR



Re: Oscillation with Hycas AGC Amplifier

Larry Acklin
 

I second that LM386 thought.

cribbed from Stackexchange.com-

  • GAIN CONTROL To make the LM386 a more versatile amplifier, two pins (1 and 8) are provided for gain control. With pins 1 and 8 open the 1.35 kΩ resistor sets the gain at 20 (26 dB). If a capacitor is put from pin 1 to 8, bypassing the 1.35 kΩ resistor, the gain will go up to 200 (46 dB). If a resistor is placed in series with the capacitor, the gain can be set to any value from 20 to 200. Gain control can also be done by capacitively coupling a resistor (or FET) from pin 1 to ground.

Gain = 15,000 x 2 / (Ra + Rb)
Initially Ra + Rb = 0.150 k + 1.350 k = 1.5k
So gain = 2 x 15,000 / 1.500 = 20.
Shorting the 1.35K FOR AC increases gain to 2 x 15k/.15k = 200

Try reducing gain by pulling out the cap if it is there.

If an lm386 is overdriven, it will oscillate too.  And be careful- I seem to remember that you can't ground either of the outputs- like a headphone jack would ground one side.


73

Larry

KB3CUF


On Thu, Aug 12, 2021 at 1:57 AM Alan Jones <oalanjones@...> wrote:
Hi Rich,
I would take a look at the preamp circuit first and then the gain on the LM386
This is just a guess since I don't have your schematic in front of me.

Kind Regards,
Alan, N8WQ

On Wed, 11 Aug 2021 21:25:37 -0400, Richie Chambless <rchambless7@...> wrote:

Hi,

I've recently built a receiver using the Hycas amplifier and I am have some oscillation issues. First, here is the basic layout of my test receiver:

Antenna > 40 Meter BPF > SBL-1 > TIA Amp (copied from uBitx) > 12 Mhz SSB filter > Hycas amp (L match retuned for 12 Mhz) > SBL-1 > LM386 AF Amp with 2N3904 preamp

When I power up the Hycas amp and AF section (with no TIA, LO, or BFO running), I get a loud motorboating sound. When I jumper across the AGC off pins, the motorboating stops. When I turn the rest of the receiver on, I get a high pitched oscillation with a frequency that varies with turning C2. I can null out the squeal and here some stations, but the noise floor (hiss) is very high. But, when I jumper the Mute pins, the gain is reduced and I am able to hear stations at a comfortable level. Now, I know this module wasn't designed to be used on mute, so I know I have something wrong. Any suggestions on where to start? Is there any particular thing I need to do, such as decoupling caps or shielding? I appreciate any help you can give.

Thank you,

Rich

KM4TLR


Re: Oscillation with Hycas AGC Amplifier

Alan Jones
 

Hi Rich,
I would take a look at the preamp circuit first and then the gain on the LM386
This is just a guess since I don't have your schematic in front of me.

Kind Regards,
Alan, N8WQ

On Wed, 11 Aug 2021 21:25:37 -0400, Richie Chambless <rchambless7@...> wrote:

Hi,

I've recently built a receiver using the Hycas amplifier and I am have some oscillation issues. First, here is the basic layout of my test receiver:

Antenna > 40 Meter BPF > SBL-1 > TIA Amp (copied from uBitx) > 12 Mhz SSB filter > Hycas amp (L match retuned for 12 Mhz) > SBL-1 > LM386 AF Amp with 2N3904 preamp

When I power up the Hycas amp and AF section (with no TIA, LO, or BFO running), I get a loud motorboating sound. When I jumper across the AGC off pins, the motorboating stops. When I turn the rest of the receiver on, I get a high pitched oscillation with a frequency that varies with turning C2. I can null out the squeal and here some stations, but the noise floor (hiss) is very high. But, when I jumper the Mute pins, the gain is reduced and I am able to hear stations at a comfortable level. Now, I know this module wasn't designed to be used on mute, so I know I have something wrong. Any suggestions on where to start? Is there any particular thing I need to do, such as decoupling caps or shielding? I appreciate any help you can give.

Thank you,

Rich

KM4TLR


Oscillation with Hycas AGC Amplifier

Richie Chambless
 

Hi,

I've recently built a receiver using the Hycas amplifier and I am have some oscillation issues. First, here is the basic layout of my test receiver:

Antenna > 40 Meter BPF > SBL-1 > TIA Amp (copied from uBitx) > 12 Mhz SSB filter > Hycas amp (L match retuned for 12 Mhz) > SBL-1 > LM386 AF Amp with 2N3904 preamp

When I power up the Hycas amp and AF section (with no TIA, LO, or BFO running), I get a loud motorboating sound. When I jumper across the AGC off pins, the motorboating stops. When I turn the rest of the receiver on, I get a high pitched oscillation with a frequency that varies with turning C2. I can null out the squeal and here some stations, but the noise floor (hiss) is very high. But, when I jumper the Mute pins, the gain is reduced and I am able to hear stations at a comfortable level. Now, I know this module wasn't designed to be used on mute, so I know I have something wrong. Any suggestions on where to start? Is there any particular thing I need to do, such as decoupling caps or shielding? I appreciate any help you can give.

Thank you,

Rich

KM4TLR


Re: 5w20 build as 5w30?

Pete McQuain
 

Indeed, already ordered :)


Re: 5w20 build as 5w30?

Mont Pierce KM6WT
 

On Sat, Jul 31, 2021 at 01:27 PM, w8diz wrote:

Pete...I have one (and only one) set of extra xtals for 5W30

 

Pete, it's a good choice to go with Diz's "set" of crystals, as he pre-matches them for you for the crystal filter.

Crystals from other sources, you would need to match crystals yourself for best performance.


73
km6wt


Re: 5w20 build as 5w30?

Pete McQuain
 

Email sent, thanks!


Re: 5w20 build as 5w30?

 

Pete...I have one (and only one) set of extra xtals for 5W30

email me private via w8diz at kitsandparts dot com

-Diz

On 7/31/21 4:08 PM, Pete McQuain via groups.io wrote:

Hi,
I’ve decided that I want to build my 5w20 as a 5w30 instead. I was comparing the parts lists and schematics and it looks like the differences are in the “Bag #5” group of parts - toroids, caps and filter crystals. 

I know I can get the toroids from Diz, and I have the caps, but I didn’t see the 12mhz xtals available on the site. 

Any suggestions on an easy way to source the toroids and crystals required?

Diz - do you offer just the band-specific parts bags for sale?

73, pete k4ugg


5w20 build as 5w30?

Pete McQuain
 

Hi,
I’ve decided that I want to build my 5w20 as a 5w30 instead. I was comparing the parts lists and schematics and it looks like the differences are in the “Bag #5” group of parts - toroids, caps and filter crystals. 

I know I can get the toroids from Diz, and I have the caps, but I didn’t see the 12mhz xtals available on the site. 

Any suggestions on an easy way to source the toroids and crystals required?

Diz - do you offer just the band-specific parts bags for sale?

73, pete k4ugg


Re: 5watter clarification question

Jim Mcilroy
 

Hi Diz

Thanks for the info.

Jim  G4EQX

On 12/07/2021 19:45, w8diz wrote:

Hello Jim,

Since the two (2) parts on the PCB/Schematic are in series...it makes no difference; you can interchange them.

-Diz, W8DIZ

On 7/12/21 10:16 AM, Jim Mcilroy via groups.io wrote:
Hi
I'm building a 17m 5watter.

C24 and R12 connections on the PCB appear to be reversed compared to the schematic.
The schematic shows R12 on the emitter of Q5 which looks right followed in series by C24 which then goes to pin 1 of U1
On my PCB R12 connected to P1 of U1 receded by C24

Can anybody comment please.

With thanks

Jim  G4EQX


Re: 5watter clarification question

 

Hello Jim,

Since the two (2) parts on the PCB/Schematic are in series...it makes no difference; you can interchange them.

-Diz, W8DIZ

On 7/12/21 10:16 AM, Jim Mcilroy via groups.io wrote:
Hi
I'm building a 17m 5watter.

C24 and R12 connections on the PCB appear to be reversed compared to the schematic.
The schematic shows R12 on the emitter of Q5 which looks right followed in series by C24 which then goes to pin 1 of U1
On my PCB R12 connected to P1 of U1 receded by C24

Can anybody comment please.

With thanks

Jim  G4EQX


5watter clarification question

Jim Mcilroy
 

Hi
I'm building a 17m 5watter.

C24 and R12 connections on the PCB appear to be reversed compared to the schematic.
The schematic shows R12 on the emitter of Q5 which looks right followed in series by C24 which then goes to pin 1 of U1
On my PCB R12 connected to P1 of U1 receded by C24

Can anybody comment please.

With thanks

Jim  G4EQX


Re: 17Meter band Xtal

Larry Acklin
 

I heard a W5 calling yesterday mid day. I needed to hear that. I had even pulled out a signal gen to make sure I was on band. 

It’s dead at least for now. 

Larry


On Sun, Jun 20, 2021 at 10:44 PM Tim Tyler II <timtylerii@...> wrote:

Nicely done! My 17 is nearly complete. Not hearing any signals, but I hear rumors that the band has been regularly open.

 

Tim NC0Q

From: Larry Acklin
Sent: Sunday, June 20, 2021 9:42 PM
To: kitsandparts@groups.io
Subject: Re: [kitsandparts] 17Meter band Xtal

 

answering my own question- about 3/4 inch of green enamel wire left over, tightly twisted, across Cx was the answer. range is 18.068 to 18.093. 

 

Larry

 

On Sun, Jun 20, 2021 at 10:12 PM Larry Acklin via groups.io <acklin=gmail.com@groups.io> wrote:

looks like a gimmick cap in parallel may be the answer. So we will see. 

 

Larry

 

On Sun, Jun 20, 2021 at 7:00 PM Larry Acklin via groups.io <acklin=gmail.com@groups.io> wrote:

My minimum freq is 18.077 - how can I reduce it to .068 or so?  reduce the 4.7 pF in value? compressing turns on the inductor helped a little. 

73
Larry

 


Re: 17Meter band Xtal

Tim Tyler II
 

Nicely done! My 17 is nearly complete. Not hearing any signals, but I hear rumors that the band has been regularly open.

 

Tim NC0Q

From: Larry Acklin
Sent: Sunday, June 20, 2021 9:42 PM
To: kitsandparts@groups.io
Subject: Re: [kitsandparts] 17Meter band Xtal

 

answering my own question- about 3/4 inch of green enamel wire left over, tightly twisted, across Cx was the answer. range is 18.068 to 18.093. 

 

Larry

 

On Sun, Jun 20, 2021 at 10:12 PM Larry Acklin via groups.io <acklin=gmail.com@groups.io> wrote:

looks like a gimmick cap in parallel may be the answer. So we will see. 

 

Larry

 

On Sun, Jun 20, 2021 at 7:00 PM Larry Acklin via groups.io <acklin=gmail.com@groups.io> wrote:

My minimum freq is 18.077 - how can I reduce it to .068 or so?  reduce the 4.7 pF in value? compressing turns on the inductor helped a little. 

73
Larry

 


Re: 17Meter band Xtal

Larry Acklin
 

answering my own question- about 3/4 inch of green enamel wire left over, tightly twisted, across Cx was the answer. range is 18.068 to 18.093. 

Larry

On Sun, Jun 20, 2021 at 10:12 PM Larry Acklin via groups.io <acklin=gmail.com@groups.io> wrote:
looks like a gimmick cap in parallel may be the answer. So we will see. 

Larry

On Sun, Jun 20, 2021 at 7:00 PM Larry Acklin via groups.io <acklin=gmail.com@groups.io> wrote:
My minimum freq is 18.077 - how can I reduce it to .068 or so?  reduce the 4.7 pF in value? compressing turns on the inductor helped a little. 

73
Larry

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