Chinese Pixie Part II


ai9e_qrp@...
 

I finally got back to the workshop last night and built the Chinese Pixie I'd bought a couple months ago.  Here are my observations:


1.  The parts supplied did not match the schematic.  Too many 0.01u caps, not enough 0.1u caps, and three left overs.


2.  The holes for capacitor leads were on 0.2" centers, while the parts supplied were mini disks with 0.1" spacing.


3.  No thermal reliefs on grounded pads - took a lot of heat to solder into the ground plane.


4.  Aside from the caps, all the axial components were installed 'hairpin' style.


5.  No toroids - all inductors were molded axial type.


6.  There were extra holes for the DC input and RF output connectors so the builder could hard wire to a connector off-board if desired - a nice touch!


7.  All traces were heavy, at least 0.02" so very little risk of lifting or burning a trace.


I'll be firing it up and putting it on a scope this weekend.  Stay tuned.


73 Dave NM0S


ai9e_qrp@...
 

I fired up my Chinese Pixie last night.  The receiver is surprisingly sensitive, with MDS of about -115 dBm.  The sensitivity comes at a price, though.  The 5 kW AM station 20 miles up the road from us came through quite strong, as did a S9+ 60 Hz hum if I grounded the board.  Once night fell, and the AM station powered down, I could hear several CW stations though.

The pot on the board shifts bias on a 1N4001 diode in series with the crystal, and gives it about 2.5kHz tuning range

I tried hooking the audio output of the receiver to my laptop to see if it would work with FLDigi.  No dice.  The ground loop between the computer and antenna brought up the 60 Hz hum and overwhelmed the sound card.  Even putting a 4SLink in line for isolation did not make enough of a difference.

I keyed it and measured about 0.5W from a 9v battery, not too bad.

More observations to follow.

73 Dave NM0S


John Clements
 

Looks like you saw many of the same things I did during the build.  http://kc9on.com/ham-radio/chinese-qrp-kits/


One thing I can't check was the output.  Would be interesting to see if a LPF is needed and what harmonics are coming out.


The A/C noise is terrible with a 35+ year old power supply but moving to a battery solved that problem.  Also no dice with FLDigi decoding in the daytime and ended up using an audio filter to remove the highs.  Can't complain after making a 280 miles QSO with it.  What more fun can you have for $7 now days?

I was disappointed in the Frog, definitely not the power out as claimed but with a simple cut and wire turned the RF gain pot into a RIT control.  Rockmite (non-PIC) version is nice but ended up jumpering out the CPU and fixed the audio "squeal" issue.  Want to try the newer Rockmite (w/ PIC) and see if it's any better.

The Chinese 49-er and tuner kits arrived in the mail yesterday.  Now just need to catch up at catching up and I can build/play with those also!

72
John kc9on


Don Wilhelm <w3fpr@...>
 

You have got to be kidding - the webpage says the crystal is a 7027 and states that it in the *extra* class band.
Extra class is below 7025 kHz, so I don't believe the author of that webpage knows what he is talking about.
So much for stuff from China.  I would not pay even $7 to find out if it was worthwhile.

73,
Don W3FPR

On 7/12/2015 8:17 PM, jwc123@... [4sqrp] wrote:
 

Looks like you saw many of the same things I did during the build.  http://kc9on.com/ham-radio/chinese-qrp-kits/





John Clements
 

Whoops, had a type-o on my web page.  The Chinese rigs are coming with 7.023 crystals.  I see some of the Epay places list them going from 7.023 to 7.026 but with HC49/s "rectangular AT Strip cut" crystals supplied you probably won't get a 3KHz bend.  Maybe 2KHz Max bend and lucky to get around 2.7KHz bend if you parallel two.  Changing to the larger HC49/u "circular AT cut" might get you to a 3.5KHz bend. Still a close shave for operating in the General class with an extra class rock.

Gee Wally..... I Guess I do know maybe just a little of what I'm talking about.  Just may not type it right .001% of the time.

72
John kc9on



On Sun, Jul 12, 2015 at 10:24 PM, Don Wilhelm <w3fpr@...> wrote:
You have got to be kidding - the webpage says the crystal is a 7027 and states that it in the *extra* class band.
Extra class is below 7025 kHz, so I don't believe the author of that webpage knows what he is talking about.
So much for stuff from China.  I would not pay even $7 to find out if it was worthwhile.

73,
Don W3FPR

On 7/12/2015 8:17 PM, jwc123@... [4sqrp] wrote:
 

Looks like you saw many of the same things I did during the build.  http://kc9on.com/ham-radio/chinese-qrp-kits/






Dean LaClair
 

Rough bunch....Dang!  oughtta see me type after 3 or 4- 807's
Better yet, rip cw....lol
73 all
Dean

On Jul 12, 2015 11:24 PM, "John Clements jwc123@... [4sqrp]" <4sqrp@...> wrote:
 

Whoops, had a type-o on my web page.  The Chinese rigs are coming with 7.023 crystals.  I see some of the Epay places list them going from 7.023 to 7.026 but with HC49/s "rectangular AT Strip cut" crystals supplied you probably won't get a 3KHz bend.  Maybe 2KHz Max bend and lucky to get around 2.7KHz bend if you parallel two.  Changing to the larger HC49/u "circular AT cut" might get you to a 3.5KHz bend. Still a close shave for operating in the General class with an extra class rock.

Gee Wally..... I Guess I do know maybe just a little of what I'm talking about.  Just may not type it right .001% of the time.

72
John kc9on



On Sun, Jul 12, 2015 at 10:24 PM, Don Wilhelm <w3fpr@...> wrote:
You have got to be kidding - the webpage says the crystal is a 7027 and states that it in the *extra* class band.
Extra class is below 7025 kHz, so I don't believe the author of that webpage knows what he is talking about.
So much for stuff from China.  I would not pay even $7 to find out if it was worthwhile.

73,
Don W3FPR

On 7/12/2015 8:17 PM, jwc123@... [4sqrp] wrote:
 

Looks like you saw many of the same things I did during the build.  http://kc9on.com/ham-radio/chinese-qrp-kits/






Leland L. Bahr
 

The condenses of those that have built these rigs is, they do work "as is" with less then advertised power because the two transistors are of poor quality.  Put in two decent transistors and they put out much more power.  As for the two included cores, any ham with a little knowledge realizes the powdered iron core goes in the pi-network.  I assume the kit provider figured US hams were at least smart enough to realize this.  I have numerous examples of these rigs myself, but have not bothered to date to build them up.  When I do it, I'll make sure to use a couple adequate replacement transistors.  These little kits are a super bargain, they just need a little "tweeking".  They would make excellent little rigs to be used by a local club for local code practice amoung themselves.  Crystals to change them over to higher 40 meter frequencies a Tech can be purchased for around $2.00.  The silk screened glass PC board alone is worth $7!!!
Lee, w0vt

Extra class is below 7025 kHz, so I don't believe the author of that webpage knows what he is talking about.
So much for stuff from China.  I would not pay even $7 to find out if it was worthwhile.

73,



Leland L. Bahr
 

The condenses of those that have built these rigs is, they do work "as is" with less then advertised power because the two transistors are of poor quality.  Put in two decent transistors and they put out much more power.  As for the two included cores, any ham with a little knowledge realizes the powdered iron core goes in the pi-network.  I assume the kit provider figured US hams were at least smart enough to realize this.  I have numerous examples of these rigs myself, but have not bothered to date to build them up.  When I do it, I'll make sure to use a couple adequate replacement transistors.  These little kits are a super bargain, they just need a little "tweeking".  They would make excellent little rigs to be used by a local club for local code practice amoung themselves.  Crystals to change them over to higher 40 meter frequencies a Tech can be purchased for around $2.00.  The silk screened glass PC board alone is worth $7!!!
Lee, w0vt

Extra class is below 7025 kHz, so I don't believe the author of that webpage knows what he is talking about.
So much for stuff from China.  I would not pay even $7 to find out if it was worthwhile.

73,



Don Wilhelm <w3fpr@...>
 

I doubt that a single PI section low pass filter can achieve the -43 dB 2nd harmonic suppression that is required by the current FCC regulations.
Many old designs suffer from that same limitation.  There is no longer an exemption for QRP transmitters.
The original Pixie was OK because it was built before that regulation was in place.  But all transmitters built after January 1, 2003 must meet that requirement.  See FCC part 97.307(d).

73,
Don W3FPR

On 7/13/2015 12:40 AM, Lee l@... [4sqrp] wrote:
 

  As for the two included cores, any ham with a little knowledge realizes the powdered iron core goes in the pi-network.  I assume the kit provider figured US hams were at least smart enough to realize this.



Bill Cromwell
 

Hi,

I just got one of those kits as a door prize at the Michigan QRP Club annual picnic. I'll build it up but I'll use replacement transistors as suggested and probably get a different crystal even though I have an Extra Class ticket - just to make sure I have more hams to talk to. Thanks for the tips about the transistors and the output filters.

On 07/13/2015 12:40 AM, Lee l@w0vt.us [4sqrp] wrote:

The condenses of those that have built these rigs is, they do work "as is" with less then advertised power because the two transistors are of poor quality. Put in two decent transistors and they put out much more power. As for the two included cores, any ham with a little knowledge realizes the powdered iron core goes in the pi-network. I assume the kit provider figured US hams were at least smart enough to realize this. I have numerous examples of these rigs myself, but have not bothered to date to build them up. When I do it, I'll make sure to use a couple adequate replacement transistors. These little kits are a super bargain, they just need a little "tweeking". They would make excellent little rigs to be used by a local club for local code practice amoung themselves. Crystals to change them over to higher 40 meter frequencies a Tech can be purchased for around $2.00. The silk screened glass PC board alone is worth $7!!!
Lee, w0vt


John Clements
 

I agree Lee, we did this at our local club to generate activity and get some of the newer tech's, with rocks on their segment and the supplied 50 ohm resistor, experience in building and to show the fun they can have getting their licenses upgraded.  In short, most of these little kits won't make it on the air but we all had a blast building and making a few table-top QSO's for mere pennies.  There was enough fun that a few of the new tech's have either already upgraded or want to start a general class this fall.  Even better is getting constantly asked "what's the next project?"  Mission accomplished!