Date   
Re: End whistling into the mic

Paul Smith
 

Go to http://www.audiocheck.net/index.php and download a 1kHz pure sine test file via your soundcard. Free... I use it a lot for testing here.

Solder Paste Extruder

Arv Evans
 

Ken, KM4NFQ

That solder paste extruder is a great idea.  I have used these tubes of solder paste for
several years but always fought with expressing enough, but not too much, of the paste.

Tomorrow I will be in my workshop building one of your devices.  I really like the concept.

It seems possible that the solder paste extruder could also be adapted to a CNC Mill
or a 3D printer and used with appropriate G-Code to place small solder paste dots
for oven-baking of components to the PCB. 

Arv  K7HKL
_._

ARROW Bus to Hamvention

John Wasciuk
 

January 26, 2018
 
2878 Ticknor Ct
Ann Arbor, MI 48104-6921
 
Dear Fellow Radio Amateurs & Friends of ARROW Communication Association,

Once again, this year, The ARROW Communication Association of Ann Arbor, Michigan is sponsoring its annual round-trip by bus to Hamvention on Saturday, May 19, 2018. Details are at:


This trip has run since 2002. We have sold out the last four years! We have had riders come from all over. They have come from Kalamazoo and Grand Rapids. In 2017, John, VE3IPS came down from Toronto to be with us. You can see some fine photos and a great video on his web site:


As in any endeavor of this kind, we appreciate any additional positive word to be spread around via web pages, news letters and on the air!

For $65.00 ($55.00 before April 1), we offer a free continental breakfast, space at our flea market table and, most of all, PRIZES! It is probably complete coincidence, but a number of the products we have been given have then made it into the Product Review column of QST (QRP Labs, QRPme and Borden Radio Company come to mind).

I am putting this email on a number of blogs and email lists for the benefit of our donors. While the bus may be local or regional, our sponsors sell internationally. ARROW would like to return their generosity with a bit of publicity.

If it is all right with the moderator of this list, we’d like to post another email when we are farther along with our 2018 campaign. We try to list our sponsors and a bit about them and the package they have sent for our lucky passengers.

A list of previous donors can be seen below.

We thank you all for your kind attention. We look forward to seeing you at Hamvention and on the bus!

73,

John F. Wasciuk
WA8TON / VO1TON / VO1HV
Activities Coordinator,
ARROW Communication Association
Ann Arbor, Michigan
jwasciuk at gmail dot com

List of donors 2014-2017:

Amateur Accessories, Inc
American Radio Supply
American Hakko Products, Inc
Borden Radio Company
Buckmaster International HamCall
Comet Anetnna
Daiwa Meters
Connect Quick (Ironworks Design LLC)
Connect Systems Inc
Debco Electronics
Digi-Key Electronics
DX Engineering
EAE Sales
Elecraft
Far Circuits
Five Dash
Fox Delta
Global TSCM Group Inc KN2C dot US
Ham Radio Outlet
Ham-Sters
HamTestOnline
Heil Sound
Hip Ham Shirts
KB6NW CW Geek (No-Nonsense Study Guides)
Klingenfuss Publications
MCM Electronics
MFJ
Mike’s Electronic Parts
MPD Digital
North Georgia QRP Club
NW Digital Radio
Pacific Antenna QRP Kits
Peebles Originals
QRP Labs
QRPMe
RT Systems
Skilman
Tennadyne Corporation / Cubex Quads
The RF Adapter Guy
Tigertronics
Universal Radio
West Mountain Radio

Re: Something has been blown

Jerry Gaffke
 

If the IRF510's still draw some current through PA-PWR during transmit,
and that current changes when you adjust the gate bias with RV2 and RV3
(adjust this very carefully, as it quickly goes to hundreds of mA)
then the IRF510's are probably just fine.

Regarding cheap IRF510's on ebay, you might read this old thread:
    https://groups.io/g/BITX20/topic/5554568
They cost $1 on mouser for singles, below $0.50 if you buy lots, and you know who made it.
I don't see much point in buying on ebay.

As Arv says, make sure you have a good 50 ohm dummy load when testing.
Perhaps get four Xicon 200 ohm 3W metal film resistors (mouser 283-200-RC)
when buying the spare IRF510's.

Jerry, KE7ER


On Thu, Jan 25, 2018 at 07:31 pm, Arv Evans wrote:
Since there is no short with the IRF-510 devices in place but not connected to the chassis, it is 
possible that the antenna was disconnected, shorted, or some other anomaly.  Unfortunately
MOSFETs used as RF power amplifiers tend to self-destruct if the load is not of proper
impedance.  Too low an impedance and they will overheat, and too high an impedance and
they will go into oscillation and destroy themselves with high current. 

As Bernie KC9SGV has suggested replacement devices are relatively inexpensive from Ebay
vendors.  Some will probably raise the issue of Ebay sourced parts being less than perfect
but I have been using Ebay sourced IRF-510's for over 10 years with no problems. 

Re: Second batch of uBITX shipping? #ubitx

Mikael
 

Someone posted that order date 14th december had been shipped but that was some days ago.

Anyone with a later order date later than 14th been informed of shiping yet?

IRF510 amplifier failures

Arv Evans
 

Hello

The problem with IRF510 RF amplifiers failing seems to be a recurring one for those who
are not quite careful with antenna matching, bias level, and drive level.  As a way to start
looking into this situation I have performed some on-line searches to see how others are
And there is much more out there to be Google searched and reviewed.

There are a number of potentially useful ideas contained in those articles and discussions,
but nothing that obviously applies directly to the problem of blowing IRF510 devices at only
a few watts of power if the antenna is mis-matched.  Mention of using small resistance values
in series with gate drive is interesting, as is use of pi-net attenuators between exciter and
RF PA gate...to help control impedance?  While we look upon the MOSFET internal capacitance
as being a problem, it is interesting that some designs add a capacitor on the drain side of
things, apparently to limit the upper frequency capability and reduce 'spikes'.  The discussion
on single-ended versus push-pull is interesting from a technical view, but did not introduce
anything obvious that could help.

I suppose we have to first determine just what the exact cause of IRF510 failure might be,
then use that as the basis for designing a suitable solution.

Arv  K7HKL
_._




uBitx enclosure

at91r40008
 

The front panel is still plastic at this time. I painted in black to look more esthetic :)
The plug on the left is a mini XLR for the mike. On the right is a function switch.
In the back is another mini XLR for the USB connection for software update. I need
to find countersunk screws for the display.
I am going to install the Raduino X from WA6ISP Mike Haegen, it has way more
IOs available. I received it Monday but didn't have the time to
install it.


73, Yvon NU6I

Re: Second batch of uBITX shipping? #ubitx

Dgyuro
 

Ordered 17 Dec. still waiting.  

Sent from my iPhone

On Jan 25, 2018, at 9:43 PM, mikael.madsen@... wrote:

Someone posted that order date 14th december had been shipped but that was some days ago.

Anyone with a later order date later than 14th been informed of shiping yet?

Re: Something has been blown

chris gress <Chrisg0wfh@...>
 

I got these from a UK supplier I think from eBay or amazon can not remember they are good parts not fakes I have 3 bitx not blown a pa yet each one has a restive bridge swr unit fitted so protected when turning chris

On 26 Jan 2018 04:35, "Jerry Gaffke via Groups.Io" <jgaffke=yahoo.com@groups.io> wrote:
If the IRF510's still draw some current through PA-PWR during transmit,
and that current changes when you adjust the gate bias with RV2 and RV3
(adjust this very carefully, as it quickly goes to hundreds of mA)
then the IRF510's are probably just fine.

Regarding cheap IRF510's on ebay, you might read this old thread:
    https://groups.io/g/BITX20/topic/5554568
They cost $1 on mouser for singles, below $0.50 if you buy lots, and you know who made it.
I don't see much point in buying on ebay.

As Arv says, make sure you have a good 50 ohm dummy load when testing.
Perhaps get four Xicon 200 ohm 3W metal film resistors (mouser 283-200-RC)
when buying the spare IRF510's.

Jerry, KE7ER



On Thu, Jan 25, 2018 at 07:31 pm, Arv Evans wrote:
Since there is no short with the IRF-510 devices in place but not connected to the chassis, it is 
possible that the antenna was disconnected, shorted, or some other anomaly.  Unfortunately
MOSFETs used as RF power amplifiers tend to self-destruct if the load is not of proper
impedance.  Too low an impedance and they will overheat, and too high an impedance and
they will go into oscillation and destroy themselves with high current. 

As Bernie KC9SGV has suggested replacement devices are relatively inexpensive from Ebay
vendors.  Some will probably raise the issue of Ebay sourced parts being less than perfect
but I have been using Ebay sourced IRF-510's for over 10 years with no problems. 


Re: IRF510 amplifier failures

M Garza <mgarza896@...>
 

Here is another:

In the middle of the page, is this:

"I destroyed many IRF510 FETs during testing. In fact I blew a small hole in one and another into several pieces. It was quite a shock when the first one was destroyed because it made a loud noise like a rifle being fired.

Once I got tired of replacing the FETs, I built a current sense circuit, which shuts off the bias once the amplifier draws more than about 3 amps from the PSU. I think this circuit is essential. You can build it into the Power Supply or into the Amplifier. I built it into the Amplifier because the power supply, which is also homemade, does not limit until 7 amps. With the current limit circuit the amplifier now survives transmitting into any SWR from an open circuit to a short."

There is a schematic for the current limiting circuit that is used.  This might be something to incorporate into the design.  It is only 7 more parts.


Marco - KG5PRT


On Thu, Jan 25, 2018 at 10:48 PM, Arv Evans <arvid.evans@...> wrote:
Hello

The problem with IRF510 RF amplifiers failing seems to be a recurring one for those who
are not quite careful with antenna matching, bias level, and drive level.  As a way to start
looking into this situation I have performed some on-line searches to see how others are
And there is much more out there to be Google searched and reviewed.

There are a number of potentially useful ideas contained in those articles and discussions,
but nothing that obviously applies directly to the problem of blowing IRF510 devices at only
a few watts of power if the antenna is mis-matched.  Mention of using small resistance values
in series with gate drive is interesting, as is use of pi-net attenuators between exciter and
RF PA gate...to help control impedance?  While we look upon the MOSFET internal capacitance
as being a problem, it is interesting that some designs add a capacitor on the drain side of
things, apparently to limit the upper frequency capability and reduce 'spikes'.  The discussion
on single-ended versus push-pull is interesting from a technical view, but did not introduce
anything obvious that could help.

I suppose we have to first determine just what the exact cause of IRF510 failure might be,
then use that as the basis for designing a suitable solution.

Arv  K7HKL
_._





Re: Second batch of uBITX shipping? #ubitx

Ralph Richard
 

15th and no word

Virus-free. www.avast.com

Re: Something has been blown

 

You will surely have burnt power tracks. Trace the final power line.

Raj

At 26/01/2018, you wrote:
now, with finals away from the metal chasis I am testing if I have output. The power meter and needle doesnt move at all. I do get about 1,3amp drain when ptt and i can hear myself on other radio though.
I have tested with another watt metter with no joy either

maybe its too weak to be afected

Re: IRF510 amplifier failures

Arv Evans
 

Marco - KG5PRT

That is very interesting indeed.  Implementing this current based bias control
should be easy and could be compact. 


Inline image 1
from: http://www.g0kla.com/scpa/SimpleCheapPA.php

If I understand this correctly...
  • Voltage drop across R1 forward biases T2 to ON state
    This lights the LED.
  • Voltage on the collector of T2 turns T1 OFF, removing supply voltage
    to the 5V bias regulator in the RF PA circuit.

I was looking toward a similar control based on reflected power but the current
based approach is easier, as long as it works.  This adds another project to my
to-do list.

Thanks for the URL.

Arv  K7HKL
_._


On Thu, Jan 25, 2018 at 10:11 PM, M Garza <mgarza896@...> wrote:
Here is another:

In the middle of the page, is this:

"I destroyed many IRF510 FETs during testing. In fact I blew a small hole in one and another into several pieces. It was quite a shock when the first one was destroyed because it made a loud noise like a rifle being fired.

Once I got tired of replacing the FETs, I built a current sense circuit, which shuts off the bias once the amplifier draws more than about 3 amps from the PSU. I think this circuit is essential. You can build it into the Power Supply or into the Amplifier. I built it into the Amplifier because the power supply, which is also homemade, does not limit until 7 amps. With the current limit circuit the amplifier now survives transmitting into any SWR from an open circuit to a short."

There is a schematic for the current limiting circuit that is used.  This might be something to incorporate into the design.  It is only 7 more parts.


Marco - KG5PRT


On Thu, Jan 25, 2018 at 10:48 PM, Arv Evans <arvid.evans@...> wrote:
Hello

The problem with IRF510 RF amplifiers failing seems to be a recurring one for those who
are not quite careful with antenna matching, bias level, and drive level.  As a way to start
looking into this situation I have performed some on-line searches to see how others are
And there is much more out there to be Google searched and reviewed.

There are a number of potentially useful ideas contained in those articles and discussions,
but nothing that obviously applies directly to the problem of blowing IRF510 devices at only
a few watts of power if the antenna is mis-matched.  Mention of using small resistance values
in series with gate drive is interesting, as is use of pi-net attenuators between exciter and
RF PA gate...to help control impedance?  While we look upon the MOSFET internal capacitance
as being a problem, it is interesting that some designs add a capacitor on the drain side of
things, apparently to limit the upper frequency capability and reduce 'spikes'.  The discussion
on single-ended versus push-pull is interesting from a technical view, but did not introduce
anything obvious that could help.

I suppose we have to first determine just what the exact cause of IRF510 failure might be,
then use that as the basis for designing a suitable solution.

Arv  K7HKL
_._






Re: IRF510 amplifier failures

Jerry Gaffke
 

A suitable fast-blow fuse or polyswitch in the PA-PWR line into the board should be sufficient
to protect the IRF510's from too much current.
The polyswitch is like a fuse, except it resets once it cools down after you remove power.
A thermal sensor on the IRF510 heatsink that at least turns on a front panel LED might be a good idea.

This old post here from Allison is informative, well worth re-reading every few months:
    https://groups.io/g/BITX20/message/22597
As she says, lots of things can kill an IRF510, but the most common is heat if you have a good amp design.
Powering at 28v for 55W from a push-pull pair, she didn't see trouble when driving improper antenna impedances.

I'd think that if powered at 12v, and if they have a reasonable heatsink, and if you don't screw up 
when fiddling with the gate bias pots at rv2 and rv3, or drop a screwdriver into the wrong spot,
the IRF510's should not blow.  Even when driving a non-existent antenna, the RF voltages at the drains
go up some without a load, but not drastically, T11 is just a 1:2 voltage transformer.
Driving a 0 ohm antenna might be a bit worse since the currents will go up, but probably survivable.

Jerry, KE7ER


On Thu, Jan 25, 2018 at 09:11 pm, M Garza wrote:

There is a schematic for the current limiting circuit that is used.  This might be something to incorporate into the design.  It is only 7 more parts.

 

Re: IRF510 amplifier failures

M Garza <mgarza896@...>
 

Jerry,
I do not disagree, I have a fuse inline with both power lines.  When a fuse blows, you dont know if there has been damage or not.
In my opinion, it would be better to prevent the situation from being able to happen.  This idea seems to have worked for the builder, 
since he made specific mention of it. 
"With the current limit circuit the amplifier now survives transmitting into any SWR from an open circuit to a short."

Marco - KG5PRT


On Thu, Jan 25, 2018 at 11:37 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
A suitable fast-blow fuse or polyswitch in the PA-PWR line into the board should be sufficient
to protect the IRF510's from too much current.
The polyswitch is like a fuse, except it resets once it cools down after you remove power.
A thermal sensor on the IRF510 heatsink that at least turns on a front panel LED might be a good idea.

This old post here from Allison is informative, well worth re-reading every few months:
    https://groups.io/g/BITX20/message/22597
As she says, lots of things can kill an IRF510, but the most common is heat if you have a good amp design.
Powering at 28v for 55W from a push-pull pair, she didn't see trouble when driving improper antenna impedances.

I'd think that if powered at 12v, and if they have a reasonable heatsink, and if you don't screw up 
when fiddling with the gate bias pots at rv2 and rv3, or drop a screwdriver into the wrong spot,
the IRF510's should not blow.  Even when driving a non-existent antenna, the RF voltages at the drains
go up some without a load, but not drastically, T11 is just a 1:2 voltage transformer.
Driving a 0 ohm antenna might be a bit worse since the currents will go up, but probably survivable.

Jerry, KE7ER


On Thu, Jan 25, 2018 at 09:11 pm, M Garza wrote:

There is a schematic for the current limiting circuit that is used.  This might be something to incorporate into the design.  It is only 7 more parts.

 


Re: Something has been blown

César EA3IAV
 

Hi follks for the the ideas!
Antenna was matched with less than 1.4 swr
transistors were isolated and tested.

The only thing I can think of is that maybe, before considering to have the fets atached to the box I may shorted them by accident while initial testing

One doubt: even if they are blown, why i can transmit and be received in a nearby receiver? is it possible?
why it drains power if they are blown?

maybe it is just ine of them blown?

this afternont I will inspect tracks. I have some spare irf510 from ebay, but i was trying not to swap them because I don’t know if they are legit and the checking scenario could go very crazy with errrstuc fets...

Re: uBitx TX performance with frequency

Alex - PA1FOX
 

This may be a futile attempt if the intermediate gain stages (pre-driver and drivers) fall off with frequency too.  I have not done this myself yet… still on my list… to actually publish a table showing the output at each stage with frequency to determine what needs attention BEFORE the PA.  Then a change to the PA makes full sense.

William, I made some measurements on the TX chain without the PA. In my case this is up to the 2N2219's as I use the original schematic. The overall gain dropped 6dB from 3.5 up to 30Mhz. This should have some influence but is not a huge problem. With the power drive input which the 2N2219's generate for the IRF's it was clear that the IRF's were hardly doing anything at the high frequencies. I've played around with bias inductors and different impedance levels at the gates of the IRF's but apart from increasing or decreasing the overall gain for all frequencies, there was not much change in frequency gain curve.
What influences most is the output transformer of the IRF's. The trifilair setup is a good starting point but I could optimize the PA efficiency by adding and removing a winding at the primary side of the transformer. (So one winding ends up bifilair.) It's not ideal though.

With the change to RD16HHF1 (not the HVF1) I have kept the FT43-37 output coil. It could be a bit small for this, so I ordered binocular coils with a slightly larger size (BN43-202) to use as an output transformer. Yes, it also helps that the RD16 series is desigined for 12 volts. The IRF's lose their lazyness at 24 volts.

I'll post the results of the experiments for those who said to be interested. I find it very interesting myself as well.

73, Alex
PA1FOX

Re: Second batch of uBITX shipping? #ubitx

Stig oz8pz-oz8wsp-oz8wsr
 

Yes, i order 15.12.2017 and i Got reply from Paypal that it was send to day by Indian post. Now i just sit waithing.
73, Oz8pz stig
Sendt fra min iPad

Den 26. jan. 2018 kl. 05.43 skrev mikael.madsen@...:

Someone posted that order date 14th december had been shipped but that was some days ago.

Anyone with a later order date later than 14th been informed of shiping yet?

Re: Second batch of uBITX shipping? #ubitx

dj0hf
 

Ordered on the 16th December - Nothing yet.

73
Ian
DJ0HF/G3ULO

Re: uBitx TX performance with frequency

Lawrence Galea
 

Agree.
Mine hasn't arrived yet so cannot check anything yet.Regards
Lawrence


On Thu, Jan 25, 2018 at 3:15 PM, K9HZ <bill@...> wrote:

This may be a futile attempt if the intermediate gain stages (pre-driver and drivers) fall off with frequency too.  I have not done this myself yet… still on my list… to actually publish a table showing the output at each stage with frequency to determine what needs attention BEFORE the PA.  Then a change to the PA makes full sense.

 

 

Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ

 

Owner - Operator

Big Signal Ranch – K9ZC

Staunton, Illinois

 

Owner – Operator

Villa Grand Piton – J68HZ

Soufriere, St. Lucia W.I.

Rent it: www.VillaGrandPiton.com

Like us on Facebook! facebook icon

 

 

email:  bill@...

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Alex Buurlage
Sent: Thursday, January 25, 2018 3:37 AM
To: BITX20@groups.io
Subject: Re: [BITX20] uBitx TX performance with frequency

 

Bob,

Yes, I've seen similar behaviour on my homebrew uBitx. Increasing the drive will overload the PA at 80 meters but will hardly increase the power output at the high bands. I even made a change in the driver circuit that decreases the gain below 10MHZ so I could crank up the overall gain of the TX chain more trying to get more output at 14MHz and up. No success. After extensive experiments I've decided to replace the IRF510's with RD16HHF1 mosfets (not pin-compatible!).

I am now optimizing the output transformer and impedance levels but so far the TX power ranges from 10 watts at 80m to 8 watts at 17m. The 15m and up LPF is not finished yet, but reviewing the specs of the RF16HHF1 I don't expect much further power drop at 28 MHz.

Secondly I like the idea of the housing of these mosfets being the source, so a direct grounding to the case is easy. No insulation material needed and a better RF ground.

A slight disadvantage is that the bias current of the RD16HHF1 is a little higher, but that's ok for me.
If you should make such a change with the commercial PCB version, beware of the pin incompatibility.

73, Alex
PA1FOX