Date   

Re: uBitx v5 issue

Bob Lunsford
 

Don't recall if my V6 had one but I remember seeing a picture of the regulator and it had a about a 3/4-in square heat regulator attached to the regulator. If one is in your parts drawer, I think it would be wise to attach it to the regulator. Or, you could bend up a small strip of aluminum and make one. No real danger of shorting and no need to insulate it from the tab. It would provide peace of mind when the regulator heats up and most of the heat is drawn away and dissipated.

Bob — KK5R

On Monday, November 23, 2020, 5:03:34 PM EST, Curt via groups.io <wb8yyy@...> wrote:


Bill

great you are checking these things as you assemble.  do examine the schematic and you will see what Jerry is citing - funny thing I was once worried as you!  oh yes - when you power up and touch the regulator on the raduino - don't be alarmed when you discover it is quite warm.  and that your BFO calibration may be way off. 

welcome to the global bitx community.  73

curt


Re: uBitx v5 issue

Jerry Gaffke
 

I think Iz is right, that DC path does help with static on the antenna, 
which can get quite substantial with nothing more than the wind whistling past.
Evan is also right, the DC path does not protect Q90 from something like
a nearby FM or TV broadcast station due to the 30mhz LPF not allowing it through.

HF will get through the 30mhz LPF, and likely get at least somewhat snubbed out by the diodes in the first mixer.

Gordon GIbby has pointed out that the base-emitter diode of Q90 will conduct
only on positive RF peaks from a nearby (VHF?) transmission, causing C80 to charge up.
The resulting negative voltage on the base during negative peaks can exceed the Vebo spec
of a 2n3904, 6 volts max, and blow out Q90.  He suggests a 1n4148 or similar, anode at Q90-emitter,
cathode at Q90-base, to prevent Q90-base from going more than a diode drop below the emitter, and thus
avoid a violation of Vebo.

Farhan has suggested that there might be more birdies in the receiver if the back-to-back diodes are
added, due to the wideband nature of everything between antenna and first mixer.  The diodes will
create lots of harmonics, creating lots of new mixer products that could sneak through the IF filters.

Most uBitx owners haven't bothered worrying about protecting Q90,
but a few have been bit.

Jerry, KE7ER


On Mon, Nov 23, 2020 at 04:39 PM, Evan Hand wrote:
iz,
The dc path does not really help in protecting the rig in my opinion.  Q90 is the first driver stage in the transmitter, it is connected before the receiver low pass filter, and has been known to fail when the antenna is connected and there are strong nearby RF signals.  There is a preventative measure that I and some others have taken to protect that device.  Back to Back 1n4148 diodes across pins 12 and 16 of K1 would be some protection from strong RF.  Lightning would be beyond the simple diode protection.  A lightning arrestor on the feed line is a better solution to protect against damage from large static discharges, or better yet ground all antennas when storms are near

My opinions so there could be better solutions.  Feedback always welcome.
73
Evan
AC9TU. 


Re: uBitx v5 issue

Evan Hand
 

iz,
The dc path does not really help in protecting the rig in my opinion.  Q90 is the first driver stage in the transmitter, it is connected before the receiver low pass filter, and has been known to fail when the antenna is connected and there are strong nearby RF signals.  There is a preventative measure that I and some others have taken to protect that device.  Back to Back 1n4148 diodes across pins 12 and 16 of K1 would be some protection from strong RF.  Lightning would be beyond the simple diode protection.  A lightning arrestor on the feed line is a better solution to protect against damage from large static discharges, or better yet ground all antennas when storms are near

My opinions so there could be better solutions.  Feedback always welcome.
73
Evan
AC9TU. 


Re: V6 BFO alignment problems after installing AGC

KE2GKB
 

If you continue to have issues Jack feel free to reach out to me or David (N8DAH), Here or at info @ kit-projects and we can help fix and make things right if need be! Almost a thousand happy customers. Let us know how your BFO calibration goes!

-- Tim Keller - KE2GKB https://shop.kit-projects.com


Re: V6 BFO alignment problems after installing AGC

Jack Hunt
 

Update - I tracked down the problem. I had soldered the ground of the BCI filter to what I thought was ground, it was not...

Now I have noise consistently within the band on the BFO alignment tool. Now I just need to do the frequency calibration. I'll do that tomorrow when propagation is better for WVV.

73s


Re: uBitx v5 issue

iz oos
 

I am not totally sure, but that DC Path at the antenna input might provider some degree of protection in case of statics.


Il lun 23 nov 2020 11:07 PM Bill Robbins <wa8cdu@...> ha scritto:
Thanks Curt. 


On Nov 23, 2020, at 5:03 PM, Curt via groups.io <wb8yyy=yahoo.com@groups.io> wrote:

Bill

great you are checking these things as you assemble.  do examine the schematic and you will see what Jerry is citing - funny thing I was once worried as you!  oh yes - when you power up and touch the regulator on the raduino - don't be alarmed when you discover it is quite warm.  and that your BFO calibration may be way off. 

welcome to the global bitx community.  73

curt


Re: uBitx v5 issue

Bill Robbins
 

Thanks Curt. 


On Nov 23, 2020, at 5:03 PM, Curt via groups.io <wb8yyy@...> wrote:

Bill

great you are checking these things as you assemble.  do examine the schematic and you will see what Jerry is citing - funny thing I was once worried as you!  oh yes - when you power up and touch the regulator on the raduino - don't be alarmed when you discover it is quite warm.  and that your BFO calibration may be way off. 

welcome to the global bitx community.  73

curt


Re: uBitx v5 issue

Curt
 

Bill

great you are checking these things as you assemble.  do examine the schematic and you will see what Jerry is citing - funny thing I was once worried as you!  oh yes - when you power up and touch the regulator on the raduino - don't be alarmed when you discover it is quite warm.  and that your BFO calibration may be way off. 

welcome to the global bitx community.  73

curt


Re: uBitx v5 issue

Jerry Gaffke
 

Antenna connector looks shorted to ground because there is a DC path through K3-13,11, K1-12,14, L1,L2,L3,L4, T2-1,6
Jerry, KE7ER


On Mon, Nov 23, 2020 at 12:33 PM, Bill Robbins wrote:
I am just completing my V5.  No power applied yet.   Everything is remove from the board and it lays naked in front of me.  The following connectors are installed; Power, Raduino, Audio, as well as the IFR510's.

My problem is that the both leads of the antenna connector, presumably ground and lead, show continuity to ground.  They are shorted. I find no solder bridges anywhere.

Ideas??

Bill


uBitx v5 issue

Bill Robbins
 

I am just completing my V5.  No power applied yet.   Everything is remove from the board and it lays naked in front of me.  The following connectors are installed; Power, Raduino, Audio, as well as the IFR510's.

My problem is that the both leads of the antenna connector, presumably ground and lead, show continuity to ground.  They are shorted. I find no solder bridges anywhere.

Ideas??

Bill


Re: New PCB available for WA2EBY linear amp #linear-amp

Ken K0KV
 

The bare board should be available on www.amateurradiokits.in  in a few days.  A kit with most of the components will be available later.  

50V is too high - 28V is the absolute max.  It requires at least 4A. 


Re: V6 BFO alignment problems after installing AGC

Jack Hunt
 

Hi Lori's,
Thank you for your input. After posting this I did wonder about a potential ground loop. 

I have noticed that the radio is a lot less sensitive. A +10 station on my Yaesu was lost in the noise on my ubitx, but I put this down to poor BFO alignment.

73s
Jack 2E0GDV


On Mon, Nov 23, 2020 at 07:53 PM, IW4AJR Loris wrote:
Hi Jack 2E0GDV,
 
the problem you filmed in the video would seem to derive from a strange ground loop that somehow affects the receiver, perhaps due to the two ciscuiti added in cascade or perhaps to the arrangement of the AGC switch.
I can't help you more because in my case I don't have this problem, instead, the sensitivity reduction seems to be a typical "disease" of this circuit, in my µBITS.V6 are lost  about 2 S points (10/15 dBµV), I think it is due to the internal resistance of the 2N7000 in series with the antenna, which is always present and which, even if polarized, has a significant loss.
Obviously all is only my opinion, I may be wrong in the measures or have a bit obsolete instrumentation, but my ear does not deceive me, the sensitivity drops a lot!
73 de IW4AJR Loris


Re: V6 BFO alignment problems after installing AGC

IW4AJR Loris <lorisbollina@...>
 

Hi Jack 2E0GDV,
 
the problem you filmed in the video would seem to derive from a strange ground loop that somehow affects the receiver, perhaps due to the two ciscuiti added in cascade or perhaps to the arrangement of the AGC switch.
I can't help you more because in my case I don't have this problem, instead, the sensitivity reduction seems to be a typical "disease" of this circuit, in my µBITS.V6 are lost  about 2 S points (10/15 dBµV), I think it is due to the internal resistance of the 2N7000 in series with the antenna, which is always present and which, even if polarized, has a significant loss.
Obviously all is only my opinion, I may be wrong in the measures or have a bit obsolete instrumentation, but my ear does not deceive me, the sensitivity drops a lot!
73 de IW4AJR Loris


Re: New PCB available for WA2EBY linear amp #linear-amp

Rafael Diniz
 

Can I buy somewhere this marvelous amp? Does it work in 50V PSU?

Cheers,
Rafael PU2UIT

On 11/23/20 4:33 PM, Ken K0KV wrote:
Andy, 
Regarding the multi-band LPF board - I needed one that was
PC-controllable because I mainly operate remotely (shack is upstairs,
PC is in family room).   So I designed my own board, which uses relays
to switch the LPF's in and out for each band.  It can be controlled
from a simple contact closure (e.g. an Alexa-controlled relay) or via
digital outputs from an Arduino. 
 


Also - you're right, I should have mentioned the toroid kit - it's
super convenient.  I decided not to buy it because I already had some
of the cores on hand.


Re: New PCB available for WA2EBY linear amp #linear-amp

Ken K0KV
 

Andy, 
Regarding the multi-band LPF board - I needed one that was PC-controllable because I mainly operate remotely (shack is upstairs, PC is in family room).   So I designed my own board, which uses relays to switch the LPF's in and out for each band.  It can be controlled from a simple contact closure (e.g. an Alexa-controlled relay) or via digital outputs from an Arduino. 
 


Also - you're right, I should have mentioned the toroid kit - it's super convenient.  I decided not to buy it because I already had some of the cores on hand.


Re: New PCB available for WA2EBY linear amp #linear-amp

Ken K0KV
 

Leonard - your manual was among the best guides that I found while researching and eventually building the amp.  I think I've still got a browser tab opened to it on my shack computer.  Kudos & 73,

Ken 


V6 BFO alignment problems after installing AGC

Jack Hunt
 

Hi everyone,

I installed the AGC board from kit projects, following which I had some gain issues. I think that was my fault now, but I thought that maybe the BFO needed aligning. So I did that, but still had problems. So I tried again and noticed the following behaviour (see attached video). When I touch the radio or wiggle the coax, the noise characteristics change dramatically.

Does this point to anything in particular that I might have broken?

I have also installed the BCI filter after the AGC board (after just due to space). The AGC switch is mounted on the front of the unit and the volume input to the AGC board has the 10ohm resistor in series.

73s
Jack 2E0GDV


Re: uBitX v.6 schematic / driver and finals transistor symbols / #ubitxv6 #v6

Arv Evans
 

Todd

Exactly.  The dual nomenclature indicates that you can use either 
one type or the other type of devices.  The base-to-base line on 
associated schematic is just a shortcut to simplify drawings, or to 
confuse new builders.  Adding a second set of pads for non-IRF 510 
devices is the icing on the cake that keeps people coming back to 
the BITX-20 discussion group to ask what  is going on!    8-)

Arv
_._

On Sun, Nov 22, 2020 at 10:27 PM Todd Carney <carneytf@...> wrote:
Arv,

Many thanks. As you indicated in another reply, though, the similar appearance of the finals pair is to show a one-or-the-other situation. That is, either the IRF510s or the RD15HVs, is that right? Similar symbology, different purpose? --Todd K7TFC

On Sun, Nov 22, 2020 at 6:31 PM Arv Evans <arvid.evans@...> wrote:
This type schematic layout has become fairly common in recent years, especially 
for situations where a pair of devices are connected in parallel.  Drawing the base 
leads up, over, and down (with a bridge over the leads from pin 3) would possibly 
be more complex than the way it was done in your schematic.  It is also possibly 
closer to the way the runs on a PCB would be arranged if they need to be as short 
as possible .

Arv


Re: New PCB available for WA2EBY linear amp #linear-amp

kc0wox Leeper
 

Mike Kossar, wa2eby, Is who you want to thank. He designed the amplifier. All I did was write an assembly manual. and component location chart.
Leonard
kc0wox.com


Re: uBitX v.6 schematic / driver and finals transistor symbols / #ubitxv6 #v6

IW4AJR Loris <lorisbollina@...>
 

TNX Evan !

Loris


On Mon, Nov 23, 2020 at 11:15 AM, Evan Hand wrote:
The harmonic issues were related to relay selection and board layout.  Those can be fixed in older versions with relay replacement.  Since it is the feedback from the low pass filters, changing the MOSFET should not really change the output.  I do not know of anyone trying it, so you could be right.

Both the harmonics and spur issues were fixed in the v5 and v6 boards.  I too can confirm that the problems are not found in the v5 that I have (one of the main reasons that I purchased a v5).  On ubitx.net you can find the recommended fixes for v3 and v4 boards.  The relay replacement did solve the harmonic issues with both of the v4 boards that I have.

The above is my interpretation of the data that I have reviewed or observed.  Again, and feedback is welcome, especially if there is an error.
73
Evan
AC9TU

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