I removed R70,? then used small shielded cables and a relay to switch my audio filter in and out since it did not had a bypass function. The 2 NC contacts are bridged with a 1k resistor to simulate R70 in the out position and the filter is connected to the NO contacts. One could of course use a dpdt switch instead the relay.I chose a small dip relay to keep the actual audio connection short and only route DC from the in/out switch to the relay
John
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Jerry
I am thinking it should not matter which lm386 to use at the output. The gain distribution is nicely arranged so the audio filter should work well between the audio amplifiers. Yes keeping RF out of audio on transmit is a challenge, so minimizing audio in wire seems best. I suggest your switch to bypass the hypermite be as close to the it as possible.?
Curt
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Hi
I captured the schematics from Ashar Farhans FDIM 2021 presentation "sBITX - An Open-Source SDR the YOU Can Hack!"
So I started hacking!
Attached is a rendering of my Sbitx board. The x-tals, transformers and coils are through hole components and will be mounted on the opposite side of the other components. RF-filter and tx-amplifier will be on another board. In the first setup I will use the lpf and bpf from qrplabs.
Size of the board is 50mm by 80mm.
I will mill and drill the board tomorrow and then begin mounting components.
I use an AudioInjector board that sits on top of a RPi4 and I can see a nice peak on the screen when injecting a tone. So the receive part of the software is working. The setup and compile was very easy.
I haven't tried the transmit part yet.
73 de oz9ny, Niels
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Hello All,
I just put together a Hi-Per-Mite CW audio filter. Would like to install it in the UBITXv6. Where to break the audio chain? I have the schematic, but no board layout. I'm thinking the top of RV4, the volume control pot.
Another idea - U1, the LM386 audio amplifier, is SOCKETED. I could pull the chip, bend out pin 3,
the positive audio input, and just solder to the pin. Of course, I would then have to sneak some little wire into the socket itself.
And then there's the challenge of turning it on & off - or at least, getting it in & out of the signal path. Front panel switches are nice. Not much space though. The whole R/H side is dedicated to the tuning knob. As it should be. Tuning is, after all, the main thing one does with a radio. There is a modicum of space on the L/H side, hiding behind the TSW Raduino card. Just about enough space for the a couple of tiny toggle switches - one for the filter, another one - later - for AGC.
Or maybe I should dig into the TSW Raduino source to add filter control to it...? Maybe CW mode wants the CW filter enabled?
One concept I have thought of - glue a tiny reed switch to the underside of the cabinet top, and enable a function by laying a magnet on it. The cabinet is aluminum, magnetism just goes through.
I don't really like piping low-level audio around the box. Can lead to hum, RF feedback, all sorts of unpleasantness. Although I did recently get a hunk of RG316 coax, just for such things. But to avoid that, I need a relay. Or diode/transistor switching. All this makes a filter in a separate box look good. What makes a separate box look bad though is AGC. I feel that AGC is best picked off the output of the filter - because otherwise strong out-of-audio-band signals can make it pump.
- Jerry KF6VB
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Re: Cheap Chinese Linear LPF
That amp uses the IRFZ24N FET, seems a better choice than the IRF510
for 12v operation on 20,40,80m.? Not so good at higher frequencies or higher supply voltages.
Compared to the IRF510, it has about the same thermal resistance and gate threshold voltage.
The Vds breakdown is 55v instead of 100v for the IRF510.
A much lower on resistance of 0.07 vs 0.54v for the IRF510.
The bad news is that the total gate charge is 20nC vs 8.3nC.
Would be interesting to see how well the IRFZ24N works in a uBitx.
Jerry, KE7ER
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On Sat, May 29, 2021 at 05:26 PM, Ashhar Farhan wrote:
I have just finished building a version of W6JL's linear. It has fantastic! performance. 40 watts upto 14 Mhz, 30 watts on 21 Mhz with -30 db IMDR. The changes I made were to replace the output transformer with one made by stacking FT37-43 toroids (4x2) and simplifying the biasing arrangment.?
The biggest challenge is to safely get the heat out of the transistors to outside air.
?
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Re: Cheap Chinese Linear LPF
John,
Thanks for the description.
Teflon covered wire is recommended if building a high powered output transformer
that might get hot.? But you seem to have solved the hot thing by going to a better core.
I'll keep this business of using a scrap of teflon coax in mind,
it could save me from buying some expensive teflon covered wire.
Using the braid as the primary is an interesting trick, but I would probably just strip?
the outer coating and braid off of the inner wire, use that for both windings.
Jerry
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On Sat, May 29, 2021 at 10:40 AM, John Cunliffe W7ZQ wrote:
Jerry,
I started with the latest kit.?
The output transformer was done as follow. I had ultra small Teflon coax in my junk box so I took a piece, removed a piece of insulation from one end, tinned it and stripped it back leaving a small amount of braid to attach a bare wire to as one side of the primary. The center became one side of the secondary. Then I made 2 full turns on the binocular core, marked the cable and removed it. Removed the outer insulation of the extra cable that was not inside the core so I ended up with about? 5 inches of cable with? ~2.5 inch of insulation? removed. I then tinned the area close to the insulation and scored it with an exacto knife so that just about 1/16 inch of braid was left.and removed the rest of the braid. So, at this point the cable is as follows . one side center wire tinned and the about 1/16 braid has a piece of bare wire then a 2.5 inch long piece of cable with insulation and braid with the insulation ending showing 1/8 (or shorter) of braid and the center going on another ~2 inches (I used a random long enough piece to make the task easier and then trimmed back the center) now I wound the cable end with the insulation and braid on the torroid for full 2 turns and attach a piece of bare wire to the braid for the second primary connection. So now it looks like this: A binocular core with 2 turns of coax with 2 connections to the shields, one side center about 1 inch and the other side center about 2 inch. Now take that 2 inch center piece and put it through the core one more time for a full turn. Now you have 2 turns of the shield as primary and 3 turns of the center as the secondary. The 100pf cap went parallel to the primary winding it improves the output power. I might build a transformer with 2 cores to see if it is still needed. Why Teflon? Because I had it and? because it doesn't melt when soldering to it. Tinning the screen of Teflon coax is easy and trimming it also.
John
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Re: Cheap Chinese Linear LPF
On Sat, May 29, 2021 at 04:53 AM, Edward Reynolds wrote:
did a quick look/see thru the manual, my Yeasu FT-101E was a pice of cake compared to this transmitter, thanks for the link
Funny, I was just reading some more of the 6B transmitter manual. On page 23 it talks about needing to fill and maintain the level of the DC filament supply electrolytic capacitor with "capacitor fluid".?(Reminds me of a YouTube video where they talked about a garage that told a customer they needed to have their headlight fluid changed.) Good thing we no longer need to oil and replace bearings in our motor generator sets. And our capacitors are of the revolutionary maintenance free versions.? Wow, 881 watts (21.5V x 41A) just to run the final amp filament. (And there's a bunch more tubes in the transmitter.) And this is "only" a 1KW transmitter. Tom, wb6b
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On Sat, May 29, 2021 at 04:35 PM, Arv Evans wrote:
http://www.gronkradio.net/
The "AllStar" RoIP protocol they mention looks interesting. That for dedicated nodes and a WebRTC interface for web browser based control look like a good combination.? Tom, wb6b
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Re: Cheap Chinese Linear LPF
I have just finished building a version of W6JL's linear. It has fantastic! performance. 40 watts upto 14 Mhz, 30 watts on 21 Mhz with -30 db IMDR. The changes I made were to replace the output transformer with one made by stacking FT37-43 toroids (4x2) and simplifying the biasing arrangment.? The biggest challenge is to safely get the heat out of the transistors to outside air.
What transistors does it use?
?
I notice they also see a LPF board for 41 dollars.
?
I may pick one up and add it to my list of projects.
?
Mike N2MS
?
?
?
?
On 2021-05-28 19:41, Aaron K5ATG via wrote:
Is there a link for this amp?
--
*** Not really. Go on Ebay, search for "100W HF Shortwave", and you
will see
lots of listings for it. It's the one with a clear plastic "roof" on
spacers.
?
- Jerry KF6VB
?
?
'72
Aaron K5ATG
?
?
Links:
------
?
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On Sat, May 29, 2021 at 4:40 PM Tom, wb6b < wb6b@...> wrote: On Sat, May 29, 2021 at 11:33 AM, Curt wrote:
that might help with diminishing number of club stations around.?
I agree. If clubs would pool their resources and set up a remotely operateable club station, that could be a core asset to form a club around. Or bring back life to existing ones.
An internet solution to the internet problem of people not wanting to physically having to drive to a club station location (even before covid). However the community it provides for the club would increase the motivation for people to meet together, hopefully in person soon, at a club meeting.
Generally clubs provide their stations with better equipment, antenna towers and location than most hame have at home. Now with background noise being such an issue, a club station in a low noise location would be great.
And for emergency use, if the club station was located at a hospital, fire station or such, in an emergency the club operators could go to the physical location to provide the communication if the internet is down.?
Additionally, the club could set up a ham band WiFi (mesh?) network to allow remote operation when the internet is down. (is it possible/legal to control a HF station from a 440mhz handheld transceiver?)
Tom, wb6b
?
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Re: Cheap Chinese Linear LPF
Seriously, if you want to try hollow-state, look to some of the
older ARRL Radio Amateur's Handbooks.? My 1st transmitter was a
home-brew effort, starting with a 1625 (the 12-volt version of the
807) scavenged from an ARC-5 TVI generator.? The circuit is easy
to duplicate, and you only need a suitable power transformer.? If
you can find one, an old hollow-state TV transformer will do very
nicely.? The 1625 doesn't require neutralizing (the 6146 or 6146-B
does).? The TV mentioned will also provide enough tubes for the
oscillator & driver stages.? The metalwork is up to your own
ingenuity.? A modern frequency control should be easy to design,
or try & find an old FT-243 crystal & go real retro.? You
might also look at some of the older amateur equipment, if you can
find the manuals.? The Heath HW-16 would give you some ideas.
73
Gerry Sherman
Sent by the Thunderbird
On 2021-05-29 12:54 p.m., Arv Evans
wrote:
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Show quoted text
Tom
That
crystal box is quite interesting.? I worked for AT&T most
of my career and?
was
heavily involved with Western Electric while at Bell Labs.?
That was the?
real
AT&T, before Judge Green dissolved?the company in 1984.
Several
times I have wondered if it would be possible to build a retro
uBITX?
using
full size components and vacuum?tubes.? Problem though is at
my age?
I
don't have time to keep up with advances in solid state, so
delving into?
hollow-state
is probably a non-starter for me.
Arv
_._
On Sat, May 29, 2021 at 12:21
AM Tom, wb6b < wb6b@...> wrote:
On
Fri, May 28, 2021 at 09:26 PM, Ashhar Farhan wrote:
Arv, maybe it is time to do a retro-bitx
I've still have this crystal oven, maybe I could connected it
with a Arduino Nano to make a true retro Raduino. Or get out
the Comet cleanser and start grinding it up to 75 meters.?
Here are some more design ideas for such a project (Should be
able to squeeze a uBitx in there somewhere):
By the way, this xtal oven has a place in history at the nexus
of Hearst Broadcasting in Los Angeles, a motor-coach bus line
entrepreneur, Don Lee Broadcasting (KFI), the NBC Red and Blue
networks and the birth of KABC radio.
Tom, wb6b
|
On Sat, May 29, 2021 at 03:40 PM, Tom, wb6b wrote:
most hame have at home
Should be: most hams have at home.?
|
On Sat, May 29, 2021 at 11:33 AM, Curt wrote:
that might help with diminishing number of club stations around.?
I agree. If clubs would pool their resources and set up a remotely operateable club station, that could be a core asset to form a club around. Or bring back life to existing ones. An internet solution to the internet problem of people not wanting to physically having to drive to a club station location (even before covid). However the community it provides for the club would increase the motivation for people to meet together, hopefully in person soon, at a club meeting. Generally clubs provide their stations with better equipment, antenna towers and location than most hame have at home. Now with background noise being such an issue, a club station in a low noise location would be great. And for emergency use, if the club station was located at a hospital, fire station or such, in an emergency the club operators could go to the physical location to provide the communication if the internet is down.? Additionally, the club could set up a ham band WiFi (mesh?) network to allow remote operation when the internet is down. (is it possible/legal to control a HF station from a 440mhz handheld transceiver?) Tom, wb6b ?
|
I had purchased one ( actually several) of those Chinese 70 watt linears. They use IRF530s for the RF transistors. I connected one of these to my uBitx years ago when I first bought my V3. I used it exclusively at that time on 20 meters and it worked fine, putting out about 50 watts. I have posted in the past some of my uBitx mods to improve power output. When I learned about all the intermod product issues with the V3, and trying some of the posted mods to solve the problem, I was not successful. It became clear that the V3 was not worth modifying anymore. I decided to try the Softrock SDR radio. I modified he Softrock so it could be used on all HF bands, and connected it the uBitx using the uBitx RF output stage on LPFs and retaining the Arduino to control the uBitx. The way the uBitx is designed, it is easy to have a different supply voltage (keep it under 25 volts unless you want to change the aluminum bypass caps). I changed the IRF510s to IRF520s and increased the output amplifier supply voltage to 19 volts. With this configuration, I have up to 52 watts rms output. I think that the same output and LPF filter modifications can be made on any uBitx and provide a similar output power. The only caveat is that the Softrock has 1 watt of drive. I am not sure how much drive power the uBitx provides to the final, so some additional mod may be required to reproduce the power level I have achieved, but a think a significant increase in power can be obtained with the drive as is. I have attached my schematics and design notes. The output stage is on page 7. With the uBitx, the microphone AGC may also be helpful. The SWR bridge could also be incorporated.
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Re: Cheap Chinese Linear LPF
Could you please post a picture of what this looks like. I'm very interested !
Thanks, Max KG4PID
On Saturday, May 29, 2021, 10:45:55 AM CDT, John Cunliffe W7ZQ <n2nep@...> wrote:
I redid the output transformer using sub miniature 50 ohm teflon coax , with the RD16HHF1 and no other changes but a 100pf cap I am getting between 20 and 25W on all bands @13.5V on the finals and 12V on the main board. I did this after I observed the unit with an infra red camera and noticed that the original output torroid gets quite hot on some bands with only 10 watts out. The new transformer stays cool, no losses through heating. It is build on a 43-202 binocular core.
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Now THAT is a very good idea, and one reason for a remote operation set-up!
Bob
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On 5/29/21 2:33 PM, Curt via groups.io wrote:
Well I can¡¯t imagine too many folk hacking into someone¡¯s rig to do ham radio.
well if we adopt folk who can¡¯t have a rig in their apartment or whatever to use our station when we aren¡¯t that might help with diminishing number of club stations around.
curt
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Well I can¡¯t imagine too many folk hacking into someone¡¯s rig to do ham radio.?
well if we adopt folk who can¡¯t have a rig in their apartment or whatever to use our station when we aren¡¯t that might help with diminishing number of club stations around.?
curt
|
Re: Cheap Chinese Linear LPF
Tom
That crystal box is quite interesting.? I worked for AT&T most of my career and? was heavily involved with Western Electric while at Bell Labs.? That was the? real AT&T, before Judge Green dissolved?the company in 1984.
Several times I have wondered if it would be possible to build a retro uBITX? using full size components and vacuum?tubes.? Problem though is at my age? I don't have time to keep up with advances in solid state, so delving into? hollow-state is probably a non-starter for me.
Arv _._
On Sat, May 29, 2021 at 12:21 AM Tom, wb6b < wb6b@...> wrote: On Fri, May 28, 2021 at 09:26 PM, Ashhar Farhan wrote:
Arv, maybe it is time to do a retro-bitx
I've still have this crystal oven, maybe I could connected it with a Arduino Nano to make a true retro Raduino. Or get out the Comet cleanser and start grinding it up to 75 meters.?
Here are some more design ideas for such a project (Should be able to squeeze a uBitx in there somewhere):
By the way, this xtal oven has a place in history at the nexus of Hearst Broadcasting in Los Angeles, a motor-coach bus line entrepreneur, Don Lee Broadcasting (KFI), the NBC Red and Blue networks and the birth of KABC radio.
Tom, wb6b
|
Re: Cheap Chinese Linear LPF
Jerry,
I started with the latest kit.?
The output transformer was done as follow. I had ultra small Teflon coax in my junk box so I took a piece, removed a piece of insulation from one end, tinned it and stripped it back leaving a small amount of braid to attach a bare wire to as one side of the primary. The center became one side of the secondary. Then I made 2 full turns on the binocular core, marked the cable and removed it. Removed the outer insulation of the extra cable that was not inside the core so I ended up with about? 5 inches of cable with? ~2.5 inch of insulation? removed. I then tinned the area close to the insulation and scored it with an exacto knife so that just about 1/16 inch of braid was left.and removed the rest of the braid. So, at this point the cable is as follows . one side center wire tinned and the about 1/16 braid has a piece of bare wire then a 2.5 inch long piece of cable with insulation and braid with the insulation ending showing 1/8 (or shorter) of braid and the center going on another ~2 inches (I used a random long enough piece to make the task easier and then trimmed back the center) now I wound the cable end with the insulation and braid on the torroid for full 2 turns and attach a piece of bare wire to the braid for the second primary connection. So now it looks like this: A binocular core with 2 turns of coax with 2 connections to the shields, one side center about 1 inch and the other side center about 2 inch. Now take that 2 inch center piece and put it through the core one more time for a full turn. Now you have 2 turns of the shield as primary and 3 turns of the center as the secondary. The 100pf cap went parallel to the primary winding it improves the output power. I might build a transformer with 2 cores to see if it is still needed. Why Teflon? Because I had it and? because it doesn't melt when soldering to it. Tinning the screen of Teflon coax is easy and trimming it also.
John
|
Re: Cheap Chinese Linear LPF
John,
What kit did you start with?
How did you use that teflon coax in an output transformer?
I'm guessing you removed the outer braid, and thus had teflon coated wire.
Though at 20 watts, the voltages aren't high enough to require teflon.
Seems the primary improvement is in using the 43-202 core.
>???no other changes but a 100pf cap
Where did that cap go and why?
Jerry, KE7ER
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On Sat, May 29, 2021 at 08:45 AM, John Cunliffe W7ZQ wrote:
I redid the output transformer using sub miniature 50 ohm teflon coax , with the RD16HHF1 and no other changes but a 100pf cap I am getting between 20 and 25W on all bands @13.5V on the finals and 12V on the main board. I did this after I observed the unit with an infra red camera and noticed that the original output torroid gets quite hot on some bands with only 10 watts out. The new transformer stays cool, no losses through heating. It is build on a 43-202 binocular core.
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