Date   
Re: New FT8 Digital Mode Easier on IRF510?

AA7US
 

Adam,

Is it acceptable to use a heavier gauge (larger diameter) wire when winding a larger toroid such as the FT50-43?

Thank you,

John
AA7US

---In CHINA_QRP@..., <rongxh@...> wrote :

This is why our recommendation is that you change the ferrite toroid from FT37-43 to FT50-43 or even bigger.

Re: New FT8 Digital Mode Easier on IRF510?

Adam Rong
 

You don't have to worry about IRF510 itself because it has a good heat sink of the bottom case. It is the saturation of the final transformer T3 that causes the problem if the transmit time is too long and power keeps too high. When the transformer is no longer functioning as a transformer, the load of IRF510 will change and it might cause its melting. This is why our recommendation is that you change the ferrite toroid from FT37-43 to FT50-43 or even bigger.

SSB voice will be fine as the power will vary all the time based on the voice, so there is no problem found.

Thanks,
Adam

于 2017-8-12 1:47, landrjoh@... [CHINA_QRP] 写道:

 

Hey gang,


In looking over the characteristics of the new weak signal FT8 digital mode, I noticed it has a sustained TX time of only 15 seconds (versus nearly 50 seconds for JT9 and JT65).  Presumably this is followed by a minimum 15 second RX period... probably a bit longer.


Wouldn't this new FT8 digital mode be a lot easier on the IRF510 final amplifier found in our KN-7QA and CS-series transceivers compared to JT9 and JT65?  It should cause a lot less heat buildup right?


The following excerpt is from the version 1.8.0 release candidate WJST-X software:


Brief Description of the FT8 Protocol
		-------------------------------------

WSJT-X Version 1.8.0 includes a new mode called FT8, developed by K9AN
and K1JT.  The mode name "FT8" stands for "Franke and Taylor, 8-FSK
modulation".  FT8 uses 15-second T/R sequences, provides 50% or
better decoding probability down to -20 dB on an AWGN channel, and 
maintains good performance on Doppler-spread fading channels.  An
auto-sequencing facility includes an option to respond automatically
to the first decoded reply to your CQ.  FT8 QSOs are 4 times faster
than those made with JT65 or JT9.  FT8 is an excellent mode for HF
DXing and for situations like multi-hop E_s on 6 meters, where deep
QSB may make fast and reliable completion of QSOs desirable.

Some important characteristics of FT8:

  - T/R sequence length: 15 s
  - Message length: 75 bits + 12-bit CRC
  - FEC code: LDPC(174,87)
  - Modulation: 8-FSK, tone spacing 6.25 Hz
  - Constant-envelope waveform
  - Occupied bandwidth: 50 Hz
  - Synchronization: 7x7 Costas arrays at start, middle, and end
  - Transmission duration: 79*1920/12000 = 12.64 s
  - Decoding threshold: -20 dB; several dB lower with AP decoding
  - Multi-decoder finds and decodes all FT8 signals in passband
  - Optional auto-sequencing and auto-reply to a CQ response
  - Operational behavior similar to JT9, JT65

We plan to implement signal subtraction, two-pass decoding, and use of
a priori (AP) information in the decoder.  These features are not yet
activated in v1.8.0.

We haven't yet finalized what the three extra bits in the message
payload will be used for.  Suggestions are welcome!

	-- Joe, K1JT, for the WSJT Development Team



New FT8 Digital Mode Easier on IRF510?

AA7US
 

Hey gang,


In looking over the characteristics of the new weak signal FT8 digital mode, I noticed it has a sustained TX time of only 15 seconds (versus nearly 50 seconds for JT9 and JT65).  Presumably this is followed by a minimum 15 second RX period... probably a bit longer.


Wouldn't this new FT8 digital mode be a lot easier on the IRF510 final amplifier found in our KN-7QA and CS-series transceivers compared to JT9 and JT65?  It should cause a lot less heat buildup right?


The following excerpt is from the version 1.8.0 release candidate WJST-X software:


Brief Description of the FT8 Protocol
		-------------------------------------

WSJT-X Version 1.8.0 includes a new mode called FT8, developed by K9AN
and K1JT.  The mode name "FT8" stands for "Franke and Taylor, 8-FSK
modulation".  FT8 uses 15-second T/R sequences, provides 50% or
better decoding probability down to -20 dB on an AWGN channel, and 
maintains good performance on Doppler-spread fading channels.  An
auto-sequencing facility includes an option to respond automatically
to the first decoded reply to your CQ.  FT8 QSOs are 4 times faster
than those made with JT65 or JT9.  FT8 is an excellent mode for HF
DXing and for situations like multi-hop E_s on 6 meters, where deep
QSB may make fast and reliable completion of QSOs desirable.

Some important characteristics of FT8:

  - T/R sequence length: 15 s
  - Message length: 75 bits + 12-bit CRC
  - FEC code: LDPC(174,87)
  - Modulation: 8-FSK, tone spacing 6.25 Hz
  - Constant-envelope waveform
  - Occupied bandwidth: 50 Hz
  - Synchronization: 7x7 Costas arrays at start, middle, and end
  - Transmission duration: 79*1920/12000 = 12.64 s
  - Decoding threshold: -20 dB; several dB lower with AP decoding
  - Multi-decoder finds and decodes all FT8 signals in passband
  - Optional auto-sequencing and auto-reply to a CQ response
  - Operational behavior similar to JT9, JT65

We plan to implement signal subtraction, two-pass decoding, and use of
a priori (AP) information in the decoder.  These features are not yet
activated in v1.8.0.

We haven't yet finalized what the three extra bits in the message
payload will be used for.  Suggestions are welcome!

	-- Joe, K1JT, for the WSJT Development Team


Re: JT65 operation with CS-series or KN-Q7A plus Sandwich?

AA7US
 

THANK YOU Junichi!

Wow!  This is an excellent resource and very informative.

73,

John
AA7US


---In CHINA_QRP@..., <mx6s@...> wrote :

John,

See the following page. You may need translation site.
An builder in JA modified his KN-Q7A+digital VFO to JT65 machine.
He uses a larger core and cooling fan. Without them he blown MOS-FETs.
Though the KN-Q7A/CS40 are designed as SSB equipment, additional
mods enable it to work digital mode. What a fun !  


Junichi JL1KRA

Re: JT65 operation with CS-series or KN-Q7A plus Sandwich?

qrpjl1kra
 

John,

See the following page. You may need translation site.
An builder in JA modified his KN-Q7A+digital VFO to JT65 machine.
He uses a larger core and cooling fan. Without them he blown MOS-FETs.
Though the KN-Q7A/CS40 are designed as SSB equipment, additional
mods enable it to work digital mode. What a fun !  


Junichi JL1KRA

Re: JT65 operation with CS-series or KN-Q7A plus Sandwich?

Adam Rong
 

John,

Yes. It is for all bands. It is a wide band transformer.

Thanks,
Adam

在 2017年8月8日,下午11:13,landrjoh@... [CHINA_QRP] <CHINA_QRP@...> 写道:

 

Hi Adam,


Is the substitution of an FT50-43 toroid for T3 a recommended upgrade for any frequency band of KN-Q7A / CS-series transceiver if we want to try digital modes (long transmission times)?

Thank you,

John
AA7US

---In CHINA_QRP@..., wrote :

My first idea is that the final transformer T3 should be replaced by an FT50-43 toroid to avoid saturation.

Re: JT65 operation with CS-series or KN-Q7A plus Sandwich?

AA7US
 

Hi Adam,

Is the substitution of an FT50-43 toroid for T3 a recommended upgrade for any frequency band of KN-Q7A / CS-series transceiver if we want to try digital modes (long transmission times)?

Thank you,

John
AA7US

---In CHINA_QRP@..., <rongxh@...> wrote :

My first idea is that the final transformer T3 should be replaced by an FT50-43 toroid to avoid saturation.

Re: How to Reduce CS-series Power?

AA7US
 

Thank you for the reply Adam.

I don't have a CS-series transceiver working on 20M (or higher) yet.  I'm still building.

Now I do already have a 10W amplifier for 40M, 30M, and 20M which I use with very low power CW rigs and thought it might be nice to be able use it with the CS-20 and a SLA battery (~12.5 vDC).  The 10W amplifier is limited to 1W input power as built.

I think I'll just build myself a step attenuator box similar to this one:


Problem solved!

73,

John
AA7US

---In CHINA_QRP@..., <rongxh@...> wrote :

It is not a good idea to reduce power by reducing IRF510's bias because it will make it work in poor situation.

How much power can you get so far? If you can get 5 watt or more, adding a power amplifier of 10 watt seems not very justified. If you really need higher power, you can consider raising the power supply voltage a little bit to somewhere at 14 volt.

Thanks,
Adam

Re: LCD Display for Sandwich

AA7US
 

Hi Larry,

I think you already know that I want at least one! :)

John
AA7US

---In CHINA_QRP@..., <larry.lovell@...> wrote :

If there is sufficient demand, a kit or partial kit will be made available depending on demand.

Please comment on what you think.

Larry, N7RGW

LCD Display for Sandwich

n7rgw
 

After experimenting with several options, I have come up with a simple method to add an LCD display to the Sandwich.

I use an I2C buss LCD display.  I need to add only two wires to the sandwich.  I modify the code slightly and thus I get a frequency readout.

Attached is a standalone display attached to the sandwich.  I added a 5 volt regulator to supply power to the display since it does not like the 8 volts where the sandwich is connected on the Radio board.

I also created a box using a choc perfboard with a Li-Ion battery pack to power the radio and the LCD display.

I have the code available on my website along with the dual band code. qrvtronics.com

I do not have a complete kit available for this, yet, but Adam is having built a couple of faceplates for the standard box.  If there is sufficient demand, a kit or partial kit will be made available depending on demand.

I used Anderson Power Poles to allow recharge of the battery pack as well as access for external power.

Please comment on what you think.

Larry, N7RGW

Re: How to Reduce CS-series Power?

Adam Rong
 

John,

It is not a good idea to reduce power by reducing IRF510's bias because it will make it work in poor situation.

How much power can you get so far? If you can get 5 watt or more, adding a power amplifier of 10 watt seems not very justified. If you really need higher power, you can consider raising the power supply voltage a little bit to somewhere at 14 volt.

Thanks,
Adam

在 2017年8月1日,上午12:30,landrjoh@... [CHINA_QRP] <CHINA_QRP@...> 写道:

 

Does anyone know if there's a safe way to REDUCE the transmit power of a CS-series transceiver using the existing circuitry?  Would simply reducing the IRF510's bias current do the trick or would that harm the IRF510?


I ask because I'm interested in exploring the use of an external 10W RF amplifier for 20M.  It has a limit on the input power it can accept.


Thanks,


John

AA7US

How to Reduce CS-series Power?

AA7US
 

Does anyone know if there's a safe way to REDUCE the transmit power of a CS-series transceiver using the existing circuitry?  Would simply reducing the IRF510's bias current do the trick or would that harm the IRF510?


I ask because I'm interested in exploring the use of an external 10W RF amplifier for 20M.  It has a limit on the input power it can accept.


Thanks,


John

AA7US

Re: Sandwich VFO Noise

AA7US
 

Thank you for the suggestions gents.

I removed the coax shield ground connections at the Sandwich VFO and left them at the main PCB so only one end of the coax is grounded.  Unfortunately there was no change in the noise.

I also tested it both with and without an additional insulated ground wire running between the Sandwich VFO and main PCB (like the manual calls for).  This didn't make any difference either.

I believe I've narrowed down the noise source to the tuning encoder.  But I'm also beginning to think maybe this noise was always been present... even before I moved with the capacitors and added the coax jumpers.  I suspect I've become overly fixated on it and it's really not significant.

73,

John
AA7US

---In CHINA_QRP@..., <larry.lovell@...> wrote :

Ground just one side of the coax.  You have probably created what is called a ground loop.

Re: Sandwich VFO Noise

n7rgw
 

Ground just one side of the coax.  You have probably created what is called a ground loop.


On Thursday, July 27, 2017 8:52 PM, "zack hackiz hackizzz@... [CHINA_QRP]" wrote:


 
Try grounding just one side of the coax.


On Thursday, July 27, 2017 9:31 PM, "landrjoh@... [CHINA_QRP]" wrote:


 
I recently completed building a CS-40.  Everything works great.

The Sandwich VFO was connected to the main PCB via two bare 0.1uF (104) capacitors and a separate insulated ground wire just as shown in the Sandwich VFO and CS-series assembly manuals.

I couldn't leave well enough alone and have already started making some modifications.  A modification I made today was to relocate the two 0.1uF capacitors down to the main PCB and from there running a couple of RG-174 coaxes back up to the Sandwich VFO.  The shields on the coax have been soldered to grounds on both the main PCB and the Sandwich VFO.  Assuming those shields provide adequate ground paths, I removed the separate insulated ground wire previously run between the main PCB and Sandwich VFO.

With this mod in place I'm now hearing a brief noise each time I change the frequency when rotating the tuning knob.  I don't THINK this noise was there before, or if it was, it wasn't as noticeable.  The best way I can describe this noise is it sounds "digital" which leads me to think it must be coming from the Sandwich VFO.  It's not so bad I can't live with it, especially since I don't hear it except when changing frequencies.

By chance does anyone have a suggestion on how I might eliminate or suppress this noise?

73,

John
AA7US




Re: Sandwich VFO Noise

zack hackiz
 

Try grounding just one side of the coax.


On Thursday, July 27, 2017 9:31 PM, "landrjoh@... [CHINA_QRP]" wrote:


 
I recently completed building a CS-40.  Everything works great.

The Sandwich VFO was connected to the main PCB via two bare 0.1uF (104) capacitors and a separate insulated ground wire just as shown in the Sandwich VFO and CS-series assembly manuals.

I couldn't leave well enough alone and have already started making some modifications.  A modification I made today was to relocate the two 0.1uF capacitors down to the main PCB and from there running a couple of RG-174 coaxes back up to the Sandwich VFO.  The shields on the coax have been soldered to grounds on both the main PCB and the Sandwich VFO.  Assuming those shields provide adequate ground paths, I removed the separate insulated ground wire previously run between the main PCB and Sandwich VFO.

With this mod in place I'm now hearing a brief noise each time I change the frequency when rotating the tuning knob.  I don't THINK this noise was there before, or if it was, it wasn't as noticeable.  The best way I can describe this noise is it sounds "digital" which leads me to think it must be coming from the Sandwich VFO.  It's not so bad I can't live with it, especially since I don't hear it except when changing frequencies.

By chance does anyone have a suggestion on how I might eliminate or suppress this noise?

73,

John
AA7US


Sandwich VFO Noise

AA7US
 

I recently completed building a CS-40.  Everything works great.

The Sandwich VFO was connected to the main PCB via two bare 0.1uF (104) capacitors and a separate insulated ground wire just as shown in the Sandwich VFO and CS-series assembly manuals.


I couldn't leave well enough alone and have already started making some modifications.  A modification I made today was to relocate the two 0.1uF capacitors down to the main PCB and from there running a couple of RG-174 coaxes back up to the Sandwich VFO.  The shields on the coax have been soldered to grounds on both the main PCB and the Sandwich VFO.  Assuming those shields provide adequate ground paths, I removed the separate insulated ground wire previously run between the main PCB and Sandwich VFO.

With this mod in place I'm now hearing a brief noise each time I change the frequency when rotating the tuning knob.  I don't THINK this noise was there before, or if it was, it wasn't as noticeable.  The best way I can describe this noise is it sounds "digital" which leads me to think it must be coming from the Sandwich VFO.  It's not so bad I can't live with it, especially since I don't hear it except when changing frequencies.

By chance does anyone have a suggestion on how I might eliminate or suppress this noise?

73,

John
AA7US

Re: Yet another BITX on Choc Perf Board

AA7US
 

Beautiful work Adam!

John
AA7US

Yet another BITX on Choc Perf Board

Adam Rong
 

Gang,

A photo is more than thousands of words.

Thanks,
Adam

Re: Bias current problems

AA7US
 


That's exactly how I plan to wire up a power switch for mine.

73,

John
AA7US 

---In CHINA_QRP@..., <johncronhelm@...> wrote :

I could perhaps could cut the axial lead after the large diode connected to the power supply and connect a power lead to both cut ends to check bias current. When I am finished with the tests I can make it into a switch to turn the radio on and off.

Re: Bias current problems

JOHN CRONHELM
 

Thanks,At last I have got it now.   I have no fused power cable from my gel cell. I could perhaps could cut the axial lead after the large diode connected to the power supply and connect a power lead to both cut ends to check bias current. When I am finished with the tests I can make it into a switch to turn the radio on and off.
What do you think?
73 de John vo1jcc.


On Jul 22, 2017, at 9:54 PM, Robert Hudson vk2aor@... [CHINA_QRP] <CHINA_QRP@...> wrote:

 

Hi John


I used a power cable plugged into my fused supply and removed the fuse and using crocodile clips on my AVO 7 multimeter  so it is in series with my power supply, the red lead goes to the plus supply and the black lead goes to the radio.  The negative has no connection.   Hope that helps.

Bob Hudson