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Re: DSB transceiver for Digital mode

Adam Rong
 

Folks,

This is a bit history for D4D: A simple QRP transceiver kit for FT8.

D4D stands for DSB transceiver for Digital modes. It is a Double Sided Band transceiver kit designed for digital modes, especially for FT8. If you have chance to try FT8, you will be amazed by the strong decoding capability due to the communication protocol, digital signal processing and software. I still remember clearly a YouTube video by W6LG who communicated with a bulb. I started to think how much the transceiver could be simplified if you have a moderate antenna like a full sized dipole or EFHW instead of a bulb. A DSB transceiver is much simpler than a SSB transceiver, however it was never used for FT8 as far as I know. I did some experiments on my Choc perf board, a specially designed perf board for RF circuit experiments. I started with a direct conversion receiver for FT8 and it worked okay. Then I built a DSB transmitter and the transmitted signal can be decoded. By referring to the DSB designs of AA7EE, VK3YE and ZL2BMI, I combined them using only one NE602 and a PTT switch and it gave me success to make a few FT8 QSO’s. Personally I really enjoyed it because a manual PTT switch will save power consumption and circuit complexity, but you will need to well sync with computer, although it was not really a problem for me. Per request from a few hams, I found a VOX control circuit and modify the hold time to be compatible with FT8, and I put them together and made a few improvements on the signal purity and frequency stability, and it finally became our D4D. Do we have to worry about the unwanted Lower Side Band? Maybe, but for a transmitter of 1-watt, it is not really a big problem. Is it just a toy for a transmitter of 1-watt and only half of the power will be effective? Not really, as I can easily make a few QSO’s as far as 1500 miles range for 40-meter band.

Thanks,
Adam


在 2019年4月26日,上午9:05,Adam Rong via Groups.Io <rongxh@...> 写道:

Ron,

I use 14.070MHz HC-49U crystals and pull them high about 4kHz. The crystals were customized before and I have enough stock. They work perfectly for 14.074MHz.

Thanks,
Adam


Re: DSB transceiver for Digital mode

Adam Rong
 

Ron,

I use 14.070MHz HC-49U crystals and pull them high about 4kHz. The crystals were customized before and I have enough stock. They work perfectly for 14.074MHz.

Thanks,
Adam


Re: DSB transceiver for Digital mode

Ron Stone
 

Adam,

Glad to see that you're going forward with 20 meter version sooner rather than later.  Are you getting customized crystals for 14.074 Mhz or is it anothet frequency crystal that has to be pulled a bit?  If so what frequency is it for 20 mtrs?  Thanks.

Ron (ka3j)


Re: DSB transceiver for Digital mode

Adam Rong
 

80-meter 3.573MHz will be added. Crystals are being customized. Think of a 80-m radio of 1-watt to make a few QSO's? Great fun!

Thanks,
Adam


Re: DSB transceiver for Digital mode

Furtuna Mircea
 

Hello.
Cut the crystal around 1mm around the crystal, scratch the crystal very carefully, just a little, and measure it frequently.
It will be a slight increase of 30 maximum 100kz.
Verified method, step by step.
Mircea-YO9IOF

On Wednesday, April 24, 2019, 7:46:13 PM GMT+3, Adam Rong <rongxh@...> wrote:


Folks,

I have placed order for PCB two days ago. The first batch is 350 pcs.

I have finalized the parts value and will place order for parts tomorrow. The RF output is 1-watt at 12V for 14.074MHz, and a bit bigger for 7.074MHz. The spurious suppression is better than -50dBc.

I hope to start kitting for the first 5 pcs on May 4. If it goes smoothly, I might take order to ship these kits early, so you can send a few test reports ahead of time than the usual customers. Stay tuned and I hope you will like it.

Thanks,
Adam


Re: DSB transceiver for Digital mode

Adam Rong
 

Folks,

I have placed order for PCB two days ago. The first batch is 350 pcs.

I have finalized the parts value and will place order for parts tomorrow. The RF output is 1-watt at 12V for 14.074MHz, and a bit bigger for 7.074MHz. The spurious suppression is better than -50dBc.

I hope to start kitting for the first 5 pcs on May 4. If it goes smoothly, I might take order to ship these kits early, so you can send a few test reports ahead of time than the usual customers. Stay tuned and I hope you will like it.

Thanks,
Adam


Re: FT8 DSB VOX

John Kirby <n3aaz_qrp_1@...>
 

 
Adam,

I understand and thanks for the reply

72 73
John
N3AAZ


Re: FT8 DSB VOX

Adam Rong
 

John,

No. I will keep the schematic paper based only for customers for a period of time.

Thanks,
Adam

在 2019年4月22日,上午1:20,John Kirby <n3aaz_qrp_1@...> 写道:

Adam,

Sounds good !
Will you release the schematic even if preliminary ?

72 73
John
N3AAZ


Re: DSB transceiver for Digital mode

Adam Rong
 

Jim,

I would leave it for customers’ modification. We have added a crystal in the front end as the filter. We will have to switch both.

Thanks,
Adam

在 2019年4月22日,上午12:48,Jim <KH2SR@...> 写道:

What about having both crystals and then adding a switch to go between the FT8 and JS8 frequencies?


Re: FT8 DSB VOX

John Kirby <n3aaz_qrp_1@...>
 

Adam,

Sounds good !
Will you release the schematic even if preliminary ?

72 73
John
N3AAZ


Re: DSB transceiver for Digital mode

Jim
 

What about having both crystals and then adding a switch to go between the FT8 and JS8 frequencies?


Re: DSB transceiver for Digital mode

Adam Rong
 

Technically it is possible. Just change the crystal and I might be able to customize it. However, we will need to consider the unwanted LSB signal will go into FT8 spectrum and it might cause interference although the power is still QRPp level.

If we want to experiment, just pull high the crystal a bit to see how high it can go, maybe 7075 or 7076 but not easy to get 7078 for a HC49S holder crystal.

Thanks,
Adam

在 2019年4月21日,下午10:39,Jim <KH2SR@...> 写道:

Would it be possible to make this rig operate on the JS8CALL frequency of 7.078 instead? 


Re: FT8 DSB VOX

Adam Rong
 

Good job on the modification. It saves $ and time.

I sent 4 kits to domestic hams based on the first version PCB, and 3 of them completed the building, although they did have a few questions and mistakes.  1 more person will start building tomorrow. 2 of them logged QSO’s so far and 2 of them told me they got about 2 watts when it is powered by 13.8V. 1 of them told me the design is mature, so I will start PCB massive production tomorrow.

Thanks,
Adam

在 2019年4月21日,下午11:53,John Kirby <n3aaz_qrp_1@...> 写道:

Adam,

My RockMite mod for FT8 DSB (NOVOX (yet hi hi))

John
N3AAZ
<20190421_113518.jpg>


Re: FT8 DSB VOX

John Kirby <n3aaz_qrp_1@...>
 
Edited

ps ...

Q2 has no FT8 function (yet)

John N3AAZ


Re: FT8 DSB VOX

John Kirby <n3aaz_qrp_1@...>
 

Adam,

My RockMite mod for FT8 DSB (NOVOX (yet hi hi))

John
N3AAZ


Re: DSB transceiver for Digital mode

Jim
 

Would it be possible to make this rig operate on the JS8CALL frequency of 7.078 instead? 


Re: FT8 DSB VOX

Adam Rong
 

John,

Looks good. How did you modify your RockMite 40 to transmit DSB?

My technique is just to live with it as the signal is QRPp level, hihi.

Thanks,
Adam

在 2019年4月21日,下午6:49,John Kirby <n3aaz_qrp_1@...> 写道:

 Adam,

Modified RockMite 40 (7030), no VOX yet, for simplex FT8 DSB to shack FT991 :>)

Anxious waiting to learn your LSB suppression technique!

TNX AGN
72 73
John
N3AAZ
<20190420_170232.jpg>
<20190420_165627.jpg>


Re: FT8 DSB VOX

John Kirby <n3aaz_qrp_1@...>
 

 Adam,

Modified RockMite 40 (7030), no VOX yet, for simplex FT8 DSB to shack FT991 :>)

Anxious waiting to learn your LSB suppression technique!

TNX AGN
72 73
John
N3AAZ


Re: Simple FT8 DSB rig

Adam Rong
 

Ron,

I built a SSB FT8 radio based on my KN-Q7A PCB and it works okay. If you check out my previous post, I even added a VOX circuit for this rig.

However this SSB concept is very common, and I am trying something new. The result is very promising and the unwanted LSB band is not so harmful as the power is QRPP level.

Thanks,
Adam


Re: DSB transceiver for Digital mode

Adam Rong
 

Folks,

Let’s use this thread to update the status. The test is done. I have tested both 7074 and 14074 radios. I need to update PCB to include a minor fix.

I will accept order and start to ship after Hamvention in May. I have lots of work to do considering my limited spare time.

Compared with the open schematic, I have modified several areas to improve TX signal purity and frequency stability. The added VOX circuit works as planned. I understand now that the DSB circuit concept I have adopted has some potential issue to cause self-oscillating. It seems that my fix is effective and still simple.

I can build this kit in a bit more than one hour. If you take time, you can enjoy a whole evening to build and test this rig. I have to standardize the name of this rig: D4D, no matter what it was called, either DSB FT8 BD6CR, FT8 DSB VOX or else.

Thanks,
Adam

在 2019年4月10日,上午8:03,Adam Rong via Groups.Io <rongxh@...> 写道:

May I call it D4D - DSB transceiver for Digital mode? This 1-watt DSB transceiver will provide lots of fun of building and operating. The VOX circuit will provide even more convenience to the operator. Thanks to the strong capability of digital mode and computer, this rig is not a toy. You can easily make FT8 contacts of 300-1500 miles range with a moderate antenna like full sized dipole  or EFHW.

The photos are for the prototype based on CRK-10A enclosure. It looks quite close to the final version. We will run testing in the following weeks. The initial test looks promising. We plan to take orders in about a month. We will start with 7074 version for FT8. The price will be very reasonable. Stay tuned and spread the word if you guys are interested.

<WechatIMG16.jpeg><WechatIMG17.jpeg>

Thanks,
Adam

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